JP3828458B2 - DYNAMIC PRESSURE BEARING, SPINDLE MOTOR USING THE SAME, AND DISK DRIVE DEVICE PROVIDED WITH THE SPINDLE MOTOR - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrodynamic bearing, a spindle motor using the same, and a disk drive device including the spindle motor.
[0002]
[Prior art]
As a bearing means for rotatably supporting the rotor of the spindle motor, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-105445, a pair of thrust plates are arranged on the upper and lower portions in the axial direction of the fixed shaft. Lubricating oil (oil) is held between the outer peripheral surface of the fixed shaft located between the thrust plates and the inner peripheral surface of the rotor in the radial direction, and this lubricating oil is moved in a predetermined direction by the rotation of the rotor. A radial bearing portion is formed by forming a dynamic pressure generating groove for generating a supporting pressure for supporting a radial load applied to the rotor by moving it, and in the axial direction of each thrust plate facing each other. Lubricating oil is held between the side surface and the axially outer side surface of the rotor facing this axial direction, and this lubricating oil is moved in a predetermined direction by the rotation of the rotor. Thus, a dynamic pressure generating groove for generating a support pressure for supporting a thrust load applied to the rotor is formed to form a pair of thrust bearing portions, and the rotor that faces the outer peripheral surface of the thrust plate in the radial direction A first taper seal portion having a radial interval changing between the inner circumferential surface of the seal plate and an axially outer surface of the thrust plate and an axially inner surface of the seal cap opposed in the axial direction. There is a structure in which a second taper seal portion in which the axial interval changes is formed, and the first and second taper seal portions have a structure for preventing leakage of lubricating oil to the outside of the bearing.
[0003]
In such a configuration, since the bearing structure is symmetrical and gives the same characteristics to any posture, it is easy to obtain stable rotation of the spindle motor, and dynamic pressure generation is performed only on one side of the thrust plate. Since the grooves need only be formed, there is an advantage that the yield of member processing is improved.
[0004]
[Problems to be solved by the invention]
In the oil seal structure in the above conventional example, the first and second taper seal portions are configured continuously, and the interface position of the oil in the normal state is between the outer peripheral surface of the thrust plate and the inner peripheral surface of the rotor. It is in the first taper seal portion where the gap dimension of the radial gap formed therebetween changes, and is formed between the upper surface of the thrust plate and the lower surface of the seal cap by the action of centrifugal force during steady rotation. By entering the second taper seal part where the gap size of the gap in the axial direction changes, the volume of the seal part is increased, and the oil interface is directed inward in the radial direction. Is pressed toward the thrust bearing portion to prevent oil from flowing out.
[0005]
The taper seal part gradually increases the gap size of the gap formed in the seal part as the distance from the bearing part increases, causing a difference in capillary force depending on the formation position of the oil interface, and the amount of oil retained in the bearing part is reduced. When it decreases, oil is supplied from the taper seal part, and when the volume of oil retained in the bearing part increases due to temperature rise or the like, it has a function of accommodating the increase.
[0006]
However, when the rotation speed of the spindle motor is further increased, the influence of centrifugal force on the oil becomes stronger, so that the amount of oil flowing from the first taper seal portion to the second taper seal portion increases. At this time, if the second taper seal portion is provided in a direction orthogonal to the rotation axis due to dimensional constraints, a sufficient volume cannot be secured, and there is a concern that oil may flow out of the bearing. is there.
[0007]
Further, due to an increase in the influence of centrifugal force due to an increase in speed, the oil is peeled off from the outer peripheral surface of the thrust plate in the first taper seal portion and is stuck to the inner peripheral surface of the rotor.
[0008]
During high-speed rotation, the oil moves radially outward in the thrust bearing portion due to centrifugal force, and the amount of oil retained is reduced. As described above, the taper seal portion has a function of supplying oil when the amount of oil retained in the bearing portion decreases, but the state where the oil sticks to the inner peripheral surface of the rotor by the action of centrifugal force. Then, the continuity of the oil is lost, and the supply of oil to the bearing portion becomes insufficient. Therefore, in the thrust bearing portion, not only the amount of oil retained becomes insufficient, the bearing rigidity is lowered and the rotation support becomes unstable, but also the sliding contact between the thrust plate and the rotor occurs and seizure occurs. .
[0009]
In addition, in order to form the first taper seal portion, the rotor has an inner peripheral surface facing the outer peripheral surface of the thrust plate. In such a case, for example, even if the specifications of the radial bearing portion are common, when the diameter of the thrust bearing portion is different due to the load capacity or the like, it is necessary to use a rotor with a different design. The common use of members is not achieved, and the cost reduction of the motor is hindered. Furthermore, since the inner peripheral surface of the rotor is located on the outer peripheral portion of the thrust bearing portion, it becomes difficult to process the outer surface in the axial direction of the rotor that requires high-precision processing, and the processing method is also limited. Limited improvement in accuracy with respect to flatness and surface roughness.
