JP3927392B2 - 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 bearing portions d and d is formed between the shaft b and the shaft b.End ofBetween the upper surface of the disc-shaped thrust plate e projecting radially outward from the outer peripheral surface of the member and the flat surface of the step formed on the sleeve c, and the lower surface of the thrust plate e and the sleevecA pair of thrust bearing portions g and g are formed between the thrust bushing f that closes the opening.
[0004]
Shaft b, thrust plate e and sleeve c, and thrust bushfA series of minute gaps are formed between them, and oil is continuously held in these minute gaps without being interrupted as a lubricating fluid (such an oil holding structure is hereinafter referred to as a “full-fill structure”). ), Herringbone grooves d1, d1 and g1, g1 for inducing dynamic pressure in the oil when the rotor a rotates are formed on the radial bearing portions d, d and the thrust bearing portions g, g, respectively. ing.
[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 to 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 is maximized at the center of the bearing, whereas the internal pressure of the oil is reduced 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. The internal pressure decreases and eventually decreases to below atmospheric pressure and becomes negative pressure.
[0008]
When negative pressure occurs in the oil, for example, the air dissolved in the oil appears as bubbles when filling the oil, and eventually the bubbles expand by volume due to temperature rise, etc., causing the oil to leak out of the bearing Problems that affect the durability and reliability of the motor, or problems that affect the rotational accuracy of the spindle motor, such as the generation of vibrations due to the contact of the dynamic pressure generating grooves with air bubbles and the deterioration of NRRO (non-repetitive vibration component) To do.
[0009]
The present invention provides a fluid dynamic bearing capable of reducing the cost by simplifying the structure and eliminating the adverse effects of bubbles by preventing the generation of negative pressure in the oil and the fluid dynamic bearing. It is an object to provide a spindle motor using a disk drive and a disk drive using the spindle motor.
[0010]
[Means for Solving the Problems]
  The fluid dynamic pressure bearing of the present invention is
  A hollow cylindrical sleeve;
  A shaft that is radially opposed to the inner peripheral surface of the sleeve via a gap;
  A disc-shaped thrust plate extending radially outward at the end of the shaft and facing the sleeve in the axial direction through a gap;
  A bush mounted on the end of the sleeve, covering the shaft portion and the thrust plate facing the sleeve together with the sleeve, and axially facing the thrust plate and the shaft via a gap;
  In the gap formed between the shaft, the thrust plate, the sleeve, and the bush, are continuously held without interruption, and near the open end of the sleeveIn the worldA fluid dynamic pressure bearing that supports relative rotation of the shaft, the thrust plate, the sleeve, and the bush using fluid dynamic pressure induced by the oil. ,
  Between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, a radial dynamic pressure bearing portion for inducing fluid dynamic pressure in the oil during the relative rotation is configured,
  An open-side thrust dynamic pressure bearing portion that induces a fluid dynamic pressure toward the oil inward in the radial direction at the time of the relative rotation is configured between the closed end surface of the sleeve and the open-side surface of the thrust plate. And
The open side thrust dynamic pressure bearing portion is configured such that the pressure on the radially inner side of the thrust plate is higher than the pressure on the radially outer side,
  Between the bush and the surface on the closing side of the thrust plate, a closing-side thrust dynamic pressure bearing portion that induces a fluid dynamic pressure toward the oil radially inward during the relative rotation is configured,
  Further, the radial dynamic pressure bearing portion is formed with a dynamic pressure generating groove for inducing a fluid dynamic pressure in the axial direction and toward the thrust plate with respect to the oil during the relative rotation,
  The radial fluid dynamic bearing portion induces the oil in the axial direction and the total fluid dynamic pressure toward the thrust plate side is A, and the open-side thrust dynamic pressure bearing portion is directed inward in the radial direction induced by the oil. When the fluid dynamic pressure is B, the relationship of A> B is satisfied (claim 1).
[0011]
This configuration relates to a fluid dynamic pressure bearing having a full-fill structure.
