JP4959078B2 - Hydrodynamic bearing spindle motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluid dynamic bearing spindle motor in which a rotor is supported on a stator by a fluid dynamic pressure bearing having a radial dynamic pressure bearing portion and a pair of upper and lower thrust dynamic pressure bearing portions.
[0002]
[Prior art]
FIG. 4 is a longitudinal sectional view of a conventional hydrodynamic bearing spindle motor (first conventional example) exaggeratedly showing a minute gap including a bearing gap. In this spindle motor, a rotor including a rotor magnet 7 is rotatably supported by a stator including a stator coil 8 by a T-shaped fluid dynamic pressure bearing. The rotor magnet 7 is attached to the inner peripheral surface of the cylindrical portion 6 a of the rotor frame 6. The rotor frame 6 also functions as a cup-shaped hub. The rotor frame 6 is press-fitted into the upper end of the shaft 2 of the flanged shaft 1 that is a rotating shaft, and is fixed to the rotating shaft. The stator coil 8 is attached to the outer peripheral surface of the stepped sleeve 4 erected on the base substrate 9.
[0003]
The hydrodynamic bearing includes a flanged shaft 1 formed by press-fitting a ring-shaped flange 3 into a shaft 2, a stepped cylindrical sleeve 4 into which the flanged shaft 1 is rotatably fitted, and a thrust holding member. 5. The minute gaps r1, r2, r3, r4, r5 and r6 formed between these bearing constituent members are filled with lubricating oil. The tapered minute gap S formed between the upper outer peripheral surface of the shaft member 2 and the inner peripheral surface of the thrust retainer member 5 functions to prevent the lubricating oil from leaking to the outside by utilizing capillary action and surface tension. This is a capillary seal.
[0004]
A pattern of a radial dynamic pressure generating groove G1 such as a herringbone groove is formed on the lower outer peripheral surface of the shaft member 2 forming the radial bearing gap r5, and the inner peripheral surface of the small diameter cylindrical portion of the stepped cylindrical sleeve 4 Is a flat surface.
[0005]
The thrust bearing gap includes the first thrust bearing gap r2 formed by the upper surface of the ring-shaped flange 3 and the lower surface of the thrust holding member 5, the lower surface of the ring-shaped flange 3 and the large-diameter cylindrical portion of the stepped cylindrical sleeve 4. And a second thrust bearing gap r4 formed by the bottom surface. A thrust dynamic pressure generating groove G2 as shown in FIG. 5 is formed on the upper surface and the lower surface of the ring-shaped flange 3.
[0006]
The fluid dynamic pressure spindle motor shown in FIG. 4 is practical, but has a problem in that the direction and position of the rotation axis may fluctuate because the distance between the upper and lower thrust bearing portions is short. A fluid dynamic pressure spindle motor (second conventional example) that solves this problem is disclosed in Japanese Patent Laid-Open No. 8-130852.
[0007]
That is, FIG. 3 is a longitudinal sectional view of a fluid dynamic pressure spindle motor of a second conventional example provided with an H-shaped fluid dynamic pressure bearing. In the spindle motor, a rotor including a rotor magnet 32 is rotatably supported by a stator including a stator coil 24 by a fluid dynamic pressure bearing. The rotor magnet 32 is attached to the inner peripheral surface of the cylindrical portion 36 d of the rotor frame 36. The rotor frame 36 also functions as a cup-shaped hub. The stator coil 24 is attached to the outer peripheral surface of the fixed sleeve body 12 erected on the base substrate 39.
[0008]
The rotating shaft body 16 is a flanged shaft having an H-shaped cross section in which an upper flange portion 16b and a lower flange portion 16d are provided above and below the shaft portion 16a. The radial dynamic pressure bearing portion is configured by externally fitting the sleeve portion 12a of the fixed sleeve body 12 to the shaft portion 16a via a lubricant. The radial dynamic pressure generating groove G1 is formed on the outer peripheral surface of the shaft portion 16a.
