JP2003184867A - Dynamic pressure bearing device and spindle motor equipped with the bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means capable of discharging smoothly air bubbles generated in a thrust bearing gap. <P>SOLUTION: A thrust bearing surface and a thrust receiving surface are provided in either of or both of two members rotating relatively and lubricant fluid is filled in the thrust bearing gap between both surfaces and further a dynamic pressure generating groove is formed in at least either of the thrust bearing and thrust receiving surfaces, so that a thrust dynamic pressure bearing portion is constructed. At an outer peripheral side of the thrust dynamic pressure bearing portion, a sealing gap linking thereto is formed in an approximately axial line direction, so that an interface between lubricant fluid and air is formed in the sealing gap. In either of peripheral surfaces of the two members neighboring a connection between an outer peripheral clearance allowing gap of the thrust bearing gap and the sealing gap there is provided an agitating means for agitating lubricant fluid positioned in the connection and in the vicinity thereof. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device for supporting two members rotatably in a thrust direction by using a lubricating fluid such as oil, and a spindle motor using the same.

2. Description of the Related Art Conventionally, as a bearing of a spindle motor, in order to rotatably support two members such as a shaft member and a sleeve member, a fluid pressure of a lubricating fluid such as oil interposed between the two members. Various types of dynamic pressure bearing devices have been proposed. For the applicant of the present application, Japanese Patent Application No. 200
0-104042 (JP 2001-289243 A)
As shown in FIG. 1 and the like, the thrust dynamic pressure bearing portion and the radial dynamic pressure bearing portion adjacent to the thrust dynamic pressure bearing portion can be continuously filled with lubricating fluid so that both bearing portions can cooperate to support the load during rotation, We have proposed a bearing structure that prevents bubbles from accumulating at the boundary between both bearings. FIG. 8 shows a schematic configuration of a spindle motor 1 for driving a recording disk using this kind of dynamic pressure bearing device. Motor base 2 consisting of the base of the recording disk drive or a bracket fixed to this base
A cylindrical support wall 3 is integrally provided with the stator 4, and a stator 4 is externally fitted and fixed to the outer peripheral surface of the support wall 3. A cylindrical sleeve member 5 is fitted and fixed to the inner peripheral surface of the support wall 3, and a cap member 6 is provided on the lower surface of the motor base 2 so as to close the lower end opening of the support wall 3, and the cap member 6 and A cover member 7 is attached to the lower surface of the motor base 2 so as to cover the joint between this and the motor base 2.
The rotor 8 that rotates at a high speed with respect to the motor base 2 includes an inverted cup-shaped rotor hub 10 that holds a recording disk 9,
A shaft portion 11 having an upper end integrally fixed to a rotation center of a substantially disk-shaped upper wall portion 10a of the rotor hub 10, and a cylindrical peripheral wall portion 1 that hangs downward from an outer peripheral edge portion of the upper wall portion 10a.
The cylindrical rotor magnet 12 is fixed to the inner peripheral surface of the rotor 0b and faces the stator 4 in the radial direction with a predetermined gap.
The recording disk 9 is held by inserting the center hole of the recording disk 9 into the peripheral wall portion 10b of the rotor hub 10 and placing it on the flange portion 10c at the lower end of the peripheral wall portion 10b. It is fixed integrally. The upper wall portion 10a of the rotor hub 10 also serves as the thrust plate portion of the dynamic pressure bearing device, and the shaft portion 11 and the upper wall portion 10a constitute a shaft member that serves as a rotating side member of the dynamic pressure bearing device. Rotor 8
The shaft portion 11 of the shaft member 1 is fitted and inserted into the sleeve member 5, and
A pair of upper and lower radial bearing surfaces, which are the cylindrical outer peripheral surfaces of 1, respectively radially oppose the pair of upper and lower radial receiving surfaces, which are the cylindrical inner peripheral surfaces of the sleeve member 5, through radial bearing gaps 13, respectively, and a rotor hub. An annular thrust bearing surface, which is the lower surface of the upper wall portion 10a of the axial member 10, is axially opposed to an annular thrust receiving surface, which is the upper end surface of the sleeve member 5, with a thrust bearing gap 14 interposed therebetween. The lower end portion of the shaft portion 11 is located in a stepped recess 5a formed on the inner circumference of the lower end portion of the sleeve member 5, and the annular stopper 15 having a diameter larger than that of the shaft portion 11 is fitted to the lower end portion of the shaft portion 11. By housing this in the stepped recess 5a, the shaft 11 is prevented from coming off from the sleeve member 5. Between the pair of radial bearing gaps 13, an annular air intervening portion 16 having a larger dimension than the radial bearing gap 13 is provided, and a lubricating fluid such as oil is provided in the upper radial bearing gap 13 and the thrust bearing gap 14. 17 is continuously filled and held over both bearing gaps 13 and 14, and the lower radial bearing gap 13 is provided.
Also, the lubricating fluid 17 is filled and held. More specifically, the upper wall portion 1 surrounds the upper outer periphery of the sleeve member 5.
0a through a cylindrical inner circumferential surface of a circumferential projection 10d and a conical outer circumferential surface of the upper portion of the sleeve member 5 from an annular tapered sealing gap 18 formed substantially axially. Bearing gap 14 and upper radial bearing gap 1
3 through the upper radial bearing gap 13 of the air interposition part 16
The lubricating fluid 17 is continuously filled up to the portion facing the lower radial bearing gap 13 through the lower radial bearing gap 13 from the portion facing the lower radial bearing gap 13 of the air intervening portion 16. Lower end surface of shaft 11 and stopper 1
The space surrounded by 5 is continuously filled.
The lubricating fluid 16 in the thrust bearing gap 14 contacts external air at the gas-liquid interface formed in the sealing gap 17 on the outer peripheral side thereof, and the lubricating fluid 17 in both radial bearing gaps 13
The first air passages 18 in the radial direction, which are provided through the sleeve member 5 so as to communicate with each other through the air interposition portion 16, respectively.
And the lubricating fluid 17 in the lower radial bearing gap 13 is formed by the sleeve member 5 and the cap member 6 in contact with the external air through the vertical second air passage 19 formed by the sleeve member 5 and the support wall 3. It is in contact with the outside air through the radial third air passage 20 and the second air passage 19. On one or both of the radial bearing surface and the radial receiving surface forming the upper radial bearing gap 13, a dynamic pressure for moving the lubricating fluid 17 in the upper radial bearing gap 13 to the thrust bearing gap 14 side is axially generated. An upper radial dynamic pressure generating groove formed of an unbalanced herringbone-shaped groove is formed, which generates a radial load supporting pressure and a moving pressure in the thrust direction of the lubricating fluid 17 in the upper radial bearing gap 13. The upper radial dynamic pressure bearing portion is configured, and one or both of the radial bearing surface and the radial receiving surface forming the lower radial bearing gap 13 is provided with the lubricating fluid 17 of the radial bearing gap 13 For generating lower radial dynamic pressure consisting of herringbone-shaped grooves so that dynamic pressure is generated to move to the center side of There is formed, which causes the lower radial dynamic pressure bearing portion for generating a radial load supporting pressure is formed. Further, one or both of the thrust bearing surface and the thrust receiving surface forming the thrust bearing gap 14, in this example, the thrust receiving surface, the lubricating fluid 17 in the thrust bearing gap 14 is moved to the inner diameter side, that is, the upper radial bearing gap 13 side. A thrust dynamic pressure generating groove formed of a spiral groove is formed so as to generate a dynamic pressure that causes the radial bearing gap 13 to pass through the lubricating fluid 17 in the thrust bearing gap 14.
A thrust dynamic pressure bearing unit that generates moving pressure in the direction is configured. The lubricating fluid moving pressure of the upper radial dynamic pressure bearing portion and the lubricating fluid moving pressure of the thrust dynamic pressure bearing portion act so as to increase the pressure toward the boundary portion between the two dynamic pressure bearing portions, so that the levitation force with respect to the rotor 8 is increased. As a result, thrust direction support is realized. By the way, in the dynamic pressure bearing device using the liquid such as the oil as the lubricating fluid as described above, the rotating side member can be held in a non-contact state by the dynamic pressure effect at the time of high speed rotation, but the function at the time of non-rotation is Since there is no impact, the rotary member will freely move within the bearing gap if an external impact is applied. In particular, since there is no restraining force in the axial direction other than gravity and the magnetic force between the stator and the rotor magnet, when a disturbance is applied during non-rotation, the rotating member moves greatly. Normally, the radial bearing gap (the minute gap in the part that generates the dynamic pressure) is as narrow as several μm, but the thrust bearing gap (the minute gap in the part that generates the dynamic pressure) is as large as several tens μm, so If it moves within the range of the bearing gap, when the rotary member abruptly moves in the thrust direction, the pressure decreases due to the squeeze effect at a portion where the gap of the thrust dynamic pressure bearing portion expands, so-called cavitation occurs. That is, when the rotating member vibrates thrust with respect to the stationary member, the dynamic pressure fluctuation width ΔP of the narrowest portion (hill portion between adjacent grooves) in the thrust bearing gap where the flow resistance of the lubricating fluid is the largest becomes large. . When the fluctuation pressure P = P0−ΔP (generated when the gap is opened) from the static pressure P0 becomes a certain value or less, the air dissolved in the lubricating fluid 17 is vaporized and bubbles are generated. Bubbles are generated in the lubricating fluid not only when the motor is stopped, but
It is possible even when the motor is rotating. For example, at the outer peripheral end of the dynamic pressure generating groove formed on the thrust bearing surface or the thrust receiving surface of the thrust dynamic pressure bearing portion, a negative pressure portion is generated due to the relative rotation of the thrust bearing surface and the thrust receiving surface. However, this negative pressure may evaporate the air dissolved in the lubricating fluid and generate bubbles. The bubbles generated in this way try to move to a more stable location due to the amount of dynamic pressure associated with the amount of gap fluctuation in each part, the pressure difference due to surface tension, etc. The surface area is small and the energy is small, and it becomes stable. If these air bubbles are not smoothly discharged to the outside and stay in the bearing gap, they will grow together and grow to a large size, and in some cases will form a ring shape to occupy the main part of the bearing part and prevent oil film breakage (air ring). Wake up,
Not only will the normal bearing function not be exhibited, but there is also the risk of abnormal vibrations occurring or the parts coming into contact with each other and causing serious damage such as the seizure phenomenon. In the above dynamic pressure bearing device, the thrust bearing gap 14 and the upper radial bearing gap 13
In addition to the structure in which is directly connected, the lubricating fluid moving pressure of the upper radial dynamic pressure bearing part and the lubricating fluid moving pressure of the thrust dynamic pressure bearing part increase the pressure toward the boundary part of both dynamic pressure bearing parts. Since it is configured, the bubbles trying to stay in this boundary portion act so as to move to the low pressure side, that is, in the radial outer circumferential direction of the thrust dynamic pressure bearing portion, and are discharged to the outside through the sealing gap 18. It will be.