[0010]
According to the present invention, the seal strength can be enhanced and the oil supply to the thrust bearing portion can be stabilized in response to further high-speed rotation, and the volume in the taper seal portion can be increased, so that a sufficient amount of oil can be supplied. In addition, it is possible to reduce the cost by making the parts common, and further, it is possible to reduce the cost, and further, it is possible to increase the accuracy of member processing, and a spindle motor using the dynamic pressure bearing, An object of the present invention is to provide a disk drive device provided with this spindle motor.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, a hydrodynamic bearing according to the present invention includes a shaft, an annular thrust plate protruding radially outward from an outer peripheral surface of the shaft, and one surface in the axial direction of the thrust plate. And a hollow cylindrical sleeve having a radial surface that is continuous with the thrust surface and a radial inner surface that is radially opposed to the shaft through a minute gap. The lubricating oil is held between the outer peripheral surface of the shaft and the radial inner peripheral surface of the sleeve, and a dynamic bearing for generating dynamic pressure is provided in the lubricating oil, thereby providing a radial bearing portion. A thrust bearing portion is configured, wherein a lubricating oil is held between one axial surface of the thrust plate and the thrust surface, and a dynamic pressure generating groove for inducing a dynamic pressure in the lubricating oil is provided. Is composed, The thrust surface of the sleeve is located at an axial end of the sleeve; The thrust plate has a substantially conical shape formed in an inclined surface shape so that an outer diameter is reduced as at least a part of an outer peripheral surface moves away from one surface in the axial direction. An annular bushing member having a ring-shaped portion whose inner peripheral surface is formed in an inclined surface shape so that the inner diameter increases from the radially inner side toward the outer side. The inner peripheral surface of the sleeve is fitted to the outer peripheral portion of the axial end of the sleeve. Between the inner peripheral surface of the ring-shaped portion and the outer peripheral surface of the substantially conical thrust plate, and is inclined from the radially outer side to the inner side with respect to the rotational axis, and A taper seal portion in which a gap dimension of the gap gradually increases as the distance from the thrust bearing portion increases, and an interface of the lubricating oil held by the thrust bearing portion is formed in the taper seal portion. (Claim 1).
[0012]
As described above, according to the present invention, in a hydrodynamic bearing that uses lubricating oil such as oil as a working fluid, the tapered seal on the thrust bearing portion side is inclined with respect to the rotational axis, thereby being parallel to the rotational axis. Or, compared with the case where the taper seal portion is configured in the orthogonal direction, the volume in the taper seal portion increases, and even during high-speed rotation, the lubricating oil is not divided by centrifugal force, and the thrust from the taper seal portion is reduced. A structure that can stably supply lubricating oil to the bearing is adopted.
[0013]
With this configuration, even during high-speed rotation, the lubricating oil is not peeled off from the outer peripheral surface of the thrust plate by centrifugal force, and the continuity of the lubricating oil is not lost at the outer peripheral portion of the thrust plate. Further, since the interface of the lubricating oil is also directed in the direction inclined with respect to the rotation axis, the centrifugal force acts in the direction of pressing down the interface of the lubricating oil, so that the seal strength is maintained high.
[0014]
In addition, the member constituting the taper seal portion in cooperation with the thrust plate is a bush member separate from the sleeve, so that the processing of the inner peripheral surface of the ring-shaped portion of the bush member is facilitated. By adjusting the dimension of the member in the radial direction, the diameter of the thrust bearing portion can be changed without changing the design on the sleeve side. For this reason, it becomes possible to use a sleeve in common with bearings of various specifications.
[0015]
Furthermore, since there is no wall structure on the outer peripheral portion of the thrust surface of the sleeve, it is possible to make an optimum selection of the thrust surface processing method and tools as necessary, and to determine the flatness and surface roughness of the thrust surface. It is possible to improve the accuracy with respect to the thickness.
[0016]
Further, in the hydrodynamic bearing of the present invention, the thrust surfaces are respectively formed at both ends in the axial direction of the sleeve, and the thrust plates are disposed adjacent to both ends of the radial inner peripheral surface, Further, the bush member is also attached to the sleeve in correspondence with the pair of thrust plates (Claim 2).
[0017]
By adopting a structure in which a pair of thrust bearing portions are arranged adjacent to both ends of the radial inner peripheral surface constituting the radial bearing portion, the support force by the thrust bearing portions from both ends of the radial bearing portion is opposite in the axial direction. It will act in the direction and the load support will be stable.
[0018]
Furthermore, in the hydrodynamic bearing of the present invention, the bush member is provided with an annular flat plate member having a central opening on the axially outer side of the ring-shaped portion, and the inner periphery of the flat plate member The surface is opposed to the outer peripheral surface of the shaft through a minute gap, and the taper seal portion passes through a minute gap defined between the inner peripheral surface of the flat plate member and the outer peripheral surface of the shaft. It is characterized by being open to the outside (claim 3).
