JP2006226388A - Bearing mechanism, spindle motor using bearing mechanism and recording disk drive equipped with spindle motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing mechanism allowing a low electric current and low cost by eliminating a flange, to provide a spindle motor using the bearing mechanism and to provide a recording disk drive equipped with the spindle motor. <P>SOLUTION: A first part 21 and a second part 22 of a shaft 20 and a connection portion 23 for connecting these parts are formed and a latching portion 33 or a latching member 50 or 60 of a separate member is disposed in a housing 30 in contact with a sleeve 10. The inner diameter of the latching portion 33 (or the latching member 50, 60) is disposed axially above the connection portion 23, and formed larger than the second part 22 of the shaft 20 and smaller than the first part 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrodynamic bearing mechanism having a lubricating fluid, a spindle motor using the hydrodynamic bearing mechanism, and a recording disk driving apparatus equipped with the spindle motor.

  In recent years, applications other than personal computers for signal recording and reproducing devices such as hard disk drive devices have increased. In particular, the increase in mounting of this hard disk drive device on a portable device is remarkable. At the time of porting, reduction of the current of the hard disk drive device has become an important issue as it leads to the battery life of the portable device. In addition, as the demand for mobile devices increases, the number of new entrants has increased, and price reduction due to intensifying competition is inevitable. Along with this, the price reduction of hard disk drive devices and spindle motors is an important issue.

  FIG. 9 is a cross-sectional view showing a conventional bearing mechanism. Referring to FIG. 9, a shaft 2 is inserted so as to be rotatably supported by a hollow cylindrical sleeve 1. At the lower end portion of the shaft 2, a flange portion 2 a that prevents the shaft 2 and serves as a thrust bearing is formed. Further, a concave portion 1a for accommodating the flange portion is formed in the lower portion of the sleeve 1, and a thrust plate 3 is provided so as to cover the concave portion 1a (see Patent Document 1 as such a conventional bearing mechanism). ).

US Patent Publication No. 2003-0174914

  However, the formation of the flange portion 2a increases the weight of the flange portion 2a and the fluid resistance generated by the rotation of the flange portion 2a, making it difficult to reduce the current. Moreover, the unit price has increased due to an increase in the number of parts by the flange portion 2a. Even if the flange portion 2a is manufactured integrally with the shaft 2, the processing cost of the shaft 2 increases. Therefore, an increase in the price of the bearing mechanism becomes an unavoidable problem.

  Accordingly, the present invention provides a bearing mechanism that realizes a reduction in current and a cost by eliminating the flange portion 2a, a spindle motor using the bearing mechanism, and a recording disk driving device equipped with the spindle motor. It is.

  According to claim 1 of the present invention, there is provided a bearing mechanism, a first part having a predetermined diameter, a second part having a smaller diameter than the first part, an outer peripheral surface of the first part, and the second part. A shaft having a connecting surface for connecting the outer peripheral surfaces of the shaft along the central axis, and a cylindrical bearing surface for inserting the first portion and supporting the shaft using fluid dynamic pressure by a lubricating fluid A sleeve, a plate that closes the first portion of the sleeve, a sleeve holding portion that holds the sleeve from the outside, and an opening hole that is disposed on the axially upper side of the connecting surface and through which the second portion is inserted. A retaining member, wherein the opening hole of the retaining member is inserted with the second portion of the shaft, and a retaining portion having an inner diameter opposed to the connecting surface in the axial direction is smaller than the first portion, 2nd from retaining part A taper portion is formed in which a gap between the inner peripheral surface of the opening hole formed on the rear side and the outer peripheral surface of the second portion decreases toward the first portion, and the taper portion An interface of the lubricating fluid is formed.

  According to claim 2 of the present invention, according to claim 1, at least a part of the sleeve is made of an oil-containing porous material.

  According to a third aspect of the present invention, according to any one of the first and second aspects, the plate and the sleeve holding portion are integrally formed.

  According to a fourth aspect of the present invention, according to any one of the first to third aspects, the dynamic pressure generating groove is provided between the outer peripheral surface of the first portion of the shaft and the inner peripheral surface of the sleeve. Two radial bearing portions are formed, and one thrust bearing portion having a dynamic pressure generating groove is formed between the end surface of the first portion of the shaft and the plate.

