JP3984449B2 - Fluid dynamic bearing, spindle motor using the same, and disk drive using the spindle motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluid dynamic pressure bearing, a spindle motor using the fluid dynamic bearing, and a disk drive device using the spindle motor.
[0002]
[Prior art]
Conventionally, as a bearing of a spindle motor used in a disk drive device for driving a recording medium such as a hard disk, a lubricating fluid such as oil interposed between the shaft and the sleeve in order to support the shaft and the sleeve so as to be relatively rotatable. Various fluid dynamic pressure bearings utilizing the fluid pressure have been proposed.
[0003]
As shown in FIG. 1, a spindle motor using such a conventional fluid dynamic pressure bearing has an outer peripheral surface of a shaft b integrated with the rotor a and an inner periphery of a sleeve c through which the shaft b is rotatably inserted. A pair of radial bearings d, d is formed between the upper surface of the disk-shaped thrust plate e and the sleeve b projecting radially outward from the outer peripheral surface of one end of the shaft a. A pair of thrust bearing portions g, g are formed between the flat surface of the stepped portion and between the lower surface of the thrust plate e and the thrust bushing f that closes one opening of the sleeve b.
[0004]
A series of minute gaps are formed between the shaft b and the thrust plate e and the sleeve c and the thrust bush d, and oil is continuously held in these minute gaps without interruption as oil. (Such an oil retaining structure is hereinafter referred to as a “full-fill structure”), the radial bearing portions d and d and the thrust bearing portions g and g are herrings for inducing dynamic pressure in the oil when the rotor a rotates. Bone grooves d1, d1 and g1, g1 are formed, respectively.
[0005]
The radial bearing portions d and d and the thrust bearing portions g and g are formed with herringbone grooves d1, d1 and g1, g1 formed by connecting a pair of spiral grooves, and according to the rotation of the rotor a. The maximum dynamic pressure is generated at the central portion of the bearing portion where the connecting portion of the spiral groove is located, and the load acting on the rotor a is supported.
[0006]
[Problems to be solved by the invention]
In such a spindle motor, a taper seal portion h is formed in the vicinity of the upper end portion of the sleeve c located on the opposite side in the axial direction to the thrust bearing portions g and g, and the surface tension of the oil and the atmospheric pressure are balanced. Interface. That is, the internal pressure of the oil in the taper seal portion h is maintained at a pressure substantially equal to the atmospheric pressure.
[0007]
Now, when the rotor a starts to rotate, the oil is drawn into the center side of each radial bearing part d, d and thrust bearing part g, g by pumping by the dynamic pressure generating grooves d1, d1, g1, g1. On the other hand, the fluid dynamic pressure reaches a maximum at the center of the bearing, but the internal pressure of the oil decreases at the end of the bearing. On the other hand, at the end of the radial bearing portion adjacent to the taper seal portion h, the interface moves in the taper seal portion h according to the fluctuation of the oil internal pressure, and the atmospheric pressure and the oil internal pressure are antagonized. Although it is possible, oil and thrust held between the pair of radial bearing portions d and d in the region between the bearing portions, that is, between the outer peripheral surface of the shaft b and the inner peripheral surface of the sleeve c. In the area around the plate e, the oil held near the outer peripheral portion of the thrust plate located between the thrust bearing portions g and g is in accordance with the pumping of the dynamic pressure generating grooves d1, d1 and g1, g1. In some cases, the internal pressure decreases and eventually decreases to below atmospheric pressure and becomes negative pressure.
[0008]
If the motor continues to operate in a state where a negative pressure is generated in a portion that is originally filled with oil, bubbles are generated in that portion. This has the property of dissolving air in the oil, and when the oil is in contact with the atmospheric pressure and the part below the atmospheric pressure, the air melts from the atmospheric pressure side and dissolves into the negative pressure part below the atmospheric pressure. This is due to the action. If air bubbles are generated inside the bearing in this way, oil leaks to the outside of the bearing, affecting the durability and reliability of the spindle motor, or vibration caused by contact of the dynamic pressure generating groove with the air bubbles. There arises a problem that affects the rotation accuracy of the spindle motor, such as occurrence of NRRO and deterioration of NRRO (non-repetitive shake component).