By the way, the bearing gap in the dynamic pressure bearing device is required to maintain a minute gap in a portion that generates dynamic pressure, that is, a portion that functions as a bearing, but a portion excluding the dynamic pressure generating portion. That is, the inner peripheral edge and the outer peripheral edge of the thrust bearing gap 14 and the upper and lower edges of the upper and lower radial bearing gaps 13 have a gap dimension of a portion that does not function as a bearing in order to reduce loss due to viscous resistance of the lubricating fluid. It is made larger than the bearing gap. For example, in the dynamic pressure bearing device shown in FIG.
As shown in FIG. 9, the upper end surface of the outer peripheral portion of the sleeve member 5 corresponding to the outer peripheral side of the thrust bearing gap 14 is chamfered to form a relief surface 5 b. An escape gap 21 is formed in which the gap size continuously increases toward the radially outer side. However, in such a bearing structure, the clearance for clearance 21 is interposed between the thrust bearing clearance 14 and the sealing clearance 18, and the thrust bearing clearance 1
4 is arranged in a state where the escape gap 21 and the seal gap 18 which are continuous with each other are substantially orthogonal to each other. In addition, the seal gap 18 needs to be formed in a tapered shape so as to widen in the direction away from the bearing gap. Since the clearance of the connecting portion 22 between the clearance for clearance 21 and the clearance for sealing 18 is unavoidably narrow, as shown by the arrow in FIG. Large vortices of the lubricating fluid 17 are independently generated in the gap 18 and the gap 18, respectively.
In the escape gap 21, the lubricating fluid 17 is in contact with the wall surface of the rotor hub 10, and therefore the rotor 8
With the rotation, the lubricating fluid 17 near the wall surface rotates at the same speed as the rotor 8 and receives a large centrifugal force, so that the lubricating fluid 17 in this portion faces the upper side outward and the lower side inward (clockwise in FIG. 9). Vortex 1 is generated. On the other hand, in the sealing gap 18, as the rotor 8 rotates, the lubricating fluid 17 in contact with the inner wall surface 18x of the circumferential protrusion 10d facing the sealing gap 18 of the rotor hub 10 also rotates at substantially the same flow rate. But sleeve 5
Since the tapered outer peripheral surface 18y facing the sealing gap 18 is a stationary wall surface, the flow velocity of the lubricating fluid 17 contacting this portion is zero. Since the sealing gap 18 becomes larger as it goes downward, the lubricating fluid 17 below the axial center line of the sealing fluid 18 goes downward as compared with the lubricating fluid 17 near the outer peripheral surface 18y on the upper side of the sealing gap 18. As a result of the increase in the pressure gradient and the flow velocity, the lubricating fluid 17 in the sealing gap 18 generates a vortex 2 in which the inner peripheral side is directed downward and the outer peripheral side is directed upward (counterclockwise in FIG. 9). . Here, as described above, the bubbles generated in the lubricating fluid 17 in the bearing gap move in the radial outer circumferential direction of the thrust dynamic pressure bearing portion having a low pressure when the motor rotates, but the bubbles are generated in the flow of the vortex 1. Although it moves by riding, it cannot be discharged to the outside unless it moves on the lower vortex 2. As a result of the two vortices mentioned above having their own vortex flow, it is difficult for bubbles to transfer from vortex 1 to vortex 2,
In addition, since the opening direction of the sealing gap 18 is opposite to the gravity, and the buoyancy applied to the bubbles is applied in the opposite direction to the opening,
Bubbles will be more difficult to be discharged. As a result, the air ring described above is likely to occur. The present invention is
The present invention has been made in view of the above problems of the conventional technology, and its purpose is particularly to improve the dynamic performance of the structure in which the sealing gap is connected to the outer peripheral end of the thrust bearing gap in the substantially axial direction. It is an object of the present invention to provide a means for smoothly discharging bubbles generated in the bearing gap in the pressure bearing device.