  According to a fifth aspect of the present invention, according to any one of the first to fourth aspects, the retaining portion and the sleeve holding portion are integrally formed, and the end surface of the sleeve and the retaining portion are in contact with each other. It is characterized by touching.

  According to a sixth aspect of the present invention, in the bearing mechanism according to any one of the first to fifth aspects, the retaining member has a substantially covered cylindrical shape, and a cylindrical portion that contacts the outer peripheral surface of the sleeve; And a lid portion that contacts the end surface of the sleeve, the second portion of the shaft is inserted into the lid portion, and an opening hole whose inner diameter facing the connecting surface in the radial direction is smaller than that of the first portion. A first gap is provided between the outer peripheral surface of the second portion and the inner peripheral surface of the opening hole, and a second gap is provided between the outer peripheral surface of the cylindrical portion and the inner peripheral surface of the sleeve holding portion. The first gap portion and the second gap portion gradually expand toward the opening side, and an interface of the lubricating fluid is formed at the first gap portion and the second gap portion. .

  According to a seventh aspect of the present invention, according to any one of the first to sixth aspects, a dynamic pressure generating groove is provided between the connecting surface of the shaft and the retaining portion facing the connecting surface. The bearing part which has is provided.

  According to an eighth aspect of the present invention, the spindle motor is rotatably supported with respect to the base by the base, the stator fixed to the base, and the bearing mechanism according to any one of the first to seventh aspects. And a rotor magnet attached to the periphery of the rotor so as to face the stator.

  According to a ninth aspect of the present invention, according to any one of the first to eighth aspects, a magnetic yoke is attached to the base so as to face the rotor magnet in the axial direction.

  According to a tenth aspect of the present invention, according to any one of the first to eighth aspects, the magnetic center of the rotor magnet is located above the center of the axial height of the stator. To do.

  According to an eleventh aspect of the present invention, a recording disk drive device is equipped with the spindle motor according to any one of the eighth to tenth aspects.

  According to the first to sixth aspects of the present invention, the shaft can be easily prevented from coming off by the shaft and the retaining portion, and the thrust bearing portion is formed between the end surface of the first portion of the shaft. Therefore, it is possible to delete a flange that has been conventionally required. By forming the sleeve in a substantially cylindrical shape, the bearing portion requiring accuracy can be manufactured in a simple shape, so that it can be manufactured at low cost, leading to a reduction in the price of the motor. Furthermore, by forming this sleeve with an oil-containing porous material, the sleeve can be manufactured at a lower cost. And further price reduction of the motor can be realized.

  Further, by removing the flange from the shaft body which is a rotating body, fluid resistance due to the lubricating fluid applied to the flange is eliminated. As a result, the fluid resistance due to rotation decreases, so that the power consumption of the motor can be reduced.

  According to the seventh aspect of the present invention, by forming the dynamic pressure generating groove in the connecting portion that connects the first portion and the second portion of the shaft, the fluid pressure between the retaining portion and the connecting portion increases, and the shaft Direct contact between the sleeve and the sleeve holding portion is prevented, and a buffering effect due to fluid pressure is also exhibited.

  According to the eighth aspect of the present invention, an inexpensive spindle motor can be provided by using the bearing mechanism according to any one of the first to fifth aspects.

  According to the ninth aspect of the present invention, by arranging the yoke below the rotor magnet, it is possible to adjust the shaft floating by the thrust bearing by always acting on the lower side in the axial direction by the attractive force of the rotor magnet.

  According to the tenth aspect of the present invention, the same effect as that of the seventh aspect can be obtained by disposing the magnetic center of the rotor magnet on the upper side in the axial direction from the stator center.

  According to the eleventh aspect of the present invention, an inexpensive recording disk drive device can be provided by mounting the spindle motor according to any one of the seventh to ninth aspects.

  An embodiment according to the present invention will be described with reference to FIGS.

  FIG. 1a) is a schematic cross-sectional view showing one embodiment in an embodiment according to the present invention, and b) is an enlarged view of a two-dot chain line portion. 2 and 3 are schematic cross-sectional views showing other embodiments in the same manner. FIG. 2c) is a semicircular cross-sectional view of the retaining member. FIG. 3c) is a top view of a).

<Example 1>
Referring to FIG. 1, a sleeve 10 has a hollow cylindrical shape, and a shaft 20 is inserted therein so as to be rotatably supported. On the inner peripheral surface of the sleeve 10, two dynamic pressure generating grooves 11 and 12 that are separated in the axial direction are formed, and each serves as a radial bearing portion.

