JP2008185179A - Fluid bearing device, spindle motor equipped with it, and recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure fluid bearing device capable of improving durability and reliability by preventing generation of negative pressure in the bearing even when receiving impact or vibration; a spindle motor equipped with it; and a recording and reproducing device. <P>SOLUTION: This spindle motor 1 is provided with a radial bearing part 42 having a radial dynamic pressure generation groove 41 formed on the inside surface of a sleeve 32 and relatively rotatably supporting the sleeve 32 and a shaft 31 through oil 34. A tapered seal part 36 of a tapered structure having one end in the axial direction of the shaft 31 faced to the atmosphere is formed among an outer peripheral surface in a different diameter part 31b of the shaft 31, a sleeve cap 32b being a part of the sleeve 32 and an inner peripheral surface. On the sleeve cap 32b attached to an upper part of the sleeve 32, a slit 39 making the tapered seal part 36 communicate with the radial bearing part 42 is formed along the radial direction of the shaft 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device mounted on a motor that rotationally drives a recording disk such as a magnetic disk or an optical disk, and more particularly to a hydrodynamic bearing device that can be miniaturized as a portable device and a spindle provided with the hydrodynamic bearing device. The present invention relates to a motor and a recording / reproducing apparatus.

Conventionally, as a bearing of a spindle motor used in a recording apparatus that rotationally drives a disk-shaped recording medium such as a magnetic disk, an optical disk, or a magneto-optical disk, a lubricating fluid such as oil interposed between a shaft and a sleeve is used. There has been proposed a hydrodynamic bearing device that uses fluid pressure to support both in a relatively rotatable manner.
A series of minute gaps are formed between the shaft and the sleeve, and at least one of the shaft and the sleeve has a dynamic pressure generating groove (radial dynamic pressure generating groove) formed along the circumferential direction of the rotating shaft. ) And a dynamic pressure generating groove (thrust dynamic pressure generating groove) formed in the radial direction of the rotating shaft. Further, oil as a lubricating fluid is held in these minute gaps. Among the configurations of such a hydrodynamic bearing device, there is a so-called one-bag structure in which a taper seal portion is formed at the end of a series of minute gaps and exposed to the atmosphere.

In the hydrodynamic bearing device with a single bag structure, when the shaft as the shaft member starts to rotate, the oil is drawn into the center side of each radial bearing portion and thrust bearing portion by pumping by the dynamic pressure generating groove, and the center of the bearing On the other hand, the fluid dynamic pressure becomes maximum at the portion, but the internal pressure of the oil is reduced and negative pressure is generated on the end portion side of the bearing.
When negative pressure is generated in the oil, for example, the air dissolved in the oil appears as bubbles when filling the oil, and eventually the bubbles expand in volume due to a temperature rise or a low pressure environment. Problems such as leakage may affect the durability and reliability of the spindle motor.
In Patent Document 1, a longitudinal groove (communication hole) that communicates the upper end surface and the lower end surface with the outer peripheral surface of the sleeve member, and a longitudinal groove and the inner peripheral surface of the sleeve member communicate with the upper end surface of the sleeve member. An invention is disclosed in which a lateral groove is formed to circulate a lubricating fluid. That is, the lubricating fluid is continuously held by the lubricating fluid filled in the minute gap in the vertical groove and the horizontal groove, and the lubricating fluid filled in the minute gap and the lubricating fluid held in the vertical groove and the horizontal groove are circulated. Thus, the internal pressure of the lubricating fluid is adjusted to prevent the negative pressure from being generated, and the bubbles in the minute gaps of the bearing are discharged to the outside.
JP 2003-314536 A (published on November 6, 2003)

However, in a hydrodynamic bearing device of a type in which the position of the taper seal portion in the radial direction of the shaft is different from the position of the radial bearing portion, for example, the shaft moves up and down due to impact, vibration, etc. A minute gap between the taper seal portion and the inside of the bearing is temporarily divided by the contact between the member forming the portion, for example, the cap member and the shaft, or the flange and the sleeve. In this case, the following problem occurs.
That is, when vibration or impact is applied to the hydrodynamic bearing device, the relative position between the shaft and the sleeve changes drastically in the vertical direction, and oil as a lubricating fluid inside the bearing is pushed out to the taper seal portion. At this time, a member forming a part of the taper seal portion, for example, a cap member and the shaft are in contact with each other, and a minute gap connecting the taper seal portion and the inside of the bearing is temporarily blocked. For this reason, the oil that has been pushed out and flowed into the tapered seal portion cannot return to the inside of the bearing such as the inner peripheral surface of the sleeve. In this case, a large negative pressure is generated inside the bearing, and for example, air or the like dissolved in the lubricating fluid may be generated as bubbles when the lubricating fluid is filled. When the above phenomenon is repeated, the generated bubble grows large, and when it moves to the opening side, the lubricating fluid is pushed out to cause leakage. For this reason, there exists a possibility of having a bad influence on durability and performance of a fluid dynamic bearing device.

  SUMMARY OF THE INVENTION An object of the present invention is to prevent a negative pressure from being generated inside a bearing even when subjected to vibration or shock, and to improve durability and reliability, and a spindle provided with the same The object is to provide a motor and a recording / reproducing apparatus.

  A hydrodynamic bearing device according to a first invention includes a sleeve, a shaft, a lubricating fluid, a bearing portion, a thrust plate, an opening portion, and a groove portion. The sleeve has an insertion hole. The shaft is disposed in the insertion hole of the sleeve so as to be rotatable relative to the sleeve, and has a main body portion and a different diameter portion having a different radius from the main body portion. The lubricating fluid is filled in a gap formed between the sleeve and the shaft. The bearing portion has a dynamic pressure generating groove formed on at least one of the inner peripheral surface of the sleeve and the outer peripheral surface of the main body portion of the shaft, and supports the sleeve and the shaft so as to be relatively rotatable via a lubricating fluid. ing. The thrust plate is fixed to one end side in the axial direction of the shaft with respect to the sleeve. The opening is formed by the outer peripheral surface of the different diameter portion of the shaft and the inner peripheral surface of the sleeve, and the other end side in the axial direction of the shaft faces the atmosphere. The groove portion is formed in at least one of the sleeve and the shaft along the radial direction of the shaft, and communicates the opening portion and the bearing portion.

Here, a bearing portion that supports the sleeve and the shaft so as to be relatively rotatable via a lubricating fluid having a dynamic pressure generating groove formed on at least one of the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, and a different diameter of the shaft Formed by the outer peripheral surface of the sleeve and the inner peripheral surface of the sleeve, for example, provided with an opening having a taper structure in which the gap gradually increases in the axial direction of the shaft and the other end facing the atmosphere In the hydrodynamic bearing device, a groove portion that communicates the bearing portion and the opening portion is disposed along the radial direction of the shaft.
The insertion hole is a hole through which a shaft such as a shaft is inserted. Also, the different diameter part of the shaft means a large diameter part (for example, a flanged shaft) and a small diameter part (flangeless stepped shaft) having a larger radius than the main body part of the shaft forming the bearing part. Shall be included. The sleeve includes, for example, a sleeve cap for preventing the sleeve from coming off in the axial direction of the shaft in a hydrodynamic bearing device including a flangeless stepped shaft. That is, in the case of a flangeless stepped shaft, the groove may be formed in a portion where the stepped portion of the shaft and the sleeve cap abut, and in the case of a flanged shaft, the groove portion and a part of the sleeve. What is necessary is just to be formed in the contact part.

