JP4147086B2 - Spindle motor and disk drive device provided with the spindle motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin and small-diameter spindle motor for driving a recording disk having an outer diameter of, for example, 1 inch, and a disk drive apparatus including the spindle motor.
[0002]
[Prior art]
Conventionally, as a spindle motor bearing used in a disk drive device for driving a recording disk such as a hard disk, a lubricating fluid such as oil interposed between the shaft and the sleeve to support the shaft and the sleeve so as to be relatively rotatable. Various hydrodynamic bearings utilizing the fluid pressure have been proposed.
[0003]
The configuration of a spindle motor having such a conventional hydrodynamic bearing will be described. The shaft is rotatably supported at the center of the sleeve via a pair of upper and lower radial fluid bearings, and the sleeve is fixed to the base integrally. Thus, a fixing member is configured. A hub for mounting a magnetic disk is attached to the upper end of the shaft that protrudes upward through the center of the sleeve. The outer diameter surface of the lower end of the shaft has a retaining function and a thrust fluid bearing. The thrust plate which comprises is rotatably fixed. The thrust plate is accommodated in a stepped recess provided in the lower portion of the sleeve.
[0004]
The radial bearing surface constituting the radial fluid bearing is formed on the outer peripheral surface of the shaft, and the radial bearing surface opposite to this is formed on the inner diameter surface of the sleeve, and at least one of these shaft and the radial receiving surface of the sleeve is used for generating dynamic pressure. Grooves are formed.
[0005]
Further, a thrust receiving surface constituting the thrust fluid bearing is formed on both upper and lower planes of the thrust plate, and a thrust bearing surface facing this is formed on the inner surface of the recess at the lower portion of the sleeve and the upper surface of the thrust cover, A dynamic pressure generating groove is formed on at least one of the thrust bearing surfaces of the thrust plate, the sleeve, and the thrust cover. (For example, refer to Patent Document 1).
[0006]
However, in recent years, disk drive devices using such spindle motors have begun to be applied to small devices such as portable information terminals, and there is an increasing demand for further thinning.
[0007]
For this reason, the applicant of the present application eliminates the need for a thrust plate for constituting the thrust bearing portion, enables the motor to be reduced in size and thickness, and increases the distance between the radial bearing portions as much as possible to achieve a desired bearing. A spindle motor for a disk drive device capable of obtaining rigidity has been proposed (see Patent Document 2).
[0008]
More specifically, a thrust bearing portion is formed between the upper end surface of the sleeve through which the shaft is inserted and the lower surface of the rotor hub, and a pair of radial bearing portions is formed by the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve. In addition, the oil is continuously held between the thrust bearing portion and the radial bearing portion adjacent to the thrust bearing portion, and a desired levitation force is applied to the rotor by the cooperation of both the bearing portions. By magnetic attraction to the side, it balances with the levitation force of the rotor generated in the thrust bearing part and one radial bearing part.
[0009]
Also, the oil held in the pair of radial bearing portions is separated in the axial direction by the air held in the air interposed portion formed between the shaft and the sleeve, and forms a gas-liquid interface between the oil and air, respectively. The oil held in the thrust bearing portion is held by forming a gas-liquid interface between oil and air in a taper seal portion formed on the radially outer side of the thrust bearing portion. . In other words, the oil retained in the hydrodynamic bearing is separated into the oil retained between the thrust bearing portion and the radial bearing portion adjacent to the thrust bearing portion and the oil retained in the other radial bearing portion, respectively. It becomes the structure divided | segmented by and hold | maintained.
[0010]
[Patent Document 1]
JP 2000-197306 A (page 2-4, Fig. 1-3)
[Patent Document 2]
Japanese Unexamined Patent Publication No. 2000-113582 (page 5-6, FIG. 2)
[0011]
[Problems to be solved by the invention]
However, recently, due to the diversification of devices in which these disk drive devices are used, it is necessary to maintain stable performance even in various environments, and most of such small devices are driven by rechargeable batteries. Therefore, in order to withstand long-term use, further reduction in power consumption has been demanded.
[0012]
On the other hand, in the case of a hydrodynamic bearing using oil as a working fluid, the characteristics of oil are likely to change due to fluctuations in the external environment such as temperature and pressure, so that the application range is naturally limited.
[0013]
Also, in a hydrodynamic bearing using oil as a working fluid, loss due to viscous resistance increases when the oil viscosity is low and the sound is low, and the power consumption of the spindle motor increases.
[0014]
SUMMARY OF THE INVENTION An object of the present invention is to provide a spindle motor that can be reduced in size, thickness and cost, can be used stably even under various environments, and can be driven with low power consumption. is there.