[0009]
The present invention prevents negative effects due to air bubbles by preventing the occurrence of negative pressure in the oil, and can reduce the loss due to the viscous resistance of the oil and increase the efficiency. An object of the present invention is to provide a simple fluid dynamic pressure bearing, a spindle motor using the same, and a disk drive using the spindle motor.
[0010]
[Means for Solving the Problems]
The fluid dynamic pressure bearing according to the present invention includes a hollow cylindrical sleeve, a shaft that is radially opposed to the inner peripheral surface of the sleeve via a gap, and extends radially outward at one end of the shaft. And a disc-shaped thrust plate whose one surface is axially opposed to one end surface of the sleeve via a gap, and the other surface of the thrust plate mounted on one end of the sleeve and the end surface of the shaft. and the bush which faces in the axial direction through the, to function as a continuous held by Rutotomoni tapered seal without interruption it into the gap formed respectively between said shaft and said thrust plate and the sleeve and the bush interface only in the vicinity of the other end of the sleeve comprises an oil that is one form, the shaft and the thrust plate and the sleeve as well as A fluid dynamic pressure bearing that supports relative rotation with a bush using fluid dynamic pressure induced by the oil, and between the one end surface of the sleeve and one surface of the thrust plate, One thrust dynamic pressure bearing portion for inducing a fluid dynamic pressure inward in the radial direction of the oil is configured, and between the bush and the other surface of the thrust plate, a radial direction is applied to the oil during the relative rotation. The other thrust dynamic pressure bearing portion that induces the fluid dynamic pressure toward the inside is configured, and a pair of radial dynamic pressure bearing portions are disposed between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft. axially configured apart, wherein the pair of radial dynamic pressure bearing portion, with herringbone grooves of symmetrical shape in the axial direction as the dynamic pressure generating grooves are formed, the one and the other thrust dynamic in The bearing portion, the spiral groove to induce hydrodynamic directed radially inwards is provided as a dynamic pressure generating grooves each, the interface of the oil is formed in proximity to the other end face of the sleeve, the pair Between the oil interface and the radial dynamic pressure bearing portion adjacent thereto, at least one of the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, A spiral groove is formed to urge the oil toward the thrust plate during rotation and to keep the internal pressure of the oil held in the gap located between the dynamic pressure bearing portions at or above the atmospheric pressure at all times. (Claim 1).
[0011]
This configuration relates to a fluid dynamic pressure bearing having a full-fill structure.
[0012]
In addition to the herringbone groove formed as a dynamic pressure generating groove in the radial dynamic pressure bearing part, a spiral groove is provided adjacent to the radial bearing part configured on the interface side of the oil, so that the oil against the oil at the time of relative rotation A fluid dynamic pressure (this pressure is hereinafter referred to as “indentation pressure”) is generated in the axial direction and toward the thrust plate, and this indentation pressure is generated between the end surface of the sleeve and one surface of the thrust plate. It becomes larger than the fluid dynamic pressure directed inward in the radial direction induced by one of the thrust dynamic pressure bearing portions formed therebetween. Therefore, the indentation pressure by the spiral groove is slightly canceled by one thrust dynamic pressure bearing portion, but is still transmitted to the oil held on the outer peripheral portion of the thrust plate while maintaining the oil internal pressure equal to or higher than the atmospheric pressure.
[0013]
That is, in a fluid dynamic pressure bearing with a full-fill structure, the internal pressure of oil held in the gaps between the bearing portions, which tend to be negative due to pumping of the dynamic pressure generating grooves formed in the bearing portions, is always high. Since the pressure is maintained above the atmospheric pressure, problems such as generation of bubbles due to negative pressure and leakage of oil and deterioration of NRRO caused by the retention of bubbles in the oil are solved.
[0014]
Furthermore, a seal function is achieved by forming a spiral groove between the interface of the oil and the radial dynamic pressure bearing adjacent to the radial dynamic pressure bearing, so as to apply indentation pressure to the oil. And oil leakage to the outside of the bearing is effectively prevented.
[0015]
The pair of radial dynamic pressure bearing portions formed between the spiral groove and one of the thrust dynamic pressure bearing portions is formed with herringbone grooves having a symmetrical shape in the axial direction. The dynamic pressure generated in the bearing portion does not become an unbalanced pressure gradient in the axial direction. Therefore, the pair of radial dynamic pressure bearing portions does not interfere with the pushing pressure of the spiral groove.