As a result, even if the hydrodynamic bearing device is subjected to impact or vibration, for example, when the shaft and the sleeve violently move up and down between the sleeve cap and the thrust plate in the axial direction, the shoulder portion of the shaft and the sleeve do not move. It is possible to prevent the gap between the two members from being blocked when abutting. That is, since the lubricating fluid can move through the groove portion that communicates the opening and the bearing portion, it is possible to prevent a negative pressure from being generated inside the bearing. In addition, not only the bearing portion (radial bearing portion) formed by the inner peripheral surface of the sleeve and the outer peripheral surface of the main body portion of the shaft but also, for example, between the thrust plate and the end portion of the shaft. Also included are a bearing portion (thrust bearing portion) formed in the above, a communication hole communicating the upper end surface and the lower end surface of the sleeve, and the like.
As a result, even when the hydrodynamic bearing device is subjected to a large impact or vibration, it is possible to prevent a negative pressure from being generated inside the bearing, so that the lubricating fluid caused by the generation of bubbles in the lubricating fluid filled inside the bearing It is possible to improve the durability and reliability of the hydrodynamic bearing device by preventing the occurrence of problems such as leakage.

A hydrodynamic bearing device according to a second aspect of the present invention is the hydrodynamic bearing device according to the first aspect of the present invention, wherein the sleeve includes a sleeve main body portion arranged on the outer peripheral side of the main body portion of the shaft, and a different diameter portion of the shaft. And a sleeve cap disposed on the outer peripheral side.
Here, in the flangeless type hydrodynamic bearing device, the sleeve has a sleeve cap disposed on the outer peripheral side of the shaft of the different diameter portion, and for example, the groove portion is formed on the bearing portion side surface of the sleeve cap. Has been.
Here, the sleeve cap is a part of the sleeve, and is provided to prevent the shaft from slipping out in the axial direction of the shaft.
Even when the sleeve cap is provided as described above, the groove portion may be formed on the shaft side, that is, the shoulder portion described above.

As a result, even in a flangeless type hydrodynamic bearing device, by preventing the generation of negative pressure inside the bearing, leakage of the lubricating fluid due to the generation of bubbles in the lubricating fluid filled inside the bearing It is possible to improve the durability and reliability of the hydrodynamic bearing device by preventing the occurrence of problems such as sticking out.
A hydrodynamic bearing device according to a third aspect of the present invention is the hydrodynamic bearing device according to the first or second aspect of the present invention, wherein the different diameter portion is formed by a flange portion projecting annularly in the radial direction of the shaft.
Here, in the hydrodynamic bearing device of the type having a flange portion protruding in the radial direction on a part of the shaft, for example, the groove portion is formed on the surface of the flange portion on the bearing portion side.
Even when the flange portion is provided as described above, a groove portion may be formed on the sleeve side.

As a result, even in a hydrodynamic bearing device of a type having a flange portion on the shaft, the generation of bubbles in the lubricating fluid filled in the bearing is prevented by preventing negative pressure from being generated inside the bearing. It is possible to improve the durability and reliability of the hydrodynamic bearing device by preventing the occurrence of problems such as leakage of the lubricating fluid.
A hydrodynamic bearing device according to a fourth invention is the hydrodynamic bearing device according to any one of the first to third inventions, wherein the groove portions are provided at equal intervals along the circumferential direction.
Here, the groove portions are arranged at equal intervals along the annular direction. For example, when three groove portions are provided, adjacent groove portions as viewed from the center of the shaft have an angle of 120 degrees. is doing.
This makes it possible to disperse the lubricating fluid that moves between the bearing portion and the opening in a well-balanced manner, and to maintain a good flow of the lubricating fluid.

A hydrodynamic bearing device according to a fifth aspect of the present invention is the hydrodynamic bearing device according to any one of the first to fourth aspects of the present invention, wherein the sum of the cross-sectional areas of the grooves by the plane along the circumferential direction of the shaft is: It is larger than the sum of the cross-sectional areas of the bearing gap between the shaft and the sleeve including the groove cross-sectional area of the dynamic pressure generating groove by a plane orthogonal to the axial direction of the shaft.
Here, the total cross-sectional area of the groove portion by the plane along the circumferential direction of the shaft, in other words, the total cross-sectional area of the bearing gap between the shaft and the sleeve including the cross-sectional area of the groove portion along the circumferential direction of the sleeve, It is formed so as to be larger than the sum of the cross-sectional areas of the bearing gaps between the shaft and the sleeve including the groove cross-sectional area of the dynamic pressure generating groove by the surface orthogonal to the axial direction of the shaft.
Thereby, since a gap sufficiently larger than the gap between the shaft and the sleeve is provided in the groove portion, the lubricating fluid can be more smoothly moved to the gap side of the bearing portion. As a result, it is possible to more reliably prevent the negative pressure from being generated inside the bearing.

A hydrodynamic bearing device according to a sixth invention is the hydrodynamic bearing device according to any one of the first to fifth inventions, wherein the shaft connects the outer peripheral surfaces of the main body portion and the different diameter portion of the shaft. A first clearance (B) in the axial direction of the shaft between the shoulder portion of the sleeve and the sleeve, which is a surface substantially parallel to the radial direction, a depth (E) in the groove portion, and a bearing portion formed between the shaft and the sleeve. The relationship of the second gap (A) in the radial direction of the shaft satisfies the following relational expression (1).
B + E> A (1)
Here, in the relationship between the clearance of the bearing portion, the depth of the groove portion, and the first clearance (for example, the clearance between the shoulder portion and the sleeve cap in the radial direction of the shaft), the depth of the groove portion and the first clearance The depth of the groove is formed so that the sum of the two becomes larger than the gap of the bearing.

The first gap in the axial direction of the shaft between the shoulder portion and the sleeve includes, for example, a case where the distance becomes 0 due to contact between the shoulder portion and the sleeve due to vibration or the like of the hydrodynamic bearing device. Moreover, the depth of a groove part means the distance in the axial direction of the shaft in a groove part.
As a result, the lubricating fluid flowing in the groove communicating the bearing and the opening is more likely to flow than the lubricating fluid flowing in the bearing. As a result, it is always possible to supply a larger amount of lubricating fluid through the groove portion than the amount of lubricating fluid to be drawn into the bearing portion, and the generation of negative pressure inside the bearing can be prevented more reliably. it can. Furthermore, even when the shoulder portion and the sleeve are in contact with each other, it is possible to reliably obtain the same effect as described above.

