JP4401068B2 - DYNAMIC PRESSURE BEARING, SPINDLE MOTOR HAVING THE DYNAMIC PRESSURE BEARING, AND DISK DRIVE DEVICE USING THE SPINDLE MOTOR - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic pressure bearing, a spindle motor provided with the dynamic pressure bearing, and a disk drive device using 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]
In recent years, disk drive devices using such spindle motors have started to be applied to small devices such as portable information terminals, and demands for further thinning are increasing.
[0004]
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 that can obtain rigidity has been proposed (see Patent Document 1).
[0005]
A spindle motor using such a dynamic pressure bearing is shown in FIG. The spindle motor shown in FIG. 1 (a) forms a thrust bearing portion S for generating a floating force of the rotor a between the bottom surface of the rotor a and the upper end surface of the sleeve b, and is integral with the rotor a. An upper radial bearing for acting on the alignment of the rotor a and prevention of collapse via an air interposition part d communicating with the outside air between the outer peripheral surface of the shaft c and the inner peripheral surface of the sleeve b. R1 and lower radial bearing portion R2 are configured. A stator f is attached to a base member e to which the sleeve b is fixed, and a rotor magnet g is fixed to the rotor a so as to face the stator f.
[0006]
A schematic configuration of the thrust bearing portion S and the upper radial bearing portion R1 in the spindle motor will be described with reference to FIGS. 1 (b) and 1 (c). As shown in an enlarged view in FIG. 1B, the thrust bearing portion S formed between the bottom surface of the rotor a and the upper end surface of the sleeve b has an inner radius in the direction indicated by an arrow A in FIG. A pump-in type spiral groove SG for inducing the flow of oil toward the side is provided, whereby a support force in the floating direction of the rotor a is obtained. A specific shape of the spiral groove SG provided in the thrust bearing portion S is illustrated in FIG. Further, in the upper radial bearing portion R1 disposed radially inward of the thrust bearing portion S, as shown in FIG. 1B, the air intervening portion d side is more than the spiral groove portion RS1 located on the thrust bearing portion S side. Is provided with a herringbone groove HG1 having an unbalanced shape in the axial direction in which the dimension in the axial direction is set longer in the spiral groove part RS2, and thereby the radial support on the upper end side of the shaft c is provided. Power is obtained. At this time, since the pumping force of the spiral groove portion RS2 with respect to the oil exceeds the pumping force of the spiral groove portion RS1 by the difference in the axial dimension, the dynamic pressure toward the thrust bearing portion S side in the upper radial bearing portion R1. Occurs.
[0007]
Although the shape of the dynamic pressure generating groove is not particularly illustrated, the lower radial bearing portion R2 has a herring having a symmetrical shape in the axial direction in which the axial dimensions of the pair of spiral groove portions are set substantially equal. A bone groove HG2 is provided, and thereby a radial supporting force on the lower end side of the shaft c is obtained. Further, a ring-shaped member h made of a ferromagnetic material is arranged at a position facing the rotor magnet g of the base member e in the axial direction, and magnetic attraction acting between the rotor magnet g and the ring-shaped member h. A supporting force in a direction to suppress the floating of the rotor a is obtained by force. The levitation force due to the dynamic pressure generated in the thrust bearing portion S and the magnetic attractive force acting between the rotor magnet g and the ring-shaped member h are balanced to support the axial load applied to the rotor a.
[0008]
By having the hydrodynamic bearing having the above-described configuration, the spindle motor shown in FIG. 1A can simplify the structure of the motor and reduce the cost without significantly reducing the bearing rigidity. It has the merit of becoming.
[0009]
[Patent Document 1]
JP 2000-197309 A (page 4-6, FIG. 2).
[0010]
[Problems to be solved by the invention]
Incidentally, in the spindle motor shown in FIG. 1, the bottom surface of the rotor a and the sleeve b in the region radially inward of the thrust bearing portion S (shown as a region P surrounded by a one-dot chain line in FIG. 1B). Is set so that the gap between the upper end surface and the thrust bearing portion S is substantially the same.