[0017]
In the present invention, the fluid dynamic pressure bearing having a full-fill structure can be used to simplify the structure of the bearing portion, and the dynamic pressure generating groove formed in the thrust dynamic pressure bearing portion can be a spiral groove. Thus, the diameter of the thrust plate can be reduced, so that the viscous resistance of the oil due to the peripheral speed of the thrust plate is suppressed, and the efficiency can be increased.
[0018]
Further, the spindle motor of the present invention includes a bracket that holds the stator, a rotor that rotates relative to the bracket, a rotor magnet that is fixed to the rotor and generates a rotating magnetic field in cooperation with the stator, and the rotor in a spindle motor having a fluid dynamic bearing for supporting the rotation of the fluid dynamic bearing it is characterized by a fluid dynamic bearing according to claim 1 (claim 2).
[0019]
Since the fluid dynamic pressure bearing for supporting the rotation of the rotor has the configuration as described above, the problem of bubbles staying in the oil is eliminated, and oil leakage to the outside of the bearing and deterioration of the NRRO are prevented. Therefore, the reliability and durability are excellent, and the efficiency of the bearing is improved. Therefore, the loss during rotation can be reduced and the power consumption can be reduced. Moreover, the cost can be reduced by employing a fluid dynamic pressure bearing having a full-fill structure.
[0020]
In addition, the disk drive device of the present invention includes a housing, a spindle motor that is fixed inside the housing and rotates the recording medium, and a disk drive device on which a disk-shaped recording medium capable of recording information is mounted. A disk drive device having information access means for writing or reading information at a required position of a recording medium, wherein the spindle motor is the spindle motor according to claim 2. 3).
[0021]
Since the spindle motor of the present invention is excellent in reliability and durability, can suppress power consumption, and can be reduced in cost, it has high rotational accuracy, durability, and low power consumption. In addition, the present invention can be suitably used in a disk drive device that drives a hard disk for which cost reduction is required. However, the present invention is not limited to this. It can also be used in the same disk drive device.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a fluid dynamic pressure bearing according to the present invention, a spindle motor using the same, and a disk drive device using the spindle motor will be described below with reference to FIGS. 2 to 6. The present invention will be described below. The present invention is not limited to the examples.
[0023]
(1) Configuration of Spindle Motor The spindle motor shown in FIG. 2 includes a rotor hub 2 in which a hard disk (shown as a disk plate 53 in FIG. 6) is held on the outer periphery, a shaft 4 attached to the rotor hub 2, and a shaft. And a bracket 8 provided with a rotor composed of a disc-shaped thrust plate 6 extending radially outward from the outer peripheral surface of the free end portion 4 (the end opposite to the side attached to the rotor hub 2). And a sleeve 10 fixed to the cylindrical boss portion 8a. A rotor magnet 12 is attached to the inner surface side of the rotor hub 2 by means such as adhesion, and a stator 14 is disposed on the bracket 8 so as to face the rotor magnet 12 in the radial direction.
[0024]
As shown in FIGS. 2 and 3, the sleeve 10 is formed with a through hole 10a penetrating the sleeve 10 in the axial direction. The shaft 4 forms a minute gap with the through hole 10a. It is inserted. On one opening side (the bracket 8 side) of the through hole 10a, a first step portion 10a1 is formed corresponding to the thrust plate 6, the inner diameter is larger than the through hole 10a, and the first end portion 10a1 A second step portion 10a2 whose inner diameter is further expanded continuously is formed. The flat surface of the first step portion 10a1 forms a minute gap with the upper surface of the thrust plate 6, and the inner peripheral surface of the first step portion 10a1 forms a gap with the outer peripheral surface of the thrust plate 6. Forming. A thrust bush 16 that closes the opening of the through hole 10 a is attached to the second step portion 10 a 2, and this thrust bush 16 is located between the lower surface of the thrust plate 6 and the end surface on the free end side of the shaft 4. A gap is formed.