[0012]
  The dynamic pressure generating groove formed in the radial dynamic pressure bearing portion is shaped to generate fluid dynamic pressure in the axial direction and toward the thrust plate side, and the fluid dynamic pressure induced by the dynamic pressure generating groove of this radial dynamic pressure bearing portion isOpen sideBy configuring it to be greater than the radially inward fluid dynamic pressure induced in the thrust dynamic pressure bearing part, the fluid dynamic pressure generated in the radial dynamic pressure bearing part is slightly offset by the thrust dynamic pressure bearing part. However, the oil 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]
Further, in the fluid dynamic pressure bearing according to the present invention, the dynamic pressure generating groove formed in the radial dynamic pressure bearing portion includes a herringbone groove formed by connecting a pair of spiral grooves, and of the pair of spiral grooves, The spiral groove located on the interface side of the oil is formed in an asymmetric shape with respect to other spiral grooves so as to induce the total fluid dynamic pressure A (Claim 2).
[0015]
  By connecting a pair of spiral grooves having an asymmetric shape in the axial direction, a difference occurs in the pumping pressure of each thrust groove. As a radial dynamic pressure bearing part, the pressure for supporting the load in the radial direction appears at the connecting part of the spiral groove where the fluid dynamic pressure generated in the radial dynamic pressure bearing part is maximized, but is located on the oil interface side. Pumping pressure by spiral grooveOcclusion sideThe pressure in the axial direction from the oil interface side to the thrust plate side, that is, from the radial dynamic pressure bearing portion side to the thrust dynamic pressure bearing portion side (such as this) (Hereinafter referred to as “indentation pressure”).
[0016]
  In this case, the axial pressure gradient of the fluid dynamic pressure generated by the herringbone groove formed in the radial dynamic pressure bearing portion, the end face of the sleeve, and the thrust plateOpen sideComposed between the face ofOpen sideIn consideration of the radial pressure gradient of the fluid dynamic pressure generated by the dynamic pressure generating groove formed in the thrust dynamic pressure bearing portion, the internal pressure of the oil retained in the outer peripheral portion of the thrust plate is at least equal to or higher than atmospheric pressure. Therefore, the axial dimension of the spiral groove located on the oil interface side of the pair of spiral grooves constituting the herringbone groove formed on the radial dynamic pressure bearing portion is the same as that of the spiral groove located on the thrust plate side. By setting it to be larger than the axial dimension, it is possible to apply a sufficient pushing pressure to the oil.
[0017]
  Furthermore, the fluid dynamic pressure bearing of the present invention comprises the aboveOpen sideas well asOcclusion sideThe thrust dynamic pressure bearing portion is provided with a spiral groove for inducing a fluid dynamic pressure inward in the radial direction as a dynamic pressure generating groove.
[0018]
According to this configuration, by adopting a fluid dynamic pressure bearing having a full-fill structure, the structure of the bearing portion can be simplified, 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.
[0019]
In addition, the fluid dynamic pressure bearing according to the present invention is further provided with another radial dynamic pressure between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, between the radial dynamic pressure bearing portion and the thrust plate. The bearing portion is configured, and the other radial dynamic pressure bearing portion is provided with a herringbone groove formed by connecting a pair of spiral grooves having a symmetrical shape in the axial direction as a dynamic pressure generating groove. It is characterized (claim 4).
[0020]
By configuring a pair of radial dynamic pressure bearings apart in the axial direction, the radial load acting during rotation can be supported at both ends of the shaft, and external vibration or impact is applied It is possible to restore the normal state of the shaft falling or touching around in a short time.
[0021]
In addition, the herringbone groove formed on the radial dynamic pressure bearing portion located on the oil interface side of the radial dynamic pressure bearing portion is configured to apply indentation pressure to the oil, thereby providing a sealing function. This effectively prevents oil from leaking outside the bearing.
[0022]
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 A spindle motor comprising a fluid dynamic pressure bearing that supports the rotation of the fluid dynamic pressure bearing, wherein the fluid dynamic pressure bearing is the fluid dynamic pressure bearing according to any one of claims 1 to 4 (claim 5).
[0023]
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.
[0024]
  Furthermore, the disk drive device of the present invention is a disk drive device to which a disk-shaped recording medium capable of recording information is mounted. The housing, a spindle motor fixed inside the housing and rotating the recording medium, and the recording device A disk drive device having information access means for writing or reading information at a required position on a medium, wherein the spindle motor is the spindle motor according to claim 5.6).