[0011]
Normally, the gap size in the region P that does not contribute to the generation of dynamic pressure is set to be several times larger than the gap size of the thrust bearing portion S, more specifically, the gap size is set to several μm in the bearing portion. On the other hand, in the region P, it is possible to reduce the loss during rotation due to the viscosity of the oil by setting it to have a large gap size of about several tens of μm. By providing a region having such a large gap size adjacent to the bearing portion, when a disturbance such as an impact or vibration is applied when the motor that does not act on dynamic pressure is stationary, vibration in the axial direction of the rotor a due to the disturbance is expanded. It was newly discovered. Such non-operating vibration is caused by the fact that the oil held by the thrust bearing portion S escapes to the region P having a large gap when the rotor a is pressed against the sleeve b due to a disturbance, thereby reducing the damping effect by the oil. It is believed that this is due to
[0012]
Thus, the vibration of the rotor “a” becomes large even when not operating, so that the vibration of the disk mounted on the rotor “a” also increases, and there is a concern that this may be broken by contact with the head disposed close to the disk. . Therefore, in order to avoid this, the region P located on the radially inner side of the thrust bearing portion S is also set to have substantially the same gap size as the bearing portion.
[0013]
Further, when bubbles are mixed in the oil, the bubbles are caused by the pumping action by the herringbone groove HG1 provided in the upper radial bearing portion R1 and the spiral groove SG provided in the thrust bearing portion S. They are collected in a region P located inward in the radial direction of S. However, since the region P is a minute gap having substantially the same gap size as that of the bearing portion and no dynamic pressure groove is formed, the bubbles collected in this region P are surrounded even when the rotor a rotates. Only the flow in the direction will occur, and it will stay there.
[0014]
The bubbles staying in the region P on the radially inner side of the thrust bearing portion S are aggregated while flowing in the circumferential direction as the motor rotates, and eventually become a single band of air in the circumferential direction. Thus, when a band of air is generated in the oil in the region P, abnormal vibration during operation, deterioration of NRRO (non-repetitive vibration component), or the radial direction of the oil due to the spiral groove SG provided in the thrust bearing portion S. There is a possibility that the flow to the inner side is hindered, and a predetermined levitation force cannot be obtained, resulting in an abnormal rise of the rotor a. The reason why bubbles are mixed in the oil is, for example, the spiral groove portion located on the air interposition portion d side due to carelessness of the operator in the oil injection process or unbalanced pumping of the herringbone groove HG1 when the motor rotates. It is conceivable that the oil interface is disturbed due to the lower end of the RS 2 being exposed to the air, whereby the air is entrained in the oil and appears as bubbles.
[0015]
The object of the present invention is to eliminate even if air bubbles are mixed in the oil continuously held between the thrust bearing and the upper radial bearing due to the operator's problem or machining error. Is to provide a simple hydrodynamic bearing.
[0016]
Another object of the present invention is to provide a highly reliable spindle motor and a disk drive device using this spindle motor, by providing the hydrodynamic bearing as the bearing means, thereby avoiding problems due to bubbles. That is.
[0017]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a thrust bearing portion that generates dynamic pressure acting in one axial direction on the oil held in the minute gap, and a radially inner side of the thrust bearing portion. In a dynamic pressure bearing comprising a radial bearing portion that generates a dynamic pressure acting in a radial direction with respect to oil disposed and held in a minute gap,
The thrust bearing portion is provided with a dynamic pressure generating groove array in the circumferential direction by a pump-in type spiral groove that induces a flow toward the radially inward side with respect to the oil as a dynamic pressure generating groove,
The radial bearing portion has a dynamic pressure generated by a herringbone groove having an unbalanced shape in the axial direction so that a maximum dynamic pressure generated with respect to the oil appears as a dynamic pressure generating groove in a biased manner toward the thrust bearing portion. The generation groove row is provided in the circumferential direction,
Between the thrust bearing portion and the radial bearing portion, the oil is continuously held in each minute gap without interruption, and forms a dynamic pressure generating groove array of the thrust bearing portion. Spiral groove More than one The spiral groove is provided so as to extend radially inward from the other spiral grooves. The plurality of spiral grooves are equally spaced in the circumferential direction. Arranged,
Extends radially inward from the other spiral grooves Multiple The spiral groove is provided with a larger width in the circumferential direction than the other spiral groove,
Between the radial bearing portion and the thrust bearing portion, a radially inwardly extending region filled with the oil is provided,
Extends radially inward from the other spiral grooves Multiple The spiral groove extends from the inner end of the thrust bearing portion toward the radially inner region and is provided over the entire radial direction of the radially inner region. To do.
