JP2001187914A - Thrust dynamic pressure bearing device and its making method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep preferable thrust dynamic characteristics for a long time by satisfactorily prevent deformation of a thrust plate with a simple structure. SOLUTION: A ratio of axial spacings La, Lb from axial both end surfaces of a thrust plate 23 to fitting/junction parts of a shaft member 21 is regulated within a proper range in respect to axial length Lh of the fitting/junction part. Junctional strength of the thrust plate 23 to the shaft member 21 is distributed evenly in an axial direction. The degree of deformation of the thrust plate 23 is suppressed to extremely minimum extent as not to influence dynamic characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thrust hydrodynamic bearing device for supporting a shaft member and a bearing member so as to be relatively rotatable in a thrust direction by a predetermined dynamic pressure of a lubricating fluid, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, magnetic disks, polygon mirrors,
Various proposals have been made regarding dynamic pressure bearing devices for supporting various types of rotating bodies such as optical disks at high speed. In the thrust bearing portion of this dynamic pressure bearing device, as shown in FIG. 9, for example, a dynamic pressure surface on the thrust plate 2 side fitted and fixed to the shaft member 1, and a bearing sleeve constituting the thrust bearing member 3 and the dynamic pressure surface on the counter plate 4 side are arranged so as to oppose each other in the axial direction via a predetermined narrow gap, and a lubricating fluid such as air or oil is injected into the opposing gap. . Fluid pressurizing means such as a dynamic pressure generating groove (not shown) is formed on at least one of the opposed dynamic pressure surfaces, and lubricated by the pumping action of the fluid pressurizing means during rotation. The fluid is pressurized, and the resulting dynamic pressure of the lubricating fluid causes the shaft member 1 and the thrust bearing members 3 and 4 to be rotatably supported in the thrust direction while relatively floating. Has become.

A fixing hole 2a is provided at the center of the thrust plate 2 used in such a thrust dynamic pressure bearing device so as to penetrate therethrough, and the fixing hole 2a is connected to the shaft member. The first and second members 2 and 1 are fitted and fixed to the first member 1 by an insertion joining means such as press-fitting or shrink fitting. In other words, the insertion joining means applies a predetermined compressive stress to the outer peripheral surface of the shaft member 1 from the inner peripheral wall surface of the fixing hole 2 a of the thrust plate 2.
Is generated toward the center in the radial direction to form a fitting joint Lh, and the thrust plate 2 itself generates a strong tightening force with respect to the shaft member 1.

At this time, when the fixing hole 2a of the thrust plate 2 is inserted into the shaft member 1, usually, the shaft end portion of the shaft member 1 and the openings at both ends in the axial direction of the fixing hole 2a are formed. In the cross-sectional shape, the chamfers 5, 6, and 7 having a linear shape or a curved shape are formed. These chamfers 5, 6, 7 are formed by diagonally cutting off the peripheral edge of the shaft end portion of the shaft member 1 and the opening at both ends in the fixing hole 2a. By providing the chamfers 5, 6, and 7, the tip area of the shaft end portion of the shaft member 1 is reduced outward, and the opening area of the fixing hole 2a is increased outward. As a result, the work of inserting the two members 1 and 2 can be easily performed.

[0005]

However, as shown in FIG. 9 described above, the sizes of the double-sided portions 5, 6, 7 provided on the shaft member 1 and the thrust plate 2, respectively, are different from each other. If the dimensional relations differ by more than a certain value, the action of the compressive stress left on the thrust plate 2 itself by the insertion joining means such as the press-fitting or shrink fitting described above becomes asymmetric in the axial direction. As a result, the thrust plate 2 may be deformed by itself. The deformation at that time is to bend in an umbrella shape or an arc shape toward the one having the largest dimension among the chamfered portions 5, 6, and 7 described above.

If the thrust plate 2 is deformed due to such a cause, the right angle between the shaft member 1 and the thrust plate 2 will be deviated, and the thrust plate 2 and the thrust bearing member 3, 4 cannot be maintained, and the dynamic pressure characteristics are significantly reduced. In addition, since the gap of the thrust dynamic pressure bearing portion becomes uneven in the circumferential direction, the balance of the pumping force by the fluid pressurizing means such as the groove for generating dynamic pressure is lost, and a predetermined floating amount is obtained. At the same time, the minimum number of revolutions required for floating is increased, and in the worst case, contact occurs in the bearing portion to accelerate the progress of wear and shorten the life of the device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thrust hydrodynamic bearing device having a simple structure and capable of favorably preventing deformation of a thrust plate, and a method of manufacturing the same.