A hydrodynamic bearing device according to a seventh aspect of the present invention is the hydrodynamic bearing device according to the second aspect of the present invention, wherein the sleeve cap includes a sleeve abutting portion that abuts on an outer peripheral side end portion of the sleeve main body portion, and an axial direction of the shaft. A recessed lubricating fluid reservoir, and a shaft engaging portion that engages with a shoulder that is a surface substantially parallel to the radial direction of the shaft that connects the outer peripheral surfaces of the main body portion and the different diameter portion of the shaft, in order from the outer peripheral side. The distance (D) between the lubricating fluid reservoir and the sleeve body in the axial direction of the shaft, the distance (C) between the shaft engaging portion and the sleeve body in the axial direction of the shaft, and the depth (E) in the groove The relationship of the maximum gap (F) in the opening satisfies the following relational expressions (2) and (3).
E <D-C (2)
E <F (3)
Here, in relation to the clearance between the sleeve cap and the shoulder, the height of the lubricating fluid reservoir, the depth of the groove, and the maximum clearance in the opening, the height of the lubricating fluid reservoir determines the relationship between the sleeve cap and the shoulder. The length obtained by drawing the gap is larger than the depth in the groove, and the depth in the groove is smaller than the maximum gap in the opening.
As a result, even if the lubricating fluid filled in the bearing portion and the opening is reduced and the liquid level of the lubricating fluid in the opening is lowered, air flows into the bearing through the groove. This can be prevented. Furthermore, even if a lubricating fluid pool formed by a sleeve and a sleeve cap is provided inside the bearing, it is possible to ensure the function of gas-liquid separation.

A hydrodynamic bearing device according to an eighth invention is the hydrodynamic bearing device according to any one of the first to seventh inventions, wherein the lubricating fluid is a maximum volume of bubbles generated inside the bearing at the opening. It is filled so that a void is secured.
Here, the volume of the lubricating fluid filled in the opening is set to a volume obtained by subtracting the volume of bubbles expected to be generated inside the bearing from the maximum volume that can be filled in the opening.
Thus, even if bubbles generated inside the bearing flow into the opening and push the lubricating fluid away, the lubricating fluid is not pushed to the outside of the opening. As a result, it is possible to prevent loss of durability and reliability due to leakage of the lubricating fluid from the opening.
A spindle motor according to a ninth aspect includes the hydrodynamic bearing device according to any one of the first to eighth aspects, a base, a stator, a rotor magnet, and a hub. The stator is fixed to the base. The rotor magnet is arranged to face the stator and constitutes a magnetic circuit together with the stator. The hub fixes the rotor magnet.

According to this, even when the spindle motor is used in a situation where it receives a large impact, durability and reliability can be improved.
A recording / reproducing apparatus according to a tenth aspect of the invention includes the spindle motor according to the ninth aspect of the invention and information access means. The information access means writes or reads information to or from a required position of a recording medium fixed to the hub and capable of recording information.
According to this, even when the recording / reproducing apparatus is used in a situation where it receives a large impact, it is possible to improve durability and reliability.

  According to the hydrodynamic bearing device of the present invention, the durability of the spindle motor can be prevented by preventing negative pressure from being generated inside the bearing and generating and expanding bubbles in the lubricating fluid even when subjected to impact or vibration. And reliability can be improved.

A spindle motor 1 equipped with a hydrodynamic bearing device according to an embodiment of the present invention will be described with reference to FIGS.
In the following description, the vertical direction in FIG. 1 is expressed as “axial direction”, the upward direction as “axially upper side” (axially outer side), and the downward direction as “axially lower side” (axially outer side). These do not limit the mounting direction of the actual hydrodynamic bearing device 30.
[Spindle motor 1 overall configuration]
As shown in FIG. 1, the spindle motor 1 according to the present embodiment is a device for rotationally driving a recording disk (recording medium) 5, and mainly includes a rotating member 10, a stationary member 20, and a hydrodynamic bearing device. 30.
The rotating member 10 mainly has a hub 11 on which the recording disk 5 is mounted and a rotor magnet 12.

The hub 11 is formed of, for example, stainless steel (for example, martensitic or ferritic stainless steel, for example, DHS1) that is an iron-based metal material, and is press-bonded to the shaft 31. It is integrated with the shaft 31. Further, the hub 11 is integrally formed with a disk mounting portion 11a for mounting the recording disk 5 on the outer peripheral portion.
The rotor magnet 12 is fixed to the outer peripheral surface of the hub 11 and constitutes a magnetic circuit together with a stator 22 described later. The rotor magnet 12 is made of a magnet material having a high energy product, such as a neodymium-iron-boron resin magnet, and the surface is subjected to an epoxy resin coating, nickel plating, or the like for rust prevention treatment and chipping prevention treatment. Yes.

The recording disk 5 is mounted on the disk mounting portion 11a, and is held down between the clamper and the disk mounting portion 11a by being pressed downward in the axial direction by, for example, a clamper (not shown).
As shown in FIG. 1, the stationary member 20 mainly includes a base 21 and a stator 22 fixed to the base 21.
The base 21 also serves as a housing of the recording / reproducing device, and includes a first base portion 21 a that becomes a base portion of a hydrodynamic bearing device 30 described later, and a second base portion 21 b for attaching the stator 22. The base 21 is made of an aluminum metal material or an iron metal material.
The stator 22 is fixed to the second base portion 21 b and is disposed at a position facing the rotor magnet 12. The stator core of the stator 22 is formed by laminating silicon steel plates having a thickness of 0.15 to 0.20 mm.

[Detailed Configuration of Fluid Bearing Device 30]
As shown in FIG. 2, the hydrodynamic bearing device 30 is fixed to an opening formed in a substantially central portion of the base 21, and supports the rotating member 10 in a rotatable state with respect to the stationary member 20. The hydrodynamic bearing device 30 is mainly configured to include a shaft 31, a sleeve 32, a thrust plate 33, and oil (lubricating fluid) 34 as a lubricating fluid. Of these, the sleeve 32 and the thrust plate 33 constitute a stationary member, and the shaft 31 constitutes a rotating member.
The shaft 31 is a ferrous metal material such as stainless steel (for example, SUS303, which is an austenitic stainless steel, ASK8000 having a higher manganese content than a normal austenitic stainless steel, SUS420, which is a martensitic stainless steel, or the like. ) Or a cylindrical member formed of ceramics or the like that extends in the axial direction, and is rotatably inserted into a bearing hole (insertion hole) 32d of the sleeve 32. Specifically, the shaft 31 is disposed so as to be relatively rotatable with respect to the sleeve 32 and the thrust plate 33 through a gap. The shaft 31 includes a main body portion 31a, a different diameter portion 31b having a smaller diameter than the main body portion 31a on the outer side in the axial direction adjacent to the main body portion 31a, and a different diameter portion 31b near the outer end portion of the shaft 31. Has a convex portion 31c having a further reduced diameter. Further, a shoulder portion 31d that is a surface parallel to the radial direction of the shaft 31 is formed between the outer peripheral surface of the main body portion 31a and the outer peripheral surface of the different diameter portion 31b in the shaft.