  The shaft 20 has a first portion 21 that faces the inner peripheral surface of the sleeve 10 through a minute gap, a second portion 22 that is positioned axially above the first portion 21 and has a smaller diameter than the first portion 21. Formed from. A connecting portion 23 that connects the first part 21 and the second part 22 is formed at the boundary between the first part 21 and the second part 22.

  A cylindrical housing 30 disposed so as to surround the sleeve 10 is fixed to the outer peripheral surface of the sleeve 10. A disc-shaped thrust plate 40 is fixed to the lower end portion 31 of the housing 30. A dynamic pressure generating groove 41 is formed on the upper surface of the thrust plate 40. The thrust plate 40 and the lower end surface 21a of the first portion 21 of the shaft 20 are opposed to each other through a minute gap in the axial direction to form a thrust bearing portion. Then, the shaft 20 is lifted by the dynamic pressure generating groove 41 of the thrust plate 40.

  Further, the lubricating fluid is filled so as to fill the radial bearing portion and the thrust bearing portion without substantial interruption. Thereby, the shaft 20 is rotatably supported by each bearing portion by the fluid pressure of the lubricating fluid.

  The housing 30 also has a retaining portion 32 that is reduced in diameter so as to contact the upper end surface 13 of the sleeve 10. The inner diameter of the retaining portion 32 is larger than the outer diameter of the second portion 22 of the shaft 20 and smaller than the outer diameter of the first portion 21. Thereby, even if the shaft 20 is lifted to the upper side in the axial direction by the thrust bearing portion, the connection portion 23 of the shaft 20 comes into contact with the retaining portion 32 via the lubricating fluid, so that the floating can be restricted. In other words, it becomes a stopper. Further, by inclining the inner peripheral surface of the retaining portion 32 radially outward with respect to the outer peripheral surface of the second portion 22 of the shaft 20, these gaps are gradually narrowed downward in the axial direction, thereby stabilizing the interface. Can be realized.

  Lubricating fluid can be circulated by providing at least one communication path (dotted line portion in FIG. 1) at the contact portion between the sleeve 10 and the housing 30, the thrust plate 40 and the retaining portion 32. Since each dynamic pressure generating groove is formed so that dynamic pressure is generated in the direction of the arrow in the figure, the lubricating fluid circulates in the direction of the dashed-dotted arrow (described in the sleeve 10) through the communication path. As a result, the lubricating fluid can correct the fluid pressure imbalance during rotation and can achieve stable rotation. Although the communication path is provided on the sleeve 10 side in the drawing, the communication path only needs to be provided between the members that contact the sleeve 10 and is not limited thereto. For example, a communication path may be provided on the housing 30 side.

  Further, by forming the dynamic pressure generating groove 23 a in the connecting portion 23 of the shaft 20, the fluid pressure in the axial gap with the retaining portion 32 can be increased. In particular, the fluid pressure can be further increased by the action of the lubricating fluid flowing in from the communication path of the sleeve 10 (dotted line in FIG. B) and the dynamic pressure generating groove 23a. This can provide a buffering action between the shaft 20 and the retaining portion 32, and the connecting portion 23 and the retaining portion of the shaft 20 can be moved even if the shaft 20 moves upward in the axial direction due to an external impact or the like. Since the fluid pressure between the two is large, the moving force is reduced. As a result, direct contact between the shaft 20 and the retaining portion 32 can be prevented, and a highly reliable bearing mechanism can be provided.

  Since the retaining portion 33 and the dynamic pressure generating groove 41 of the thrust plate 40 can serve as a flange, it is possible to eliminate the flange from the bearing mechanism, thereby reducing current and cost. Can be realized.

<Example 2>
With reference to FIG. 2, the case where a retaining part is another member is demonstrated. Since the sleeve 10 and the shaft 20 are not changed in shape, the same numbers are used.

  Referring to a), the housing 30a has a bottomed cylindrical shape, and the sleeve 10 is fixed to the inner peripheral surface of the cylindrical portion 31a so as to contact the bottom portion 32a. A dynamic pressure generating groove is formed in the bottom portion 32a to form a thrust bearing portion.

  The shaft 20 is inserted into the inner peripheral surface of the sleeve 10 so as to be rotatably supported, and floats at the time of rotation by a dynamic pressure generating groove in the bottom 32a of the housing 30a.