[0008]

In order to achieve the above object, in the thrust dynamic pressure bearing device according to the first aspect, the shaft member is fixed by fitting a fixing hole to the shaft member. The thrust plate, a thrust bearing member disposed so as to sandwich the thrust plate in the axial direction, and a thrust dynamic pressure bearing portion formed in an opposing gap between the thrust plate and the thrust bearing member. A thrust dynamic pressure, comprising: a lubricating fluid; and a fluid pressurizing means for generating a dynamic pressure in the lubricating fluid. The thrust dynamic pressure supporting the shaft member and the thrust bearing member so as to be relatively rotatable by the dynamic pressure generated in the lubricating fluid. In the bearing device,
The thrust plate and the shaft member are fitted with a predetermined length Lh in the axial direction by insertion joining means for applying a compressive stress from the inner peripheral wall surface of the fixing hole of the thrust plate to the outer peripheral surface of the shaft member. The relationship between the outer diameter OD, the same inner diameter ID, and the thickness T in the coaxial direction of the thrust plate is fixed as OD-ID = 4T / α (where α ≦ 4).
For each of the axial distances La and Lb from each axial end face of the thrust plate to each end of the axial length Lh at the fitting joint, Lb La ≦ α when ≦ La
It is set so that Lb ≦ αLa when Lb or La ≦ Lb.

Further, in the thrust dynamic pressure bearing device according to the second aspect, the insertion joining means according to the first aspect is a press-fitting means or a shrink fitting means.

Further, in the thrust hydrodynamic bearing device according to the third aspect, the axial gaps La and Lb according to the first aspect are provided.
Are set so that La ≦ 0.2 Lh or Lb ≦ 0.2 Lh with respect to the axial length Lh of the fitting joint.

Further, in the thrust hydrodynamic bearing device according to the fourth aspect, each of the axial distances La and Lb according to the first aspect may be a chamfered portion formed at a shaft end portion of the shaft member or the chamfered portion. Each of the chamfered portions formed in the axially opposite end opening portions of the fixing holes of the thrust plate or a combination thereof is defined by each of the chamfered portions, and each of the chamfered portions has a linear shape or a curved line shape in a cross-sectional shape. It has been done.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a thrust hydrodynamic bearing device, wherein: a shaft member; a thrust plate fixed by fitting a fixing hole to the shaft member; Thrust bearing members disposed so as to face each other in the axial direction, a lubricating fluid injected into a thrust dynamic pressure bearing portion formed in an opposing gap between the thrust plate and the thrust bearing member, and the lubricating fluid. Fluid pressurizing means for generating dynamic pressure,
A method of manufacturing a thrust dynamic pressure bearing device that supports the shaft member and the thrust bearing member so as to be relatively rotatable by dynamic pressure generated in the lubricating fluid, wherein the thrust plate and the shaft member are separated by the thrust plate. A predetermined length L in the axial direction by insertion joining means for applying a compressive stress from the inner peripheral wall surface of the fixing hole to the outer peripheral surface of the shaft member.
h, wherein the outer diameter OD and the inner diameter ID of the thrust plate are fixed.
OD-ID = 4T / α.
For α that satisfies (where α ≦ 4), each axial distance La from each axial end face of the thrust plate to each end of the axial length Lh at the fitting joint portion. Lb and Lb are set so that La ≦ αLb when Lb ≦ La or Lb ≦ αLa when La ≦ Lb.

Further, in the method of manufacturing a thrust dynamic pressure bearing device according to a sixth aspect, the thrust plate and the shaft member according to the fifth aspect are moved from the inner wall surface of the fixing hole of the thrust plate to the outside of the shaft member. In the step of fixing with a joining means for applying a compressive stress to the surface, a press-fitting means or a shrink fitting means is adopted as the inserting and joining means.

Further, in the method of manufacturing a thrust hydrodynamic bearing device according to a seventh aspect, each of the axial distances La and Lb according to the fifth aspect is set with respect to the axial length Lh of the fitting joint. And La ≦ 0.2Lh or Lb ≦
Manufacturing is performed with the setting set to 0.2 Lh.

In the method of manufacturing a thrust hydrodynamic bearing device according to the eighth aspect, the axial distance La according to the fifth aspect is provided.
And Lb are each defined by a chamfer formed at the shaft end of the shaft member or a chamfer formed at both axial openings of the fixing hole of the thrust plate or a combination thereof. In this case, each of the chamfered portions is formed into a linear shape or a curved line shape in a cross-sectional shape.

According to the present invention having such a configuration,
The ratio of the axial distances La and Lb from the axial end surfaces of the thrust plate to the fitting joint with the shaft member is defined within an appropriate range with respect to the axial length Lh of the fitting joint. By doing so, the joining force of the thrust plate to the shaft member is evenly distributed along the axial direction, and as a result, the degree of deformation of the thrust plate is suppressed to a very small amount within a range that does not affect the dynamic pressure characteristics Will be able to

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. Prior to that, the overall structure of a hard disk drive (HDD) to which the present invention is applied will be described with reference to the drawings.

The entire shaft-rotating HDD spindle motor shown in FIG. 1 has a stator set 10 as a fixing member.
And a rotor set 20 as a rotating member attached to the stator set 10 from above in the figure. Among them, the stator set 10 has a fixed frame 11 screwed to a fixed base (not shown). The fixed frame 11 is formed of an aluminum-based metal material to reduce the weight. However, an inner peripheral side of an annular bearing holder 12 formed so as to stand substantially at the center of the fixed frame 11. A bearing sleeve 13 as a fixed bearing member formed in a hollow cylindrical shape is joined to the bearing holder 12 by press fitting or shrink fitting. The bearing sleeve 13 is formed of a copper-based material such as phosphor bronze in order to facilitate machining of a small-diameter hole or the like.