The sleeve 32 is a substantially cylindrical member having a bearing hole 32d extending in the axial direction formed of, for example, pure iron, stainless steel, copper alloy, and sintered metal, and is fixed to the base 21. . The sleeve 32 includes a sleeve main body 32a disposed at a position facing the outer peripheral side of the main body 31a of the shaft 31, a sleeve cap 32b at a position facing the outer peripheral side of the different diameter part 31b of the shaft 31, The sleeve main body portion 32a includes a communication hole 32c that communicates the upper end surface and the lower end surface.
The sleeve cap 32b is a cylindrical member having an inner peripheral surface smaller than the sleeve main body portion 32a for preventing the shaft 31 from slipping outward in the axial direction, and is a member forming an oil reservoir. . The sleeve cap 32b will be described in detail later.

The communication hole 32c is a hole for communicating the upper end surface and the lower end surface of the sleeve main body portion 32a, and is provided for circulating the lubricating fluid.
The thrust plate 33 is formed of stainless steel (for example, SUS420) or cemented carbide steel (for example, FB10), which is an iron-based metal material, and is substantially circular formed at the lower end of the sleeve 32 in the axial direction. It arrange | positions so that the opening part of may be closed.
Here, each part comprised by the stationary member 20 and the rotation member 10 is demonstrated.
A herringbone-shaped radial dynamic pressure generating groove (dynamic pressure generating groove) 41, which is well known in the art, is formed on the inner peripheral surface of the sleeve main body 32a, and the upper surface of the thrust plate 33 (the surface facing the shaft 31). ) Is provided with a thrust dynamic pressure generating groove 43. For this reason, a radial bearing portion (bearing portion) 42 including a radial dynamic pressure generating groove 41 is formed between the main body portion 31 a of the shaft 31 and the sleeve 32. Further, a thrust bearing portion 44 including a thrust dynamic pressure generating groove 43 is formed between the shaft 31 and the thrust plate 33.

The taper seal portion 36 is a gap formed by the outer peripheral surface of the different-diameter portion 31b of the shaft 31 and the inner peripheral surface of the sleeve cap 32b, and the gap increases toward the outer side in the axial direction. The outer edge faces the atmosphere. In the present embodiment, the outer peripheral surface of the different-diameter portion 31b has a tapered structure, thereby forming a shape in which the gap increases toward the outer side in the axial direction. This makes it possible to hold oil using capillary action.
The hub 11 is fixed to the outer peripheral surface of the convex portion 31 c by press-fitting, bonding, laser welding, or the like, and has a structure that rotates with the rotation of the shaft 31.
The oil 34 is filled in a clearance formed between the shaft 31 including the radial bearing portion 42 and the thrust bearing portion 44, the sleeve 32, and the thrust plate 33, and the communication hole 32c. And as oil 34, low viscosity ester oil etc. can be used, for example.

As described above, the hydrodynamic bearing device 30 is a flangeless shaft type constituted by a radial bearing portion and a thrust bearing portion.
[Operation of spindle motor 1]
Here, the operation of the spindle motor 1 will be described with reference to FIGS. 1 and 2.
In the spindle motor 1, when the stator 22 is energized, a rotating magnetic field is generated and a rotational force is applied to the rotor magnet 12. Thereby, the rotating member 10 can be rotated together with the shaft 31 with the shaft 31 as the rotation center.
When the shaft 31 rotates, support pressures in the radial direction and the axial direction are generated in the respective dynamic pressure generating grooves 41 and 43. Thereby, the shaft 31 is supported in a non-contact state with respect to the sleeve 32. That is, the rotating member 10 can be rotated in a non-contact state with respect to the stationary member 20, thereby realizing high-precision high-speed rotation of the recording disk 5.

[Detailed structure of sleeve cap 32b]
Here, the arrangement and the like of the sleeve cap 32b will be described with reference to FIGS.
As described above, the sleeve cap 32b is disposed outside the sleeve main body portion 32a in the axial direction of the shaft 31. As shown in FIG. 3, the sleeve cap 32b has a sleeve contact portion 32f, an oil reservoir portion (lubricating fluid reservoir portion) 32g, and a shaft engaging portion 32h in order from the outer peripheral side. .
The sleeve contact portion 32f is a portion that fixes the sleeve cap 32b to the sleeve main body portion 32a, and is fixed in contact with a part of the outer peripheral surface of the sleeve main body portion 32a and a part of the upper end surface of the sleeve main body portion 32a. Has been.
The oil reservoir 32 g is recessed outward in the axial direction of the shaft 31. The oil reservoir 32g forms an oil reservoir 38 for storing oil 34 between the upper end surface of the sleeve main body 32a and the sleeve cap 32b. As shown in FIG. 3, a step surface 32 ab is processed in the axially lower side of the sleeve main body portion 32 a that forms the oil reservoir portion 38. As a result, a protruding portion 32aa protruding upward in the axial direction is formed. By forming the stepped surface 32ab, the accuracy of attaching the sleeve cap 32b can be improved, and the accuracy of the gap between the slit 31 formed in the sleeve cap 32b and the shaft 31 can also be improved. Moreover, even if the adhesive used for bonding the sleeve cap 32b and the sleeve main body 32a leaks out by forming the protruding portion 32aa, the adhesive leaked out by the protruding portion 32aa is blocked and communicated. It is possible not to move to the hole 32c side.

The shaft engaging portion 32h is an annular protrusion that protrudes toward the sleeve main body 32a when viewed from the oil reservoir 32g, and has a surface that faces the shoulder 31d of the shaft 31. Moreover, it has a surface which opposes the different diameter part 31b of the shaft 31, and forms a part of the taper seal part 36 mentioned above. As shown in FIG. 4, the shaft engaging portion 32 h is provided with three slits (groove portions) 39 facing the radial direction of the shaft 31.
Here, as shown in FIGS. 5 (a) and 5 (b), when the spindle motor 1 receives an impact or vibration in the vertical direction (axial direction), first, as shown in FIG. 5 (a). Thus, a force that moves downward in the axial direction with respect to the sleeve 32 acts on the shaft 31. At this time, the gap between the lower end surface of the shaft 31 and the thrust plate 33 is reduced, and the oil 34 is pushed out from the taper seal portion 36 by the amount of the oil 34 existing there. Then, as shown in FIG. 5B, when the shaft 31 moves axially upward with respect to the sleeve 32, a gap between the lower end surface of the shaft 31 and the thrust plate 33 is formed again, and the taper is tapered. A force acts in a direction in which the oil 34 pushed out to the seal portion 36 is sucked into the bearing gap. At this time, in the conventional hydrodynamic bearing device, the oil flow path becomes smaller as the shaft moves upward in the axial direction with respect to the sleeve. For this reason, the oil corresponding to the gap between the shaft and the thrust plate cannot sufficiently flow into the bearing gap, and there is a possibility that negative pressure is generated in the bearing gap.