[0019]
The outflow resistance of steam generated by vaporization of lubricating oil by setting the radial dimension of the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the flat plate member as small as possible. Since the vapor pressure in the vicinity of the interface of the lubricating oil can be kept high by increasing the value of, the further transpiration of the lubricating oil can be effectively prevented.
[0020]
In addition, in the dynamic pressure bearing of the present invention, the dynamic pressure generating groove formed in the thrust bearing portion is pumped in such that a dynamic pressure acting radially inward with respect to the lubricating oil is induced. A spiral groove of a type is formed, and the dynamic pressure generating groove formed in the radial bearing portion is induced so that a dynamic pressure acting toward the thrust bearing portion side with respect to the lubricating oil is induced. An unbalanced herringbone groove is formed in the axial direction, and the lubricating oil is continuously held between the thrust bearing portion and the radial bearing portion. Item 4).
[0021]
By making the dynamic pressure generating groove of the thrust bearing part a pump-in type spiral groove, the outer diameter of the thrust plate can be reduced and the peripheral speed can be reduced, and the spiral groove is a herringbone groove. Since the viscous resistance of the lubricating oil is small compared to the above, it is possible to suppress the loss at the bearing portion and increase the efficiency.
[0022]
Furthermore, in the hydrodynamic bearing according to the present invention, an air intervening portion communicating with the outside air is formed between the outer peripheral surface of the shaft and the radial inner peripheral surface at a substantially central portion in the axial direction of the radial inner peripheral surface. A pair of the radial bearing portions are formed adjacent to both ends in the axial direction of the air interposition portion (Claim 5).
[0023]
By forming an air intervening part between the outer peripheral surface of the shaft and the radial inner peripheral surface, and forming a pair of radial bearings on both axial sides of the air interposing part, the bearing span (distance between the bearings) of the radial bearing part Since the support of the radial load is stabilized, it is possible to restore the shaft to the normal state in a short time when the shaft falls or touches when external vibration or impact is applied. Become.
[0024]
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 hydrodynamic bearing that supports the rotation of the hydrodynamic bearing, wherein the hydrodynamic bearing is the hydrodynamic bearing according to any one of claims 1 to 5 (claim 6).
[0025]
By using the above-mentioned dynamic pressure bearing as a spindle motor bearing, not only high-speed and high-precision rotation support is possible, but also the bearing portion is prevented from seizing, so it has excellent reliability and durability. It is possible to reduce the cost of the motor, and the thrust surface constituting the thrust bearing part can be processed easily and with high accuracy. The rotor can be supported stably.
[0026]
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 6 (claim 7). ).
[0027]
The spindle motor of the present invention not only enables high-speed and high-precision rotation support, but also enables cost reduction, and therefore drives a hard disk that requires high rotation accuracy and cost reduction. Although it can be used suitably in a disk drive device, it is not limited to this, It can be similarly used in a disk drive device that drives a fixed type such as a hard disk or a removable recording medium such as a CD-ROM or DVD. .
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a dynamic pressure bearing according to the present invention, a spindle motor using the dynamic pressure bearing, and a disk drive device including the spindle motor will be described with reference to FIGS. 1 to 3. It is not limited to each Example shown below.
[0029]
The illustrated spindle motor includes a bracket 2, a shaft 4 whose one end is fitted and fixed in a central opening provided in the bracket 2, and a rotor 6 that is rotatable relative to the shaft 4. Is provided. The rotor 6 is located on the outer peripheral portion of a rotor hub 6a on which a recording disk (shown as a disk plate 53 in FIG. 3) is placed, and a minute gap in which the lubricating oil 8 is held, located on the inner peripheral side of the rotor hub 6a. And a sleeve 6b supported by the shaft 4. A rotor magnet 10 is fixed to the inner peripheral portion of the rotor hub 6a by means such as adhesion, and the stator 12 is mounted on the bracket 2 so as to face the rotor magnet 10 in the radial direction.
[0030]
A through hole 66b1 that penetrates the sleeve 6b in the axial direction is formed at a substantially central portion of the sleeve 6b so as to form a minute gap between the inner peripheral surface of the sleeve 6b and the outer peripheral surface of the shaft 4 so that the lubricating oil 8 is retained. An annular upper thrust plate 14 and a lower thrust plate 16 projecting outward in the radial direction are attached to an upper portion and a lower portion of 4, respectively.