A stator core 14 made of a laminated body of electromagnetic steel sheets is fitted on the outer peripheral mounting surface of the bearing holder 12. A drive coil 15 is wound around each salient pole portion provided on the stator core 14.

Further, a rotating shaft 21 constituting the above-described rotor set 20 is rotatably inserted into a center hole provided in the bearing sleeve 13. That is, the dynamic pressure surface formed on the inner peripheral wall of the bearing sleeve 13 is disposed so as to radially oppose the dynamic pressure surface formed on the outer peripheral surface of the rotary shaft 21, The radial dynamic pressure bearing part RB is formed. More specifically, the dynamic pressure surface on the bearing sleeve 13 side and the dynamic pressure surface on the rotary shaft 21 side of the radial dynamic pressure bearing portion RB are several μm.
The lubricating fluid, such as oil, magnetic fluid, or air, is injected into the bearing space formed by the minute gap so as to be continuous in the axial direction.

Further, on at least one side of both the dynamic pressure surfaces of the bearing sleeve 13 and the rotating shaft 21, for example, a herringbone-shaped radial dynamic pressure generating groove (not shown) is divided into two blocks in the axial direction. When rotating, the lubricating fluid is pressurized by the pumping action of the radial dynamic pressure generating groove to generate a dynamic pressure, and the dynamic pressure of the lubricating fluid causes the dynamic pressure of the lubricating fluid to be described later together with the rotating shaft 21. The rotary hub 22 is configured to be axially supported in the radial direction.

Further, a capillary seal portion RS is arranged at the upper end of the bearing space constituting each of the radial dynamic pressure bearing portions RB in the figure. The capillary seal portion RS is such that the gap is gradually enlarged toward the outer side of the bearing by the inclined surface formed on the rotating shaft 21 or the bearing sleeve 13 side, and is set, for example, from 20 μm to 300 μm. I have. The capillary seal portion RS is configured such that the level of the lubricating fluid is located in both cases of rotation and stop of the motor.

Further, the rotary hub 22 constituting the rotor set 20 together with the rotary shaft 21 is formed of a substantially cup-shaped member made of an aluminum-based metal so as to mount a recording medium such as a magnetic disk (not shown). , The rotary hub 22
Of the rotary shaft 21
Are integrally joined by press fitting or shrink fitting.

The rotary hub 22 has a substantially cylindrical body 22a on which a recording medium disk is mounted on the outer periphery, and a back yoke 22b The annular drive magnet 22c is attached via the. This annular drive magnet 22c
Are disposed close to each other so as to annularly face the outer peripheral end face of the stator core 14 described above.

On the other hand, as shown in FIG. 2, a disc-shaped thrust plate 23 is fixed to the tip of the rotating shaft 21 at the lower end in the drawing. The thrust plate 23 is disposed so as to be accommodated in a cylindrical recess formed in the center of the bearing sleeve 13 at the lower end in the drawing, and the thrust plate 23 is provided in the recess of the bearing sleeve 13. The dynamic pressure surface provided on the upper side surface of the thrust plate 23 in the drawing is opposed to the dynamic pressure surface provided on the bearing sleeve 13 so as to be close to the axial direction. A dynamic pressure generating groove is formed on at least one of the opposed dynamic pressure surfaces in a usual manner, and the thrust plate 23 and the bearing sleeve 13 are formed.
The upper thrust dynamic pressure bearing portion SBa is formed in the opposing gap between the two dynamic pressure surfaces.

Further, a counter plate 16 made of a disc-shaped member having a relatively large diameter is arranged so as to approach the lower dynamic pressure surface of the thrust plate 23 in the drawing. The counter plate 16 is fixed so as to close the lower end side opening of the bearing sleeve 13, and a dynamic pressure surface provided on the upper surface side of the counter plate 16 in the drawing and a lower side of the thrust plate 23 in the drawing. A lower thrust dynamic pressure bearing portion SBb is also formed by forming a dynamic pressure generating groove in the proximity opposing gap between the dynamic pressure generating surface and the dynamic pressure generating surface as usual.

As described above, both the dynamic pressure surfaces on the thrust plate 23 side forming a set of thrust dynamic pressure bearing portions SBa, SBb disposed adjacent to each other in the axial direction, the bearing sleeve 13 and the counter opposed thereto. Both the dynamic pressure surfaces on the plate 16 side are axially opposed to each other with a small gap of several μm therebetween, and a lubricating fluid such as oil, a magnetic fluid, and air is filled in a bearing space formed by the small gap. , And is injected so as to be continuous in the axial direction through the outer peripheral passage of the thrust plate 23.

Further, at least one of the dynamic pressure surfaces of the thrust plate 23 and the dynamic pressure surfaces of the bearing sleeve 13 and the counter plate 16 has a herringbone-shaped thrust dynamic pressure as shown in FIG. The generation groove DG is divided into two blocks in the radial direction and is annularly recessed, and when rotating, the thrust dynamic pressure generation groove D
The lubricating fluid is pressurized by the pumping action of G to generate a dynamic pressure, and the dynamic pressure of the lubricating fluid causes the aforementioned rotary shaft 2 to rotate.
1 and the rotating hub 22 are configured to be axially supported in the thrust direction.