In the present embodiment, at this time, even if the sleeve cap 32b and the shoulder portion 31d of the shaft 31 come into contact with each other, the taper seal portion 36 and the bearing interior (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44). The passage of the oil 34 is secured by providing the slit 39. Thereby, even if the sleeve cap 32b and the shoulder portion 31d of the shaft 31 come into contact with each other, the oil 34 can move to the bearing clearance side through the slit 39 provided in the sleeve cap 32b. It is possible to prevent negative pressure from being generated in the bearing portion 42, the oil reservoir 38, the communication hole 32c, and the thrust bearing portion 44), and to suppress the generation and expansion of bubbles.
Here, the relationship between the sectional area of the slit 39 and the groove sectional area of the radial dynamic pressure generating groove 41 formed in the radial bearing portion 42 will be described in detail.

The shaft engaging portion 32h is an annular member having an inner diameter of 2.75 mm and an outer diameter of 3.32 mm. The slits 39 are formed at three equal intervals in the annular direction, and are formed in a fan-side shape with an inner angle of 30 degrees. The height (depth) of the slit 39 in the axial direction of the shaft 31 is 20 μm. With these specifications, the sectional area of the slit 39 formed in the shaft engaging portion 32h, that is, the total sectional area along the circumferential direction of the slit 39 that connects the tapered seal portion 36 and the radial bearing portion 42 is as follows. , Approximately 0.04 mm ² .
On the other hand, the radial dynamic pressure generating groove 41 formed in the radial bearing portion 42 is formed on the inner peripheral surface of the sleeve main body portion 32a, and the inner diameter of the sleeve main body portion 32a is, for example, 3 mm. A total of eight grooves are formed with a depth of 0.005 mm and a groove width ratio of 40% with respect to the inner peripheral surface of the sleeve main body portion 32a. The total groove cross-sectional area of the radial dynamic pressure generating groove 41 formed by these specifications is about 0.01 mm ² .

In the spindle motor 1 of the present embodiment, the sum of the sectional areas of the slits 39 (about 0.04 mm ² ) includes the shaft 31 and the sleeve 32 including the groove sectional area (about 0.01 mm ² ) of the radial dynamic pressure generating groove 41. It is designed to be larger than the sum (about 0.03 mm ² ) of the sectional area of the bearing gap between the ^two . It is assumed that the diameter of the shaft 31 is 2.996 mm and the inner diameter of the sleeve 32 is 3 mm.
Thereby, the flow of the oil 34 which flows to the radial dynamic pressure generating groove 41 side formed in the radial bearing portion 42 can be sufficiently ensured. As a result, a larger amount of oil 34 can be supplied through the slit 39, so that the inside of the bearing (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust, etc. can be obtained even during vibration in the spindle motor 1 described above. It is possible to more reliably prevent the negative pressure from being generated in the bearing portion 44).

[Example 1]
When the spindle motor 1 receives an impact in the vertical direction, a slit 39 disposed in the sleeve cap 32b for communicating the radial bearing portion 42 and the taper seal portion 36 is formed inside the bearing (radial bearing portion 42, oil reservoir). 38, the following simulation was performed to confirm the effect of preventing negative pressure from being generated in the communication hole 32c and the thrust bearing portion 44). Specifically, as shown in FIG. 6, the gap G in the axial direction of the shaft 31 between the lower end surface of the sleeve cap 32 b and the shoulder 31 d of the shaft 31 is 25 μm, and the radial bearing portion 42 and the taper seal portion 36. Of the hydrodynamic bearing device having the slit 39 communicating with the hydrodynamic bearing device and the hydrodynamic bearing device not having the slit 39 when the vibration is applied in the vertical direction (the radial bearing portion 42, the oil reservoir 38, the communication A simulation was performed on the pressure drop in the hole 32c and the thrust bearing portion 44).

Here, the upper and lower strokes, that is, the cycle of 25 μm reciprocation is performed in 0.5 seconds, and the amount of oil 34 moving at this time is 7.07 × 10 ⁻³ m / second, and the flow rate is half a stroke. It is assumed that the gap change is continuous at a constant period (0.25 seconds). As a result of simulation under these conditions, a graph of the pressure drop inside the bearing as shown in FIGS. 7A and 7B was obtained.
FIG. 7A is a graph showing the pressure drop inside the bearing in the hydrodynamic bearing device without the slit 39. According to this, as the time changes, the gap G becomes smaller and eventually becomes zero. This indicates that the sleeve cap 32b is in contact with the shoulder 31d due to vibration in the vertical direction. And it turns out that the pressure inside a bearing is also falling rapidly, as the change of this time, ie, the clearance gap G, becomes small. Looking at the pressure inside the bearing at this time, it has reached −100 kPa, so in fact, bubbles are generated before reaching this point, and it is considered that the pressure drop is reduced.

FIG. 7B is a graph showing the pressure drop inside the bearing in the hydrodynamic bearing device in which the slit 39 is provided. Also in this case, with the change of time, the gap G becomes smaller and eventually becomes zero. However, unlike the case of FIG. 7A, a large pressure drop does not occur inside the bearing even at the stroke end (immediately before Gap = 0) (the maximum value is −0.3 kPa). This is probably because the flow path resistance can be kept low by providing the slit 39, and thus the pressure drop inside the bearing can be suppressed.
As described above, from the simulation results, by providing the slit 39 for communicating the radial bearing portion 42 and the taper seal portion 36, the inside of the bearing (the radial bearing portion 42, the oil reservoir 38, the communication hole 32c, the thrust bearing portion 44). ) Can be suppressed, and as a result, it has been confirmed that the generation of bubbles can be suppressed.

[Features of spindle motor 1]
(1)
3 and 4, the spindle motor 1 of the present embodiment has a radial dynamic pressure generating groove 41 formed on the inner peripheral surface of the sleeve 32, and the sleeve 32 and the shaft 31 are connected via an oil 34. A radial bearing portion 42 is provided that is rotatably supported. Further, a taper structure in which one end of the shaft 31 in the axial direction faces the atmosphere between the outer peripheral surface of the different diameter portion 31b of the shaft 31 and the sleeve cap 32b which is a part of the sleeve 32 and the inner peripheral surface. A taper seal portion 36 is formed. The sleeve cap 32 b attached to the upper portion of the sleeve 32 is formed with a slit 39 that communicates the tapered seal portion 36 and the radial bearing portion 42 along the radial direction of the shaft 31.