In order to achieve the above-mentioned object, in the present invention, one and the other of the two members which rotate relative to each other are thrust bearing surfaces orthogonal to the axis of rotation, and the thrust bearing surfaces are opposed thereto. A thrust bearing surface for filling the thrust bearing gap between the thrust bearing surface and the thrust bearing surface with a lubricating fluid, and generating a supporting pressure for the lubricating fluid on at least one of the thrust bearing surface and the thrust bearing surface. A thrust dynamic pressure bearing portion is formed by forming a groove for dynamic pressure generation, and the gap size is expanded on the outer peripheral side of the thrust dynamic pressure bearing portion as it goes away from the thrust bearing gap. A hydrodynamic bearing device which is formed substantially in the axial direction and in which the interface between the lubricating fluid filled in the thrust bearing gap and air is formed in the sealing gap. Gap for relief formed on the outer periphery of the thrust bearing gap (clearance gap dimension than the thrust bearing gap communicates the thrust bearing clearance and the sealing gap is greater)
An agitating means for agitating the lubricating fluid in the connection part and its vicinity is provided on the peripheral surface of either of the two members facing the connection part between the connection part and the sealing gap (claim 1). In the dynamic pressure bearing device having such a configuration,
When the two members are relatively rotated, the connecting portion between the escape gap and the sealing gap, which communicates with the outer circumference of the thrust bearing gap, and the lubricating fluid in the vicinity thereof are formed on the peripheral surface of the member facing the connecting portion. Even when vortexes are formed independently in the respective lubricating fluids in the escape gap and the seal gap by being agitated by the action of the agitating means, the flow of these vortices is disturbed at the connecting portion. Bubbles are generated in the lubricating fluid in the thrust minute gap and are transferred in the outer circumferential direction of the thrust dynamic pressure bearing part, and when they are transferred to the relief gap, the bubbles that move according to the vortex flow of the lubricating fluid in the relief gap. Often moves to the vortex of the lubricating fluid in the sealing gap by taking advantage of the turbulence of the vortex flow in the connecting portion and its vicinity, and when the bubbles transfer to the vortex of the lubricating fluid in the sealing gap, The bubbles move according to the vortex of the lubricating fluid in the sealing gap and are discharged to the outside from the gas-liquid interface of the lubricating fluid. In this case, the sealing gap can function in the same manner as above regardless of whether it is opened in the gravity direction or in the antigravity direction. Further, in the above-mentioned dynamic pressure bearing device, when the sealing gap is expanded by tapering radially inward (Claim 2), the inner side of the sealing gap faces the gas-liquid interface and the outer side is connected. A vortex of the lubricating fluid is generated toward the portion, and the vortex of the lubricating fluid in the escape gap is in the opposite direction and becomes independent of each other.However, even in such a case, due to the action of the stirring means described above. Bubbles can be moved between both vortices, and bubbles are discharged. Further, in the above dynamic pressure bearing device, the stirring means may be composed of a plurality of protrusions provided on the surface of any member facing the connecting portion and arranged in the circumferential direction (claim 3), or the connecting portion. It may be configured by a plurality of grooves or dents provided in the surface of any member facing the portion and arranged in the circumferential direction (claim 4). In such a configuration, the relative rotation of the two members causes the protrusions, grooves, or depressions of the members facing the connecting portion to act as resistance, and the lubricating fluid in the connecting portion is agitated to connect the two vortex flows. It will be disturbed in the area and its vicinity. Further, the shape of the sealing gap, the gap size, the angle, or the stirring means may be asymmetric with respect to the rotation direction about the axis (claim 5). The relative rotation of the two members not only disturbs the flow of the lubricating fluid at the connecting portion due to the stirring action of the stirring means described above, but also causes the asymmetrical shape to make the pressure distribution of the lubricating fluid asymmetric in the circumferential direction. It becomes a three-dimensional flow, the turbulence of the vortex is promoted, and the discharging action of the bubbles is promoted. Then, using the dynamic bearing device as described above, one of the two members is integrally provided with the rotor magnet on the rotating side, and the other is fixed on the stator magnet at a position facing the rotor magnet. (Claim 6), it is possible to provide a spindle motor that avoids problems such as deterioration of dynamic pressure bearing characteristics due to accumulation of air bubbles and generation of air rings, occurrence of vibration, and start failure. Becomes