[0009]
The upper thrust dynamic pressure bearing portion is configured such that the upper annular portion of the fixed sleeve body 12 is opposed to the lower surface of the upper flange portion 16b via a lubricant. Further, the lower thrust dynamic pressure bearing portion is configured such that the upper annular portion of the fixed sleeve body 12 is opposed to the upper side surface of the lower flange portion 16d via a lubricant. The thrust dynamic pressure generating groove G2 is formed on the lower surface of the upper flange portion 16b and the upper surface of the lower flange portion 16d, respectively.
[0010]
The inner peripheral surface of the rotor frame 36 that is externally fitted to the projecting portion 16 c of the rotating shaft body 16 is clamped and fixed between the upper surface of the upper flange portion 16 b and the cap member 38.
[0011]
In the fluid dynamic pressure spindle motor of the second conventional example provided with the H-shaped fluid dynamic pressure bearing configured as described above, the rotational axis direction and position of the rotating shaft body are prevented from being shaken, and high rotational accuracy can be realized. . Further, the inner peripheral portion of the rotor frame 36 that is externally fitted to the projecting portion 16c of the rotary shaft body 16 is clamped and fixed between the upper side surface of the upper flange portion 16b and the cap member 38. The axial length of the inner peripheral surface is shorter than that in the case of fixing by press-fitting, and the upper flange portion 16b can also be used for fixing the rotor frame 36. It is described that it is highly effective in shortening the thickness, that is, in reducing the thickness.
[0012]
Although having such many features, the fluid dynamic pressure spindle motor of the second conventional example also has the following problems. First, when the cap member 38 is press-fitted into the protrusion 16c of the rotary shaft body 16, a large stress is applied to the inner peripheral portion of the upper flange portion 16b, and the upper flange portion 16b is deformed. When the upper flange portion 16b is deformed, there is a problem that both RRO and NRRO are deteriorated. Next, the lower flange portion 16d is to press-fit the fitting protrusion 16e into a fitting hole 16a1 that opens below the shaft portion 16a and is fixed to the shaft portion 16a. The lower part swells. When the lower portion of the shaft portion 16a swells, there is a problem that a galling phenomenon occurs in the radial dynamic pressure bearing portion and the shaft does not rotate. Furthermore, since the number of parts is larger than that of the fluid dynamic pressure spindle motor of the first conventional example, and the machining accuracy of each part must be high, there is a problem that the machining cost is high.
[0013]
[Problems to be solved by the invention]
The first problem to be solved is to reduce the number of parts constituting the H-shaped hydrodynamic bearing in the hydrodynamic bearing spindle motor provided with the H-shaped hydrodynamic bearing. A second problem to be solved is to provide a hydrodynamic bearing spindle motor including an H-shaped hydrodynamic bearing with good vibration.
[0014]
[Means for Solving the Problems]
The invention according to claim 1 that solves the above-mentioned problems is a hydrodynamic bearing spindle in which a rotor is supported on a stator by a fluid dynamic pressure bearing having a radial dynamic pressure bearing portion, an upper thrust dynamic pressure bearing portion, and a lower thrust dynamic pressure bearing portion. In the motor, the rotor frame to which the rotor magnet is attached and the load mounting surface is formed is also used as an upper thrust member constituting the upper thrust dynamic pressure bearing portion.
[0015]
According to a second aspect of the present invention for solving the above problems, a sleeve having an annular upper end surface and an annular lower end surface, and a flange formed at an end portion of a lower thrust member disposed opposite to the annular lower end surface A shaft, an upper thrust member disposed opposite to the upper end surface of the annular ring and fixed to the upper end portion of the shaft with flange by press fitting, an inner peripheral surface of the sleeve forming a radial gap, and an outer periphery of the shaft with flange A radial dynamic pressure generating groove provided on any one of the surfaces, a first annular dynamic pressure provided on any one of the annular upper end surface of the sleeve forming the first thrust gap and the lower surface of the upper thrust member A generating groove, a second thrust dynamic pressure generating groove provided on any one of an annular lower end surface of the sleeve forming a second thrust gap and an upper surface of the lower thrust member, The rotor including the rotor magnet is changed to the stator including the stator coil by the fluid dynamic pressure bearing configured by the lubricating oil filled in the minute clearance between the constituent members including the dial clearance, the first thrust clearance, and the second thrust clearance. The hydrodynamic bearing spindle motor is rotatably supported, and is characterized in that a rotor frame to which the rotor magnet is attached and a load mounting surface is formed is also used as the upper thrust member.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The hydrodynamic bearing spindle motor according to the first embodiment of the present invention is such that a rotor is rotatably supported by a stator by an H-shaped hydrodynamic bearing as shown in a longitudinal sectional view in FIG.