As a result, the spindle motor 1 receives an impact or vibration in the vertical direction, and the shaft 31 moves up and down relative to the sleeve 32. The shoulder 31d of the shaft 31 and the sleeve cap 32b forming the sleeve 32 come into contact with each other. Even when the gap between the two members is interrupted, the oil 34 smoothly moves from the taper seal portion 36 to the radial bearing portion 42 side through the slit 39 that connects the taper seal portion 36 and the radial bearing portion 42. Can be made. Therefore, it is possible to prevent the generation of negative pressure inside the bearing (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44).
As a result, even when the spindle motor 1 is subjected to impact or vibration, the oil 34 is prevented by preventing the generation of negative pressure inside the bearing (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44). Since the generation of bubbles and the expansion of bubbles can be suppressed, the oil 34 can be prevented from leaking and the durability and reliability of the spindle motor 1 can be improved.

(2)
In the spindle motor 1 of the present embodiment, as shown in FIG. 2, the sleeve 32 is disposed at a position facing the outer peripheral side of the body 31 a of the shaft 31, and the different diameter portion of the shaft 31. A sleeve cap 32b is included at a position facing the outer peripheral side of 31b. The sleeve cap 32b is provided to prevent the shaft 31 from slipping outward in the axial direction.
That is, even in a flangeless type spindle motor, negative pressure is prevented from being generated in the bearing 34 (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44). Generation and expansion of bubbles can be suppressed. As a result, it is possible to prevent the oil 34 from leaking due to the generation and expansion of bubbles, thereby improving the durability and reliability of the spindle motor 1.

(3)
In the spindle motor 1 of the present embodiment, as shown in FIG. 4, three slits 39 are formed at equal intervals in the annular direction, and the adjacent slits 39 as viewed from the center of the shaft 31 are 120 degrees each. Have an angle.
As a result, the oil 34 that moves between the radial bearing portion 42 and the taper seal portion 36 can be efficiently dispersed, and the amount of oil 34 that moves between the gaps can be secured in a well-balanced manner. .
(4)
In the spindle motor 1 of the present embodiment, the total cross-sectional area in the circumferential direction of the slit 39 (about 0.04 mm ²⁾ is the shaft 31 including the groove cross-sectional area of the radial hydrodynamic grooves 41 (about 0.01 mm ²⁾ It is designed to be larger than the total cross-sectional area (about 0.03 mm ² ) of the bearing gap with the sleeve 32.

This ensures a sufficient amount of oil 34 flowing in the slit 39 that allows the radial bearing portion 42 and the taper seal portion 36 to communicate with each other. ) Can be more reliably prevented from generating a negative pressure.
[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.
(A)
In the spindle motor 1 of the above embodiment, the example in which the hydrodynamic bearing device 30 of the present invention is applied to the flangeless type spindle motor 1 has been described. However, the present invention is not limited to this.

For example, as shown in FIG. 8, the present invention can be applied to a hydrodynamic bearing device 130 of a type having a flange portion protruding in the radial direction of the shaft at a part of the shaft. Hereinafter, the hydrodynamic bearing device 130 will be described. Here, description of the entire spindle motor is omitted, and only a part of the hydrodynamic bearing device 130 constituted by the sleeve 132 and the shaft 131 will be described.
As shown in FIG. 8, the shaft 131 includes a main body portion 131 a and a disk-shaped thrust flange (different diameter portion, flange portion) 131 b extending in a direction orthogonal to the axial direction of the shaft 131. Yes. The thrust flange 131b is housed in a recess 132b formed in the sleeve 132, and is configured to hold the rotating sleeve 132.
As shown in FIG. 8, the sleeve 132 has a sleeve main body portion 132a, a concave portion 132b, and a communication hole 132c. The sleeve main body portion 132 a is disposed at a position facing the main body portion 131 a and the shaft 131 in the radial direction. As described above, the recess 132b is disposed at a position facing the thrust flange 131b and the shaft 131 in the radial direction. The communication hole 132 c is formed so as to communicate between the upper end surface and the lower end surface of the sleeve 132, and at least one is formed along the axial direction of the shaft 131.

A radial dynamic pressure generating groove (dynamic pressure generating groove) 141 is formed on the inner peripheral surface of the sleeve main body 132a. Thus, a radial bearing portion (bearing portion) 142 including the radial dynamic pressure generating groove 141 is formed between the main body portion 131a and the sleeve main body portion 132a.
The taper seal portion (opening portion) 136 is a gap formed by the outer peripheral surface of the thrust flange 131b of the shaft 131 and the recess 132b, and the gap increases toward the outside in the axial direction. The end faces the atmosphere. In FIG. 8, since the outer peripheral surface of the thrust flange 131b has a taper structure, a shape is formed in which the gap increases toward the outer side in the axial direction. This makes it possible to hold oil using capillary action.
Oil (lubricating fluid) 134 is filled in a gap formed between the shaft 131 including the radial bearing 142 and the sleeve 132. And as oil 134, low viscosity ester oil etc. can be used, for example.

  As shown in FIG. 8, grooves (grooves) 139 facing the radial direction of the shaft 131 that connect the taper seal portion 136 and the radial bearing portion 142 are provided on the bearing inner surface of the thrust flange 131b. It has been. Thereby, for example, even if the spindle motor including the hydrodynamic bearing device 130 is subjected to vibration or the like up and down, and the thrust flange 131b and the upper end surface of the sleeve main body 132a come into contact with each other, the taper seal portion 136 and the bearing interior (radial bearing portion) 142, the communication hole 132c, etc.) can be prevented from being completely blocked. That is, even if the thrust flange 131b and the upper end surface of the sleeve main body 132a come into contact with each other, the oil 134 can be circulated through the groove 139 provided in the thrust flange 131b. It is possible to prevent negative pressure from being generated in the holes 132c and the like, and to prevent generation of bubbles.

The same effect can be obtained even when the groove 139 is formed on the sleeve 132 side.
Here, the example in which the radial dynamic pressure generating groove 141 is formed on the inner peripheral surface of the main body portion 132a of the sleeve 132 has been described. However, the present invention is not limited to such a configuration, and faces the sleeve main body portion 132a. A dynamic pressure generating groove may be formed on the outer peripheral surface of the main body 131a.
(B)
In the above embodiment, the example in which the hydrodynamic bearing device 30 of the present invention is applied to the flangeless spindle motor 1 has been described. However, the present invention is not limited to this.
For example, as shown in FIG. 12, the present invention can also be applied to a shaft rotation type hydrodynamic bearing device 230 using a flange type shaft having a flange portion 231b at the lower end portion of the shaft 231.

Specifically, since the slit 231c is provided on the upper surface of the flange portion 231b, even when an impact or vibration is applied in the axial direction and the shaft 231 moves violently in the vertical direction with respect to the sleeve 232a, the shaft 231 is provided. The bearing gap between the side surface and the sleeve 231a and the gap between the flange portion 231b and the thrust plate 233 are not blocked. As a result, by preventing the occurrence of negative pressure in the bearing gap, oil can be prevented from leaking out due to the generation or expansion of bubbles in the bearing gap, and the highly reliable hydrodynamic bearing device 230 can be provided as described above. The effect of can be obtained.
(C)
In the spindle motor 1 of the above-described embodiment, the example in which the slit 39 is disposed on the surface of the shaft engaging portion 32h facing the shoulder portion 31d of the shaft 31 has been described. However, the present invention is not limited to this.