[0031]
At both ends in the axial direction of the sleeve 6b, corresponding to the upper thrust plate 14 and the lower thrust plate 16, there are an upper thrust surface 6b2 and a lower thrust surface 6b3 that are larger in diameter than the outer diameters of the upper and lower thrust plates 14, 16. Is formed. An annular and hollow cylindrical upper bushing member 18 and lower bushing member 20 are mounted on the outer peripheral portions of the upper thrust surface 6b2 and the lower thrust surface 6b3. The open end portions of the upper and lower bush members 18 and 20 are closed by the upper seal cap 22 and the lower seal cap 24.
[0032]
Further, an annular protrusion 6b4 protruding outward in the radial direction is formed between the upper and lower thrust surfaces 6b2 and 6b3 on the outer peripheral portion of the sleeve 6b. The outer peripheral surface of the annular protrusion 6b4 and the rotor hub The inner peripheral surface of 6a is fastened by means such as press fitting.
[0033]
A fine gap for holding the lubricating oil 8 is formed between the upper thrust portion 6b2 and the lower surface (the inner surface in the axial direction) of the upper thrust plate 14, and the rotation of the rotor 6 is formed on the upper thrust surface 6b2. Accordingly, a dynamic pressure generating groove 26a for generating dynamic pressure in the lubricating oil 8 is formed, and the upper thrust bearing portion 26 is configured.
[0034]
Further, a minute gap for holding the lubricating oil 8 is formed between the lower thrust surface 6b3 and the upper surface (the inner surface in the axial direction) of the lower thrust plate 16, and the flat portion of the lower thrust surface 6b3 The lower thrust bearing portion 28 is formed by forming a dynamic pressure generating groove 28a for generating dynamic pressure in the lubricating oil 8 as the rotor 6 rotates.
[0035]
The dynamic pressure generating grooves 26a and 28a formed in the thrust bearing portions 26 and 28 are pump-in type spiral grooves so that the generated dynamic pressure is pumped through the lubricating oil 8 toward the shaft 4, respectively. . The dynamic pressure generating grooves are formed on the inner surfaces in the axial direction of the upper and lower thrust plates 14 and 16 or on both surfaces of the upper and lower thrust surfaces 6b2 and 6b3 and the inner surfaces in the axial direction of the upper and lower thrust plates 14 and 16. It is also possible to do.
[0036]
As described above, when the dynamic pressure generating grooves 26a, 28a of the upper and lower thrust bearing portions 26, 28 are spiral grooves, herringbone grooves configured by combining a pair of spiral grooves opposite to each other are used. In comparison, since the outer diameters of the upper and lower thrust plates 14 and 16 can be reduced, the influence of the lower thrust bearing portion 28 on the magnetic circuit portion including the rotor magnet 10 and the stator 12 can be reduced. Sufficient driving torque can be obtained. Further, since the spiral groove has a smaller viscous resistance of the lubricating oil 8 generated when the spindle motor rotates than the herringbone groove, the loss in the upper and lower thrust bearing portions 26 and 28 is reduced, and the electrical efficiency of the spindle motor is improved. The power consumption can be reduced.
[0037]
As shown in a partially enlarged view in FIG. 2, the outer peripheral surface of the upper thrust plate 14 extends from the outer peripheral end of the inner surface in the axial direction substantially parallel to the rotation axis, and then radially inward. It is formed in the conical surface 14a inclined with respect to the rotation axis toward the center. In addition, the inner peripheral surface of the upper bush member 18 has a gap dimension formed between the inner peripheral surface and the conical surface 14a of the upper thrust plate 14 in the radial direction and the conical surface 14a. An annular ring-shaped portion 18a formed on the inclined surface 18a1 so as to gradually expand as it moves away from the 22nd side, that is, the upper thrust bearing portion 26, protrudes radially inward from the inner peripheral surface of the upper bush member 18. It is provided as follows. The ring-shaped portion 18a can also be configured separately from the upper bush member 18.
[0038]
The lubricating oil 8 held by the upper thrust bearing portion 26 passes through a gap substantially parallel to the rotation axis formed between the upper thrust plate 14 and the inner peripheral surface of the upper bushing member 18, and passes through the upper thrust plate. An interface is formed and held in the gap formed between the conical surface 14a and the inclined surface 18a1 of the ring-shaped portion 18a, and the gap dimension gradually increases toward the upper seal cap 22 side. That is, a gap formed between the conical surface 14 a of the upper thrust plate 14 and the inclined surface 18 a 1 of the ring-shaped member 18 a functions as the upper taper seal portion 30.
[0039]
In this case, as will be described in detail later, the conical surface 14a of the upper thrust plate 14 and the inclined surface 18a of the ring-shaped portion 18a that form the upper taper seal portion 30 are subjected to centrifugal force that causes the lubricating oil 8 to flow through the upper thrust bearing portion 26 during rotation. The angle is set in the direction that acts to push in to the side.