[0015]
Another object of the present invention is to provide a disk drive device that can be applied to small equipment such as a portable information terminal and can be used for a long time and has high reliability by including the spindle motor. Is to provide.
[0016]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1A spindle motor comprising a substantially cup-shaped rotor defining a cavity therein, a shaft that rotates integrally with the rotor, and a cylindrical sleeve that is closed at one end through which the shaft is inserted. A dynamic pressure generating groove having a shape that allows gas to flow radially inward is formed on the opening side end surface of the sleeve provided on the lower side in the axial direction or on the opening side end surface of the sleeve and the surface of the rotor on the upper side in the axial direction. As a result, a thrust bearing portion using gas as the working fluid is configured, and the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve are opposed to each other in the radial direction, and a radial bearing portion using gas as the working fluid is configured. ,
The radial bearing portion is provided with an axial groove as a dynamic pressure generating groove, and the dynamic pressure generated in the thrust bearing portion is substantially between the closed end surface of the sleeve and the end surface of the shaft. An air chamber having substantially the same pressure is formed, and the rotor is given a floating force by the cooperation of the thrust bearing portion and the air chamber.And the rotor is generated in the thrust bearing portion.What is the direction of dynamic pressure action?Magnetic back pressure is applied in the opposite direction.
[0017]
In the above configuration, air and other gases are less susceptible to changes in properties such as viscosity due to temperature changes than liquids such as oil, so the loss during rotation caused by viscous resistance should be reduced even when used in low-temperature environments. It is possible to reduce power consumption. In addition, even when used in a high temperature environment, a decrease in support rigidity due to a decrease in viscosity is suppressed, so that it can be used stably in various environments.
[0018]
In addition, gas is less compressible than liquid and is a compressible fluid, so when trying to obtain a predetermined support rigidity, the dimensions of the bearing are relatively large compared to a bearing that uses oil. In general, it is difficult to apply to small and thin spindle motor bearings, but by supporting the rotor with magnetic back pressure instead of the bearing as in the above configuration. By minimizing bearing formation and maximizing the area occupied by individual bearings even within limited dimensions, it can also be applied to ultra-small spindle motors that drive small-diameter disks with an outer diameter of 1 inch, for example. It becomes.
[0019]
The invention described in claim 22. The spindle motor according to claim 1, wherein the radial bearing portion is provided with a dynamic pressure generating groove having a shape for allowing a gas to flow in the axial direction as a dynamic pressure generating groove.
[0020]
The invention according to claim 33. The spindle motor according to claim 1, wherein an opening-side end surface of the sleeve faces the surface of the rotor via a gap in an axial direction.
[0021]
The invention according to claim 44. The spindle motor according to claim 1, wherein a small protrusion is provided on the end surface of the shaft facing the closing end surface of the sleeve in the axial direction..
[0022]
The invention described in claim 5In the spindle motor according to claim 1.,The shaft is composed of a shaft member and a hollow cylindrical outer cylinder member fitted to the outer peripheral surface of the shaft member, and an upper end portion of the radial bearing portion is provided between the shaft member and the outer cylinder member. A communication hole that connects the bottom end and the bottom end is formed.
0023]
Claim6In the disk drive device in which a recording disk capable of recording information is rotationally driven, a housing, a spindle motor fixed inside the housing and rotating the recording disk, and writing or writing information on the recording disk A disk drive device having information access means for reading, wherein the spindle motor is a disk drive device.5A disk drive comprising the spindle motor described in any of the above.
0024]
By the way, the invention described in the claims other than claim 1 relates to the configuration according to the embodiment of the present invention, and in order to avoid redundant description, the operational effects and the effects of the configuration of the invention according to each claim The principle will be described in detail in the following embodiments of the present invention.
0025]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of a spindle motor and a disk drive device using the spindle motor according to the present invention will be described with reference to the drawings. In the description of the present embodiment, the vertical direction of each drawing is referred to as “vertical direction” for convenience, but the direction in the actual mounting state of the spindle motor is not limited.
0026]
(referenceExample 1)
First, refer to FIG. 1 and FIG.First1'sreferenceThe spindle motor according to the embodiment will be described. The spindle motor shown in FIG. 1 has a shaft 4 erected substantially at the center of the bracket 2 and a rotor hub 6 that is rotatably supported by the shaft 4. The shaft 4 includes a columnar shaft portion 4a whose lower end in the axial direction is fixed to the bracket 2, and an outer cylinder portion 4b that is fitted to the outer peripheral surface of the shaft portion 4a.