For example, a slit may be provided on the shoulder side of the shaft to ensure communication between the taper seal portion and the inside of the bearing. Moreover, you may form a slit not only in any one but on both surfaces which oppose. Also in this case, the same effect as the spindle motor 1 according to the above embodiment can be obtained.
(D)
In the spindle motor 1 of the above embodiment, the sum of the sectional areas of the slits 39 (about 0.04 mm ² ) includes the shaft 31 and the sleeve 32 including the groove sectional area (about 0.01 mm ² ) of the radial dynamic pressure generating grooves 41. An example in which the relationship between the cross-sectional area of the slit 39 and the groove cross-sectional area of the radial dynamic pressure generating groove is specified to be larger than the total cross-sectional area (about 0.03 mm ² ) of the bearing gaps between Explained. However, the present invention is not limited to this.

For example, as shown in FIG. 9, the clearance A in the radial direction of the shaft 31 formed in the radial bearing portion 42, the depth E of the slit 39, and the axial direction of the shaft 31 between the shoulder portion 31d and the sleeve cap 32b. Even if the relationship with the first gap B is specified, it is always possible to supply a larger amount of oil 34 through the slit 39 than the amount of oil 34 to be drawn into the radial bearing portion 42. Therefore, similarly to the spindle motor 1 of the above embodiment, it is possible to prevent negative pressure from being generated in the bearing (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44). Obtainable.
That is, a clearance (first clearance) B in the axial direction of the shaft 31 between the shoulder portion 31d and the sleeve cap 32b, a depth E of the slit 39, and a clearance (second clearance) formed in the radial bearing portion 42. A spindle motor whose relationship with A satisfies the following expression (1) may be used.
B + E> A Formula (1)

(E)
In the spindle motor 1 of the above embodiment, as shown in FIG. 10, the distance C in the axial direction of the shaft 31 between the lower end surface of the shaft engaging portion 32h and the upper end surface of the sleeve main body portion 32a, and the bottom of the oil reservoir portion 32g. A distance D in the axial direction of the shaft 31 between the end surface and the upper end surface of the sleeve main body portion 32a, a depth E of the slit 39, and a maximum gap F in the radial direction of the shaft 31 between the taper seal portion 36 and the sleeve cap 32b, However, it may be designed so as to satisfy both the following expressions (2) and (3).
E <D-C Formula (2)
E <F Formula (3)
Accordingly, the oil 34 filled in the bearing (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44) and the taper seal portion 36 is reduced for some reason, and the taper seal portion 36 is reduced. Even when the liquid level of the oil 34 is lowered, air is prevented from flowing into the bearing (the radial bearing portion 42, the oil reservoir 38, the communication hole 32c, the thrust bearing portion 44) through the slit 39. be able to. Furthermore, even when the oil reservoir 38 formed by the sleeve main body portion 32a and the sleeve cap 32b is provided, it is possible to ensure the function of gas-liquid separation.

(F)
In the spindle motor 1 of the above embodiment, as shown in FIG. 4, an example in which three slits 39 arranged in the sleeve cap 32 b are provided at equal intervals in the annular direction has been described. However, the present invention is not limited to this.
For example, the slits may be provided at least at one place, and may be provided at two places or at four or more places. The number of slits can be freely designed within a range in which the strength as a shaft retaining prevention can be maintained. Further, the slits are not necessarily arranged at regular intervals. However, it is possible to disperse the oil that moves between the inside of the bearing and the taper seal in a well-balanced manner, and to maintain good oil flow. Is desirable.

(G)
In the spindle motor 1 of the above-described embodiment, as illustrated in FIG. 4, the slit 39 disposed in the sleeve cap 32 b is described as an example in which the shape of the slit 39 is formed in a fan shape. However, the present invention is not limited to this.
For example, the slit may be formed so that the circumferential cross-sectional area is the same on the inner peripheral side and the outer peripheral side of the sleeve cap. Further, the direction of the slit does not necessarily coincide with the radial direction, and may have an angle with respect to the radial direction.
(H)
In the spindle motor 1 of the above embodiment, the amount of oil 34 filled in the taper seal portion 36 is not particularly limited, but the amount of oil 34 to be filled can be designed as follows.

That is, the maximum volume of air bubbles generated inside the bearing (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44) is predicted, and the maximum volume capable of filling the taper seal portion 36 with oil 34 is expected. From the amount, it may be filled with an amount of oil in which the volume corresponding to the maximum volume of bubbles expected to be generated is removed in advance.
As a result, even if bubbles generated inside the bearing (radial bearing portion 42, oil reservoir 38, communication hole 32c, thrust bearing portion 44) flow into the taper seal portion 36 and push the oil 34 away, the oil 34 is a taper seal. It is possible to prevent the portion 36 from being pushed to the outside. As a result, it is possible to avoid a decrease in durability and reliability due to the oil 34 leaking from the taper seal portion 36.
(I)
In the spindle motor 1 of the above embodiment, the example in which the radial dynamic pressure generating groove 41 is formed on the inner peripheral surface of the sleeve 32 and the thrust dynamic pressure generating groove 43 is formed on the thrust plate 33 has been described. However, the present invention is not limited to this.

For example, the radial dynamic pressure generating groove may be formed on the outer peripheral surface of the shaft, and the thrust dynamic pressure generating groove may be formed on the surface of the shaft facing the thrust plate. Moreover, you may form not only in one mentioned above but in both. The radial dynamic pressure generating groove may be one set.
(J)
In the spindle motor 1 of the above-described embodiment, the example in which the stator 22 is disposed opposite to the outer peripheral side of the rotor magnet 12 has been shown, but the present invention is not limited to this. For example, a so-called outer rotor type spindle motor in which a stator is disposed opposite to the inner peripheral side of the rotor magnet may be used. Further, a so-called flat motor in which a ring-shaped magnet and an air-core coil are arranged to face each other in the axial direction may be used.

(K)
In the above embodiment, an example in which the present invention is applied to the spindle motor 1 has been described. However, the present invention is not limited to this.
For example, as shown in FIG. 11, the spindle motor 1 having the above-described configuration is mounted, and information recorded on the recording disk 5 is reproduced by the recording head 60a, and information is recorded on the recording disk 5. The present invention can also be applied to the recording / reproducing apparatus 60.
As a result, it is possible to obtain a recording / reproducing apparatus that can be reduced in size and thickness and can ensure vibration resistance and suppress the generation of noise even when used in a situation where large vibrations are assumed. .