  An annular retaining member 50 is disposed on the upper end surface 13 of the sleeve 10 so as to contact the inner peripheral surface of the cylindrical portion 31 a of the housing 30 a and the upper end surface 13 of the sleeve 10. With reference to b), the inner diameter of the retaining member 50 is made larger than the outer diameter of the second portion 22 of the shaft 20 and smaller than the outer diameter of the first portion 21. Thereby, the retaining effect can be obtained as in the first embodiment. Further, by inclining the inner peripheral surface of the retaining member 50 radially outward with respect to the outer peripheral surface of the second portion 22 of the shaft 20, the same effect as in the first embodiment can be obtained.

  The circulation of the lubricating fluid is basically the same as in the first embodiment. However, instead of the thrust plate 40, a recess may be provided in the contact portion of the bottom 32a of the housing 30a with the sleeve 10 to form a communication path. Moreover, you may provide the recessed part 51 in the contact part with the sleeve 10 of the retaining member 50 like c). Thereby, the same effect as Example 1 can be acquired.

<Example 3>
FIG. 3 shows a modification of the retaining member of the second embodiment. Since the shapes of the sleeve 10 and the shaft 20 are not changed, the same numbers are used for explanation. The hatched portion in c) indicates a retaining member.

  The housing 30b has a bottomed cylindrical shape, and the sleeve 10 is fixed to the inner peripheral surface of the cylindrical portion 31b so as to contact the bottom portion 32b. A dynamic pressure generating groove is formed in the bottom portion 32b to form a thrust bearing portion. Further, a part of the upper inner peripheral surface of the cylindrical portion 31b is inclined radially outward as it goes upward in the axial direction.

  The retaining member 60 has a hollow covered cylindrical shape, and the lid portion 61 abuts on the upper end surface 13 of the sleeve 10. The cylindrical portion 62 of the retaining member 60 is fixed to the outer peripheral surface of the sleeve 10. The housing 30b is provided with a stepped portion 33b for accommodating the cylindrical portion 62 of the retaining member 60. And the step part 33b of the housing 30b and the lower end surface of the cylindrical part 62 of the retaining member 60 form a minute gap in the axial direction. The cylindrical portion 62 of the retaining member 60 and the stepped portion 33b of the housing 30b are in contact with each other, and this contact portion is fixed by welding or the like. However, referring to c), a concave portion is formed in a part of the cylindrical portion 62, and a minute gap 62a is formed between the step portion 33b of the housing 30b.

  A shaft 20 is rotatably supported on the inner peripheral surface of the sleeve 10 and is filled with a lubricating fluid without substantially interrupting the radial bearing portion and the thrust bearing portion as in the first embodiment. As a result, a first interface is formed in the first gap, which is a minute gap between the outer peripheral surface of the shaft 20 and the retaining member 60, and the outer peripheral surface of the inner peripheral surface of the cylindrical portion 31 b of the housing 30 b and the cylindrical portion 62 of the retaining member 60. A second interface is formed in the second gap, which is a gap with the surface. Further, since the minute gap 62a communicates with the communication path, the first interface and the second interface can communicate with each other through the communication path.

  The circulation of the lubricating fluid is basically the same as in the first embodiment. However, instead of the thrust plate 40, a recess may be provided in the contact portion of the bottom 32b of the housing 30b with the sleeve 10 to form a communication path. Further, a concave portion may be provided on the inner peripheral surface of the lid portion 61 and the cylindrical portion 62 that are the contact portions of the retaining member 60 with the sleeve 10. Thereby, the same effect as Example 1 can be acquired.

  The inner diameter of the shaft insertion hole 63 of the retaining member 60 is set to be larger than the outer diameter of the second portion 22 of the shaft 20 and smaller than the outer diameter of the first portion 21. Thereby, the effect of retaining can be obtained as in the first embodiment.

  Since a chamfered portion 64a is formed on the inner peripheral edge of the shaft insertion hole 64 of the retaining member 60 so as to be radially outward as it goes upward in the axial direction, the first gap between the outer peripheral surface of the shaft 20 and the retaining member 60 is Spreads upward in the axial direction. Further, since the upper inner peripheral surface of the cylindrical portion 31b of the housing 30b is inclined outward in the radial direction as it goes upward in the axial direction, the second gap widens toward the upper side in the axial direction. Accordingly, it is possible to stabilize the interface formed in the first gap and the second gap.