[0025]
Since the spindle motor of the present invention is excellent in reliability and durability, can suppress power consumption, and can be reduced in cost, high rotation accuracy, durability, and low power consumption can be achieved. 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, and a fixed recording medium such as a hard disk or a removable recording medium such as a CD-ROM or DVD is driven. It can also be used in the same disk drive device.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a fluid dynamic pressure bearing according to the present invention, a spindle motor using the fluid dynamic bearing, and a disk drive device using the spindle motor will be described with reference to FIGS. 2 to 4. The present invention will be described below. The present invention is not limited to the examples.
[0027]
(1) Configuration of spindle motor
The spindle motor shown in FIG. 2 has a rotor hub 2 on which a hard disk (shown as a disk plate 53 in FIG. 4) is held on the outer periphery, a shaft 4 attached to the rotor hub 2, and a free end portion of the shaft 4 (rotor hub). And a cylindrical boss portion 8 a provided on the bracket 8. The rotor is composed of a disc-shaped thrust plate 6 extending radially outward from the outer peripheral surface of the side opposite to the side attached to the side 2. And a sleeve 10 fixed to the head. 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.
[0028]
  The sleeve 10 is formed with a through hole 10a penetrating the sleeve 10 in the axial direction, and the shaft 4 is inserted into the through hole 10a with a minute gap. Through hole 10a'sA first step portion 10a1 corresponding to the thrust plate 6 is formed on the opening side (bracket 8 side), the inner diameter is larger than the through hole 10a, and the inner diameter is further continuous with the first end portion 10a1. A second stepped portion 10a2 that expands 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.
[0029]
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. An 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.
[0030]
(2) Configuration of bearing
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.
[0031]
  The herringbone groove 18 has a spiral groove on the annular groove 4a side.Occlusion sideThe dimension in the axial direction is larger than the spiral groove ofOcclusion sideA pumping pressure that exceeds the pumping pressure by the spiral groove on the thrust plate 6 side is generated. The herringbone groove 18a maximizes the fluid dynamic pressure generated at the connecting portion of the spiral groove in accordance with the rotation of the shaft 4 and generates the necessary load supporting pressure. At the same time, the spiral groove portion on the annular groove 4a sideOcclusion sideFor the amount of unbalance of the pumping force with the spiral groove portion, a pushing pressure (total fluid dynamic pressure A) for pushing the oil from the interface side toward the thrust plate 6 side is generated. Due to this pushing pressure, the oil internal pressure increased by the upper radial dynamic pressure bearing portion 18 is transmitted to the thrust plate 6 side.
[0032]
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.
[0033]
The herringbone groove 20a formed in the lower radial dynamic pressure bearing portion 20 has an inclination angle, a groove depth, a total length, and a width dimension with respect to the rotation axis so that each spiral groove portion generates substantially the same pumping force. It is set to be the same, that is, each spiral groove is line-symmetric with respect to the connecting portion. Accordingly, in the lower radial dynamic pressure bearing portion 20, the fluid dynamic pressure generated at the axial center (the connecting portion of the spiral groove) of the bearing portion is maximized, and the pushing pressure toward the oil in any axial direction is reduced. It does not occur.
[0034]
  Formed on the sleeve 10It is the end face of the obstruction sideOn the flat surface of the first step portion 10a1, a dynamic pressure generating groove array by the spiral groove 22a is formed concentrically with the thrust plate 6,Open sideBetween the upper surface of the thrust plate 6Open side thrust hydrodynamic bearingAn upper thrust dynamic pressure bearing portion 22 is configured. The spiral groove 22a has a pump-in shape so that 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 the direction in which the thrust plate 6 moves away from the first step portion 10a1 is obtained.
[0035]
  Furthermore,It is the surface on the obstruction sideOn 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 24a is formed concentrically with the thrust plate 6, and the lower surface of the thrust plate 6 BetweenIt is a closing side thrust dynamic pressure bearing partA lower thrust dynamic pressure bearing portion 24 is configured. 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.