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a spindle motor according to the present invention will be described below with reference to the drawings. Figure 1
6 shows essential parts when the present invention is applied to the recording disk driving spindle motor described in FIG. 8, and the same reference numerals as those used above denote the same or corresponding ones. To do. First, FIGS. 1 and 2 show the first embodiment, which is different from those described with reference to FIGS. 8 and 9 in that the sealing gap 18 and the escape gap are formed on the outer peripheral surface of the sleeve member 5 as the fixed member. The point is that an agitating means including a plurality of protrusions 23 is provided on the outer peripheral surface 5c of the connecting portion which faces the connecting portion 22 with respect to 21. This plurality of protrusions 2
3 are arranged on the outer peripheral surface 5c of the connecting portion at substantially equal intervals in the circumferential direction. In the hydrodynamic bearing device having such a configuration, when the rotor 8 rotates, as described above, large vortices of the lubricating fluid 17 are independently generated in the relief gap 21 and the sealing gap 18. On the other hand, as the inner wall surface 18x of the circumferential projection 10d facing the connecting portion 22 is rotationally moved, the lubricating fluid 17 in contact therewith moves, and the outer peripheral surface of the connecting portion of the sleeve member 5 that is dragged by the inner surface 18x and faces the connecting portion 22. 5c
When the lubricating fluid 17 in the vicinity also moves, the movement of the lubricating fluid 17 in this portion is hindered by the plurality of projections 23 protruding from the outer peripheral surface 5c of the connecting portion, and the flow of the lubricating fluid 17 is disturbed, so that the connecting portion 22 And the lubricating fluid 17 in the vicinity thereof is agitated. As a result, as shown in FIG.
The flow of the vortex 1 of the lubricating fluid 17 and the flow of the vortex 2 of the lubricating fluid 17 in the sealing gap 17 are disturbed in the vicinity of the connecting portion 22, respectively, and the lubricating fluids 17 of the respective vortices 1 and 2 are mixed in the vicinity of the connecting portion 22. Will be done. Therefore, even if the bubbles are mixed in the lubricating fluid 17 in the thrust bearing gap 14 and are transferred to the escape gap 21 and ride on the flow of the vortex 1, the bubbles follow the flow of the vortex 1 and the vicinity of the connecting portion 22. When it reaches, the air is dispersed in the connection part 22 and its vicinity, and some of the bubbles come to ride on the flow of the vortex 2, which is carried to the gas-liquid interface in the sealing gap 18 according to the flow of the vortex 2 and Will be discharged to.
In this case, all the bubbles riding on the flow of the vortex 1 do not transfer to the vortex 2 in a short time, but since the lubricating fluid 17 is constantly stirred in the connecting portion 22, the bubbles riding on the flow of the vortex 1 Are gradually taken into the vortex 2 and sequentially discharged to the outside. FIG. 3 shows a second embodiment of the present invention. In this embodiment, a plurality of recesses (recesses) are formed on the outer peripheral surface 5c of the connecting portion facing the connecting portion 22 between the sealing gap 18 and the clearance 21 on the outer peripheral surface of the sleeve member 5.
By arranging and arranging 24 at substantially equal intervals in the circumferential direction, a stirring means for stirring the connecting portion 22 and the lubricating fluid 17 in the vicinity thereof is configured. Also in the second embodiment, as in the case of the first embodiment, with the rotational movement of the lubricating fluid 17 in the vicinity of the outer peripheral surface 5c of the connecting portion of the sleeve member 5,
The lubricating fluid 17 is disturbed when passing through the recess 24 of the outer peripheral surface 5c of the connecting portion, and the connecting portion 22 and the lubricating fluid 1 in the vicinity thereof are disturbed.
Since 7 is agitated, the bubbles mixed in the vortex 1 of the lubricating fluid 17 in the escape gap 21 are easily transferred to the vortex 2 of the lubricating fluid 17 in the sealing gap 18, and the gas-liquid interface in the sealing gap 18 is increased. Will be discharged to the outside. In the third embodiment shown in FIG. 4, in place of the projections 23 and the recesses 24 described above, a large number of minute dimples (dimples) 25 are formed in order to facilitate the processing on the outer peripheral surface 5c of the connecting portion of the sleeve member 5. The recess 25 is formed on almost the entire outer peripheral surface 5c of the connecting portion, and the same effect as described above is exhibited. In the fourth embodiment shown in FIG. 5 and FIG. 6, a plurality of dynamic pressure grooves (spiral grooves) 43 having a pump-out function as stirring means are formed on the outer peripheral surface 5c of the connecting portion of the sleeve member 5. , The lubricating fluid 17 in the connecting portion 22
In addition, a moving pressure toward the sealing gap 18 side is generated. Therefore, the lubricating fluid 17 in the connecting portion 22 and its vicinity moves toward the sealing gap 18 side while being stirred by the action of the dynamic pressure groove 43, and as a result,
A flow of the lubricating fluid 17 is newly generated so that the vortex 1 of the escape gap 21 enters the vortex 2 of the sealing gap 18, and bubbles mixed with the lubricating fluid 17 moving according to the flow of the vortex 1 cause the flow of the vortex 2 to flow. The lubricant easily moves to the lubricating fluid 17, and the bubbles are discharged to the outside from the gas-liquid interface of the sealing gap 18. In this case, the dynamic pressure grooves 26 formed on the outer peripheral surface 5c of the coupling portion are arranged at equal intervals in the circumferential direction as shown in FIG. 6 (a), and as shown in FIG. 6 (b). The grooves 26 may be provided unevenly in the circumferential direction, and as shown in FIG. 6C, one dynamic pressure groove 26 may be formed over the entire circumference in the circumferential direction. Particularly in the case of FIG. 6B, the dynamic pressure groove 2
Since 6 are provided unevenly in the circumferential direction, the vortex 1 of the lubricating fluid 27
It is possible to further disturb the flow of the lubricant 17 while invading the vortex 2 into the region of the vortex 2. Further, in the case of FIG. 6C, the pressure distribution can be made asymmetric in the circumferential direction. Becomes a three-dimensional flow, the stirring action is effectively performed, and the effect of the present invention is increased. Although the embodiments of the hydrodynamic bearing device and the spindle motor using the same according to the present invention have been described above, the present invention is not limited to such embodiments and various modifications can be made without departing from the scope of the present invention. Can be modified. For example, in the above-described embodiment of the present invention, the protrusion 23 and the recess 2 as the stirring means
4, the recess 25 and the dynamic pressure groove 26 are formed in the sleeve member 5 as the fixed side member, but the invention is not limited to this, and the rotating side member facing the connecting portion 22, that is, the circumferential protrusion of the rotor hub 10a. It may be formed on the inner wall surface 18x of 10d, or may be formed on both the stationary side member and the rotating side member. It is also desirable that these agitating means are provided unevenly in the circumferential direction to make the pressure distribution asymmetric in the circumferential direction, and it is effective to make the axial asymmetry. further,
In addition to the above-mentioned stirring means, as shown in FIG. 7, the taper angle θ of the sealing gap 18 is uneven in the circumferential direction (θ1 to θ1).
θ2) or the radial gap size G of the connecting portion 22 can be made nonuniform (G1 to G2) in the circumferential direction.
Due to the non-uniform pressure distribution in the circumferential direction at
The effect of more effective stirring can be expected. Further, in the above-described embodiment, the outer peripheral side of the thrust bearing gap is formed in the axial direction so that the sealing gap communicating with the thrust bearing gap is widened downward, but is not limited to this. Instead, the present invention can be similarly applied to the case where the gap for sealing has a shape in which the size of the gap widens upward.

As described above, according to the hydrodynamic bearing device of the present invention, the lubricating fluid in the vicinity of the connecting portion between the escape gap and the sealing gap, which communicates with the outer periphery of the thrust bearing gap, and the lubricating fluid in the vicinity of the gap. The lubricating fluid is agitated by the action of the agitating means formed on the peripheral surface of the member facing the connecting portion, and the vortex flow of the lubricating fluid generated in each of the escape gap and the sealing gap is disturbed in the connecting portion. Therefore, the bubbles in the lubricating fluid transferred from the thrust bearing gap to the escape gap can be moved to the vortex of the lubricating fluid in the sealing gap, and can be discharged to the outside. It is possible to prevent air bubbles from accumulating due to air bubbles remaining, to avoid adverse effects such as generation of vibration and wear of bearing members, and to obtain stable bearing performance. Then, using the above-mentioned dynamic pressure bearing device,
By having one of the two members as the rotating side and integrally including the rotor magnet and the other as the fixed side and having the stator at a position facing the rotor magnet, the other member is relatively disposed with respect to the one member. A rotating spindle motor can be configured, and a spindle motor that avoids deterioration of dynamic pressure bearing characteristics or deterioration of rotation characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part showing a first embodiment of the present invention, in which a relief gap and a part of a sealing gap formed between a sleeve of a spindle motor and a rotor hub are enlarged.

FIG. 2 is a perspective view of a part of the sleeve shown in FIG.

FIG. 3 is a perspective view of a part of the sleeve showing the second embodiment of the present invention.

FIG. 4 is a perspective view of a part of the sleeve showing the third embodiment of the present invention.

FIG. 5 is a perspective view of a part of the sleeve showing the fourth embodiment of the present invention.

6 is a development view illustrating a dynamic pressure groove on the outer peripheral surface of the coupling portion of the sleeve, FIG. 6A is an example corresponding to FIG. 5, and FIG.
Is a modification, and (C) is another modification.

FIG. 7 is a partial sectional view of a rotor hub and a sleeve showing another embodiment of the present invention.

FIG. 8 is a sectional view of a spindle motor provided with a dynamic pressure bearing device which is the basis of the present invention.

FIG. 9 is a partial cross-sectional view of a conventional dynamic pressure bearing device.

[Explanation of symbols]

1 Spindle motor 4 stator 5 Sleeve member 10 rotor hub 12 rotor magnet 91B Thrust bearing surface 10 Shaft member 11 rotor magnet 14 Thrust bearing clearance 17 Lubricating fluid 18 Seal gap 21 Clearance gap 22 Connection 23 Protrusion 24 recess 25 hollows 26 Dynamic pressure groove

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[Procedure amendment]

[Submission date] December 13, 2001 (2001.12.
13)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Dynamic bearing device and spindle motor using the same

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device for supporting two members rotatably in a thrust direction by using a lubricating fluid such as oil, and a spindle motor using the same.

[0002]

2. Description of the Related Art Conventionally, as a bearing of a spindle motor, in order to rotatably support two members such as a shaft member and a sleeve member, a fluid pressure of a lubricating fluid such as oil interposed between the two members. Various types of dynamic pressure bearing devices have been proposed. For the applicant of the present application, Japanese Patent Application No. 200
0-104042 (JP 2001-289243 A)
As shown in FIG. 1 and the like, the thrust dynamic pressure bearing portion and the radial dynamic pressure bearing portion adjacent to the thrust dynamic pressure bearing portion can be continuously filled with lubricating fluid so that both bearing portions can cooperate to support the load during rotation, We have proposed a bearing structure that prevents bubbles from accumulating at the boundary between both bearings.