Here, the above-described thrust plate 23 and the rotating shaft 21 are fixed to each other by insertion joining means such as press-fitting or shrink fitting. That is, as shown in FIG. 4 in particular, a fixing hole 23a for insertion into the rotating shaft 21 is formed in the center portion of the thrust plate 23 so as to penetrate in the axial direction. A compressive stress is applied from the inner peripheral wall surface of the fixing hole 23a to the outer peripheral surface of the rotating shaft 21 by the insertion joining means such as the press-fitting or shrink fitting. That is, the insertion joining means
By generating a stress remaining inside the thrust plate 23 toward the center in the radial direction, a strong tightening force is generated on the thrust plate 23 itself with respect to the rotating shaft 21, and the fitting connection having the axial length Lh is performed. The thrust plate 23 is fixed to the rotating shaft 21 side by such insertion and joining means.

At this time, as shown in FIGS. 2 and 4, the fixing holes 23a of the thrust plate 23 are formed.
In the opening portions at both ends in the axial direction of the chamfered portions Ca,
Cb are formed, and the rotating shaft 2
A chamfered portion Cc having a shape obtained by cutting off the peripheral edge of the shaft end portion is formed at the front end portion (the lower end portion in FIG. 2) of the shaft 1. Each of these chamfers C in the present embodiment
a, Cb, and Cc are so-called chamfers formed so as to form a linear shape in cross-sectional shape.
Each chamfered portion Ca, Cb on the thrust plate 23 side
Therefore, the opening portions at both ends of the fixing hole 23a are enlarged outward in the axial direction, and the tip area at the shaft end portion is reduced outward by the chamfered portion Cc on the rotating shaft 21 side. Thus, the operation of inserting the thrust plate 23 and the rotating shaft 21 can be easily performed.

On the other hand, such chamfers Ca, Cb,
In the case where Cc is provided, the axial length Lh of the fitting portion is reduced by that much, and the joining force is reduced. However, in the present embodiment, both ends of the thrust plate 23 in the axial direction are reduced. The following configuration is adopted so that the two joining forces on the side do not become unbalanced with each other.

That is, as shown particularly in FIG. 2, in the present embodiment, the thrust plate 23
, The axial distances La, Lb or Tb from each of the axial end faces to the axial end Lh of the fitting joint are defined so as to have an appropriate dimensional relationship. In addition, the axial distance La on the upper side in the figure and the axial distance Lb or Tb on the lower side in the figure are set to have a dimensional relationship within a specific range.

More specifically, the thrust plate 2
When OD is the outside diameter, ID is the inside diameter, and T is the thickness in the axial direction, the axial distance La is defined as follows: α satisfying OD−ID = 4T / α (α ≦ 4) When the dimensional relationship with Lb or Tb is Lb ≦ La, La
≦ αLb or Tb, or Lb or Tb ≦ αLa when La ≦ Lb or Tb.

In the above equation, the larger value of Lb or Tb is used. When Tb is larger, Lb in the claims of the present application corresponds to Tb. Will be done. That is, when the chamfered portion Cc on the rotating shaft 21 side has a smaller axial dimension than the chamfered portions Ca and Cb on the thrust plate 23 side,
Since the chamfered portion Cc on the side of the rotating shaft 21 does not shorten the length Lh of the fitting joint, the condition setting is performed only by considering the dimensional relationship between the two-sided chamfered portions Ca and Cb on the thrust plate 23 side. However, if the axial dimension of the chamfered portion Cc on the rotating shaft 21 side is formed to be larger than the chamfered portion Cb on the thrust plate 23 side, the chamfered portion Cc on the rotating shaft 21 side is used. Axial dimension Tb of
Is set in consideration of the above.

Each of the axial distances La and Lb or Tb is within 20% of the axial length Lh of the fitting joint, that is, La ≦ 0.2Lh, or Lb or Tb ≦ It is set to be 0.2 Lh. Note that also for Lb or Tb in the above equation,
The larger value is used, and when Tb is large, Lb in the claims of the present application corresponds to Tb. By defining such a dimensional relationship, the joining forces at both ends in the axial direction of the thrust plate 23 are balanced with each other.

That is, as in the present embodiment, the axial gaps La and Lb or Tb from the axial end faces of the thrust plate 23 to the fitting joint with the rotary shaft 21.
If the ratio of b to each other is defined within an appropriate range with respect to the axial length Lh of the fitting joint, the joining force of the thrust plate 23 to the rotating shaft 21 is evenly distributed along the axial direction. As a result, the degree of deformation of the thrust plate 23 is suppressed to a very small amount within a range that does not affect the dynamic pressure characteristics. In this regard, the inventor of the present application was able to clearly confirm, for example, based on the following experimental data.

When the amount of deformation of the thrust plate 23 from the neutral position was measured while variously changing the dimensional relationship between the thrust plate 23 and the chamfered portions Ca, Cb, Cc, as shown in Table 1 below, for example. became.