[0036]
(3) Shaft support method
The shaft support method by each dynamic pressure bearing portion configured as described above will be described in detail below. 3 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. This is a pressure distribution diagram schematically developed as a concept by developing the relative relationship of the oil pressure distribution. However, since the spindle motor pressure distribution is axisymmetric, the rotational axis centered by the alternate long and short dash line in FIG. 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. 3 are the same as the numbers given to the respective bearing portions in FIG.
[0037]
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. In the upper radial dynamic pressure bearing portion, the pumping pressure of the herringbone groove 18a having an unbalanced shape in the axial direction generates an indentation pressure acting on the thrust plate 6 from the interface side to the oil.
[0038]
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 becomes the atmospheric pressure or more due to the pushing pressure against the oil generated in the upper radial dynamic pressure bearing portion 18, and the negative pressure Occurrence is prevented.
[0039]
In the lower radial dynamic pressure bearing 20, oil is pumped with substantially uniform pressure from both ends of the bearing in the axial direction toward the center of the bearing by the herringbone groove 20 a having a shape balanced in the axial direction. The pressure gradient of the fluid dynamic pressure is symmetric in the axial direction, and does not induce indentation pressure acting on the oil in any axial direction. Further, in the lower thrust dynamic pressure bearing portion 24, the oil is pumped by the spiral groove 24a from the outer circumferential end of the bearing toward the rotation axis side of the thrust plate 6 with a substantially uniform pressure. The pressure gradient is rotationally symmetric and does not induce circumferential flow with respect to the oil. Therefore, the pressing pressure of the upper radial dynamic pressure bearing portion 18 against the oil by the herringbone groove 18a is not affected by the lower radial dynamic pressure bearing portion 20 and the lower thrust dynamic pressure bearing portion 24.
[0040]
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 gap dimension is overwhelmingly smaller than the minute gap between the flat surface and the upper side surface of the thrust plate 6, and the herringbone groove has a higher pumping force than the spiral groove. Accordingly, the axial pressure gradient of the fluid dynamic pressure generated by the herringbone groove 18a formed in the upper radial dynamic pressure bearing portion 18 and the fluid dynamic pressure generated by the spiral groove 22a formed in the upper thrust dynamic pressure bearing portion 22 are determined. The axial direction of the spiral groove portion located on the annular groove 4a side of the pair of spiral groove portions constituting the herringbone groove 18a formed in the upper radial dynamic pressure bearing portion 18 in consideration of the radial pressure gradient By making the dimension larger than the axial dimension of the spiral groove portion located on the thrust plate 6 side, it becomes possible to apply a sufficient indentation pressure to the oil, and the oil flow in the upper thrust dynamic pressure bearing portion 22 Always higher than pressure.
[0041]
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 against the oil generated by the upper radial dynamic pressure bearing portion 18 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.
[0042]
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 upper radial bearing portions 18 and 20 is suppressed, and the pressure toward the outer peripheral portion of the thrust plate 6 decreases. Therefore, the occurrence of over-levitation that causes the shaft 4 to rise more than necessary is suppressed.
[0043]
Further, as described above, the dynamic pressure generating groove of the upper radial dynamic pressure bearing portion 18 located on the oil interface side is unbalanced in the axial direction so as to apply pressure to the oil from the interface side to the thrust plate 6 side. By forming the herringbone groove 18a in the shape, the oil interface is always drawn into the upper radial dynamic pressure bearing portion 18 side when the motor rotates, and the sealing function by the annular groove 4a is enhanced, and the oil is supplied to the outside of the bearing. Leakage can be effectively prevented.
[0044]
(4) Configuration of the disk drive device
FIG. 4 shows a schematic diagram of an 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 for reading and writing information with respect to the disk plate 53 is disposed inside the housing 51. The head moving mechanism 57 supports a head 56 for reading and writing 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.
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
The bracket 8 is fixed to a housing of the disk drive device (shown as a housing 51 in FIG. 4) by means such as screws, but this housing is used as the bracket 8 by integrating the housing and the bracket. It is also possible.
[0049]
【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.
[0050]
In the fluid dynamic pressure bearing according to claim 2 of the present invention, it is possible to reliably prevent the generation of bubbles in the oil.