FIG . 8 shows a schematic structure of a recording disk driving spindle motor 1 using this type of dynamic pressure bearing device. A cylindrical support wall 3 is integrally provided on a motor base 2 including a base of a recording disk drive or a bracket fixed to the base, and a stator 4 is externally fitted and fixed to an outer peripheral surface of the support wall 3. A cylindrical sleeve member 5 is fitted and fixed to the inner peripheral surface of the support wall 3, and a cap member 6 is provided on the lower surface of the motor base 2 so as to close the lower end opening of the support wall 3, and the cap member 6 and A cover member 7 is attached to the lower surface of the motor base 2 so as to cover the joint between this and the motor base 2.

The rotor 8 which rotates at a high speed with respect to the motor base 2 has an inverted cup-shaped rotor hub 10 which holds a recording disk 9 and a substantially disc-shaped upper wall portion 10 of the rotor hub 10.
a shaft portion 11 having an upper end integrally fixed to the center of rotation of a, and an inner peripheral surface of a cylindrical peripheral wall portion 10b that hangs downward from the outer peripheral edge portion of the upper wall portion 10a. The recording disk 9 has a cylindrical rotor magnet 12 that faces in the radial direction with a gap therebetween, and the recording disk 9 has its center hole fitted into the peripheral wall portion 10 b of the rotor hub 10.
It is held by being placed on the collar portion 10c at the lower end of 0b, and is integrally fixed to the rotor hub 10 by a clamp (not shown). The upper wall portion 10a of the rotor hub 10 also serves as the thrust plate portion of the hydrodynamic bearing device, and the shaft portion 11 and this upper wall portion 10a
And constitute a shaft member which serves as a rotation side member of the dynamic pressure bearing device.

[0005] shaft portion 11 of the rotor 8 are fitted inside the sleeve member 5, upper and lower pair of upper and lower radial bearing surface is a cylindrical outer peripheral surface of the shaft portion 11 is cylindrical inner peripheral surface of the sleeve member 5 Of the rotor hub 10 and the radial receiving surfaces of the rotor hub 10 in the radial direction via the radial bearing gaps 13.
An annular thrust bearing surface, which is the lower surface of the upper wall portion 10a, axially faces the annular thrust receiving surface, which is the upper end surface of the sleeve member 5, with a thrust bearing gap 14 in between. Shaft 1
The lower end of the shaft member 1 is located in a stepped recess 5a formed on the inner circumference of the lower end of the sleeve member 5, and an annular stopper 15 having a diameter larger than that of the shaft 11 is fitted to the lower end of the shaft 11. By being accommodated in the stepped recess 5a, the shaft portion 11 is prevented from coming off from the sleeve member 5.

Between the pair of radial bearing gaps 13 is provided an annular air intervening portion 16 having a larger gap size than the radial bearing gap 13, and oil or the like is provided in the upper radial bearing gap 13 and thrust bearing gap 14. Lubricating fluid 1
7 is continuously filled and held in both bearing gaps 13 and 14, and a lubricating fluid 17 is also filled and held in the lower radial bearing gap 13. More specifically, the upper wall portion 10a surrounds the upper outer periphery of the sleeve member 5.
From the annular tapered sealing gap 18 formed substantially in the axial direction between the cylindrical inner peripheral surface of the circumferential projection 10d integrally provided on the upper surface and the conical outer peripheral surface of the upper portion of the sleeve member 5. Through the gap 14 and the upper radial bearing gap 13, the lubricating fluid 17 is continuously filled up to the portion of the air interposition part 16 that faces the upper radial bearing gap 13, and the lubricating fluid 17 faces the lower radial bearing gap 13 of the air interposition part 16. From the portion, through the lower radial bearing gap 13, the stepped recess 5a,
The space surrounded by the cap member 6, the lower end surface of the shaft portion 11 and the stopper 15 is continuously filled.

[0007] Lubricating Fluid 1 in the thrust bearing gap 14
6 is in contact with the external air at the gas-liquid interface formed in the sealing gap 17 on the outer peripheral side thereof, and the lubricating fluid 17 in both radial bearing gaps 13 is applied to the sleeve member 5 via the air intervening portion 16 so as to communicate therewith. Transparent radial first
1 through the air passage 18 and the vertical second air passage 19 formed by the sleeve member 5 and the support wall 3,
Further, the lubricating fluid 17 in the lower radial bearing gap 13
Is in contact with the outside air through the radial third air passage 20 and the second air passage 19 formed by the sleeve member 5 and the cap member 6.

[0008] One or both of the radial bearing surface and the radial receiving surface to form an upper radial bearing gap 13, so that the dynamic pressure to move the lubricant 17 of the upper radial bearing gap 13 in the thrust bearing gap 14 side is generated An upper radial dynamic pressure generating groove composed of an axially unbalanced herringbone-shaped groove is formed to generate a radial load supporting pressure and also to form an upper radial bearing gap 1
An upper radial dynamic pressure bearing portion for generating a moving pressure in the thrust direction is formed in the lubricating fluid 17 of No. 3, and one or both of the radial bearing surface and the radial receiving surface forming the lower radial bearing gap 13 are formed. , A lower radial dynamic pressure generating groove formed of a herringbone-shaped groove is formed so as to generate a dynamic pressure for moving the lubricating fluid 17 in the radial bearing gap 13 to the center side of the radial bearing gap 13, thereby supporting the radial load. A lower radial dynamic pressure bearing unit that generates pressure is configured.

Further, one or both of the thrust bearing surface and the thrust receiving surface that forms a thrust bearing gap 14,
In this example, the lubricating fluid 17 in the thrust bearing gap 14 is applied to the thrust receiving surface on the inner diameter side, that is, the upper radial bearing gap 13.
A thrust dynamic pressure generating groove formed of a spiral groove is formed so as to generate a dynamic pressure for moving the bearing to the side.
A thrust dynamic pressure bearing portion that generates moving pressure in three directions is configured. The lubricating fluid moving pressure of the upper radial dynamic pressure bearing portion and the lubricating fluid moving pressure of the thrust dynamic pressure bearing portion act so as to increase the pressure toward the boundary portion between the two dynamic pressure bearing portions, so that the levitation force with respect to the rotor 8 is increased. As a result, thrust direction support is realized.

In the hydrodynamic bearing device using a liquid such as oil as a lubricating fluid as described above, the rotary member can be held in a non-contact state by the dynamic pressure effect at high speed rotation, but at the time of non-rotation. Since it does not have such a function, if a shock is applied from the outside, the rotary member will move freely within the bearing clearance. In particular, since there is no restraining force in the axial direction other than gravity and the magnetic force between the stator and the rotor magnet, when a disturbance is applied during non-rotation, the rotating member moves greatly.

[0011] Normally, the radial bearing gap (small gap portion for generating the dynamic pressure) is several μm and narrow (small gap portion for generating the dynamic pressure) thrust bearing gap is several tens μm
Therefore, if the rotating side member moves within the range of this bearing gap, if the rotating side member suddenly moves in the thrust direction,
At a place where the gap of the thrust dynamic pressure bearing portion is widened, the pressure decreases due to the squeeze effect and so-called cavitation occurs. That is, when the rotating member vibrates thrust with respect to the stationary member, the dynamic pressure fluctuation width ΔP of the narrowest portion (hill portion between adjacent grooves) in the thrust bearing gap where the flow resistance of the lubricating fluid is the largest becomes large. . Static pressure P0
Fluctuating pressure from P = P0-ΔP (occurs when the gap opens)
When the value becomes less than a certain value, the air dissolved in the lubricating fluid 17 is vaporized and bubbles are generated.