[0025]
A minute gap formed between the inner circumferential surface of these through holes 10a and the outer circumferential surface of the shaft 4, a minute gap between the flat surface of the first step portion 10a1 and the upper side surface of the thrust plate 6, and the first The gap between the inner peripheral surface of the step portion 10a1 and the outer peripheral surface of the thrust plate 6, and further, the gap between the thrust bush 16 and the lower side surface of the thrust plate 6 are all continuous. The oil is continuously held in the gap without interruption. On the outer peripheral surface of the shaft 4 in the vicinity of the rotor hub 2 mounting portion side, the radial clearance dimension of the minute gap formed between the inner peripheral surface of the through hole 10a gradually increases toward the rotor hub 2 side. The annular groove 4a is provided, and an oil interface is formed between the annular groove 4a and the inner peripheral surface of the through hole 10a, and functions as a taper seal 17.
[0026]
(2) Configuration of Bearing Part Next, each bearing part will be described with reference to FIGS.
[0027]
On the inner peripheral surface of the through hole 10a of the sleeve 10, a pair of spiral grooves inclined in a direction opposite to the rotational direction is connected to the inner side in the axial direction of the annular groove 4a of the shaft 4. A circumferential dynamic pressure generating groove array is formed by a “<”-shaped herringbone groove 18 a, and an upper radial dynamic pressure bearing portion 18 is formed between the outer peripheral surface of the shaft 4.
[0028]
In addition, a pair of spiral grooves that are adjacent to the first stepped portion 10a1 and that incline in opposite directions that induce fluid dynamic pressure in the oil when the rotor 6 rotates are formed on the inner peripheral surface of the through hole 10a of the sleeve 10. A circumferential dynamic pressure generating groove row is formed by a herringbone groove 20 a having a substantially “<” shape formed by connecting the two, and the lower radial dynamic pressure bearing portion 20 is formed between the outer peripheral surface of the shaft 4. Is configured.
[0029]
Herringbone grooves 18a and 20a formed on the upper and lower radial dynamic pressure bearing portions 18 and 20 have an inclination angle with respect to the rotation axis, a groove depth, so that each spiral groove portion generates substantially the same pumping force. The overall length and the width dimension are substantially the same, that is, each spiral groove is set to be line-symmetric with respect to the connecting portion.
[0030]
On the flat surface of the first step portion 10 a 1 formed on the sleeve 10, a dynamic pressure generating groove array by the spiral groove 22 a is formed concentrically with the thrust plate 6, and between the upper side surface of the thrust plate 6. An upper thrust dynamic pressure bearing portion 22 is configured. The spiral groove 22a has a pump-in shape so that a dynamic pressure (fluid dynamic pressure B) acting on the inner side in the radial direction, that is, on the shaft 4 side, is generated according to the rotation of the thrust plate 6. Due to the fluid dynamic pressure generated by the groove 22a, a shaft support force that acts in a direction in which the thrust plate 6 moves away from the first step portion 10a1 is obtained.
[0031]
Further, on the inner surface of the thrust bushing 16 facing the lower surface of the thrust plate 6 in the axial direction, a dynamic pressure generating groove array by the spiral groove 24 a is formed concentrically with the thrust plate 6. A lower thrust dynamic pressure bearing portion 24 is formed between the side surfaces. Similar to the spiral groove 22 a formed in the upper thrust dynamic pressure bearing portion 22, the spiral groove 24 a acts on the inside of the radial direction in response to the rotation of the thrust plate 6, that is, on the rotation center side of the thrust plate 6. The thrust plate 6 floats with respect to the thrust bushing 16 by the fluid dynamic pressure generated by the spiral groove 22a.
[0032]
As described above, the dynamic pressure generating grooves formed in the upper and lower thrust dynamic pressure bearing portions 22 and 24 are the spiral grooves 22a and 24a, so that the herringbone groove is provided as the dynamic pressure generating groove in the thrust dynamic pressure bearing portion. Compared to the case, the efficiency as a bearing is improved.
[0033]
In other words, as described above, the herringbone groove has a substantially “<” shape formed by connecting a pair of spiral grooves inclined in directions opposite to the rotation direction. By pumping oil from both ends of the bearing portion toward the spiral groove connection portion during rotation, a pressure distribution in a mountain shape with the spiral groove connection portion at the top is obtained. On the other hand, in the spiral grooves 22a and 24a, the center portion of the bearing portion, that is, the outer peripheral portion of the shaft 4 in the upper thrust dynamic pressure bearing portion, and the substantial base including the rotational axis portion of the shaft 4 in the lower thrust dynamic pressure bearing portion 24. It becomes the pressure distribution of the shape.