  According to the present invention, the durability and reliability of the spindle motor can be improved by preventing negative pressure from being generated inside the bearing even when subjected to impact or vibration, and generating and expanding bubbles in the lubricating fluid. For example, it can be widely applied to a disk drive device, a reel drive device, a capstan drive device, a drum drive device, and the like.

1 is a cross-sectional view of a spindle motor including a hydrodynamic bearing device according to an embodiment of the present invention. The expanded sectional view of the hydrodynamic bearing device contained in FIG. The expanded sectional view of the sleeve cap vicinity contained in FIG. The top view of the sleeve cap in the X surface of FIG. (A), (b) is an internal sectional view which shows a motion of each member when the spindle motor of FIG. 1 receives a vibration and an impact up and down. The expanded sectional view of the sleeve cap vicinity contained in FIG. (A) is the figure which showed the result of having simulated the pressure drop inside a bearing when not providing a slit. (B) is the figure which showed the result of having simulated the pressure drop inside a bearing in the case of providing a slit. The expanded sectional view of the flange part vicinity in the hydrodynamic bearing apparatus which concerns on other embodiment of this invention. The schematic diagram for demonstrating the relationship between the depth of a slit, and each clearance gap in the spindle motor containing the hydrodynamic bearing apparatus which concerns on other embodiment of this invention. The schematic diagram for demonstrating the relationship between the depth of a slit, and each clearance gap in the spindle motor containing the hydrodynamic bearing apparatus which concerns on other embodiment of this invention. Sectional drawing which shows the structure of the recording / reproducing apparatus which concerns on further another embodiment of this invention. Sectional drawing which shows the structure of the spindle motor which concerns on further another embodiment of this invention.

Explanation of symbols

1 Spindle motor 5 Recording disk (recording medium)
DESCRIPTION OF SYMBOLS 10 Rotating member 11 Hub 11a Disk mounting part 12 Rotor magnet 20 Stationary member 21 Base 21a 1st base part 21b 2nd base part 22 Stator 30 Fluid bearing apparatus 31 Shaft 31a Main body part 31b Different diameter part 31c Convex part 31d Shoulder part 32 Sleeve 32a Sleeve body 32aa Protruding portion 32ab Stepped surface 32b Sleeve cap 32c Communication hole 32d Bearing hole (insertion hole)
32f Sleeve contact portion 32g Oil reservoir portion 32h Shaft engagement portion 33 Thrust plate 34 Oil (lubricating fluid)
36 Taper seal (opening)
38 Oil reservoir 39 Slit (groove)
41 Radial dynamic pressure generating groove (Dynamic pressure generating groove)
42 Radial bearing (bearing)
43 Thrust dynamic pressure generating groove 44 Thrust bearing portion 60 Recording / reproducing device 60a Recording head 130 Hydrodynamic bearing device 131 Shaft 131a Body portion 131b Thrust flange (different diameter portion, flange portion)
132 Sleeve 132a Sleeve body 132b Recess 132c Communication hole 134 Oil (lubricating fluid)
136 Taper seal (opening)
139 Groove (groove)
141 Radial dynamic pressure generating groove (Dynamic pressure generating groove)
142 Radial bearing (bearing)
230 Fluid Bearing Device 231 Shaft 231b Flange 231c Slit 232a Sleeve 232b Sleeve Cap 232c Communication Hole A Clearance (Second Clearance)
B gap (first gap)
E Depth (depth)
F clearance (maximum clearance)

Claims (10)

A sleeve having an insertion hole;
A shaft which is disposed in the insertion hole of the sleeve so as to be relatively rotatable with respect to the sleeve, and has a main body portion and a different diameter portion having a different radius from the main body portion;
A lubricating fluid filled in a gap formed between the sleeve and the shaft;
It has a dynamic pressure generating groove formed on at least one of the inner peripheral surface of the sleeve and the outer peripheral surface of the main body portion of the shaft, and supports the sleeve and the shaft so as to be relatively rotatable via the lubricating fluid. Bearings to
A thrust plate fixed to one end side in the axial direction of the shaft with respect to the sleeve;
An opening formed by the outer peripheral surface of the different diameter portion and the inner peripheral surface of the sleeve, the other end side in the axial direction of the shaft facing the atmosphere,
A groove formed in at least one of the sleeve and the shaft along a radial direction of the shaft, and communicating the opening and the bearing;
A hydrodynamic bearing device. The sleeve has a sleeve main body portion disposed on the outer peripheral side of the main body portion of the shaft, and a sleeve cap disposed on the outer peripheral side of the different diameter portion of the shaft.
The hydrodynamic bearing device according to claim 1. The different diameter portion is formed by a flange portion projecting annularly in the radial direction of the shaft.
The hydrodynamic bearing device according to claim 1. The groove portions are provided at equal intervals along the circumferential direction.
The hydrodynamic bearing device according to any one of claims 1 to 3. The total cross-sectional area of the groove portion by a plane along the circumferential direction of the shaft includes the groove cross-sectional area of the dynamic pressure generating groove by a plane orthogonal to the axial direction of the shaft. Greater than the total cross-sectional area of
The hydrodynamic bearing device according to any one of claims 1 to 4. A first shoulder in the axial direction of the shaft of the sleeve and the sleeve that is a surface substantially parallel to the radial direction of the shaft that connects the outer peripheral surfaces of the main body portion and the different diameter portion of the shaft. The relationship between the gap (B), the depth (E) in the groove, and the second gap (A) in the radial direction of the shaft formed between the shaft and the sleeve in the bearing is as follows. Satisfying equation (1),
The hydrodynamic bearing device according to any one of claims 1 to 5.
B + E> A (1) The sleeve cap includes a sleeve abutting portion that abuts on an outer peripheral side end portion of the sleeve main body portion, a lubricating fluid reservoir portion recessed in the axial direction of the shaft, and the main body portion and the different diameter portion of the shaft. A shaft engaging portion that engages with a shoulder that is a surface substantially parallel to the radial direction of the shaft connecting the outer peripheral surface, and is formed in order from the outer peripheral side,
The distance (D) between the lubricating fluid reservoir and the sleeve main body in the axial direction of the shaft, the distance (C) between the shaft engaging portion and the sleeve main body in the axial direction of the shaft, and the depth ( E), the relationship of the maximum gap (F) in the opening satisfies the following relational expressions (2) and (3):
The hydrodynamic bearing device according to claim 2.
E <D-C (2)
E <F (3) The lubricating fluid is filled so that a gap corresponding to the maximum volume of bubbles generated in the bearing portion is secured in the opening.
The hydrodynamic bearing device according to claim 1. The hydrodynamic bearing device according to any one of claims 1 to 8,
Base and
A stator fixed to the base;
A rotor magnet that is disposed opposite to the stator and forms a magnetic circuit with the stator;
A spindle motor comprising a hub for fixing the rotor magnet. A spindle motor according to claim 9;
A recording / reproducing apparatus comprising: information access means for writing information to or reading information from a required position of a recording medium that can record information fixed to the hub.

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