The bubbles may be generated in the lubricating fluid not only when the motor is stopped, but also when the motor is rotating. For example, at the outer peripheral end of the dynamic pressure generating groove formed on the thrust bearing surface or the thrust receiving surface of the thrust dynamic pressure bearing portion, a negative pressure portion is generated due to the relative rotation of the thrust bearing surface and the thrust receiving surface. However, this negative pressure may evaporate the air dissolved in the lubricating fluid and generate bubbles.

The bubbles thus generated try to move to a more stable place due to the amount of dynamic pressure associated with the amount of gap variation in each portion, the pressure difference due to surface tension, and the like.
And the small bubbles are connected to each other, and the total surface area is small and the energy is small, and it becomes a stable state. If these air bubbles are not smoothly discharged to the outside and stay in the bearing gap, they will grow together and grow to a large size, and in some cases will form a ring shape to occupy the main part of the bearing part and prevent oil film breakage (air ring). Not only does this cause the bearing to fail to function normally, but there is also the danger that abnormal vibrations will occur and members will come into contact with each other, causing serious damage such as a seizure phenomenon.

In the above dynamic pressure bearing device, the thrust bearing gap 14 and the upper radial bearing gap 13 are directly connected to each other, and the lubricating fluid moving pressure of the upper radial dynamic pressure bearing portion and the thrust dynamic pressure bearing are provided. Since the lubricating fluid moving pressure of the portion is configured to increase the pressure toward the boundary portion of both the dynamic pressure bearing portions, the bubbles that try to stay in this boundary portion are on the low pressure side, that is, the thrust dynamic pressure bearing portion. It acts so as to move in the radial outer circumferential direction, and is discharged to the outside through the sealing gap 18.

[0015]

By the way, the bearing gap in the dynamic pressure bearing device is required to maintain a minute gap in a portion that generates dynamic pressure, that is, a portion that functions as a bearing, but a portion excluding the dynamic pressure generating portion. That is, the inner peripheral edge and the outer peripheral edge of the thrust bearing gap 14 and the upper and lower edges of the upper and lower radial bearing gaps 13 have a gap dimension of a portion that does not function as a bearing in order to reduce loss due to viscous resistance of the lubricating fluid. It is made larger than the bearing gap. For example, in the dynamic pressure bearing device shown in FIG.
As shown in FIG. 9, the upper end surface of the outer peripheral portion of the sleeve member 5 corresponding to the outer peripheral side of the thrust bearing gap 14 is chamfered to form a relief surface 5 b. An escape gap 21 is formed in which the gap size continuously increases toward the radially outer side.

[0016] However, in such a bearing structure, relief for clearance 21 is interposed between the thrust bearing gap 14 and the sealing gap 18, yet a relief for clearance 21 continuous to the thrust bearing gap 14 seal The clearance 18 and the sealing clearance 18 are arranged so as to be substantially orthogonal to each other. In addition, the sealing clearance 18 needs to be formed in a tapered shape so as to widen in the direction away from the bearing clearance. Since the gap between the connecting portion 22 and 18 is inevitably narrowed, as shown by the arrow in FIG. 9, when the rotor 8 rotates, a large amount of the lubricating fluid 17 is contained in the escape gap 21 and the sealing gap 18, respectively. Vortices are generated independently.

In the relief gap 21, the lubricating fluid 17 is in contact with the wall surface of the rotor hub 10. Therefore, as the rotor 8 rotates, the lubricating fluid 17 near the wall surface rotates at the same speed as the rotor 8 and a large centrifugal force is applied. Upon receiving the force, the lubricating fluid 17 in this portion generates the vortex 1 in which the upper side is directed outward and the lower side is directed inward (which is the clockwise direction in FIG. 9). On the other hand, in the sealing gap 18, as the rotor 8 rotates, the lubricating fluid 17 in contact with the inner wall surface 18x of the circumferential protrusion 10d facing the sealing gap 18 of the rotor hub 10 also rotates at substantially the same flow rate. However, since the tapered outer peripheral surface 18y of the sleeve 5 facing the sealing gap 18 is a stationary wall surface, the flow velocity of the lubricating fluid 17 contacting this portion is zero. Since the sealing gap 18 becomes larger as it goes downward, the lubricating fluid 1 that is close to the outer peripheral surface 18y on the upper side of the sealing gap 18
7, the lubricating fluid 17 below the axis of the shaft has a larger pressure gradient / flow velocity as it goes downward, and as a result, the lubricating fluid 17 in the sealing gap 18 has an inner peripheral side facing downward and an outer peripheral side facing upward. A vortex 2 that is directed (becomes a counterclockwise direction in FIG. 9) is generated.

[0018] Here, as described above, but air bubbles generated in the lubricating fluid 17 in the bearing gap moves radially outer periphery of the lower thrust dynamic pressure bearing portion of the pressure when the motor rotates, the bubble is the eddy 1 However, it cannot be discharged to the outside unless it moves on the lower vortex 2. As a result of the two vortices described above having their own vortex flow, it is difficult for bubbles to transfer from vortex 1 to vortex 2. In addition, the opening direction of the sealing gap 18 is opposite to the gravity, and the buoyancy applied to the bubbles is Bubbles are more difficult to be discharged because they are added in the direction opposite to the opening. As a result, the air ring described above is likely to occur.

The present invention has been made in view of the above problems of the prior art, and its object is to seal the outer peripheral end of the thrust bearing gap substantially in the axial direction. An object of the present invention is to provide a means for smoothly discharging bubbles generated in the bearing gap in a dynamic pressure bearing device having a structure in which the gaps are connected.

[0020]

In order to achieve the above-mentioned object, in the present invention, one and the other of the two members which rotate relative to each other are thrust bearing surfaces orthogonal to the axis of rotation, and the thrust bearing surfaces are opposed thereto. A thrust bearing surface for filling the thrust bearing gap between the thrust bearing surface and the thrust bearing surface with a lubricating fluid, and generating a supporting pressure for the lubricating fluid on at least one of the thrust bearing surface and the thrust bearing surface. A thrust dynamic pressure bearing portion is formed by forming a groove for dynamic pressure generation, and the gap size is expanded on the outer peripheral side of the thrust dynamic pressure bearing portion as it goes away from the thrust bearing gap. A hydrodynamic bearing device which is formed substantially in the axial direction and in which the interface between the lubricating fluid filled in the thrust bearing gap and air is formed in the sealing gap. Gap for relief formed on the outer periphery of the thrust bearing gap (clearance gap dimension than the thrust bearing gap communicates the thrust bearing clearance and the sealing gap is greater)
An agitating means for agitating the lubricating fluid in the connection part and its vicinity is provided on the peripheral surface of either of the two members facing the connection part between the connection part and the sealing gap (claim 1).

In the hydrodynamic bearing device having such a structure, when the two members are relatively rotated, the connecting portion between the escape gap and the sealing gap, which communicates with the outer periphery of the thrust bearing gap, and the connecting portion. In the case where the lubricating fluid in the vicinity is agitated by the action of the agitating means formed on the peripheral surface of the member facing the connecting portion, and vortices are independently formed in the respective lubricating fluids of the escape gap and the sealing gap. Even if there is, the flow of these vortices is disturbed at the connecting portions. Bubbles are generated in the lubricating fluid in the thrust minute gap and are transferred in the outer circumferential direction of the thrust dynamic pressure bearing part, and when they are transferred to the relief gap, the bubbles that move according to the vortex flow of the lubricating fluid in the relief gap. Often moves to the vortex of the lubricating fluid in the sealing gap by taking advantage of the turbulence of the vortex flow in the connecting portion and its vicinity, and when the bubbles transfer to the vortex of the lubricating fluid in the sealing gap, The bubbles move according to the vortex of the lubricating fluid in the sealing gap and are discharged to the outside from the gas-liquid interface of the lubricating fluid. In this case, the sealing gap can function in the same manner as above regardless of whether it is opened in the gravity direction or in the antigravity direction.

