WO2006118407A1

WO2006118407A1 - Hydrodynamic bearing motor having fixed shaft

Info

Publication number: WO2006118407A1
Application number: PCT/KR2006/001633
Authority: WO
Inventors: Sang-Uk Kim
Original assignee: G & W Technologies, Inc.
Priority date: 2005-05-03
Filing date: 2006-05-02
Publication date: 2006-11-09
Also published as: KR100691607B1; KR20060114883A

Abstract

Provided is a hydrodynamic bearing motor with an improved structure to stably prevent oil leakage from a bearing unit due to the centrifugal force generated during the rotation of the motor. The motor includes an oil gap formed between a rotor and a fixing body to form a hydrodynamic bearing to rotatably support the rotor. The fixing body includes a base to which a stator is fixed; and a hollow sleeve which is fixed at a center of the sleeve and in which a flange is formed in the upper portion thereof. The rotor includes a shaft, a hub to which the rotor is fixed, and a seal cover. Also, the motor includes a first taper seal which is gradually thinner in the direction of the centrifugal force to be linearly connected with the thrust bearingand formed between the bottom surface of a flange and the upper surface of the seal cover. Thus, oil leakage can be effectively prevented since oil in the taper seal is moved in the direction of the centrifugal force during the rotation of the hub and directed toward a thrust bearing.

Description

HYDRODYNAMIC BEARING MOTOR HAVING FIXED SHAFT

Technical Field

[1] The present invention relates to a hydrodynamic bearing motor, and more particularly, to a hydrodynamic bearing motor with an improved structure to stably prevent oil leakage from a bearing unit due to the centrifugal force.

Background Art

[2] A spindle motor used in a disk driving device for rotating a recording disk includes a hydrodynamic bearing to rotatably support a shaft and a sleeve by fluid pressure of a lubricant oil interposed between the shaft and the sleeve.

[3] FIGS. 1 and 2 illustrate a spindle motor having a hydrodynamicbearing, which is disclosed in Japanese Patent Laid-Open Gazette No. 2003-314535.

[4] The spindle motor includes: a hub 2 having an upper plate portion 2a and a cylindrical main wall portion 2b that extends downward from the outer circumferential surface of the upper plate portion 2a; a shaft 4, an upper end portion of which is coupled and fixed to the center of the upper plate portion 2a; a hollow sleeve 8 that rotatably supports the shaft4; a cover block 10 blocking a lower end portion of the sleeve 8; and a housing 14 having acylindrical portion 12 that is coupled to the sleeve 8.

[5] Lubricant oil is interposed between the upper end surface of the sleeve 8 and the bottom surface of the upper plate portion 2a of the hub 2, thus forming a thrust bearing 20, and lubricant oil is interposed between the shaft 4 and the sleeve 8, thus forming journal bearings 24 and 26. An oil leakage prevention structure for preventing leakage of the lubricant oil from the thrust bearing 20 is employed. The oil leakage prevention structure extends downward from the bottom surface of the upper plate portion 2a of the hub 2 with a diameter greater than the outer circumference of the sleeve 8, and an inclined surface 8 a is formed on the outer circumferential surface of the upper end portion of the sleeve 8 to form a cylindrical wall 2d, and a ring member 32 having an inclined surface 32a facing the inclined surface 8a of the sleeve 8 is formed on the inner circumferential surface of the cylindrical wall 2d. The oil leakage prevention structure forms an interface between the lubricant oil and air in a gap between the sleeve 8 and the ring member 32 and prevents oil leakage due to the centrifugal force generated by the rotation of the hub2.

[6] Since the gap is inclined toward the axis of the shaft 4, the centrifugal forceis divided along the inclined surfaces 8a and 32a, and thus, even though the centrifugal force is large, oil leakage is prevented. Disclosure of Invention

Technical Problem

[7] However, as the ring member 32 includes the inclined surface 32a, the ring member 32 cannot sufficiently prevent the hub 2 from separating from the sleeve 8, and thus, when the hub 2 receives an impulse during the rotation of the motor, sharp end portions of the ring member 32 are likely to be damaged.

Technical Solution [8] The present invention provides a hydrodynamic bearing motor that effective- lyprevents oil leakage due to a centrifugal force of a rotator during the rotation of the motor. [9] The present invention also provides a hydrodynamic bearing motor thatpreventsa rotor from separating from the motor. [10] The present invention also provides a hydrodynamic bearing motor with an improved and thin structure.

Advantageous Effects [11] First, since the first taper seal 210 is gradually thinner in the direction of the centrifugal force, when the hub 60 rotates, the oil in the first taper seal 210 is moved in the direction of the centrifugal direction and directed toward the thrust bearing 130, and thus oil leakage is effectively prevented. [12] Second, the second taper seal 220 is connected linearly with the first taper seal 210, thereby stably preventing oil leakage in spite of an external impulse when the motor is stopped. [13] Third, sincethe thrust yoke 110 facing the rotor is formed on the base 50 to prevent conical vibrations together withthe thrust bearing 130 during the rotation of the motor, and the motor can be made thin.

Description of Drawings

[14] FIG. 1 is a cross-sectional view of a conventional hydrodynamic bearing motor;

[15] FIG. 2 is a partial view of main portions of the hydrodynamic bearing motor of

FIG. 1; [16] FIG. 3 is a cross-sectional view of a hydrodynamic bearing motor according to an embodiment of the present invention;

[17] FIG. 4 is a separated view of the hydrodynamic bearing motor of FIG. 3; and

[18] FIG. 5 is a partial view of main portions of the hydrodynamic bearing motor of

FIG. 3.