<Material>
The materials constituting these bearing mechanisms will be described.

  The sleeve 10 is made of a porous material (for example, a sintered member), the shaft 20 is made of stainless steel, the housings 30, 30a, 30b are made of stainless steel by plastic working such as pressing, and the retaining members 50, 60 are made of copper-based material. ing. The housings 30, 30a, 30b and the retaining members 50, 60 may be molded from a resin material. Resin materials are suitable because they can be molded at low cost. The material of these bearing mechanisms is common to each embodiment. In particular, the porous material used for the sleeve 10, particularly the sintered member, has a simple shape like this structure because it is difficult to obtain dimensional accuracy as compared with the cutting.

<Spindle motor>
FIG. 4 is a schematic cross-sectional view of one embodiment in an embodiment of a spindle motor according to the present invention. The bearing mechanism used in this spindle motor is assumed to be Example 1. The second and subsequent embodiments are the same if the bearing mechanism of the spindle motor is changed, and will not be described.

  A covered cylindrical rotor hub 70 is attached to the upper portion of the second portion 22 of the shaft 20. The rotor hub 70 has a three-stage cylindrical portion. The first cylindrical portion 71 of the rotor hub 70 is fixed to the shaft 20, and the inner peripheral surface of the second cylindrical portion 72 is opposed to the outer peripheral surface of the cylindrical portion of the housing 30 with a slight gap in the radial direction to form a labyrinth structure. A yoke 80 is fixed to the lower side of the third cylindrical portion 73 in the axial direction, and a rotor magnet 90 is fixed to the inner peripheral surface of the yoke 80.

  The lower outer peripheral surface of the cylindrical portion of the housing 30 is fixed in contact with the inner peripheral surface of the protrusion 101 of the base 100, and the stator 110 has a small gap in the radial direction with the rotor magnet 90 on the outer peripheral surface of the protrusion 101. It arrange | positions so that it may oppose.

  On the lower side in the axial direction of the rotor magnet 90, a magnetic thrust yoke 120 is disposed on the base 100. The thrust yoke 120 and the rotor magnet 90 are attracted to each other, and a downward force is always applied. Since the bearing mechanism of the present embodiment has one thrust bearing portion, the shaft 20 always floats during rotation. The thrust yoke 120 is arranged to adjust the flying height.

  The stator 110 includes a plurality of teeth 111 extending radially in the circumferential direction and a winding 112 that winds the teeth 111. The stator 110 generates a magnetic field by energizing the winding 112, and the magnetic field and the rotor magnet 90 are mutually connected. A rotational force is generated by the action.

  FIG. 5 is a schematic cross-sectional view showing another embodiment of the spindle motor according to the present invention.

  Referring to FIG. 5, this is a spindle motor in which a housing 30 and a rotor hub 70 are integrated, and the bearing mechanism in FIG. 4 is rotated 180 degrees in the axial direction. The members other than the rotor hub are not changed in basic shape, and will be described with reference to the same figure.

  The rotor hub 130 integrated with the housing has a hollow cylindrical shape, and has an annular protrusion 132 having a small inner diameter on the lower end side in the axial direction of the hollow portion 131. The inner peripheral surface of the protrusion 132 and the hollow portion 131 and the sleeve 10 are in contact with each other and fixed.

  The shaft 20 is inserted through the inner peripheral surface of the sleeve 10 so as to be rotatably supported. A recess 133 is formed on the upper end side of the rotor hub 130. By fixing the thrust plate 40 in the recess 133, the hollow portion 131 of the rotor hub 130 is covered so as to be covered.

  A disk-like substantially cylindrical portion 134 that extends radially outward is provided below the rotor hub 130, and a yoke 80 is fixed to a radially outer lower surface 134 a of the substantially cylindrical portion 134. A rotor magnet 90 is fixed to the inner peripheral surface of the yoke 80. A thrust yoke is disposed on the base 100 on the lower side in the axial direction of the rotor magnet 90 so that a force always acts on the lower side in the axial direction.

  The stator 110 fixed to the base 100 is disposed so as to face the rotor magnet 90 via a gap in the radial direction.

  The lower part of the shaft 20 is fixed to the base 100, and a magnetic field is generated by energizing the stator 110. A rotational force is generated by the interaction between this magnetic field and the rotor magnet 90, and the rotor hub 130 rotates.