[0040]
Although the detailed structure is not shown, the outer peripheral portion of the lower thrust plate 16 also has a configuration similar to that of the outer peripheral portion of the upper thrust plate 14 between the lower thrust plate 16 and the lower bushing member 20 facing in the radial direction. A tapered seal portion 32 is formed. The configuration around the lower thrust plate 16 is substantially the same as the configuration around the upper thrust plate 14 shown in FIG.
[0041]
At this time, the minimum gap dimension of the upper taper seal portion 30 is a gap dimension of a gap formed between the outer peripheral surface of the upper thrust plate 14 and the inner peripheral surface of the upper bush member 18 and substantially parallel to the rotational axis. And the clearance dimension of the gap of the upper thrust bearing portion 26 is a rotation formed between the outer peripheral surface of the upper thrust plate 14 and the inner peripheral surface of the upper bush member 18. It is set to be smaller than the gap dimension of the gap substantially parallel to the shaft core.
[0042]
That is, when the holding amount of the lubricating oil 8 decreases in the upper thrust bearing portion 26, the lubricating oil 8 held in the upper taper seal portion 30 by the capillary force causes the outer peripheral surface of the upper thrust plate 14 and the upper bushing to move. It will be supplied to the upper thrust bearing portion 26 through a gap formed between the inner peripheral surface of the member 18 and a gap substantially parallel to the rotational axis.
[0043]
Conversely, when the lubricating oil 8 held by the upper thrust bearing portion 26 undergoes volume expansion due to a temperature rise or the like, the interface of the lubricating oil 8 moves in a direction in which the gap dimension of the upper tapered seal portion 30 is increased. The lubricating oil 8 corresponding to the increased volume is accommodated in the upper taper seal portion 30.
[0044]
In addition, since the upper taper seal portion 30 is configured to be inclined from the radially outer side to the inner side with respect to the rotation axis, the interface of the lubricating oil 8 also depends on the inclination angle of the upper taper seal portion 30. It is formed facing inward in the radial direction. Therefore, when the spindle motor rotates, the interface of the lubricating oil 8 is pressed against the upper thrust bearing portion 26 by centrifugal force, so that the seal strength is enhanced and the upper thrust plate 14 constituting the upper taper seal portion 30 is strengthened. Since the conical surface 14a and the inclined surface 18a1 of the ring-shaped portion 18a are inclined with respect to the rotational axis, the lubricating oil 8 is peeled off from the conical surface 14a due to the centrifugal force and sticks to the inclined surface 18a1. There is nothing. Therefore, even in a spindle motor that rotates at high speed, the lubricating oil 8 is prevented from flowing out from the seal portion, and the continuity of the lubricating oil 8 held from the upper taper seal portion 30 to the upper thrust bearing portion 26 is lost. The supply of the lubricating oil 8 from the upper taper seal portion 30 to the thrust bearing portion 26 is not insufficient.
[0045]
In addition, by tilting the upper taper seal part 30 with respect to the rotation axis, the size of the seal part is made larger than when the taper seal part is configured in a direction parallel or perpendicular to the rotation axis. Therefore, the volume is increased.
[0046]
Further, the dynamic pressure generating grooves 26a, 28a of the upper and lower thrust bearing portions 26, 28 are respectively pump-in type spiral grooves in which the generated dynamic pressure pumps the lubricating oil 8 radially inward. Since the dynamic pressure generated in the upper and lower thrust bearing portions 26 and 28 has a pressure gradient that increases inward in the radial direction, the upper and lower thrust bearing portions 26 and 28 are filled when the lubricating oil 8 is filled. The bubbles generated in the lubricating oil 8 held by the oil move from the radially inner side of the bearing portion having a high pressure to the radially outer side having a low pressure, and finally in the gap where the lubricating oil 8 is held. It moves to the interface side of the lubricating oil 8 of the upper and lower tapered seal portions 30, 32 having the largest gap size and the lowest pressure, and is released into the air.
[0047]
In addition, the upper and lower bushing members 18 and 20 constituting the upper and lower taper seal portions 30 and 32 together with the upper and lower thrust plates 14 and 16 are formed of a member different from the sleeve 6b, so that a radial bearing portion described later is formed. Even when the upper and lower thrust plates 14 and 16 having different diameters are used to change only the specifications of the upper and lower thrust bearing portions 26 and 28 with the same specifications such as the load capacity, the upper and lower bush members 18 and 20 are used. The same sleeve 6b can be applied by adjusting the radial dimension of the sleeve. Accordingly, since the sleeve 6b can be shared between spindle motors of different specifications, cost reduction of the motor is promoted.
[0048]
In addition, in a state where the upper and lower bush members 18 and 20 are not mounted, there is no effect on the outer peripheral portions of the upper and lower thrust surfaces 6b2 and 6b3 of the sleeve 6b constituting the upper and lower thrust bearing portions 26 and 28. There are no structures. Therefore, the processing accuracy with respect to the flatness and surface roughness of the upper and lower thrust surfaces 6b2 and 6b3 can be improved, and the processing of the dynamic pressure generating grooves 26a and 28a is facilitated.