0027]
The rotor hub 6 includes a substantially disc-shaped top plate 6a provided with a central opening 6a1 through which the tip of the shaft portion 4a is inserted, and a lower side in the axial direction from the outer peripheral edge of the top plate 6a toward the bracket 2 side. And a cylindrical wall portion 6b that hangs down. On the outer peripheral surface of the cylindrical wall portion 6b, there is provided a flange-like disc placement portion 6c on which a recording disc such as a hard disc (illustrated as a disc plate 53 in FIG. 5) is placed. A ring-shaped rotor magnet 8 is attached to the side outer peripheral surface.
0028]
The outer cylinder portion 4b and the rotor hub 6 constituting the shaft 4 are made of a ceramic material such as alumina, or a metal material such as stainless steel in which a hard coating such as diamond-like carbon coating or a lubricating coating such as molybdenum disulfide coating is formed on the surface. It is preferable to form from.
0029]
The bracket 2 has a substantially cup-like shape that opens toward the axial upper end of the shaft portion 4a, and the stator 10 is radially outward with respect to the rotor magnet 8 on the inner peripheral surface thereof. Are fixed so as to face each other through a gap. An axially upper portion of the stator 10 is a circumferential magnetic shield plate made of a ferromagnetic material in order to eliminate the influence on the recording disk due to leakage magnetic flux from a magnetic path formed between the stator 10 and the rotor magnet 8. 12 is covered.
0030]
A ring-shaped member 13 having an outer diameter larger than the diameter of the central opening 6 a 1 is attached to the outer peripheral surface of the shaft portion 4 a that protrudes upward in the axial direction from the rotor hub 6. Movement in the axial direction is restricted. That is, the engagement of the ring-shaped member 13 with the rotor hub 6 constitutes the retaining of the rotor hub 6.
0031]
Note that the upper end portions of the bracket 2 and the shaft portion 4a are fixed to a housing (illustrated as a housing 51 in FIG. 5) of a disk drive device in which the spindle motor is accommodated. In this way, by adopting a so-called both-end fixed structure in which the upper and lower ends of the spindle motor in the axial direction are fixed to the housing of the disk drive device, the housing of the disk drive device is thinned to reduce the thickness of the device. Even in such a case, the spindle motor itself can serve as a pillar in the casing, so that it is possible to ensure robustness. Further, since the rigidity of the stationary side member of the spindle motor including the bracket 2 and the shaft 4 is enhanced, the characteristics of the rotor hub 6 against disturbance such as swinging and vibration or impact are improved. The bracket 2 can be formed integrally with the housing of the disk drive device.
0032]
Then thisreferenceA configuration of the bearing portion of the spindle motor according to the embodiment will be described. An annular projection 6a2 is provided on the lower surface of the top plate 6a of the rotor hub 6 along the periphery of the central opening 6a1. When the spindle motor is stopped, the annular projection 6a2 contacts the outer cylinder 4b of the shaft 4. Touch. At this time, the radially outer side of the annular protrusion 6a2 on the lower surface of the top plate 6a of the rotor hub 6 is opposed to the upper surface of the outer cylindrical portion 4b of the shaft 4 with a gap 14 formed therebetween. The gap 14 formed between the lower surface of the top plate 6a and the upper surface of the outer cylinder portion 4b functions as a thrust bearing portion as will be described later.
0033]
Further, the outer peripheral surface of the outer cylindrical portion 4b of the shaft 4 is opposed to the inner peripheral surface of the cylindrical wall portion 6b of the rotor hub 6, and the surface is provided with a dynamic pressure generating groove 16a to operate a gas such as air. A radial bearing portion 16 is formed as a fluid. The dynamic pressure generating groove 16a formed in the radial bearing portion 16 has a spiral shape as shown in FIG. 1 with a part of the outer cylinder portion 4b exposed, and the axial direction of the spiral groove portion located on the gap 14 side. Compared to the dimension, the axial dimension of the spiral groove portion located on the air conduction path A side is set to be longer, and a herringbone shape unbalanced in the axial direction can be obtained.
0034]
Between the rotor magnet 8 and the stator 10 between the upper surface of the magnetic shield plate 12 and the lower surface of the disk mounting portion 6c and between the inner peripheral surface of the magnetic shield plate 12 and the outer peripheral surface of the cylindrical wall portion 6b. A gap that is continuous with the formed gap is formed, and a gap formed between the rotor magnet 8 and the stator 10 is formed between the cylindrical wall 6b and the lower surface of the rotor magnet 8 and the upper surface of the bracket 2. A continuous void is formed. These series of air gaps form an air conduction path A that continues from the outside of the motor to the radial bearing portion 16.