[0034]
Therefore, compared to the case where the herringbone groove is provided as a dynamic pressure generating groove, the effective area for supporting the load can be increased, and when applied to a spindle motor having the same load, the outer diameter of the thrust plate 6 is reduced. Since the peripheral speed can be kept small, the loss due to the viscous resistance of the oil is suppressed.
[0035]
In other words, compared to the case where the herringbone groove is applied as a dynamic pressure generating groove of the thrust dynamic pressure bearing portion, the loss is reduced and the power consumption of the spindle motor is suppressed while maintaining the same load performance (load supporting force). It becomes possible.
[0036]
Further, a spiral groove 19 is formed between the upper radial dynamic pressure bearing portion 18 and the taper seal 17, and the spiral groove 19 causes a thrust from the interface side to the oil in accordance with the rotation of the shaft 4. An indentation pressure that indents toward the plate 6 side is generated. Due to this indentation pressure, the oil internal pressure increased by the spiral groove 19 and the herringbone groove 18a of the upper radial dynamic pressure bearing portion 18 is transmitted to the thrust plate 6 side.
[0037]
(3) Shaft support method The shaft support method by each dynamic-pressure bearing part comprised as mentioned above is explained in full detail below. 5 shows a minute gap formed between the inner peripheral surface of the through hole 10a of the sleeve 10 and the outer peripheral surface of the shaft 4, the flat surface of the first step portion 10a1, and the upper surface of the thrust plate 6. And a gap between the inner circumferential surface of the first step portion 10a1 and the outer circumferential surface of the thrust plate 4, and further, a gap between the thrust bush 16 and the lower side surface of the thrust plate 6. Fig. 5 is a pressure distribution diagram schematically showing the relative relationship of the oil pressure distribution as a concept, but since the spindle motor pressure distribution is axisymmetric, the axis of rotation shown by the alternate long and short dash line in Fig. 5 On the other hand, the pressure distribution in the opposite region in the longitudinal section of the spindle motor is omitted. Further, the numbers shown in FIG. 5 are the same as the numbers given to the respective bearing portions in FIG.
[0038]
In accordance with the rotation of the spindle motor, in the upper and lower radial dynamic pressure bearings 18 and 20, the pumping force by the herringbone grooves 18a and 20a increases, and at the same time, the support pressure necessary to support the load in the radial direction is generated. By the pumping of the spiral groove 19 formed between the upper radial dynamic pressure bearing portion 18 and the taper seal 17, an indentation pressure acting on the thrust plate 6 side from the interface side is generated against the oil.
[0039]
At this time, the internal pressure of the oil held in the gap located on the thrust plate 6 side with respect to the upper radial dynamic pressure bearing portion 18 with the indentation pressure against the oil generated by the spiral groove 19 becomes the atmospheric pressure or more, and the generation of the negative pressure Is prevented.
[0040]
In the upper and lower radial dynamic pressure bearing portions 18 and 20, the oil is applied with substantially uniform pressure from both ends of the bearing in the axial direction toward the center of the bearing by herringbone grooves 18a and 20a having a balanced shape in the axial direction. Therefore, the pressure gradient of the generated fluid dynamic pressure is symmetric in the axial direction, and no pushing pressure acting on the oil in any axial direction is induced. Therefore, the pushing pressure against the oil by the spiral groove 19 is not affected by the upper and lower radial dynamic pressure bearing portions 18 and 20.