[Table 1]

At this time, due to the characteristics of the thrust dynamic pressure bearing,
The amount of deformation of the thrust plate 23 is desirably ± 5% or less with respect to the gap of the thrust dynamic pressure bearing portion.
When it is 5 mm, the upper limit of the amount of deformation of the thrust plate 23 is 0.000075 mm. And
In Table 1, when the above-described conditional expression is satisfied, the amount of deformation of the thrust plate 23 can be prevented from exceeding the upper limit.

As a specific example, Table 1 shows that T = 1.5
mm, ID = 3 mm (φ), but OD = 5 m
When m (φ), OD-ID = 5−3 = 2, so α that satisfies 4T / α = 2 is α = 3, which satisfies the above condition of α ≦ 4. I have. When the amount of deformation of the thrust plate 23 at this time is seen, it is understood that the above upper limit value is satisfied.

Further, as in the embodiment shown in FIG. 5 in which the corresponding members are represented by the same reference numerals, each of the axially open ends of the fixing hole 23a of the thrust plate 23 has
When the chamfered portions Ca 'and Cb' made of fillets having a curved linear shape in the cross-sectional shape are provided, the dimensional relationship based on the inflection points Pa and Pb of the two-sided chamfered portions Ca 'and Cb' is determined. The same operation and effect can be obtained by defining the same as in the above-described embodiment.

In this embodiment, the rotating shaft 21
A chamfered portion Cc ′ having a shape obtained by cutting off the peripheral edge of the tip of the rotating shaft 21 at the shaft end portion on the lower end side in the drawing.
However, since the chamfered portion Cc 'is formed with a smaller axial dimension than the chamfered portions Ca' and Cb 'on the thrust plate 23 side, the chamfered portion Cc' is fitted. The length Lh of the joint is not reduced. Therefore, as a result, similarly to the above-described embodiment, the double-sided chamfered portion C in the thrust plate 23 is obtained.
The condition may be set in consideration of only the dimensional relationship between a 'and Cb'. On the other hand, the chamfered portion Cc ′ on the rotating shaft 21 side
Of the chamfer C on the thrust plate 23 side
If it is formed with a larger dimension than a ′ and Cb ′, it is necessary to set the dimensional relationship in consideration of the axial dimension of the chamfered part Cc ′ on the rotating shaft 21 side as in the following embodiment. There is.

That is, in the embodiment according to FIG. 6 in which the corresponding members are represented by the same reference numerals,
A pair of chamfers are formed at predetermined intervals in the axial direction, and axial dimensions Ta, Tb of each of the chamfers with reference to both axial end surfaces of the thrust plate 23.
Are larger than the axial dimensions La ′ and Lb ′ of the double-sided portion on the thrust plate 23 side (Ta>).
La ′, Tb> Lb ′). In this case, since the length Lh of the fitting portion is determined by the axial dimensions Ta and Tb of the chamfered portion on the rotating shaft 21 side, the axial dimensions Ta and Tb of the chamfered portion on the rotating shaft 21 side are determined. May be set to the same conditions as in the above-described embodiment.

That is, in this case, from each of the axial end surfaces of the thrust plate 23, the rotation shaft 21
The axial distances Ta and Tb up to both ends of the axial length Lh in the fitting joint determined by the side chamfers correspond to La and Lb defined in the claims. One of the axial intervals Ta and Tb may be set so as to have a dimensional relationship within a specific range with respect to the other side.

Further, in the embodiment according to FIG. 7 in which the corresponding members are represented by the same reference numerals, the axial thickness of the thrust plate 23 decreases continuously outward in the radial direction, and the axial end faces are reduced. However, the other points are basically the same as those in the embodiment according to FIG. 5 described above. That is, each of the opening portions at both ends in the axial direction in the fixing holes 23a of the thrust plate 23,
Chamfers Ca ′ and Cb ′ each formed of a fillet having a curved linear shape in cross-sectional shape are provided, and the dimensional relationship based on the inflection points Pa and Pb of these two-sided chamfers Ca ′ and Cb ′ is as follows. The same operation and effect can be obtained by defining the same as in the above-described embodiments.

In the present embodiment, the chamfered portion Cc 'is provided at the lower end of the rotating shaft 21 in the figure, but is considered because it is smaller in dimension than the chamfered portion Cb' on the thrust plate 23 side. No need.

On the other hand, the dynamic bearing device according to the present invention can be similarly applied to a so-called fixed shaft type HDD spindle motor as shown in FIG.

That is, the entirety of the HDD spindle motor shown in FIG.
0 and a rotor set 40 as a rotating member assembled to the stator set 30 from above in the figure. The stator set 30 includes a frame 31 as a bearing support frame screwed to a fixed base (not shown), and a hollow cylindrical core holder 32 is provided substantially at the center of the frame 31. Are erected integrally.

A stator core 33 is fitted on the outer peripheral wall surface of the core holder 32, and a winding 34 is wound around each salient pole portion of the stator core 33.

On the other hand, a fixed shaft 35 is fixed to a substantially central portion of the frame 31 so as to protrude upward. The fixed shaft 35 is made of, for example, stainless steel (S
US420J2), and the upper end of the fixed shaft 35 in the figure is screwed to a fixed base (not shown) by using a female screw tap hole provided in the upper end. It has become.