[0049]
An annular recess 4a made of a pair of inclined surfaces inclined inward in the axial direction is formed at a substantially central portion of the outer peripheral surface of the shaft 4 so that a gap between the inner peripheral surface of the through hole 6b1 is enlarged. A communication hole 36 communicating with the air formed in the shaft 4 is opened in the recess 4a.
[0050]
The communication hole 36 is continuous with a vertical hole penetrating the shaft 4 in the axial direction, a first opening 36 a that opens into the concave portion 4 a of the shaft 4 extending in the radial direction from the vertical hole, and a lower taper seal portion 32. The second opening 36b is opened to a space communicating with the outside of the bearing through a minute gap defined between the inner peripheral surface of the lower seal cap 24 and the outer peripheral surface of the shaft 4. In addition, the vertical hole is sealed with sealing members 38 and 40 made of an elastic member such as rubber after the processing and cleaning of the shaft 4 are completed. That is, the space on the inner side of the bearing with respect to the upper and lower seal caps 22 and 24 is air only through a minute gap formed between the inner peripheral surface of the upper and lower seal caps 22 and 24 and the outer peripheral surface of the shaft 4. Communicating with
[0051]
The air taken into the communication hole 36 from the second opening 36b forms an annular gas interposition part 42 between the recess 4c in which the first opening 36a opens and the inner peripheral surface of the through hole 6b1, and this gas The lubricating oil 8 held in the minute gap between the outer peripheral surface of the shaft 4 and the inner peripheral surface of the through hole 6b1 by the interposition part 42 is formed between the pair of inclined surfaces of the recess 4a and the inner peripheral surface of the through hole 6b1. In the taper gap formed between them, an interface of the lubricating oil 8 is formed and divided vertically in the axial direction.
[0052]
Dynamic pressure generating grooves for generating dynamic pressure in the lubricating oil 8 as the rotor 6 rotates are provided at portions corresponding to the lubricating oil 8 that is divided and held above and below the inner peripheral surface of the through hole 6b1. 44a and 46a are formed, and the upper radial bearing part 44 and the lower radial bearing part 46 are comprised. The dynamic pressure generating grooves 44a and 46a formed in the upper and lower radial bearing portions 44 and 46 are respectively formed by the dynamic pressure generated toward the outer side in the axial direction of the lubricating oil 8, in other words, adjacent upper and lower thrusts. Herringbone grooves having an unbalanced shape in the axial direction are used so as to pump toward the bearing portions 26 and 28.
[0053]
When the lubricating oil 8 is filled, the dynamic pressure generating grooves 44a, 46a of the upper and lower radial bearing portions 44, 46 are shaped so as to pump the lubricating oil 8 toward the upper and lower thrust bearing portions 26, 28, respectively. For example, bubbles generated in the lubricating oil 8 held by the upper and lower radial bearing portions 44 and 46 move from the bearing portion having a high pressure to the interface side with the gas interposing portion 42 having a low pressure, and the gas intervening portion 42. To the outside of the bearing through the communication hole 36.
[0054]
In this configuration, the dynamic pressure generating means 26a, 28a formed in the upper and lower thrust bearing portions 26, 28 are spiral grooves, and it is not possible to generate a sufficient load supporting pressure by themselves, but the adjacent upper and lower radials are not provided. Since the bearing portions 44 and 46 are formed with the unbalanced herringbone grooves in the axial direction as the dynamic pressure generating grooves 44a and 46a, the lubricating oil 8 is respectively separated by the spiral grooves and the herringbone grooves when the spindle motor rotates. Since the pressure is fed in the direction opposite to each other, the dynamic pressure necessary to support the load applied to the rotor 6 is generated and supported by the cooperation of both bearing portions.
[0055]
Further, the upper and lower thrust bearing portions 26 and 28 and the upper and lower radial bearing portions 44 and 46 adjacent to the upper and lower thrust bearing portions 26 and 28 continuously hold the lubricating oil 8 and separate the upper and lower radial bearing portions 44 and 46. Since the gas intervening portion 42 that communicates with the air through the communication hole 36, the interface between the lubricating oil 8 and the concave portion 4 a of the upper and lower thrust bearing portions 26 and 28 located in the upper and lower taper seal portions 30 and 32. The interface of the lubricating oil 8 between the upper and lower radial bearing portions 44 and 46 located in the tapered gap defined between the pair of inclined surfaces and the through hole 6b1 is exposed to the same air pressure.
[0056]
For this reason, for example, due to centrifugal force, external impact on the spindle motor, application of vibration, etc., the interface of the lubricating oil 8 in the upper and lower taper seal portions 30, 32 or the pair of inclined surfaces of the recess 4a When one of the interfaces of the lubricating oil 8 in the tapered gap defined between the through-hole 6b1 moves in a direction away from the bearing portion, the other interface also passes through each tapered gap where each interface is located. It balances by moving to the position where the curvature radius of the interface of the lubricating oil 8 becomes equal, and is stably held without impairing the sealing effect.