0035]
When the rotor hub 6 starts to rotate, the radial bearing portion 16 pushes in the axial direction upper side, that is, the gap 14 side while taking in the outside air through the air conduction path A by the pumping action by the dynamic pressure generating groove 16a. A high-pressure fluid film is formed by air from the lower end in the axial direction to the gap 14. As described above, when the spindle motor is stopped, the rotor hub 6 is in contact with the upper surface of the outer cylindrical portion 4b at the annular protrusion 6a2, so that the air fed upward in the axial direction by the pumping action of the radial bearing portion 16 is The rotor hub 6 floats with respect to the shaft 4 and starts rotating in a non-contact manner when the pressure in the gap 14 is increased to a predetermined pressure or more. By cooperating with the radial bearing portion 16 in this manner, the gap 14 has a function as a thrust bearing portion.
0036]
Since the rotor hub 2 is levitated, a gap is generated between the annular protrusion 6a2 and the upper surface of the outer cylinder portion 4b, so that the outside air accumulated in the gap 14 is released and the levitating force of the rotor hub 6 is somewhat reduced. . However, an annular thrust yoke 18 made of a ferromagnetic material such as stainless steel is disposed on the bracket 2 at a position facing the lower surface of the rotor magnet 8 in the axial direction. The rotor hub 6 has this thrust yoke. Since the magnetic force acting between the rotor magnet 8 and the rotor magnet 8 is always attracted to the bracket 2 side, the levitation force of the rotor hub 6 generated by increasing the pressure in the gap 14 and this magnetic force are balanced. In addition, the gap between the annular protrusion 6a2 and the outer cylinder 4b does not become larger than a predetermined amount, and the floating of the rotor hub 6 is stabilized.
0037]
Thus, the structure which formed only one dynamic pressure bearing part for which high processing accuracy is required for the surface and shape between the outer peripheral surface of the outer cylinder member 4b and the inner peripheral surface of the cylindrical wall part 6b, As a result, the number of processing steps is reduced, the yield is improved, and the cost can be reduced. Further, as described above, by supporting the rotor hub 6 by magnetic back pressure instead of the bearing portion, the area occupied by the radial bearing portion 16 can be maximized among the limited dimensions by minimizing the bearing formation location. Therefore, for example, the present invention can be applied to a very small spindle motor that drives a small disk having an outer diameter of 1 inch.
0038]
Further, since the gas itself is a fluid having a viscosity lower than that of a liquid such as oil, coupled with the configuration in which only one dynamic pressure bearing portion is provided, the viscous resistance during rotation becomes as small as possible. Therefore, loss such as rotational load generated in the bearing portion is reduced, and the power consumption of the spindle motor can be reduced.
0039]
Furthermore, since gas is less susceptible to the influence of the external environment such as temperature and pressure than liquid, that is, it has a very small change in characteristics, it can be used by supporting the rotor hub 6 by using it as a working fluid. It is possible to continue to maintain a predetermined bearing rigidity even under a rough environment, and very stable rotation can be obtained.
0040]
In addition, since the contact between the rotor hub 6 and the shaft 4 when the spindle motor is stopped occurs only at the upper surface portions of the annular protrusion 6a2 and the outer cylindrical portion 4b, from the start of the spindle motor until the rotor hub 6 floats. The mechanical contact / sliding between the rotor hub 6 and the shaft 4 that occurs during the interval or from the steady rotation state until the rotor hub 6 gradually descends and completely stops is minimized, and abnormal wear occurs or occurs. Dust is prevented.
0041]
In the above configuration, the thrust bearing portion depends on the pumping action of the radial bearing portion 16, but the annular protrusion 6a2 in FIG. 1 is not provided, and the thrust bearing portion is between the lower surface of the top plate 6a. On the upper surface of the outer cylinder portion 4b constituting the portion, a spiral groove having a shape for feeding air radially outward, that is, the radial bearing portion 16 side, or a herringbone groove that is unbalanced in the radial direction, like the radial bearing portion. It is also possible to dispose a dynamic pressure generating groove and to dispose a dynamic pressure bearing that functions actively according to the rotation of the spindle motor.
0042]
By supporting the rotor hub 6 in the thrust direction by the dynamic pressure bearing, some of the advantages of the configuration in FIG. 1 are lost, but the rotor hub 6 is rotated at a relatively low rotational speed by the pumping action by the dynamic pressure generating groove. It becomes possible to surface with.