[0017]
In the hydrodynamic bearing spindle motor of the first embodiment of FIG. 1, the rotor is composed of a rotor frame 6 and a rotor magnet 7. The rotor frame 6 is a member having a disk portion 6c, an annular portion 6b, and a cylindrical portion 6a, and functions as a cup-shaped hub. The rotor magnet 7 is an annular permanent magnet and is attached to the inner peripheral surface of the cylindrical portion 6 a of the rotor frame 6. The stator includes a base substrate 9 and a stator coil 8. The base substrate 9 has a protruding cylindrical portion 9a formed at the center. The stator coil 8 is attached to the outer peripheral surface of the cylindrical portion 9 a of the base substrate 9.
[0018]
The H-shaped fluid dynamic pressure bearing in the first embodiment includes a thick sleeve 4 having an annular upper end surface and an annular lower end surface, a flanged shaft 1 having a flange 3 formed at the lower end, and a flange The rotor frame 6 is fixed to the upper end of the shaft 1 by press-fitting, and the base substrate 9 is formed with a recess in which the flange 3 is accommodated. The sleeve 4 is fitted into the cylindrical portion 9 a and fixed to the base substrate 9.
[0019]
In the H-shaped fluid dynamic pressure bearing in the first embodiment, the radial dynamic pressure generating groove G1 is provided on the outer peripheral surface of the flanged shaft 1 that forms a radial gap R3 with the inner peripheral surface of the sleeve 4. . The first thrust dynamic pressure generating groove G2 is provided on the annular upper end surface of the sleeve 4 that forms the first thrust gap R2 with the inner peripheral lower surface of the rotor frame 6. Further, the second thrust dynamic pressure generating groove G2 is provided on the annular lower end surface of the sleeve 4 that forms the second thrust gap R4 between the upper surface of the flange 3. The minute gaps R1 to R6 between the constituent members including the radial gap R3, the first thrust gap R2, and the second thrust gap R4 are filled with lubricating oil.
[0020]
In the H-shaped fluid dynamic pressure bearing in the first embodiment, the radial dynamic pressure generating groove G1 may be provided on the inner peripheral surface of the sleeve 4. Further, the first thrust dynamic pressure generating groove G <b> 2 may be provided on the inner peripheral side lower surface of the rotor frame 6. Further, the second thrust dynamic pressure generating groove G <b> 2 may be provided on the upper surface of the flange 3.
[0021]
Further, in the H-shaped fluid dynamic pressure bearing in the first embodiment, the upper end portion of the cylindrical portion 9a of the base substrate 9 that forms the minute gap R1 is made lower than the upper end surface of the sleeve 4, and as shown in FIG. A cylindrical portion that protrudes to the outer peripheral side of the upper end surface of the sleeve 4 may be formed.
[0022]
As described above, the hydrodynamic bearing spindle motor according to the first embodiment is composed of six parts, that is, the flanged shaft 1, the sleeve 4, the rotor frame 6, the rotor magnet 7, the stator coil 8, and the base substrate 9. . Therefore, the number of parts of the hydrodynamic bearing spindle motor of the first embodiment is one less than that of the hydrodynamic bearing spindle motor of the first conventional example of FIG. 4, and the hydrodynamic bearing spindle motor of the second conventional example of FIG. Two less than the bearing spindle motor. Moreover, the upper surface of the rotor frame 6 functions as a load mounting surface, and the lower surface functions as a thrust gap forming surface of the thrust dynamic pressure bearing portion. Therefore, the hydrodynamic bearing spindle motor of the first embodiment has a much better parallelism between the load mounting surface and the thrust gap forming surface than the hydrodynamic bearing spindle motors of the first and second conventional examples.