[0018]
In this way, by extending at least one of the spiral grooves formed in the thrust bearing portion to the radially inward side of the other spiral grooves, bubbles enter the radially inner region of the thrust bearing portion. Also in this case, the radial flow of oil is generated by the spiral groove up to the radially inner region of the thrust bearing portion where bubbles are likely to stay. As a result, the oil flow in the radial direction also acts on the invading bubbles, and the pressure-sealed state due to the action of the dynamic pressure generating grooves of the thrust bearing portion and the radial bearing portion is released. Discharge becomes possible.
[0019]
The invention according to claim 2 is the hydrodynamic bearing according to claim 1, The oil flow rate inward in the radial direction by the thrust bearing portion exceeds the oil flow rate in the axial direction due to pumping of the radial bearing portion. It is characterized by that.
[0020]
Furthermore, the invention according to claim 3 is a shaft, and a sleeve in which a through hole into which the shaft is rotatably inserted is formed, A bottom surface facing the upper end surface of the sleeve in the axial direction and extending radially outward from the outer peripheral surface of the shaft is fixed to the shaft. Rotor with circular top plate And A spindle motor comprising:
An upper end surface of the sleeve; The axially opposite to the upper end surface A minute gap for holding oil is formed between the bottom surface of the top plate and a dynamic pressure generating groove for inducing fluid dynamic pressure in the oil held in the minute gap according to the rotation of the rotor. A thrust bearing portion is configured by being provided,
Of the sleeve Through hole A minute gap for retaining oil is formed between the inner circumferential surface and the outer circumferential surface of the shaft, and fluid dynamic pressure is induced in the oil held in the minute gap according to the rotation of the rotor. A radial bearing is formed by providing the dynamic pressure generating groove,
The minute gap formed between the upper end surface of the sleeve constituting the thrust bearing portion and the bottom surface of the top plate has substantially the same gap dimension from the inner diameter end side to the outer diameter end side of the minute gap. Is formed as
The hydrodynamic bearing comprising the thrust bearing portion and the radial bearing portion is the hydrodynamic bearing according to claim 1 or 2.
[0021]
Furthermore, the invention described in claim 4 is a shaft, a pair of annular thrust plates protruding radially outward from the outer peripheral surface of the shaft, and one axial surface of the pair of thrust plates, respectively. A hollow cylindrical sleeve formed with a pair of thrust surfaces facing each other through a minute gap, and an outer peripheral surface of the shaft continuous with the thrust surface and a radial inner circumferential surface facing the radial direction via a minute gap. A spindle motor provided with oil is held in a minute gap formed between one axial surface of the pair of thrust plates and the pair of thrust surfaces, and induces dynamic pressure on the oil A thrust bearing portion is formed by providing the dynamic pressure generating groove, and a minute gap formed between the outer peripheral surface of the shaft and the radial inner peripheral surface of the sleeve The pair of thrust plates is configured such that a pair of radial bearings are formed in the axial direction by being provided with a dynamic pressure generating groove for holding the oil and inducing a dynamic pressure in the oil, and the thrust bearing portion is configured. The minute gaps formed between one surface of the sleeve and the pair of thrust surfaces of the sleeve are formed to have substantially the same gap dimension from the inner diameter end side to the outer diameter end side of the minute gap. The pair of thrust bearing portions and the pair of radial bearing portions constitute a pair of dynamic pressure bearings each including a pair of thrust bearing portions and a radial bearing portion, and the pair of dynamic pressure bearings are respectively claimed. It is a hydrodynamic bearing as described in 1 or 2.