0043]
(referenceExample 2)
Next, referring to FIG.The second2referenceThe spindle motor according to the embodiment will be described. In the spindle motor shown in FIG. 2, portions having substantially the same configuration as the spindle motor according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
0044]
First2referenceIn the spindle motor according to the embodiment, the gap 14 ′ that functions as a thrust bearing portion is formed between the rotor hub 6 ′ and the bracket 2.referenceIt has a configuration different from the spindle motor according to the embodiment.
0045]
That is, an annular protrusion 6b′1 protruding toward the bracket 2 is provided on the outer peripheral edge of the lower surface of the cylindrical wall 6b ′ in the rotor hub 6 ′, and the annular protrusion 6b on the lower surface of the cylindrical wall 6b ′. A gap 14 ′ is formed between the upper surface of the bracket 2 in a region radially inward of “1”. Further, since the gap 14 ′ is formed between the lower surface of the cylindrical wall portion 6b ′ and the upper surface of the bracket 2, the dynamic pressure generating groove 16a ′ in the radial bearing portion 16 ′ is provided with the spiral according to the first embodiment. The groove or herringbone groove has a shape that pumps outside air in the opposite direction in the axial direction.
0046]
At this time, even when the spindle motor is stopped, the axial direction of the radial bearing portion 16 'is determined from the gap formed between the outer peripheral surface of the shaft portion 4a and the central opening 6a1' provided in the top plate 6a 'of the rotor hub 6'. The amount of projection of the annular projection 6b′1 is determined so that the air conduction path B reaching the upper end is formed, and a gap is secured between the lower surface of the top plate 6a ′ and the upper surface of the outer cylinder portion 4b. There is a need.
0047]
Also in this configuration, it is possible to obtain the same advantages as those of the spindle motor according to the first embodiment. Moreover, it is also possible to provide a dynamic pressure bearing portion as a thrust bearing portion between the lower surface of the outer cylinder portion 6 b ′ and the upper surface of the bracket 2.
0048]
Example 1
Next, referring to FIG. 3, the spindle motor according to the present invention1The embodiment will be described. The spindle motor shown in FIG. 3 has a hollow cylindrical sleeve 23 erected in a cylindrical boss portion 22 a provided at a substantially central portion of the bracket 22 and an opening on the lower end side in the axial direction of the sleeve 23. A disk-shaped cover member 25 to be sealed, and a rotor hub 26 integrally provided with a shaft 24 inserted into a space defined by the inner peripheral surface of the sleeve 23 and the upper surface of the cover member 25. ing. The shaft 24 includes a shaft portion 24a extending from the center portion of the rotor hub 26, and an outer cylinder portion 24b fitted on the outer peripheral surface of the shaft portion 24a.
0049]
The rotor hub 26 includes a substantially disk-shaped top plate 26a formed concentrically with the shaft portion 4a, and a cylindrical wall portion that hangs downward in the axial direction from the outer peripheral edge of the top plate 26a toward the bracket 22 side. 26b. On the outer peripheral surface of the cylindrical wall portion 26b, there is provided a flange-like disk mounting portion 26c on which a recording disk such as a hard disk (illustrated as a disk plate 53 in FIG. 5) is mounted. A ring-shaped rotor magnet 28 is attached to the side outer peripheral surface.
0050]
The outer cylindrical portion 24b, the sleeve 23 and the cover member 25 constituting the shaft 24 are made of a stainless steel having a ceramic material such as alumina or a surface coated with a hard coating such as diamond-like carbon coating or a lubricating coating such as molybdenum disulfide coating. It is preferable to form from metal materials, such as.
0051]
The bracket 22 has a substantially cup-like shape that opens toward the upper end side in the axial direction of the sleeve 23, and the stator 30 is formed on the inner peripheral surface thereof from the outside in the radial direction with respect to the rotor magnet 28. It is fixed so as to face each other through a gap. An axially upper portion of the stator 30 is a circumferential magnetic shield plate made of a ferromagnetic material in order to eliminate the influence on the recording disk due to leakage magnetic flux from a magnetic path formed between the stator 30 and the rotor magnet 28. 32.
0052]
Further, an annular flange portion 23 a protruding outward in the radial direction is provided at the upper end portion of the outer peripheral surface of the sleeve 23, and the outer peripheral surface of the sleeve 23 is provided on the inner peripheral surface of the cylindrical wall portion 26 b of the rotor hub 26. A ring-shaped member 33 having an inner diameter smaller than the diameter is attached, and the movement of the rotor hub 26 in the axial direction is restricted by the ring-shaped member 33 and the flange portion 2. That is, when the ring-shaped member 33 is engaged with the flange portion 23a, the rotor hub 26 is prevented from being pulled out.