Best Mode

[19] The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. [20] According to the present invention, a hydrodynamic bearing motor has an oil gap formed between a rotor and a fixing body to form a hydrodynamic bearing to rotatably support the rotor, and a recording medium such as a platter is mounted on the rotor.

[21] Referring to FIGS. 3 and 5, the fixing body includes a base 50 to which a stator 41 is fixed and a hollow sleeve 80 which is coupled and fixed at the center of the base 50 and has a flange 83 formed atan upper portion thereof.

[22] A rotor 42 includes: a shaft 70 rotatably coupled to the hollow sleeve 80, wherein an oil gap is formed in the hole of the hollow sleeve 80 in order to form a journal bearing; a hub 60 in which an upper end portion of the shaft 70 is coupled and fixed in the center, and a cylindrical wall 61 that is extendeddownward is formed in the bottom surface of the hub 60,and an oil gap is formed between the upper surface of the flange 83 and the hub 60 to form a thrust bearing 130, and the rotor 42 facing the stator 41 is fixed; and a seal cover 90 that is coupled and fixed to the inner circumferential surface of the cylindrical wall 61 and forms a gap between the bottom surface of the flange 83 and the seal cover 90.

[23] Also, a first taper seal 210, which is gradually thinner in the direction of the centrifugal force,is formedbetween the bottom surface of the flange 83 and the upper surface 91 of the seal cover 90to be linearly connected with the thrust bearing 130.

[24] A second taper seal 220, which is gradually thinner in the upper direction,is formedbetween the inner circumferential surface 92 of the seal cover 90 and the outer circumferential surface of the sleeve 80to be linearly connected with the first taper seal 210.

[25] The first taper seal 210 is formed betweenahorizontal upper surface 91 of the seal cover 90 and a first inclined surface 81 on the bottom surface of the flange 83. The second taper seal 220 is formed between the perpendicular inner circumferential surface 92 of the seal cover 90 and a second inclined surface 82 on the outer circumferential surface of the sleeve 80.

[26] The rotor 42 is a magnet, and a thrust yoke 110 is fixed on the base 50 facing the rotor 42. Thus, the hub 60 is supported by the thrust bearing 130 in the direction of a thrust, thereby conical vibrationsof the hub 60 during the rotation of the motorbeing prevented.

[27] The thrust yoke 110 is installed in a marginal space of the base 50 to support the hub 60 magnetically. Thus, the motor can be made thin. When power is supplied to the stator 41, the shaft 70 and the hub 60 rotate by the electric magnetic force generated between the rotor 42 and the stator 41.

[28] Oil is interposed between the sleeve 80 and the shaft 70 to form upper/lower journal bearings 121 and 122, and the thrust bearing 130 is formed between the bottom surface of the hub 60 and the upper surface of the sleeve 80 to support the rotor42. [29] Since the hub 60 is attracted by the magnetic force of the thrust yoke 110 and the rotor 42 in the downward direction, the hub 60 and the seal cover 90 are prevented from separating from the motor and the hub 60 stably is stably supported in the direction of the thrust.

[30] During the rotation of the hub 60, the oil in the thrust bearing 130 is likely to leak out through the first taper seal 210 due to the centrifugal force, however, since the first taper seal 210 is gradually thinner in the direction of the centrifugal force, the oil that leaked from the first taper seal 210 is moved toward the thrust bearing 130 by the centrifugal force, thereby preventing oil leakage.

[31] Also, when the motor is stopped, the oil in the first taper seal 210 is likely to leak out by an external impulse or the like; however, the second taper seal 220 prevents oil leakage by the capillary effect.

[32] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

[1] A hydrodynamic bearing motor having a hydrodynamic bearing formed by a oil gap between a rotor and a fixing body to rotatably support the rotor, wherein the fixing body includes a base to which a stator is fixed and a hollow sleeve which is coupled and fixed to the center of the base and in which a flange is formed in an upper portion thereof, the rotor comprises: a shaft that forms an oil gap in a hole of the sleeveto form a journal bearing and is rotatably coupled to the sleeve; a hub in which an upper end portion of the shaft is coupled and fixed in the center, and a cylindrical wall that is extended downward is formed in the bottom surface of the hub, and an oil gap is formed between the upper surface of the flange and the hub to form a thrust bearing, and to which a rotor facing the stator is fixed; and a seal cover that is coupled and fixed to the inner circumferential surface of the cylindrical wall and forms a gap between the bottom surface of the flange and the seal cover, wherein a first taper seal which is gradually thinner in the direction of the centrifugal force to belinearly connected with the thrust bearing and is formed between the bottom surface of the flange and the upper surface of the seal cover.

[2] The hydrodynamic bearing motor of claim 1, further comprising a second taper seal which is gradually thinner in the upper direction between the inner circumferential surface of the seal cover and the outer circumferential surface of the sleeve and linearly connected with the first taper seal.

[3] The hydrodynamic bearing motor of claim 1, wherein the rotor is a magnet and a thrust yoke, formed of a magnetic body, is fixed on a base facing the rotor.

[4] The hydrodynamic bearing motor of claim 2, wherein the rotor is a magnet and a thrust yoke, formed of a magnetic body, is fixed on a base facing the rotor.

[5] The hydrodynamic bearing motor of claim 4, wherein the first taper seal is formed between the horizontal upper surface of the seal cover and a first inclined surface on the bottom surface of the flange.

[6] The hydrodynamic bearing motor of claim 5, wherein the second taper seal is formed between the perpendicular inner circumferential surface of the seal cover and a second inclined surface on the outer circumferential surface of the sleeve.