[0022]
In addition, the invention according to claim 5 is 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 the recording A disk drive device having information access means for writing or reading information at a required position of the disk, wherein the spindle motor is a spindle motor according to claim 3 or 4.
[0023]
By the way, the invention described in claims other than claim 1 relates to the configuration in accordance with the embodiment of the present invention. Regarding the operation effect and the principle of the configuration of the invention according to each claim, the following invention is described. This will be described in detail in the section of the embodiment and the effect of the invention.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a dynamic pressure bearing according to the present invention will be described together with a spindle motor using the same, and each embodiment of a disk drive device using the spindle motor will be described with reference to the drawings. It is not limited to the embodiment shown.
[0025]
An embodiment of the present invention will be described with reference to FIG. In this embodiment, since it has substantially the same structure as the dynamic pressure bearing used in the spindle motor shown in FIG. 1, it is shown in FIG. 1 in order to avoid redundant description. Only the difference from the dynamic pressure bearing of the spindle motor will be described.
[0026]
As shown in FIG. 2, the thrust bearing portion S is provided with a spiral groove SG1A extending inward in the radial direction from the spiral groove SG1 in addition to the pump-in type spiral groove SG1 as a dynamic pressure generating groove. This is different from the hydrodynamic bearing disclosed in FIG. That is, on the upper end surface of the sleeve b, there are nine spiral grooves SG1 arranged in a circumferential shape, and three that extend radially inward from the spiral grooves SG1 and reach the inner peripheral edge of the upper end portion of the sleeve b. The spiral grooves SG1A are provided at equal intervals in the circumferential direction to form a dynamic pressure generating groove array. These three spiral grooves SG1A are set to have a wider groove width in the circumferential direction than the other spiral grooves SG1.
[0027]
At this time, as a guideline for the groove width of the three spiral grooves SG1A, the radial flow rate in the region on the inner diameter side from the other nine spiral grooves SG1 is not limited to the upper radial regardless of the use conditions. It is necessary to exceed the oil flow rate in the axial direction due to the pumping of the herringbone groove HG1 provided in the bearing portion R1. In the present embodiment, the circumferential groove width of the nine spiral grooves SG1 is about 0.2 mm to about 0.6 mm, preferably about 0.27 mm to about 0.48 mm. The circumferential groove width of the three spiral grooves SG1A extending to the side is about 0.3 mm to about 1.5 mm, preferably about 0.2 mm to about 1.39 mm. As a result of analysis assuming that the operating environment temperature of the motor is 90 ° C. and the flying height of the rotor a (bearing clearance dimension in the thrust bearing portion S) is 4 μm, the inner diameter is larger than that of the nine spiral grooves SG1. This is a value determined by confirming that the oil flow rate in the radial direction in the region on the side exceeds the oil flow rate in the axial direction due to the pumping of the herringbone groove HG1 provided in the upper radial bearing portion R1.
[0028]
Next, the principle of bubble discharge by providing these three spiral grooves SG1A extending inward in the radial direction will be described.
[0029]
First, as described above, the dynamic pressure in the direction of the thrust bearing portion S is applied to the upper radial bearing portion R1 adjacent to the thrust bearing portion S through the region P and continuously holding oil. An unbalanced herringbone groove HG1 is provided in the generated axial direction. Further, although the spiral groove SG1A extending inward in the radial direction is provided, in the thrust bearing S according to the present embodiment, both the spiral grooves SG1 and SG1A have a pump-in shape. Therefore, dynamic pressure is generated inward in the radial direction.
[0030]
At this time, when bubbles are mixed in the oil for the above-described reasons, pumping by the herringbone groove HG1 provided in the upper radial bearing portion R1 and the spiral groove SG1 provided in the thrust bearing portion S and In FIG. 1B, which is located on the radially inner side of the thrust bearing portion S in the minute gap formed between the bottom surface of the rotor a and the upper end surface of the sleeve b due to pumping by SG1A. Bubbles are collected in a region P indicated by a one-dot chain line.