0053]
Next, the configuration of the bearing portion of the spindle motor according to this embodiment will be described. First, a dynamic pressure generating groove 27a is formed on the upper surface of the sleeve 23 by a spiral groove having a shape for feeding air outward in the radial direction or a herringbone groove unbalanced in the radial direction. Between the lower surface of 26a, the thrust bearing part 27 which uses gas, such as air, as a working fluid is comprised.
0054]
Further, the inner peripheral surface of the sleeve 23 is opposed to the outer peripheral surface of the outer cylindrical portion 24b of the shaft 24, and a dynamic pressure generating groove 36a including an axial groove is intermittently provided on the surface thereof in the circumferential direction. A radial bearing portion 36 using a gas such as a working fluid is configured.
0055]
Further, the axial dimension of the shaft 24 constituted by the shaft portion 24 a and the outer cylinder portion 24 b is somewhat shorter than the axial dimension of the space defined by the inner peripheral surface of the sleeve 23 and the upper surface of the cover member 25. Thus, an air chamber 29 that is a space in which air is held is defined between the lower surface of the distal end portion of the shaft 24 and the upper surface of the cover member 25.
0056]
Between the rotor magnet 28 and the stator 30 between the upper surface of the magnetic shield plate 32 and the lower surface of the disk mounting portion 26c and between the inner peripheral surface of the magnetic shield plate 32 and the outer peripheral surface of the cylindrical wall portion 26b. A gap that is continuous with the formed gap is formed, and a gap formed between the rotor magnet 28 and the stator 30 is formed between the cylindrical wall portion 26 b and the lower surface of the rotor magnet 28 and the upper surface of the bracket 22. The air conduction path C is formed by the series of gaps.
0057]
In such a configuration, when the spindle motor rotates, the dynamic pressure is generated by the air held in the dynamic pressure generating groove 27a of the thrust bearing 27 flowing inward in the radial direction, and the rotor hub 26 starts to float. Is done. Also in the radial bearing portion 36, dynamic pressure is generated by the dynamic pressure generating groove 36a, and the rotor hub 26 is aligned.
0058]
As the rotor hub 26 floats, the thrust bearing portion 27 is continued to the air conduction path C, and outside air is taken into the bearing by the pumping action by the dynamic pressure generating groove 27a.
0059]
As described above, when outside air is taken in by the pumping action of the thrust bearing portion 27, the air held in the air chamber defined by the lower surface of the tip end portion of the shaft 24 and the upper surface of the cover member 25 is pressurized. That is, in the spindle motor according to this embodiment, the thrust bearing portion 27 and the air chamber 29 cooperate to obtain the floating force of the rotor hub 26.
0060]
In addition, the firstreferenceAs in the case of the embodiment, also in this embodiment, the rotor hub 26 is always attracted to the bracket 2 side by the magnetic force acting between the thrust yoke 38 and the rotor magnet 28, and the bottom surface of the front end portion of the shaft 24. And the magnetic force and the floating force of the rotor hub 26 generated by increasing the pressure in the space formed between the upper surface of the cover member 25 and the upper surface of the cover member 25, the floating of the rotor hub 6 is stabilized.
0061]
Also in this configuration, it is possible to obtain the same advantages as those of the spindle motor according to the first and second reference embodiments.
0062]
In the above configuration, since the thrust bearing 27 is configured to pump air toward the air chamber 29, the radial bearing 36 does not require air to flow in the axial direction. As shown in FIG. 1, a so-called step-type hydrodynamic bearing is formed. However, instead of this, the dynamic pressure generating groove 36a provided in the radial bearing portion 36 is replaced by a spiral groove or herringbone groove shown in FIG. Is a configuration in which air is pumped to the air chamber 29 side by the pumping action of the radial bearing portion 36 as a spiral groove or herringbone groove shaped to pump air in the opposite axial direction, and the thrust bearing portion 27 is not provided. It is also possible.
0063]
When air is pumped by the radial bearing portion 36 as described above, it is necessary to keep the radial bearing portion 36 continuous with the air conduction path C even when the spindle motor is stopped. Therefore, the axial dimension of the shaft 24 needs to be larger than the axial dimension of the space defined by the sleeve 23 and the cover member 25. In this case, in order to ensure the floating of the rotor hub 26, a small protrusion is provided on the shaft center portion of the lower surface of the tip portion of the shaft portion 24a, and this is point-contacted or surface-contacted with the upper surface of the cover member 25 to It is desirable to secure 29.