[0057]
Further, the upper and lower radial bearing portions 44 and 46 are adjacent to the adjacent upper and lower thrust bearing portions 26 and 28, and the lubricating oil 8 continues from the interface of one lubricating oil 8 to the interface of the other lubricating oil 8. The dynamic pressure becomes maximum only at one point, and there is no point at which the dynamic pressure becomes minimum. Therefore, even if bubbles are included in the lubricating oil 8, a configuration can be adopted in which the pressure is automatically excluded into the air outside the bearing from the interface located in the tapered gap where the pressure is minimized.
[0058]
In this way, the bubbles generated in the lubricating oil 8 held in each bearing portion sequentially move to the low pressure side and are released into the air from the interface of each lubricating oil 8, so that the bubbles are in each bearing portion. It does not stay in the retained lubricating oil 8, and bubbles are expanded and the volume is increased when the temperature of the spindle motor rises, thereby preventing the lubricating oil 8 from leaking out of the bearing. In addition, since a special configuration for discharging bubbles is not required, the structure of the spindle motor can be simplified.
[0059]
Further, by setting the radial dimension of the gap defined between the inner peripheral surfaces of the upper and lower seal caps 22 and 24 and the outer peripheral surface of the shaft 4 as small as possible, the upper and lower portions are rotated when the spindle motor rotates. An axial gap defined between the thrust plates 14, 16 and the upper and lower seal caps 22, 24, and a radial gap defined by the outer peripheral surface of the shaft 4 and the upper and lower seal caps 22, 24, Thus, a difference occurs in the flow velocity of the air flow generated according to the rotation of the rotor 6. Therefore, the outflow resistance of the vapor (oil mist) generated by the vaporization of the lubricating oil 8 to the outside of the spindle motor is increased, and the vapor pressure near the interface of the lubricating oil 8 can be kept high. Can be prevented.
[0060]
If an oil repellent made of, for example, a fluorine-based material is applied to each of these surfaces, the lubricating oil 8 leaks out of the spindle motor due to an oil migration phenomenon when the spindle motor that does not act on the lubricating oil 8 is stopped. Can be prevented more effectively.
[0061]
FIG. 3 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 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.
[0062]
By using the spindle motor shown in FIG. 2 as the spindle motor 52 of such a disk drive device 50, not only high-speed and high-precision rotation support is possible, but also excellent in reliability and durability. .
[0063]
As described above, the hydrodynamic bearing according to the present invention, the spindle motor using the same, and the disk drive device including the spindle motor have been described. However, the present invention is not limited to such an embodiment, and the present invention is not limited thereto. Various changes and modifications can be made without departing from the scope of the above.
[0064]
For example, the gap between the upper and lower thrust plates 14, 16 and the inner peripheral surfaces of the upper and lower bush members 18, 20 that are substantially parallel to the rotational axis is the upper and lower thrust plates 14, 16. In order to hold this during machining, etc., it is provided from the need to form a flat surface on the outer peripheral portion of the upper and lower thrust plates 14, 16, but if there is no such need, Without providing, it is also possible to form a conical surface continuously with the outer peripheral end portions of the inner surfaces in the axial direction of the upper and lower thrust plates 14 and 16.
[0065]
【The invention's effect】
According to the hydrodynamic bearing of the first aspect of the present invention, the volume in the taper seal portion is increased, and even during high-speed rotation, the lubricating oil is not divided by centrifugal force, and the thrust from the taper seal portion is reduced. Lubricating oil can be stably supplied to the bearing portion. Further, even in a hydrodynamic bearing having different specifications, the sleeve can be shared, the cost can be reduced, the processing accuracy of the thrust bearing surface can be improved, and stable support can be achieved.
[0066]
According to the hydrodynamic bearing according to claim 2 of the present invention, the supporting force by the thrust bearing portion acts in opposite directions from both ends of the radial bearing portion, and the axial load is stably supported. Is possible.
[0067]
According to the hydrodynamic bearing described in claim 3 of the present invention, the radial dimension of the minute gap defined between the inner peripheral surface of the seal cap and the outer peripheral surface of the shaft is set as small as possible. By this, the outflow resistance of the steam generated by the vaporization of the lubricating oil is increased and the vapor pressure in the vicinity of the interface of the lubricating oil can be kept high, so that further evaporation of the lubricating oil can be effectively prevented. .
[0068]
According to the hydrodynamic bearing described in claim 4 of the present invention, it is possible to suppress the loss in the bearing portion and increase the efficiency.