[0031]
Thus, the region P located on the inner side of the thrust bearing portion S is in a state in which air bubbles have entered. At this time, if the region P is set to have a larger gap size than the bearing portion, In a large gap, a difference in flow velocity occurs in the oil between the bottom surface side of the rotating rotor a and the upper end surface side of the stationary sleeve b, and the oil flows due to this flow velocity difference. The air bubbles collected in are gradually discharged without staying there.
[0032]
However, when the region P and the thrust bearing portion S are formed so as to have substantially the same gap size, the bottom surface side of the rotor a and the upper end portion side of the sleeve b are within a minute gap having only a few μm. The difference in oil flow rate is reduced, and the oil flow rate in the radial direction due to the spiral grooves SG1 and SG1A and the oil flow rate in the axial direction due to the pumping of the herringbone groove HG1 provided in the upper radial bearing portion R1 antagonize. In this case, only the flow in the circumferential direction occurs in the oil, so that bubbles stay in place.
[0033]
On the other hand, as in the present embodiment, among the spiral grooves SG1 provided in the thrust bearing portion S, a spiral groove SG1A extending radially inward from the other grooves is provided. The circumferential groove width of the spiral groove SG1A is set so that the circumferential groove width is wider than that of the other spiral grooves SG1, so that when the rotor a is rotated, the radial grooves formed by the spiral grooves SG1 and SG1A The oil flow rate always exceeds the axial oil flow rate caused by the pumping of the herringbone groove HG1 provided in the upper radial bearing portion R1, and the oil flowing inward in the radial direction is caused by the spiral grooves SG1 and SG1A. A flow toward the radially outward side occurs. The bubbles collected in the region P by taking advantage of such radial flow start to move outward in the radial direction, and eventually the interface of the oil end located on the radial outer side of the thrust bearing portion S. Released into the air.
[0034]
Accordingly, the gap formed between the bottom surface of the rotor a and the upper end surface of the sleeve b is set to a minute gap equivalent to that of the thrust bearing portion S over almost the whole, so that the vibration at the time of non-operation of the rotor a due to disturbance is caused. By providing the spiral groove SG1A extending inward in the radial direction while suppressing the occurrence of various problems, it is possible to solve various problems such as abnormal vibration due to retention of bubbles, deterioration of NRRO, and abnormal floating of the rotor a. .
[0035]
Further, such a dynamic pressure bearing is applicable not only to a spindle motor having a configuration as illustrated in FIG. 1A but also to a spindle motor having another configuration. Next, an application example of such a dynamic pressure bearing to a spindle motor having another configuration will be described with reference to FIG.
[0036]
The spindle motor shown in FIG. 3 has a bracket 2, a shaft 4 whose one end is fitted and fixed in a central opening provided in the bracket 2, and is rotatable relative to the shaft 4. Rotor 6. The rotor 6 is positioned on the inner peripheral side of the rotor hub 6a on which a recording disk (shown as a disk plate 53 in FIG. 4) is placed on the outer periphery, and the shaft 4 through a minute gap in which oil is held. And a sleeve 6b supported by the shaft. 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.
[0037]
A through hole 6b1 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 in which the inner peripheral surface is held between the outer peripheral surface of the shaft 4 and oil. An annular upper thrust plate 14 and lower thrust plate 16 projecting outward in the radial direction are attached to the upper and lower portions, respectively.
[0038]
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 periphery 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.
[0039]
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.
[0040]
Between the upper thrust surface 6b2 and the lower surface (the inner surface in the axial direction) of the upper thrust plate 14, a minute gap for holding oil is formed, and the upper thrust bearing portion 26 is configured.
[0041]
Further, a minute gap for retaining oil 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 lower thrust bearing portion 28 is configured.
[0042]
Further, an upper radial bearing portion 30 and a lower radial bearing portion 32 are formed between the inner peripheral surface of the through hole 6 b 1 and the outer peripheral surface of the shaft 4.