Further , in the above-mentioned dynamic pressure bearing device, when the sealing gap is expanded by tapering radially inward (claim 2), the inner peripheral side of the sealing gap faces the gas-liquid interface. A vortex of the lubricating fluid is generated on the outer peripheral side toward the connecting portion, and the vortex of the lubricating fluid in the escape gap is in the opposite direction to be independent from each other. Even in such a case, the stirring means described above is also used. By the action of, the bubbles can be moved between both vortices, and the bubbles are discharged.

Furthermore, in the dynamic pressure bearing device, the stirring means may be constituted of a plurality of projections arranged in a protrusively provided to the circumferential direction on the surface of any member facing the connecting portion (claim 3) Alternatively, it may be constituted by a plurality of grooves or depressions which are provided in the surface of any member facing the connecting portion and are arranged in the circumferential direction (claim 4). With such a configuration,
Due to the relative rotation of the two members, the protrusions, grooves, or dents of the members facing the connecting portion act as resistance to stir the lubricating fluid in the connecting portion, and the two vortex flows are disturbed in the connecting portion and in the vicinity thereof. Will be.

Further , the shape of the sealing gap, the gap size, the angle, or the stirring means may be asymmetric with respect to the rotation direction about the axis (claim 5). The relative rotation of the two members not only disturbs the flow of the lubricating fluid at the connecting portion due to the stirring action of the stirring means described above, but also causes the asymmetrical shape to make the pressure distribution of the lubricating fluid asymmetric in the circumferential direction. It becomes a three-dimensional flow, the turbulence of the vortex is promoted, and the discharging action of the bubbles is promoted.

[0025] Then, using a dynamic pressure bearing device as described above, one of the two members integrally includes rotor magnet as a rotary side, having a stator at a position opposed to the rotor magnet and the other as a fixed side A spindle motor can be constituted by the above (Claim 6), and a spindle motor is provided which avoids problems such as deterioration of dynamic pressure bearing characteristics due to accumulation of air bubbles or generation of air rings, occurrence of vibration, defective starting, etc. It becomes possible.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a spindle motor according to the present invention will be described below with reference to the drawings. Figure 1
6 shows essential parts when the present invention is applied to the recording disk driving spindle motor described in FIG. 8, and the same reference numerals as those used above denote the same or corresponding ones. To do.

Firstly, FIGS. 1 and 2 show a first embodiment, as is different from that described in FIGS. 8 and 9, the sealing gap 18 in the outer peripheral surface of the sleeve member 5 as a stationary-side member The point is that an agitating means including a plurality of protrusions 23 is provided on the outer peripheral surface 5c of the connecting portion facing the connecting portion 22 between the escape gap 21. The plurality of protrusions 23 are arranged on the outer peripheral surface 5c of the connecting portion at substantially equal intervals in the circumferential direction.

In the hydrodynamic bearing device having such a structure, when the rotor 8 rotates, as described above, large vortices of the lubricating fluid 17 will be independently generated in the escape gap 21 and the sealing gap 18. And On the other hand, the connecting portion 22
As the inner wall surface 18x of the circumferential projection 10d facing the inner peripheral surface 10d rotates, the lubricating fluid 17 in contact therewith moves, and the lubricating fluid near the outer peripheral surface 5c of the connecting portion of the sleeve member 5 that is dragged by the inner surface 18x and faces the connecting portion 22. By moving 17 as well, the movement of the lubricating fluid 17 in this portion is hindered by the plurality of projections 23 projectingly provided on the outer peripheral surface 5c of the connecting portion, the flow of the lubricating fluid 17 is disturbed, and the connecting portion 22 and its vicinity The lubricating fluid 17 is agitated.

[0029] Consequently, as shown in FIG. 1, the vortex 1 of the lubricating fluid 17 in relief for clearance 21 and the sealing gap 1
The flow of the vortex 2 of the lubricating fluid 17 in FIG.
7 are mixed in the vicinity of the connecting portion 22. Therefore,
Even when the bubbles are mixed in the lubricating fluid 17 in the thrust bearing gap 14 and are transferred to the escape gap 21 and ride on the flow of the vortex 1, the bubbles reach the vicinity of the connecting portion 22 according to the flow of the vortex 1. At this time, the bubbles are dispersed in the connecting portion 22 and its vicinity, and some of the bubbles come to ride on the flow of the vortex 2, which is carried to the gas-liquid interface in the sealing gap 18 according to the flow of the vortex 2 and discharged to the outside. Will be done. In this case, all the bubbles riding on the flow of the vortex 1 do not transfer to the vortex 2 in a short time, but since the lubricating fluid 17 is constantly stirred in the connecting portion 22, the bubbles riding on the flow of the vortex 1 Are gradually taken into the vortex 2 and sequentially discharged to the outside.

FIG . 3 shows a second embodiment of the present invention. In this embodiment, a plurality of recesses (concavities) 24 are formed substantially in the circumferential direction on the outer peripheral surface 5c of the connecting portion that faces the connecting portion 22 between the sealing gap 18 and the escape gap 21 on the outer peripheral surface of the sleeve member 5. By arranging them at equal intervals, they form a stirring means for stirring the connecting portion 22 and the lubricating fluid 17 in the vicinity thereof.

Also in the second embodiment, as in the case of the first embodiment, the outer peripheral surface 5 of the connecting portion of the sleeve member 5 is formed.
With the rotational movement of the lubricating fluid 17 in the vicinity of c, the lubricating fluid 17 is disturbed when passing through the concave portion 24 of the outer peripheral surface 5c of the connecting portion, and the connecting portion 22 and the lubricating fluid 17 in the vicinity thereof are agitated. Therefore, the bubbles mixed in the vortex 1 of the lubricating fluid 17 in the escape gap 21 will not be mixed with the lubricating fluid 17 in the sealing gap 18.
It becomes easy to transfer to the vortex 2 and is discharged to the outside from the gas-liquid interface in the sealing gap 18.

In the third embodiment shown in FIG . 4, in place of the projections 23 and the recesses 24 described above, in order to facilitate the processing on the outer peripheral surface 5c of the connecting portion of the sleeve member 5, a large number of minute depressions (dimples) are formed. ) 25 is formed, and the recess 25 is formed on almost the entire outer peripheral surface 5c of the connecting portion, and the same effect as described above is exhibited.

In the fourth embodiment shown in FIGS. 5 and 6,
A plurality of dynamic pressure grooves (spiral grooves) 43 having a pump-out function are formed as stirring means on the outer peripheral surface 5c of the connecting portion of the sleeve member 5, and the lubricating fluid 17 in the connecting portion 22 is provided with the sealing gap 18 side. It is designed to generate a moving pressure toward. Accordingly, the lubricating fluid 17 in the connecting portion 22 and its vicinity moves toward the sealing gap 18 side while being stirred by the action of the dynamic pressure groove 43, and as a result, the vortex 1 in the escape gap 21 causes the sealing gap 18 to move.
A new flow of the lubricating fluid 17 that enters the vortex 2 occurs, and bubbles mixed in the lubricating fluid 17 that move according to the flow of the vortex 1 easily move to the lubricating fluid 17 of the vortex 2.
The bubbles are discharged to the outside from the gas-liquid interface of the sealing gap 18.