[0069]
According to the hydrodynamic bearing described in claim 5 of the present invention, it is possible to restore the shaft to the normal state in a short time when the shaft is tilted or touched when external vibration or impact is applied. It becomes.
[0070]
According to the spindle motor described in claim 6 of the present invention, not only high-speed and high-precision rotation support is possible, but also the bearing portion is prevented from being seized, and thus excellent in reliability and durability. At the same time, the cost can be reduced.
[0071]
According to the disk drive apparatus of the seventh aspect of the present invention, the disk drive apparatus can be suitably used in a disk drive apparatus that requires high rotational accuracy, durability, and reliability.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing a schematic configuration of a spindle motor according to an embodiment of the present invention.
2 is a partial enlarged cross-sectional view schematically showing a schematic configuration in the vicinity of an upper thrust plate of the spindle motor shown in FIG.
3 is a schematic diagram showing a schematic configuration of a disk drive device including the spindle motor shown in FIG. 1. FIG.
[Explanation of symbols]
4 Shaft
6b sleeve
6b2, 6b3 Thrust surface
8 Lubricating oil
14,16 Thrust plate
14a Inclined surface
18, 20 Bushing member
18a Ring-shaped part
18a1 inclined surface
26, 28 Thrust bearing
26a, 28a, 44a, 46a Dynamic pressure generating groove
30, 32 Taper seal
44, 46 Radial bearing

Claims (7)

A shaft, an annular thrust plate projecting radially outward from the outer peripheral surface of the shaft, a thrust surface facing one surface in the axial direction of the thrust plate, and an outer periphery of the shaft continuous with the thrust surface A hydrodynamic bearing comprising a hollow cylindrical sleeve having a surface and a radial inner circumferential surface opposed in a radial direction through a minute gap,
Lubricating oil is held between the outer peripheral surface of the shaft and the radial inner peripheral surface of the sleeve, and a radial bearing portion is configured by providing a dynamic pressure generating groove for inducing dynamic pressure in the lubricating oil,
A thrust bearing portion is configured by holding a lubricating oil between one axial surface of the thrust plate and the thrust surface, and providing a dynamic pressure generating groove for inducing a dynamic pressure in the lubricating oil. ,
The thrust surface of the sleeve is located at an axial end of the sleeve;
The thrust plate has a substantially conical shape formed in an inclined surface shape so that the outer diameter is reduced as at least a part of the outer peripheral surface moves away from one surface in the axial direction,
The sleeve has an inner peripheral surface of an annular bush member having a ring-shaped portion with an inner peripheral surface formed in an inclined surface shape so that the inner diameter increases from the radially inner side toward the outer side . Fitted to the outer peripheral portion of the axial end portion , and radially outward with respect to the rotational axis between the inner peripheral surface of the ring-shaped portion and the outer peripheral surface of the substantially conical thrust plate A taper seal portion that is inclined inward from the thrust bearing portion and gradually increases in distance as the distance from the thrust bearing portion is increased. A hydrodynamic bearing characterized in that an interface is formed. The thrust surfaces are respectively formed at both ends in the axial direction of the sleeve, and a pair of the thrust plates are disposed adjacent to both ends of the radial inner peripheral surface, and the bush member is also a pair of the thrust plates. The hydrodynamic bearing according to claim 1, wherein a pair of the sleeves are attached to the sleeve. The bush member is provided with an annular flat plate member having a central opening on the axially outer side of the ring-shaped portion, and the inner peripheral surface of the flat plate member is in contact with the outer peripheral surface of the shaft. And the taper seal portion is opened to the outside through a minute gap defined between the inner peripheral surface of the flat plate member and the outer peripheral surface of the shaft. The hydrodynamic bearing according to claim 1 or 2. The dynamic pressure generating groove formed in the thrust bearing portion is formed with a pump-in type spiral groove so as to induce a dynamic pressure acting radially inward with respect to the lubricating oil, and The dynamic pressure generating groove formed in the radial bearing portion is a herringbone groove having an unbalanced shape in the axial direction so as to induce a dynamic pressure acting on the lubricating oil toward the thrust bearing portion side. The dynamic pressure according to any one of claims 1 to 3, wherein the lubricating oil is continuously held between the thrust bearing portion and the radial bearing portion. bearing. Between the outer peripheral surface of the shaft and the radial inner peripheral surface, an air intervening portion communicating with the outside air is formed at a substantially central portion in the axial direction of the radial inner peripheral surface, and the radial bearing portion includes the air intervening portion. 5. The hydrodynamic bearing according to claim 1, wherein a pair is formed adjacent to both ends in the axial direction of the portion. 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 hydrodynamic bearing that supports the rotation of the rotor; In the spindle motor with
The spindle motor according to claim 1, wherein the dynamic pressure bearing is the 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 A disk drive device having information access means for reading,
The disk drive device according to claim 6, wherein the spindle motor is a spindle motor according to claim 6.

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