  Since the number of parts can be reduced by integrating the housing and the rotor hub, the cost of the spindle motor can be reduced.

  This spindle motor can be simplified in the manufacturing process, and the tact time in the process can be reduced. That is, the yoke 80 and the magnet 90 are attached to the rotor hub 130, and the sleeve 10 is fixed to the rotor hub 130 so as to contact the protrusion 132. Then, the shaft 20 is inserted into the sleeve 10 so as to be in contact with the protrusion 132, a lubricating fluid is injected from between the shaft 20 and the rotor hub 130, and the thrust plate 40 is brought into contact with and fixed to the recess 133 of the rotor hub 130. Then, the shaft 20 and the base 100 are fixed so as to match the lower surface of the base 100.

  Since all the assemblies can be fixed by the contact of the parts, dimensional management in the assembly is easy. In addition, since the assembly is a stacked type, it is possible to shift from manual assembly to mechanical assembly. As a result, the process tact can be shortened as described above, and the cost of the spindle motor can be reduced.

<Recording disk drive>
One embodiment of the recording disk drive device 200 according to the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view of the recording disk drive device 200.

  The recording disk drive device 200 includes a rectangular housing 210. The housing 210 forms a clean space in which dust, dust, etc. are extremely small, and a disk for recording information therein. A spindle motor 230 with a hard disk 220 mounted thereon is disposed. The housing 210 and the base 100 may be integrally formed.

  In addition, a head moving mechanism 240 that reads and writes information from and to the hard disk 220 is disposed inside the housing 210. The head moving mechanism 240 includes a magnetic head 241 that reads and writes information on the hard disk 220, and the magnetic head 241. The supporting arm 242 and the magnetic head 241 and the arm 242 are constituted by an actuator unit 243 that moves the arm 242 to a required position on the hard disk 220.

  By applying the spindle motor of the present invention as the spindle motor 230 of such a recording disk drive device 200, the recording disk drive device 200 can be reduced in size and thickness while ensuring a sufficient function and reliability. In addition, a highly durable recording disk drive device can be provided.

  As mentioned above, although the Example of this invention was described, this invention can be variously deformed without being limited to this.

  For example, each embodiment of the present invention is provided with one thrust bearing portion. However, the present invention is not limited to this, and the lower end surface of the shaft 30 is substantially spherical as shown in FIG. It is also possible to support by point contact by making the surface opposite to the spherical surface and eliminating the dynamic pressure bearing portion of the opposite surface.

  Further, the clearance between the retaining portion 33 and the retaining members 50, 60 of the bearing mechanism of the present invention and the shaft 20 is a clearance that extends upward in the axial direction by inclining the inner peripheral surface of the retaining portion and the retaining members 50, 60 radially outward. However, the present invention is not limited to this, and the same effect can be obtained by gradually reducing the diameter of the outer peripheral surface of the second portion 22 of the shaft 20 toward the upper side in the axial direction as shown in FIG. .

  In the spindle motor of the present invention, the thrust yoke 120 is disposed below the rotor magnet 90. However, the present invention is not limited to this. For example, as shown in FIG. 8, the magnetic force of the rotor magnet 90 may be obtained by arranging the magnetic center of the rotor magnet 90 above the axial center of the teeth 111 of the stator 110 (FIG. 8B). The alternate long and short dash lines drawn on the stator 110 and the stator 110 indicate the respective centers, and the difference in the axial direction is indicated by W.

  In the spindle motor of the present invention, the connecting portion 23 of the shaft 20 is perpendicular to the axial direction, but the present invention is not limited to this. Since the retaining portion 33 and the supporting members 50 and 60 only need to have a portion where the shaft 20 overlaps the shaft portion 20 in the axial direction, the taper in which the connecting portion 23 is reduced in diameter toward the second portion 22 of the shaft 20. It is sufficient that the retaining portion 33 and the retaining members 50 and 60 are opposed to the connecting portion 23 in the axial direction.