[0023]
Next, the hydrodynamic bearing spindle motor according to the second embodiment of the present invention is such that the rotor is rotatably supported by the stator by an H-shaped hydrodynamic bearing as shown in a longitudinal sectional view in FIG.
[0024]
In the hydrodynamic bearing spindle motor of the second embodiment of FIG. 2, the rotor is composed of a rotor frame 6 and a rotor magnet 7. The rotor frame 6 is a member having a disk portion 6c, an annular portion 6b, and a cylindrical portion 6a, and functions as a cup-shaped hub. The rotor magnet 7 is an annular permanent magnet and is attached to the inner peripheral surface of the cylindrical portion 6 a of the rotor frame 6. The stator includes a base substrate 9 and a stator coil 8. A through hole in which a fluid dynamic pressure bearing is erected is formed at the center of the base substrate 9. The stator coil 8 is attached to the outer peripheral surface of the thick sleeve 4 of the fluid dynamic pressure bearing provided upright in the through hole formed in the central portion of the base substrate 9.
[0025]
The H-shaped fluid dynamic pressure bearing in the second embodiment includes a sleeve 4 having an annular upper end surface and an annular lower end surface, a flanged shaft 1 having a flange 3 formed at the lower end, and a flanged shaft 1. The rotor frame 6 is fixed to the upper end portion by press-fitting, and the disc-shaped lid member 10 seals the open end of the housing recess of the flange 3 formed on the sleeve 4.
[0026]
In the H-shaped fluid dynamic pressure bearing in the second embodiment, the radial dynamic pressure generating groove G1 is provided on the outer peripheral surface of the flanged shaft 1 that forms a radial gap R3 with the inner peripheral surface of the sleeve 4. . The first thrust dynamic pressure generating groove G2 is provided on the lower surface on the inner peripheral side of the rotor frame 6 that forms the first thrust gap R2 between the annular upper end surfaces of the sleeve 4. Furthermore, the second thrust dynamic pressure generating groove G2 is provided on the upper surface of the flange 3 that forms the second thrust gap R4 with the annular lower end surface of the sleeve 4. The minute gaps R1 to R6 between the constituent members including the radial gap R3, the first thrust gap R2, and the second thrust gap R4 are filled with lubricating oil.
[0027]
In the H-shaped fluid dynamic pressure bearing in the second embodiment, the radial dynamic pressure generating groove G <b> 1 may be provided on the inner peripheral surface of the sleeve 4. Further, the first thrust dynamic pressure generating groove G <b> 2 may be provided on the annular upper end surface of the sleeve 4. Further, the second thrust dynamic pressure generating groove G2 may be provided on the annular lower end surface of the sleeve 4.
[0028]
In the hydrodynamic bearing spindle motor according to the second embodiment, the outer diameter of the portion from the top to the bottom of the half of the sleeve 4 in the axial direction is reduced, and the sleeve 4 is fitted on the outer peripheral surface of the small outer diameter. A cylindrical portion having an inner peripheral surface may be formed on the base substrate 9, and the sleeve 4 may be fixed to the base substrate 9.
[0029]
As described above, the hydrodynamic bearing spindle motor according to the second embodiment includes the flanged shaft 1, the sleeve 4, the rotor frame 6, the rotor magnet 7, the stator coil 8, the base substrate 9, and the disk-shaped lid member 10. It consists of parts. Therefore, the hydrodynamic bearing spindle motor of the first embodiment has the same number of parts as the hydrodynamic bearing spindle motor of the first conventional example of FIG. 4, but the hydrodynamic bearing spindle motor of the second conventional example of FIG. 1 less than Moreover, the upper surface of the rotor frame 6 functions as a load mounting surface, and the lower surface functions as a thrust gap forming surface of the thrust dynamic pressure bearing portion. Therefore, the hydrodynamic bearing spindle motor of the first embodiment has a much better parallelism between the load mounting surface and the thrust gap forming surface than the hydrodynamic bearing spindle motors of the first and second conventional examples.