[0041]
However, in the upper thrust dynamic pressure bearing portion 22, the spiral groove 22 a promotes the flow of oil inward in the radial direction to generate dynamic pressure (flow pressure). For this reason, the indentation pressure with respect to the oil generated in the upper radial dynamic pressure bearing portion 18 and the oil flow generated in the upper thrust dynamic pressure bearing portion 22 interfere with each other, but the upper and lower radial dynamic pressure bearings. The first step portion 10a1 in which the upper thrust dynamic pressure bearing portion 22 is formed in the minute gap formed between the through hole 10a of the sleeve 10 in which the portions 18 and 20 are formed and the outer peripheral surface of the shaft 4. The size of the gap is overwhelmingly smaller than the minute gap between the flat surface and the upper side surface of the thrust plate 6. Accordingly, when the axial pressure gradient of the fluid dynamic pressure generated by the spiral groove 19 and the radial pressure gradient of the fluid dynamic pressure generated by the spiral groove 22a formed in the upper thrust dynamic pressure bearing portion 22 are considered. The oil pressure in the upper thrust dynamic pressure bearing 22 is always higher than the fluid pressure.
[0042]
Therefore, the influence of the spiral groove 22a formed in the upper thrust dynamic pressure bearing portion 22 on the oil held in the gap between the inner peripheral surface of the first step portion 10a1 and the outer peripheral surface of the thrust plate 6 is affected. Without being received so much, the pushing pressure with respect to the oil generated by the spiral groove 19 is propagated to the oil held in the outer peripheral portion of the thrust plate 6 and the oil internal pressure is increased. As a result, the internal pressure of the oil is maintained at atmospheric pressure or higher, and the generation of bubbles due to the generation of negative pressure is prevented, so that various problems due to the bubbles are solved.
[0043]
It should be noted that the upper thrust dynamic pressure bearing portion 22 is caused by the fluid dynamic pressure generated in the lower thrust dynamic pressure bearing portion 24 having a larger effective area acting as a bearing than the upper thrust dynamic pressure bearing portion 22 during steady rotation of the spindle motor. A floating force larger than the flow pressure of the generated oil is applied to the thrust plate 6, the gap size of the minute gap forming the upper thrust dynamic pressure bearing portion 22 is narrowed, and the pumping force by the spiral groove 22a is strengthened. The For this reason, the indentation pressure by the spiral groove 19 is suppressed, and the pressure which goes to the outer peripheral part side of the thrust plate 6 reduces. Therefore, the occurrence of over-levitation that causes the shaft 4 to rise more than necessary is suppressed.
[0044]
Further, a spiral groove 19 is provided between the taper seal 17 and the upper radial dynamic pressure bearing portion 18, and as described above, a pressure is applied to the oil from the interface side to the thrust plate 6 side, so that the motor rotates. The oil interface is always drawn to the upper radial dynamic pressure bearing portion 18 side, the sealing function by the taper seal 17 is enhanced, and oil leakage to the outside of the bearing can be effectively prevented.
[0045]
(4) Configuration of Disk Drive Device FIG. 6 shows a schematic diagram of the internal configuration of a general disk drive device 50. The interior of the housing 51 forms a clean space with extremely small amounts of dust and the like, and a spindle motor 52 on which a disc-shaped disk plate 53 for storing information is mounted is installed. In addition, a head moving mechanism 57 that reads and writes information from and to the disk plate 53 is disposed inside the housing 51. The head moving mechanism 57 supports a head 56 that reads and writes information on the disk plate 53, and the head. The arm 55, the head 56, and the arm 55 are configured by an actuator unit 54 that moves the arm 55 to a required position on the disk plate 53.
[0046]
By using the spindle motor shown in FIG. 2 as the spindle motor 52 of such a disk drive device 50, it is possible to reduce the thickness and cost of the disk drive device 50 while obtaining a desired rotational accuracy.
[0047]
The fluid dynamic pressure bearing according to the present invention and the spindle motor and the disk drive device using the fluid dynamic bearing according to the present invention have been described above. However, the present invention is not limited to the embodiment and departs from the scope of the present invention. Various modifications or corrections can be made without any problem.
[0048]
For example, the constituent members of the bearing such as the shaft 4 and the sleeve 10 are appropriately selected from an aluminum-based material, a copper-based material, a solid metal material such as a stainless steel, or a sintered material obtained by sintering copper powder or iron powder. It can be used.
[0049]
The bracket 8 is fixed to a housing of the disk drive device (shown as a housing 51 in FIG. 6) by means such as a screw, but this housing is used as the bracket 8 by integrating the housing and the bracket. It is also possible.