A rotary hub 42 provided integrally with the bearing sleeve 41 is rotatable on the outer peripheral side of the fixed shaft 35 via a bearing sleeve 41 as a bearing member constituting the rotor set 40. It is attached to. That is, in the rotor set 40, the rotating hub 42 for supporting a predetermined recording medium (not shown) is
1 is arranged on the outer peripheral side. The rotary hub 42 has a substantially cylindrical body 42a on which a magnetic recording medium such as a magnetic disk is mounted on the outer periphery.
A drive magnet 42c is annularly mounted on the inner peripheral wall side of a through a back yoke 42b. The drive magnet 42c is disposed in close proximity to the outer peripheral end surface of each salient pole portion of the stator core 33 in a ring shape.

A pair of bearing projections 41a, 41a are formed on the inner peripheral wall of the center hole of the bearing sleeve 41 at predetermined intervals in the axial direction.
The reference numerals 1a and 41a are opposed to each other so as to approach the outer peripheral surface of the fixed shaft 35. A pair of radial dynamic pressure bearing portions RBa adjacent to each other are formed by a dynamic pressure surface provided on the inner peripheral surface of each of the bearing protrusions 41a, 41a and a dynamic pressure surface formed on the outer peripheral surface of the fixed shaft 35. , RBb are provided in parallel in the axial direction. The pair of radial dynamic pressure bearing portions RBa and RBb supports the rotary hub 42 so as to be rotatable in the radial direction with respect to the fixed shaft 35.

That is, each of the radial dynamic pressure bearing portions RB
In a and RBb, the dynamic pressure surface on the bearing sleeve 41 side and the dynamic pressure surface on the fixed shaft 35 side are circumferentially arranged via a small gap of several μm, and are separated by a predetermined distance in the axial direction. Are formed so as to be continuous. In each of these bearing spaces, lubricating oil (oil) is independently injected, and an enlarged space in which a portion between both dynamic pressure bearing portions RBa and RBb is depressed outward in the radial direction. B has an air layer in communication with the atmosphere.

A pair of radial dynamic pressure generating grooves each having a herringbone shape (not shown) are annularly arranged in parallel on at least the dynamic pressure surfaces on the bearing sleeve 41 side of the pair of dynamic pressure surfaces. When the rotary hub 42 rotates, the lubricating oil is pressurized and pressurized by the pumping action of the two radial dynamic pressure generating grooves to generate dynamic pressure, and the dynamic pressure generated by the lubricating oil is increased. The rotation hub 42 is configured to be axially supported by the pressure without contacting each other in the radial direction.

Further, each of the radial dynamic pressure bearing portions RB
Capillary seal portions as lubricating oil holding portions are provided at both ends in the axial direction of the bearing space constituting the a and RBb so as to sandwich the radial dynamic pressure bearing portions RBa and RBb from both sides in the axial direction. Each of these capillary seal portions is such that a gap between the bearing sleeve 41 and the fixed shaft 35 is gradually enlarged toward the outside of the bearing by an inclined surface formed on the bearing sleeve 41 side. The liquid level of the lubricating oil is set so as to be a predetermined position inside each capillary seal portion regardless of whether the motor rotates or stops.

Further, a disc-shaped thrust plate 36 is fixed to a tip end portion (upper end portion in the figure) of the fixed shaft 35. The thrust plate 36 is disposed so as to be accommodated in a cylindrical recess formed in the above-described center portion of the bearing sleeve 41 in the upper part of the drawing, and is provided on a bottom wall portion of the recess of the bearing sleeve 41. The lower thrust dynamic pressure bearing portion SBb is configured by the dynamic pressure surface provided on the lower surface side of the thrust plate 36 in the figure being disposed axially close to the dynamic pressure surface.

Also, a counter plate 44 made of a large disc-shaped member extends from the upper outer peripheral side of the bearing sleeve 41 to the center side so as to approach the dynamic pressure surface on the upper surface side of the thrust plate 36 in the drawing. So that it is attached. An upper thrust dynamic pressure bearing portion SBa is constituted by the dynamic pressure surface provided on the lower surface side of the counter plate 44 in the figure and the dynamic pressure surface provided on the upper surface side of the thrust plate 36 in the figure.

That is, in each of a pair of thrust dynamic pressure bearing portions SBa, SBb arranged adjacent to each other, the bearing sleeve 41 and the counter plate 4
Each of the three dynamic pressure surfaces and the two dynamic pressure surfaces at both axial end surfaces of the thrust plate 36 are axially opposed to each other with a small gap of several μm therebetween. Lubricating oil (oil) is independently injected into each bearing space consisting of a set of narrow gaps spaced apart by a predetermined distance in the axial direction through the shaft.

In the present embodiment, each of the dynamic pressure surfaces provided on both axial end surfaces of the thrust plate 36 is provided with a thrust dynamic pressure generating groove (not shown) having a herringbone shape (FIG. 3). The reference numeral DG in FIG. 2) is provided so as to be annularly parallel to each other, and when the rotary hub 42 rotates, the lubricating oil is pressurized and pressurized by the pumping action of the two thrust dynamic pressure generating grooves. Dynamic pressure occurs,
The dynamic pressure generated by the lubricating oil is configured so that the bearing sleeve 41 and the rotary hub 42 are axially supported in a non-contact state in the thrust direction.