[0043]
An axial direction as shown in FIG. 1B is used so that dynamic pressure generating grooves are generated in the upper and lower radial bearing portions 30 and 32 as dynamic pressure generating grooves, respectively, toward the thrust bearing portions 26 and 28 adjacent to each other. 2 is provided with a herringbone groove HG1 having an unbalanced shape, and the upper and lower thrust bearing portions 26 and 28 have the same structure as the thrust bearing portion S shown in FIG. The illustrated pump-in type spiral groove SG1 is provided, and a spiral groove SG1A extending inward in the radial direction is provided. That is, the rotor 6 is supported from the upper and lower parts by the bearing part of the same shape by forming a pair of the radial bearing part R1 and the thrust bearing part S on the upper and lower parts of the shaft 4 in the configuration shown in FIG. Therefore, it becomes possible to stably support even a high-load spindle motor that rotates, for example, a plurality of recording disks, and avoids various problems caused by the retention of bubbles. It becomes possible to do.
[0044]
Therefore, it is possible to suppress vibrations during non-operation of the rotor 6 due to the application of disturbance, and at the same time, it is possible to discharge bubbles mixed in the oil held by the hydrodynamic bearing. High spindle motor can be obtained.
[0045]
FIG. 4 shows a schematic diagram of an internal configuration of a general disk drive device 50. The interior of the housing 51 forms a clean space with extremely small amounts of dust and the like, and a spindle motor 52 on which a disc-shaped disk plate 53 for storing information is mounted is installed. In addition, a head moving mechanism 57 that reads and writes information from and to the disk plate 53 is disposed inside the housing 51. The head moving mechanism 57 supports a head 56 that reads and writes information on the disk plate 53, and the head. The arm 55, the head 56, and the arm 55 are configured by an actuator unit 54 that moves the arm 55 to a required position on the disk plate 53.
[0046]
By using the spindle motor of each of the above embodiments as the spindle motor 52 of such a disk drive device 50, a highly reliable disk drive device can be achieved.
[0047]
The embodiments of the hydrodynamic bearing according to the present invention and the spindle motor and the disk drive device including the hydrodynamic bearing have been described above. However, the present invention is not limited to such embodiments, and the scope of the present invention is not limited thereto. Various changes or modifications can be made without departing.
[0048]
【The invention's effect】
The hydrodynamic bearing of the present invention enables the bubbles mixed in the oil to be discharged and maintains stable performance.
[0049]
Further, in the spindle motor of the present invention, it is possible to suppress the vibration when the rotor is not operating, and at the same time, avoid the occurrence of problems due to the retention of bubbles, so that the spindle motor can be highly reliable Become.
[0050]
Further, in the disk drive device according to the present invention, the head is prevented from being damaged due to contact with the disk due to vibration during non-operation of the spindle motor, and at the same time, the problem caused by bubbles remaining in the bearing portion of the spindle motor. Occurrence is also avoided, so that a very stable and highly reliable disk drive device can be obtained.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional views showing a schematic configuration of a part of a conventional spindle motor and a bearing portion as a precondition of the present invention, and FIG. It is a top view which shows the shape of the spiral groove provided in a thrust bearing part.
FIG. 2 is a plan view showing the shape of a spiral groove according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view showing an application example of the dynamic pressure bearing of the present invention to a spindle motor.
FIG. 4 is a cross-sectional view schematically showing the internal configuration of the disk drive device.