a) is a schematic cross-sectional view of the first embodiment of the bearing mechanism according to the present invention, and b) is an enlarged view of the two-dot chain line portion of a). a) is a schematic cross-sectional view of a second embodiment of the bearing mechanism according to the present invention, b) is an enlarged view of a two-dot chain line portion of a), and c) is a semicircular cross-sectional view of a retaining member. a) is a schematic cross-sectional view of a third embodiment of the bearing mechanism according to the present invention, b) is an enlarged view of a two-dot chain line portion of a), and c) is a top view of a). It is a schematic cross section of the Example in the spindle motor which concerns on this invention. FIG. 6 is a schematic cross-sectional view of another embodiment of the spindle motor according to the present invention. 1 is a schematic cross-sectional view of a recording disk drive device according to the present invention. It is a schematic cross section of other examples in the bearing mechanism according to the present invention. a) is a schematic cross-sectional view of another embodiment of the spindle motor according to the present invention, and b) is an enlarged view of a dotted line portion showing a magnetic center and a stator center. It is a schematic cross section of the bearing mechanism in the conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sleeve 11, 12 Dynamic pressure generating groove 20 Shaft 21 1st part 22 2nd part 23 Connection part 23a Dynamic pressure generating groove 30, 30a, 30b Housing 31 Lower end part 32 Stopping part 40 Thrust plate 41 Dynamic pressure generating groove 50 Locking part 60 Stopping part 70 Rotor hub 80 Yoke 90 Rotor magnet 100 Base 110 Stator 120 Thrust yoke 130 Rotor hub

Claims (11)

A bearing mechanism,
A first part having a predetermined diameter, a second part having a smaller diameter than the first part, an outer peripheral surface of the first part, and a connection surface connecting the outer peripheral surface of the second part along the central axis. A shaft,
A sleeve having a cylindrical bearing surface in which the first portion is inserted and the shaft is supported using fluid dynamic pressure by a lubricating fluid;
A plate for closing the first part side of the sleeve;
A sleeve holding portion for holding the sleeve from the outside;
A retaining member disposed on the axially upper side of the connecting surface and having an opening hole through which the second part is inserted;
With
In the opening hole of the retaining member, the second portion of the shaft is inserted, a retaining portion having an inner diameter opposed to the connecting surface in the axial direction is smaller than the first portion, and a second portion is formed from the retaining portion. A taper portion is formed in which a gap between the inner peripheral surface of the opening hole formed on the side and the outer peripheral surface of the second portion decreases toward the first portion, and the taper portion A bearing device, wherein an interface of a lubricating fluid is formed.   The bearing device according to claim 1, wherein at least a part of the sleeve is formed of an oil-containing porous material.   The bearing device according to claim 1, wherein the plate and the sleeve holding portion are integrally formed. Two radial bearing portions having a dynamic pressure generating groove are formed between the outer peripheral surface of the first portion of the shaft and the inner peripheral surface of the sleeve,
The thrust bearing part which has a dynamic-pressure generating groove between the end surface of the said 1st site | part of the said shaft and the said plate is formed in any one of Claim 1 thru | or 3 characterized by the above-mentioned. Bearing mechanism.   The bearing mechanism according to any one of claims 1 to 4, wherein the retaining member and the sleeve holding portion are integrally formed, and an end surface of the sleeve and the retaining portion are in contact with each other. A bearing mechanism according to any one of claims 1 to 5,
The retaining portion has a substantially covered cylindrical shape, and includes a cylindrical portion that contacts the outer peripheral surface of the sleeve and a lid portion that contacts the end surface of the sleeve, and the second portion of the shaft is inserted into the lid portion. An opening hole having an inner diameter that is radially opposite to the coupling surface is smaller than that of the first part, and a first gap is provided between the outer peripheral surface of the second part and the inner peripheral surface of the opening hole. A second gap is provided between the outer peripheral surface of the cylindrical portion and the inner peripheral surface of the sleeve holding portion, and the first gap portion and the second gap portion gradually expand toward the opening side, and the first gap portion And a lubricating fluid interface is formed in the second gap.   The bearing portion having a dynamic pressure generating groove is provided between the connecting surface of the shaft and the retaining portion facing the connecting surface. The bearing mechanism described in 1. Base and
A stator fixed to the base;
It has a rotor rotatably supported with respect to a base by the bearing mechanism in any one of Claims 1 thru | or 7, and a rotor magnet attached to the rotor periphery facing the stator. Spindle motor.   9. The spindle motor according to claim 8, wherein a yoke of magnetic material is attached to the base so as to face the rotor magnet in the axial direction.   The spindle motor according to claim 8, wherein the magnetic center of the rotor magnet is positioned above the center of the axial height of the stator. 11. A recording disk drive device comprising the spindle motor according to claim 8 mounted thereon.

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