0064]
(Example 2)
Next, referring to FIG.2A spindle motor according to the embodiment will be described. FIG. 4 is a cross-sectional view showing a state in which the surface of the shaft portion 24a 'constituting the shaft 24' is exposed. In the spindle motor shown in FIG.1Parts having substantially the same configuration as the spindle motor according to the embodiment are given the same reference numerals, and the description thereof is omitted.
0065]
First of the present invention2In the spindle motor according to the embodiment, the communication hole 40 that communicates the upper end side and the lower end side in the axial direction of the radial bearing portion 36 is provided between the outer peripheral surface of the shaft portion 24a ′ and the outer cylinder portion 24b ′. In terms of being formed above1This has a different configuration from the spindle motor according to the embodiment.
0066]
That is, on the outer peripheral surface of the shaft portion 24a ′ constituting the shaft 24 ′, a single spiral groove 40a is formed continuously from the upper end portion side to the lower end portion side, and the outer periphery surface of the shaft portion 24a ′ is externally provided. By fitting the tube portion 24b ′, the spiral groove 40 is formed between the spiral groove 40a and the inner peripheral surface of the outer tube portion 254b ′. In FIG. 4, the spiral groove 40a is indicated by a broken line with respect to a portion formed on the rear surface side in the drawing direction of the shaft portion 24a.
0067]
A very slight gap is formed at the upper and lower end portions of the inner peripheral surface of the outer cylinder portion 24b ′ between the outer peripheral surface of the shaft portion 24a ′ and the upper end portion and the lower end portion of the spiral groove 40a. Circumferential recesses 24b'1 and 24b'2 extending to the upper end surface and the lower end surface are provided. The communication hole 40 continues to the radial bearing portion 36 through a slight gap formed between the recesses 24b'1, 24b'2 and the outer peripheral surface of the shaft portion 24a '.
0068]
Next, the function of the communication hole 40 will be described.
0069]
For example, a gap formed between the inner peripheral surface of the sleeve 23 and the outer peripheral surface of the outer cylindrical portion 24b is combined by combining the maximum processing tolerances of the inner peripheral surface of the sleeve 23 or the outer peripheral surface of the outer cylindrical portion 24b. When the gap dimension changes between the upper end side and the lower end side in the axial direction, an abnormal flow is induced with respect to the air. As a result, the gap formed between the inner peripheral surface of the sleeve 23 and the outer peripheral surface of the outer cylindrical portion 24b in the axial direction upper end portion side and lower end portion side, that is, between the thrust bearing portion 27 and the air chamber 29, An air pressure difference will occur. If this pressure difference is left unattended, when air flows from the lower end side in the axial direction to the upper end side, the air in the air chamber 29 cannot be increased, and the flying height of the rotor hub 26 is insufficient. Further, when air flows from the upper end side in the axial direction to the lower end side, the pressure in the air chamber 29 is increased more than necessary, and the rotor hub 2 is overlifted.
0070]
On the other hand, by providing the communication hole 40, an axial flow is induced in the air, and the axial upper end of the gap formed between the inner peripheral surface of the sleeve 23 and the outer peripheral surface of the outer cylindrical portion 24b. Even if an air pressure difference occurs between the side and the lower end side, an air flow from the high internal pressure side to the low side occurs through the communication hole 40, so that the pressure in the bearing portion can be balanced.
0071]
By providing the communication hole 40 in this way, in addition to the advantages of the configuration of the spindle motor of each of the above embodiments, the allowable range for processing errors is greatly expanded, so that the yield is improved. Further, since the axial flow of air in the radial bearing portion is allowed, the degree of freedom in design can be increased.
0072]
Further, as shown in FIG. 4, the opening portions at both ends of the communication hole 40 are respectively provided with circumferential recesses 24b′1, 24b′2 and shaft portions 24a provided on the inner peripheral surface of the outer cylinder portion 24b ′. By being positioned within a slight gap formed between the outer peripheral surface of 'and air, an air conduction resistance is generated, and the air does not flow rapidly in the communication hole 40. That is, the communication hole 40 has not only the pressure adjusting function described above but also a buffer function that suppresses sudden pressure fluctuations.
0073]
That is, when the rotor hub 26 swings due to disturbance such as vibration or impact, the gap formed in the bearing portion tends to be wide on the moving direction side of the rotor hub 26 and narrow on the opposite side. At this time, when the communication hole 40 is directly communicated with the upper and lower ends in the axial direction of the radial bearing portion 36, air easily flows from the side where the gap is to be narrowed toward the opposite side. Therefore, the pressure fluctuates rapidly, and the swing of the rotor hub 26 cannot be suppressed. However, by increasing the flow resistance at both openings of the communication hole 40, the flow of air is prevented, the vibration of the rotor hub 26 can be minimized, and the predetermined flying height can be restored without taking time. Is possible.