In this case, the dynamic pressure grooves 26 formed on the outer peripheral surface 5c of the connecting portion are arranged at equal intervals in the circumferential direction as shown in FIG. 6 (a), and as shown in FIG. 6 (b). , Dynamic pressure groove 26
May be provided unevenly in the circumferential direction, and one dynamic pressure groove 26 may be formed over the entire circumference in the circumferential direction as shown in FIG. 6C. Particularly in the case of FIG. 6B, since the dynamic pressure grooves 26 are provided unevenly in the circumferential direction, it is possible to further disturb the flow of the lubricant 17 while causing the vortex 1 of the lubricating fluid 27 to enter the region of the vortex 2. In addition, in the case of FIG. 6C, the pressure distribution can be made asymmetric in the circumferential direction, so that the flow of the lubricating fluid 17 becomes a three-dimensional flow, the stirring action is effectively performed, and the effect of the present invention is obtained. Increase.

Although the embodiments of the dynamic pressure bearing device and the spindle motor using the same according to the present invention have been described above, the present invention is not limited to such embodiments and does not depart from the scope of the present invention. Various variations and modifications are possible.

[0036] For example, in the embodiment of the present invention described above,
The case where the protrusion 23, the recess 24, the recess 25, and the dynamic pressure groove 26 as the stirring means are formed in the sleeve member 5 as the fixed-side member is shown, but the invention is not limited to this, and the connecting portion 22
Can be formed on the inner wall surface 18x of the circumferential projection 10d of the rotor hub 10a, or on both the stationary side member and the rotating side member. It is also desirable that these agitating means are provided unevenly in the circumferential direction to make the pressure distribution asymmetric in the circumferential direction, and it is effective to make the axial asymmetry.

Furthermore, in terms of having a stirring means as described above,
As shown in FIG. 7, the taper angle θ of the sealing gap 18 is made uneven in the circumferential direction (θ1 to θ2), and the radial gap size G of the connecting portion 22 is made uneven in the circumferential direction (G1 to G2). It is also possible to make the pressure distribution in the circumferential direction in the connecting portion 22 non-uniform, so that the effect of more effective stirring can be expected.

In the above embodiment, the outer peripheral side of the thrust bearing gap is formed in the axial direction so that the seal gap communicating with the thrust bearing gap is widened downward. The present invention is not limited to this, and the present invention can be similarly applied to a configuration in which the gap size for sealing widens upward.

[0039]

As described above, according to the hydrodynamic bearing device of the present invention, the lubricating fluid in the vicinity of the connecting portion between the escape gap and the sealing gap, which communicates with the outer periphery of the thrust bearing gap, and the lubricating fluid in the vicinity of the gap. The lubricating fluid is agitated by the action of the agitating means formed on the peripheral surface of the member facing the connecting portion, and the vortex flow of the lubricating fluid generated in each of the escape gap and the sealing gap is disturbed in the connecting portion. Therefore, the bubbles in the lubricating fluid transferred from the thrust bearing gap to the escape gap can be moved to the vortex of the lubricating fluid in the sealing gap, and can be discharged to the outside. It is possible to prevent air bubbles from accumulating due to air bubbles remaining, to avoid adverse effects such as generation of vibration and wear of bearing members, and to obtain stable bearing performance.

[0040] Then, using a dynamic pressure bearing device described above, 2
By having one of the two members as the rotating side and integrally including the rotor magnet and the other as the fixed side and having the stator at a position facing the rotor magnet, the other member is relatively disposed with respect to the one member. A rotating spindle motor can be configured, and a spindle motor that avoids deterioration of dynamic pressure bearing characteristics or deterioration of rotation characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part showing a first embodiment of the present invention, in which a relief gap and a part of a sealing gap formed between a sleeve of a spindle motor and a rotor hub are enlarged.

FIG. 2 is a perspective view of a part of the sleeve shown in FIG.

FIG. 3 is a perspective view of a part of the sleeve showing the second embodiment of the present invention.

FIG. 4 is a perspective view of a part of the sleeve showing the third embodiment of the present invention.

FIG. 5 is a perspective view of a part of the sleeve showing the fourth embodiment of the present invention.

6 is a development view illustrating a dynamic pressure groove on the outer peripheral surface of the coupling portion of the sleeve, FIG. 6A is an example corresponding to FIG. 5, and FIG.
Is a modification, and (C) is another modification.

FIG. 7 is a partial sectional view of a rotor hub and a sleeve showing another embodiment of the present invention.

FIG. 8 is a sectional view of a spindle motor provided with a dynamic pressure bearing device which is the basis of the present invention.

FIG. 9 is a partial cross-sectional view of a conventional dynamic pressure bearing device.

[Explanation of symbols] 1 Spindle motor 4 stator 5 Sleeve member 10 rotor hub 12 rotor magnet 14 Thrust bearing clearance 17 Lubricating fluid 18 Seal gap 21 Clearance gap 22 Connection 23 Protrusion 24 recess 25 hollows 26 Dynamic pressure groove

Continued front page    F-term (reference) 3J011 AA20 BA04 CA02 EA10 JA02                       KA02 KA03 LA05 MA12 PA03                 5H607 AA00 BB01 BB09 BB17 BB25                       CC01 DD03 DD14 GG12 GG15                       GG25 GG28 JJ10

Claims (6)

[Claims] 1. A thrust bearing surface orthogonal to the axis of rotation and a thrust receiving surface opposite to the thrust bearing surface are provided on one and the other of the two relatively rotating members, respectively, and between the thrust bearing surface and the thrust receiving surface. The thrust bearing gap is formed by filling the thrust bearing gap with a lubricating fluid and forming a dynamic pressure generating groove for generating a supporting pressure in the lubricating fluid on at least one of the thrust bearing surface and the thrust receiving surface. , A sealing gap, which communicates with the thrust bearing gap on the outer peripheral side of the thrust dynamic pressure bearing portion, is formed in a substantially axial direction so that the gap dimension expands as the distance from the thrust bearing gap increases.
A dynamic pressure bearing device in which an interface between the lubricating fluid filled in the thrust bearing gap and air is formed in the sealing gap, and the thrust bearing gap and the sealing gap are connected to each other on the outer periphery of the thrust bearing gap. An escape gap having a larger gap size than the thrust bearing gap is formed, and the connecting portion and the connecting portion are formed on the peripheral surface of one of the members facing the connecting portion between the escape gap and the sealing gap of the two members. A dynamic pressure bearing device, characterized in that stirring means for stirring the lubricating fluid in the vicinity is provided. 2. The hydrodynamic bearing device according to claim 1, wherein the sealing gap is expanded by providing a taper radially inward. 3. The hydrodynamic bearing device according to claim 1, wherein the agitating means comprises a plurality of protrusions provided on a surface of any member facing the connecting portion and arranged in a circumferential direction. 4. The hydrodynamic bearing device according to claim 1, wherein the agitating means comprises a plurality of grooves or depressions which are provided in the surface of any member facing the connecting portion and are arranged in the circumferential direction. 5. The hydrodynamic bearing device according to claim 1, wherein the shape, the size, the angle or the stirring means of the sealing gap is asymmetric with respect to the rotation direction about the axis. . 6. The dynamic pressure bearing device according to claim 1, wherein one of the two members serves as a rotating side and integrally has a rotor magnet, and the other member serves as a fixed side. And a stator at a position facing the rotor magnet.