[Explanation of symbols]
26, 28, S Thrust bearing
30, 32, R1 Radial bearing
SG, SG1, SG1A spiral groove
HG1 Herringbone groove

Claims (5)

A thrust bearing that generates dynamic pressure acting in one axial direction with respect to the oil held in the minute gap, and disposed radially inward of the thrust bearing and held in the minute gap In a dynamic pressure bearing comprising a radial bearing portion that generates a dynamic pressure acting in a radial direction on the oil that has been produced,
The thrust bearing portion is provided with a dynamic pressure generating groove array in the circumferential direction by a pump-in type spiral groove that induces a flow toward the radially inward side with respect to the oil as a dynamic pressure generating groove,
The radial bearing portion has a dynamic pressure generated by a herringbone groove having an unbalanced shape in the axial direction so that a maximum dynamic pressure generated with respect to the oil appears as a dynamic pressure generating groove in a biased manner toward the thrust bearing portion. The generation groove row is provided in the circumferential direction,
Between the thrust bearing portion and the radial bearing portion, the oil is continuously held in each minute gap without interruption, and forms a dynamic pressure generating groove array of the thrust bearing portion. a plurality of scan Pairaru groove Chi caries spiral groove, with provided so as to extend radially inwardly than the other spiral groove, the plurality of spiral grooves are arranged equiangularly,
Said another plurality of scan Pairaru groove you stretched radially inward side of the spiral groove, the width dimensions circumferential direction than said other spiral groove is provided on the large,
Between the radial bearing portion and the thrust bearing portion, a radially inwardly extending region filled with the oil is provided,
A plurality of scan Pairaru groove you stretched radially inwardly than the other spiral groove, the radially inwardly with extending from the inner end of the thrust bearing portion toward the region of the radially inward side A hydrodynamic bearing characterized by being provided over the entire radial region of the side region.   2. The hydrodynamic bearing according to claim 1, wherein an oil flow rate radially inward by the thrust bearing portion exceeds an oil flow rate in an axial direction due to pumping of the radial bearing portion. A shaft, a sleeve having a through-hole in which the shaft is rotatably inserted, and a bottom surface facing the upper end surface of the sleeve in the axial direction and extending radially outward from the outer peripheral surface of the shaft A spindle motor comprising: a rotor having a circular top plate fixed to a shaft;
Between the upper end surface of the sleeve and the bottom surface of the top plate facing the upper end surface in the axial direction, a minute gap for retaining oil is formed, and the minute gap is formed according to the rotation of the rotor. A thrust bearing portion is configured by providing a dynamic pressure generating groove for inducing fluid dynamic pressure in the retained oil,
Between the inner peripheral surface of the through hole of the sleeve and the outer peripheral surface of the shaft, a minute gap for retaining oil is formed, and the oil retained in the minute gap according to the rotation of the rotor. A radial bearing portion is configured by providing a dynamic pressure generating groove for inducing fluid dynamic pressure,
The minute gap formed between the upper end surface of the sleeve constituting the thrust bearing portion and the bottom surface of the top plate has substantially the same gap dimension from the inner diameter end side to the outer diameter end side of the minute gap. Is formed as
3. The spindle motor according to claim 1, wherein the hydrodynamic bearing including the thrust bearing portion and the radial bearing portion is the hydrodynamic bearing according to claim 1. A shaft, a pair of annular thrust plates projecting radially outward from the outer peripheral surface of the shaft, and a pair of thrusts facing each other in the axial direction of the pair of thrust plates via a minute gap A spindle motor comprising a surface and a hollow cylindrical sleeve formed with a radial inner peripheral surface that is continuous with the thrust surface and is radially opposed to the outer peripheral surface of the shaft via a minute gap,
Oil is held in a minute gap formed between one axial surface of the pair of thrust plates and the pair of thrust surfaces, and a dynamic pressure generating groove for inducing dynamic pressure in the oil is provided. Each of which constitutes a thrust bearing,
Oil is held in a minute gap formed between the outer peripheral surface of the shaft and the radial inner peripheral surface of the sleeve, and a dynamic pressure generating groove for inducing dynamic pressure in the oil is provided, thereby providing a radial bearing portion. Is configured in a pair spaced apart in the axial direction,
The minute gaps formed between one surface of the pair of thrust plates constituting the thrust bearing portion and the pair of thrust surfaces of the sleeve are respectively from the inner diameter end side to the outer diameter end side of the minute gap. Are formed to have approximately the same gap size,
The pair of thrust bearing portions and the pair of radial bearing portions constitute a pair of dynamic pressure bearings each including a pair of thrust bearing portions and a radial bearing portion, and each of the pair of dynamic pressure bearings is claimed in claim 1. Or a dynamic pressure bearing according to 2 above. 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 writing or reading information at a required position of the recording disk A disk drive device comprising:
5. The disk drive device according to claim 3, wherein the spindle motor is the spindle motor according to claim 3.

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