0074]
(Configuration of disk drive)
FIG. 5 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.
0075]
By using the spindle motor of the above embodiment as the spindle motor 52 of such a disk drive device 50, it can be applied to a small device such as a portable information terminal, and can be used for a long time and improved in reliability. It becomes possible.
0076]
The embodiments of the hydrodynamic bearing, spindle motor, and disk drive device according to the present invention have been described above. However, the present invention is not limited to such embodiments, and various modifications can be made without departing from the scope of the present invention. Or it can be modified.
0077]
For example, in the above embodiment, the shaft has a double structure in which the outer cylinder portion is fitted to the outer peripheral surface of the shaft portion. However, the shaft has an integral structure if allowed in the assembly process. It doesn't matter.
0078]
【The invention's effect】
According to the spindle motor of the present invention, it is possible to achieve a reduction in size, thickness, and cost, as well as stable rotation and low power consumption even under various environments. It becomes.
0079]
Further, according to the disk drive device of the present invention, it can be applied to a small device such as a portable information terminal, and can be used for a long time and improved in reliability.
[Brief description of the drawings]
[Figure 1]First reference formIt is sectional drawing which shows schematic structure of the spindle motor which concerns on.
[Figure 2]Second reference formIt is sectional drawing which shows schematic structure of the spindle motor which concerns on.
FIG. 3 shows the first aspect of the present invention.1It is sectional drawing which shows schematic structure of the spindle motor which concerns on this embodiment.
FIG. 4 shows the first aspect of the present invention.2It is sectional drawing which shows schematic structure of the spindle motor which concerns on this embodiment.
FIG. 5 is a cross-sectional view schematically showing the internal configuration of the disk drive device.
[Explanation of symbols]
6,6 ’rotor
4 Shaft
4a Shaft (small outer diameter)
4b Outer cylinder part (large outer diameter part)
14, 14 'clearance (thrust bearing)
16 Radial bearing

Claims (6)

In a spindle motor comprising a substantially cup-shaped rotor that defines a cavity therein, a shaft that rotates integrally with the rotor, and a cylindrical sleeve that is closed at one end through which the shaft is inserted,
A movement of a shape that causes gas to flow radially inward on the opening side end surface of the sleeve provided on the lower side in the axial direction of the bottom surface of the rotor or on the opening side end surface of the sleeve and the surface of the rotor on the upper side in the axial direction. A thrust bearing portion that uses gas as a working fluid is formed by forming the pressure generating groove,
The outer peripheral surface of the shaft and the inner peripheral surface of the sleeve are opposed to each other in the radial direction, and a radial bearing portion using a gas as a working fluid is configured.
The radial bearing portion is provided with an axial groove as a dynamic pressure generating groove, and the dynamic pressure generated in the thrust bearing portion is substantially between the sleeve-side end surface of the sleeve and the end surface of the shaft. An air chamber having substantially the same pressure is formed, and the rotor is given a levitation force by the cooperation of the thrust bearing portion and the air chamber ,
The spindle motor according to claim 1, wherein the rotor is magnetically back-pressured in a direction opposite to a direction in which the dynamic pressure generated in the thrust bearing portion is applied. Wherein the radial bearing portion, a spindle motor according to claim 1, characterized that you have hydrodynamic groove shape for flowing the gas in the axial direction is provided as the dynamic pressure generating grooves. 3. The spindle motor according to claim 1, wherein an end surface on the opening side of the sleeve faces the surface of the rotor with a gap in the axial direction . 4. The spindle motor according to claim 1, wherein a small protrusion is provided on an end surface of the shaft facing the closing side end surface of the sleeve in a lower axial direction . 5. The shaft is composed of a shaft member and a hollow cylindrical outer cylinder member fitted on the outer peripheral surface of the shaft member, and an upper end portion of the radial bearing portion is provided between the shaft member and the outer cylinder member. The spindle motor according to any one of claims 1 to 4, wherein a communication hole is formed to connect the upper end and the lower end portion . In a disk drive device in which a recording disk capable of recording information is rotationally driven, a housing, a spindle motor fixed inside the housing and rotating the recording disk, and information access means for writing or reading information on the recording disk A disk drive device comprising:
A disk drive device comprising the spindle motor according to claim 1 as the spindle motor.

Images