[0050]
【The invention's effect】
In the fluid dynamic pressure bearing according to the first aspect of the present invention, it is possible to eliminate the adverse effect caused by the bubbles generated in the oil, and to simplify the structure and reduce the cost. In addition, by making the dynamic pressure generating groove of the thrust dynamic pressure bearing portion into a spiral groove, the viscous resistance of oil can be suppressed and the efficiency can be increased.
[0052]
The spindle motor according to the second aspect of the present invention is excellent in reliability and durability, and can reduce power consumption and cost.
[0053]
In the disk drive device according to the third aspect of the present invention, since the built-in spindle motor is excellent in reliability and durability and has low power consumption, it is possible to have high rotational accuracy and durability, and low It is possible to reduce power consumption and cost.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a schematic configuration of a spindle motor using a conventional fluid dynamic pressure bearing.
FIG. 2 is a cross-sectional view showing a schematic configuration of a fluid dynamic pressure bearing and a spindle motor using the fluid dynamic bearing according to the present invention.
FIG. 3 is a cross-sectional view schematically showing a cross section of a sleeve.
FIG. 4 is a schematic view of a spiral groove formed in a thrust dynamic pressure bearing portion.
FIG. 5 is a pressure distribution diagram conceptually showing the pressure distribution of oil.
FIG. 6 is a cross-sectional view schematically showing the internal configuration of the disk drive device.
[Explanation of symbols]
4 Shaft 6 Thrust plate 10 Sleeve 16 Thrust bush (bush)
18, 20 Radial dynamic pressure bearing portion 18a, 20a Herringbone groove 19 Spiral groove 22, 24 Thrust dynamic pressure bearing portion

Claims (3)

A hollow cylindrical sleeve, a shaft that is radially opposed to the inner peripheral surface of the sleeve via a gap, and extends radially outward at one end of the shaft, and one surface is one end surface of the sleeve And a disc-shaped thrust plate opposed in the axial direction through a gap, and a bush mounted on one end of the sleeve and opposed to the other surface of the thrust plate and the end surface of the shaft in the axial direction through a gap When only near the other end of the sleeve to function as a continuous held by Rutotomoni tapered seal without interruption it into the gap formed respectively between said shaft and said thrust plate and the sleeve and the bush interface comprises an oil that is one form, the relative rotation between the shaft and the thrust plate and the sleeve and the bush A fluid dynamic bearing that supports using a fluid dynamic pressure induced in the oil,
Between one end surface of the sleeve and one surface of the thrust plate, there is configured one thrust dynamic pressure bearing portion for inducing a fluid dynamic pressure toward the oil radially inward during the relative rotation, and the bush And the other surface of the thrust plate is configured with another thrust dynamic pressure bearing portion for inducing a fluid dynamic pressure toward the oil radially inward during the relative rotation. A pair of radial dynamic pressure bearing portions are configured to be spaced apart from each other in the axial direction between the surface and the outer peripheral surface of the shaft, and the pair of radial dynamic pressure bearing portions include axial directions as dynamic pressure generating grooves. with herringbone grooves of symmetrical shape are formed on the one and the other of the thrust dynamic pressure bearing portion, the spiral groove hydrodynamic groove to induce hydrodynamic directed radially inwards, respectively And provided, the interface of the oil is formed in proximity to the other end face of said sleeve, one of the pair of the radial dynamic pressure bearing portion, a radial dynamic pressure bearing portion adjacent thereto and the interface of the oil In between the gaps, the oil is urged toward the thrust plate at the time of the relative rotation on the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, and is positioned between the hydrodynamic bearing portions. A fluid dynamic pressure bearing, characterized in that a spiral groove is formed to keep the internal pressure of oil held therein at or above atmospheric pressure. A bracket that holds the stator, a rotor that rotates relative to the bracket, a rotor magnet that is fixed to the rotor and generates a rotating magnetic field in cooperation with the stator, and a fluid dynamic bearing that supports the rotation of the rotor A spindle motor comprising: the fluid dynamic pressure bearing according to claim 1 . In a disk drive mounted with a disk-shaped recording medium capable of recording information, a housing, a spindle motor fixed inside the housing and rotating the recording medium, and writing information at a required position of the recording medium or 3. A disk drive device having information access means for reading, wherein the spindle motor is the spindle motor according to claim 2 .

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