[0051]
In the fluid dynamic pressure bearing according to claim 3 of the present invention, the viscous resistance of oil caused by the circumferential speed of the thrust plate is suppressed, and the efficiency can be increased.
[0052]
In the fluid dynamic pressure bearing according to the fourth aspect of the present invention, it is possible to have high stability and to effectively prevent oil from leaking to the outside of the bearing.
[0053]
In the spindle motor according to the fifth aspect of the present invention, it is excellent in reliability and durability, and it is possible to reduce power consumption and cost.
[0054]
In the disk drive device according to the sixth 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 pressure distribution diagram conceptually showing an oil pressure distribution.
FIG. 4 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
22, 24 Thrust dynamic pressure bearing

Claims (6)

A hollow cylindrical sleeve;
A shaft that is radially opposed to the inner peripheral surface of the sleeve via a gap;
A disc-shaped thrust plate extending radially outward at the end of the shaft and facing the sleeve in the axial direction through a gap;
A bush mounted on the end of the sleeve, covering the shaft portion and the thrust plate facing the sleeve together with the sleeve, and axially facing the thrust plate and the shaft via a gap;
Held continuously without interruption into the gap which is respectively formed between said shaft and said thrust plate and the sleeve and the bush, the oil field surface near the end of the open side of the sleeve is formed A hydrodynamic pressure bearing that supports relative rotation of the shaft, the thrust plate, the sleeve, and the bush using fluid dynamic pressure induced by the oil,
Between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, a radial dynamic pressure bearing portion for inducing fluid dynamic pressure in the oil during the relative rotation is configured,
An open-side thrust dynamic pressure bearing portion that induces a fluid dynamic pressure toward the oil inward in the radial direction at the time of the relative rotation is configured between the closed end surface of the sleeve and the open-side surface of the thrust plate. And
The open side thrust dynamic pressure bearing portion is configured such that the pressure on the radially inner side of the thrust plate is higher than the pressure on the radially outer side,
Between the bush and the surface on the closing side of the thrust plate, a closing-side thrust dynamic pressure bearing portion that induces a fluid dynamic pressure toward the oil radially inward during the relative rotation is configured,
Further, the radial dynamic pressure bearing portion is formed with a dynamic pressure generating groove for inducing a fluid dynamic pressure in the axial direction and toward the thrust plate with respect to the oil during the relative rotation,
The radial fluid dynamic bearing portion induces the oil in the axial direction and the total fluid dynamic pressure toward the thrust plate side is A, and the open-side thrust dynamic pressure bearing portion is directed inward in the radial direction induced by the oil. A fluid dynamic pressure bearing satisfying the relationship of A> B, where B is a fluid dynamic pressure.   The dynamic pressure generating groove formed in the radial dynamic pressure bearing portion is a herringbone groove formed by connecting a pair of spiral grooves, and the spiral groove located on the oil interface side of the pair of spiral grooves is The fluid dynamic pressure bearing according to claim 1, wherein the fluid dynamic pressure bearing is formed in an asymmetric shape with respect to another spiral groove so as to induce the total fluid dynamic pressure A.   3. A spiral groove for inducing fluid dynamic pressure inward in the radial direction is provided as a dynamic pressure generating groove in each of the open side and closed side thrust dynamic pressure bearing portions. The fluid dynamic pressure bearing described in 1.   Between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, another radial dynamic pressure bearing portion is formed between the radial dynamic pressure bearing portion and the thrust plate, and the other radial dynamic pressure bearing portion is configured. 4. The hydrodynamic bearing portion is provided with a herringbone groove formed by connecting a pair of spiral grooves having a symmetrical shape in the axial direction as a dynamic pressure generating groove. The fluid dynamic pressure bearing described. 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 In a spindle motor equipped with
The spindle motor according to claim 1, wherein the fluid dynamic pressure bearing is the fluid dynamic pressure bearing according to claim 1. In a disk drive device in which a disk-shaped recording medium capable of recording information is mounted,
A housing;
A spindle motor fixed inside the housing and rotating the recording medium;
A disk drive device having information access means for writing or reading information at a required position of the recording medium,
The disk drive device according to claim 5, wherein the spindle motor is a spindle motor according to claim 5.

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