Here, the above-described thrust plate 36 and the fixed shaft 35 are fixed to each other by an insertion joining means such as press-fitting or shrink fitting, and a fixing hole 36a provided in a central portion of the thrust plate 36 is provided. The thrust plate 36 is fixed to the fixed shaft 35 by applying a compressive stress from the wall surface to the outer surface of the fixed shaft 35 by the insertion joining means such as press-fitting or shrink fitting.

At this time, each of the axially open ends of the fixing hole 36a of the thrust plate 36 has
A chamfered portion C in which the peripheral corners of both openings are cut off.
a and Cb are respectively formed. The double-sided portions Ca and Cb in the present embodiment are formed of chamfers formed to have a linear cross section.
The openings at both ends in 6a are enlarged outward in the axial direction, so that the operation of inserting the thrust plate 36 and the fixed shaft 35 can be easily performed.

The thrust plate 36 in the present embodiment is also set to have the same dimensional relationship as that of the above-described embodiment shown in FIG. That is, if the reference numeral "23" indicating the thrust plate in FIG. 2 is replaced with the reference numeral "36", the reference numeral represents the one of the present embodiment, and FIG.
The axial distance La or Lb on either one of the axial distances La and Lb from each of the axial end faces of the thrust plate 36 to both ends of the axial length Lh at the fitting joint is described. , The axial distance La on the other side
Alternatively, Lb is set to have a dimensional relationship within a specific range.

More specifically, the thrust plate 3
When OD is the outer diameter, ID is the inner diameter, and T is the thickness in the axial direction, the axial distances La and Lb are satisfied for α satisfying OD−ID = 4T / α (where α ≦ 4). Is La ≦ αLb when Lb ≦ La,
Alternatively, it is set so that Lb ≦ αLa when La ≦ Lb.

Each of the distances La and Lb in the axial direction is 20% of the axial length Lh of the fitting joint.
Within, that is, La ≦ 0.2Lh or Lb ≦ 0.
It is set to be 2 Lh.

By defining the dimensional relationship in this manner, the joining forces at both axial end portions of the thrust plate 36 are balanced with each other. The joining force of the thrust plate 36 to the thrust plate 35 is evenly distributed along the axial direction. As a result, the degree of deformation of the thrust plate 23 is suppressed to a very small amount within a range that does not affect the dynamic pressure characteristics.

As mentioned above, the embodiment of the invention made by the present inventor has been described differently. However, the present invention is not limited to the above-described embodiment, and can be moderately modified without departing from the gist of the invention. Needless to say. For example, the present invention is also applied to a dynamic pressure bearing device used for a motor other than the HDD motor as in the above-described embodiment, for example, a polygon mirror driving motor or a CD-ROM driving motor. The same can be applied.

[0066]

As described above, according to the present invention, the ratio of the axial gaps La and Lb from the axial end faces of the thrust plate to the fitting joint with the shaft member is determined by the ratio of the fitting joint. By defining the axial length Lh within an appropriate range, the joining force of the thrust plate to the shaft member is evenly distributed along the axial direction, and the degree of deformation of the thrust plate does not affect the dynamic pressure characteristics. Since it is configured to keep it to a very small amount within the range, with a simple configuration,
Thrust plate deformation can be prevented well,
Suitable thrust dynamic pressure characteristics can be maintained for a long time. More specifically, the reliability of the thrust hydrodynamic bearing device can be reduced, such as reducing asynchronous runout (NRRO) in the thrust hydrodynamic bearing device, preventing wear due to contact in the bearing portion, and extending the life of the bearing. Can be greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view showing an example of the entire structure of a hard disk drive (HDD) including a shaft rotation type dynamic pressure bearing device according to an embodiment of the present invention.

FIG. 2 is an enlarged half sectional view showing a thrust hydrodynamic bearing portion of the hydrodynamic bearing device shown in FIG. 1;

FIG. 3 is an explanatory plan view showing an example of a groove for generating dynamic pressure.

FIG. 4 is an explanatory cross-sectional view illustrating a structure of a thrust plate.

FIG. 5 is an enlarged sectional explanatory view corresponding to FIG. 2 and illustrating another embodiment of the present invention.

FIG. 6 is an enlarged sectional explanatory view corresponding to FIG. 2 and showing still another embodiment of the present invention.

FIG. 7 is an enlarged sectional explanatory view corresponding to FIG. 2 and showing still another embodiment of the present invention.

FIG. 8 is an explanatory longitudinal sectional view showing an example of the entire structure of a hard disk drive (HDD) including a fixed shaft type dynamic pressure bearing device according to another embodiment of the present invention.