[0030]
In both the first embodiment and the second embodiment, the fine gap R1 that is the inlet for the lubricating oil and the capillary seal portion has a taper as employed in the first conventional example in FIG. It is desirable to form a shaped opening.
[0031]
【Effect of the invention】
A spindle motor having an H-shaped fluid dynamic pressure bearing according to the present invention, characterized in that a part of the rotor frame is also used as a thrust gap forming member of a thrust dynamic pressure bearing portion, Compared to a spindle motor equipped with a letter-shaped fluid dynamic pressure bearing, the number of parts can be reduced, and at the same time, the cost can be reduced.
[0032]
In the present invention, the rotor frame is fixed to the shaft by press-fitting, but the rotor frame that is also used as the thrust member is not deformed by the press-fitting. Further, the rotor frame according to the present invention functions as a load mounting surface on the upper surface and a thrust gap forming surface on the thrust dynamic pressure bearing portion on the upper surface, so that the thrust between the load mounting surface and the thrust dynamic pressure bearing portion is provided. The parallelism with the gap forming surface is very good. Therefore, the hydrodynamic bearing pindle motor according to the present invention has improved vibration compared to a spindle motor provided with a conventional H-shaped fluid dynamic pressure bearing.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a spindle motor provided with an H-shaped fluid dynamic pressure bearing according to a first embodiment of the present invention, exaggerating a minute gap.
FIG. 2 is a longitudinal sectional view of a spindle motor provided with an H-shaped fluid dynamic pressure bearing according to a second embodiment of the present invention, exaggerating a minute gap.
FIG. 3 is a longitudinal sectional view of a conventional spindle motor (second conventional example) provided with an H-shaped fluid dynamic pressure bearing exaggeratedly showing a minute gap.
FIG. 4 is a longitudinal sectional view of a conventional spindle motor (first conventional example) provided with a T-shaped fluid dynamic pressure bearing exaggeratedly showing a minute gap.
FIG. 5 is a diagram showing an example of a thrust dynamic pressure generating groove G2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shaft with flange 2 Shaft 3 Flange 4 Sleeve 5 Thrust holding member 6 Rotor frame 7 Rotor magnet 8 Stator coil 9 Base substrate 10 Disc-like lid member 12 Fixed sleeve body 16 Rotating shaft body 16a Shaft portion 16b Upper flange portion 16c Projecting portion 16d Lower flange portion 16e Fitting protrusion 24 Stator coil 32 Rotor magnet 36 Rotor frame 38 Cap member

Claims (1)

A sleeve having an annular upper end surface and an annular lower end surface, a flanged shaft formed at the end of a lower thrust member disposed opposite to the annular lower end surface, and opposed to the annular upper end surface; An upper thrust member fixed to the upper end portion of the flanged shaft by press-fitting, and a radial dynamic pressure generating groove provided on one of the inner peripheral surface of the sleeve and the outer peripheral surface of the flanged shaft forming a radial gap. A first thrust dynamic pressure generating groove provided on one of the annular upper end surface of the sleeve forming the first thrust gap and the lower surface of the upper thrust member, and the sleeve forming the second thrust gap. A second thrust dynamic pressure generating groove provided on one of an annular lower end surface and an upper surface of the lower thrust member, the radial gap, the first thrust gap, and the second thrust A hydrodynamic bearing spindle motor in which a rotor including a rotor magnet is rotatably supported by a stator including a stator coil by a fluid dynamic pressure bearing composed of a lubricating oil filled in a minute gap between the constituent members including the gap The rotor frame to which the rotor magnet is attached and the load mounting surface is formed is also used as the upper thrust member ,
The stator is formed so as to protrude on the upper side in the axial direction so that the sleeve is inserted and mounted in a central portion, and is formed to be disposed inside the cylindrical portion. A hydrodynamic bearing spindle motor comprising a base substrate having a recess for accommodating a lower thrust member .

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