FIG. 9 is an enlarged half sectional view showing a thrust dynamic pressure bearing portion of a conventional dynamic pressure bearing device in an enlarged manner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 13 Bearing sleeve 16 Counter plate 21 Rotating shaft 23 Thrust plate 23a Fixing hole SBa, SBb Thrust dynamic pressure bearing portion Ca, Cb, Ca ', Cb' Chamfered portion La, Lb Axial length in the chamfered portion of the thrust plate Ta , Tb Each axial length at the chamfered portion of the shaft member 35 Fixed shaft 36 Thrust plate 41 Bearing sleeve 43 Counter plate

Continued on the front page (72) Inventor Takayuki Narita 5329 Shimosuwa Town, Suwa County, Nagano Prefecture Inside Sankyo Seiki Seisakusho Co., Ltd. (72) Inventor Kazushi Miura 5329 Shimo Suwa Town, Suwa County, Nagano Prefecture Inside Sankyo Seiki Works ( 72) Inventor Masaaki Sato 5329 Shimosuwa-cho, Suwa-gun, Nagano F-term in Sankyo Seiki Seisakusho Co., Ltd. (reference) 3J011 AA02 AA04 BA08 CA02

Claims (8)

[Claims] 1. A shaft member, a thrust plate fixed by fitting a fixing hole to the shaft member, and a thrust bearing member opposed to the thrust plate so as to sandwich the thrust plate in the axial direction. And a lubricating fluid injected into a thrust dynamic pressure bearing portion formed in an opposing gap between the thrust plate and the thrust bearing member, and fluid pressurizing means for generating a dynamic pressure in the lubricating fluid. In a thrust hydrodynamic bearing device for supporting a shaft member and a thrust bearing member so as to be relatively rotatable by dynamic pressure generated in the lubricating fluid, the thrust plate and the shaft member are formed on an inner periphery of a fixing hole of the thrust plate. The shaft member is fixed at a fitting joint having a predetermined length Lh in the axial direction by insertion joining means for applying a compressive stress to the outer peripheral surface of the shaft member from the wall surface. The relationship between the outer diameter OD, the inner diameter ID, and the coaxial thickness T of the thrust plate is OD-ID = 4T / α (where α
≤ 4), each axial distance L from each axial end face of the thrust plate to each end of the axial length Lh at the fitting joint.
a and Lb are respectively La ≦ αLb or La ≦ L when Lb ≦ La
A thrust hydrodynamic bearing device, wherein Lb ≦ αLa is set in the case of b. 2. The dynamic pressure bearing device according to claim 1, wherein said insertion and joining means is press-fit means or shrink fit means. 3. Each of the axial intervals La and Lb is:
The length Lh in the axial direction of the fitting joint is set so as to satisfy La ≦ 0.2Lh or Lb ≦ 0.2h.
The thrust hydrodynamic bearing device as described in the above. 4. Each of the axial intervals La and Lb is:
A chamfered portion formed at a shaft end portion of the shaft member, or a chamfered portion formed at both axially open end portions of a fixing hole of the thrust plate, or a combination thereof, 2. The hydrodynamic bearing device according to claim 1, wherein each of the chamfered portions is formed into a linear shape or a curved linear shape in a cross-sectional shape. 5. A shaft member, a thrust plate fixed by fitting a fixing hole to the shaft member, and a thrust bearing member opposed to the thrust plate so as to sandwich the thrust plate in the axial direction. And a lubricating fluid injected into a thrust dynamic pressure bearing portion formed in an opposing gap between the thrust plate and the thrust bearing member, and fluid pressurizing means for generating a dynamic pressure in the lubricating fluid. In a method of manufacturing a thrust dynamic pressure bearing device for supporting a shaft member and a thrust bearing member so as to be relatively rotatable by dynamic pressure generated in the lubricating fluid, the thrust plate and the shaft member may be fixed to the thrust plate by a fixing hole. By means of an insertion joining means for applying a compressive stress from the inner peripheral wall surface to the outer peripheral surface of the shaft member, a fitting joint having a predetermined length Lh in the axial direction is formed. It is those having a step of wearing the outer diameter OD of the thrust plate, the relationship of the inside diameter ID and a coaxial direction thickness T, OD-ID = 4T / α (where, alpha
≤ 4), each axial distance L from each axial end face of the thrust plate to each end of the axial length Lh at the fitting joint.
a and Lb are respectively expressed as La ≦ αLb or La ≦ L when Lb ≦ La.
A method for manufacturing a thrust hydrodynamic bearing device, wherein manufacturing is performed by setting Lb ≦ αLa in the case of b. 6. The step of fixing the thrust plate and the shaft member by insertion joining means for applying a compressive stress to an outer surface of the shaft member from an inner wall surface of a fixing hole of the thrust plate, 6. The method of manufacturing a dynamic pressure bearing device according to claim 5, wherein a press-fitting means or a shrink fitting means is adopted as the joining means. 7. Each of the axial distances La and Lb is
6. The manufacturing method according to claim 5, wherein the length Lh in the axial direction of the fitting joint is set such that La ≦ 0.2 Lh or Lb ≦ 0.2 Lh. A method for manufacturing a thrust hydrodynamic bearing device. 8. Each of the axial distances La and Lb is
A chamfered portion formed at a shaft end portion of the shaft member, or a chamfered portion formed at both axially open end portions of a fixing hole of the thrust plate, or a combination thereof, which is manufactured. 6. The method according to claim 5, wherein each of the chamfered portions is formed into a linear shape or a curved line shape in a cross-sectional shape.
A manufacturing method of the dynamic pressure bearing device according to the above.