JP2003028149A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor of high reliability capable of preventing outflow of lubricant. SOLUTION: This spindle motor is provided with radial dynamic pressure bearings 3, 4 mounted between a shaft 2 and a sleeve 6 in which the shaft is inserted, through lubricant, a thrust dynamic pressure bearing mounted between a flange 8 integrally fixed to one end of the shaft and an end face of the sleeve through the lubricant, a hub 5 where the shaft is fixed in a through- hole 5a formed on its central part, and the radial dynamic pressure bearings and the thrust dynamic pressure bearing are installed on predetermined positions. A floating height of the shaft is determined to be t1>t2, when t1 is the floating height of the shaft in rated rotation under a condition the radial dynamic pressure bearings and the thrust dynamic pressure bearing are mounted in the hub in a state of positioning an opening end part of the sleeve at an upper side, and t2 is the flowing height of the shaft in rated rotation under a condition that the radial dynamic pressure bearings and the thrust dynamic pressure bearing are mounted in the hub in 180-degree oppositely to the condition that the opened end part of the sleeve is positioned at the upper side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor, for example, for a hard disk drive (hereinafter referred to as HDD) using radial and thrust dynamic pressure bearings. The present invention relates to a high dynamic pressure bearing structure.

[0002]

2. Description of the Related Art HD devices incorporated in personal computers and other devices are becoming smaller and have higher capacities.
As for the D spindle motor, further miniaturization and higher precision have been demanded. Along with this, the bearings of this kind of spindle motor have been further miniaturized,
Higher precision is required.

Conventionally, ball bearings have been widely used as bearings used in spindle motors. However, as miniaturization of spindle motors, especially smaller outer diameters progresses, ball bearings with smaller outer diameters that match the smaller spindle motors may be used, which may cause deformation of the inner and outer rings during motor assembly. It tends to be practically difficult to achieve. Moreover, noise and vibration problems are likely to occur.

In the case of a spindle motor for HDD, high speed rotation is required as the outer diameter becomes smaller, and these problems are further aggravated. Furthermore, regardless of the size of the outer diameter, there is a limit to the accuracy of the ball bearing, and it may be possible that the required specifications are not satisfied.

Therefore, as a small-sized spindle motor, a rotary sleeve portion is provided on the inner peripheral side of the base portion of the rotor hub portion, and the rotary sleeve portion is externally fitted to the fixed column portion and rotatably supported to move. A spindle motor having a pressure radial bearing has been proposed.

However, in a spindle motor for an HDD in which a magnetic head or the like is floated on the surface of a recording medium that is rotationally driven in the order of microns or submicrons for reading / writing, the axial displacement of the rotor also occurs. It must be kept sufficiently small, and the lubricant of the bearing may scatter to stain the surface of the recording medium, etc., which must be effectively prevented.

Here, an outline of a spindle motor for an HDD using a dynamic pressure bearing according to the prior art will be described. Figure 6
Is a spindle motor 30 for HDD using a dynamic pressure bearing
FIG. In FIG. 6, 1 is a motor base that serves as a base portion, and 2 is a cylindrical sleeve 6 that is fixed to the center of the motor base 1 and forms a bearing member. Shafts 3, 4
The dynamic pressure groove portions 5 provided above and below the inside of the cylindrical sleeve 6 and constituting the radial bearing are the through holes 5 in the central portion.
It is a hub having the shaft 2 fixed to a, and the hub 5 has a yoke 13 having a ring-shaped magnet 12 fixed to one side of its lower end.

Reference numeral 6 is a cylindrical sleeve fixed to the motor base 1, and 7 is a thrust plate constituting a thrust bearing attached to the lower end of the shaft 2 and to the lower end of the sleeve 6. , 8 are flanges that constitute a dynamic pressure thrust bearing integrally formed with the shaft 2 above the thrust plate 7 described in detail later. Hereinafter, the flange 8 will be described in detail. The flange 8 is made of a copper-based material, has a through hole (not shown) in the center, and is formed into a disk shape. The shaft 2 is formed in the through hole. The lower end of the shaft 2 is press-fitted or penetrated, and then bonded with an adhesive to be integrated with the shaft 2.

On the side of the motor base 1 which is the base,
The core 10 around which the coil 11 is wound is fixed to the ring-shaped magnet 12 with a predetermined distance. In addition, 15
Is a stator, 16 is a rotor, and 30 is the above-mentioned HDD spindle motor.

That is, the HDD spindle motor 30
As the stator 15 constituting the above, the motor base 1 serving as the above-mentioned base, the coil 11 fixed to the motor base 1, the core 10 around which the coil 11 is wound, and the sleeve fixed to the motor base 1 as well. It consists of 6 and 6.

As the rotor 16 rotatably arranged so as to face the above-mentioned stator 15, the shaft 2, the hub 5 to which the shaft 2 is fixed, the one side of the lower end of the hub 5, and the ring inside the hub 5 are provided. 1 to which the magnets 12 are fixed
3 and 3. The shaft 2 forming the rotor 16 is rotatably supported in the cylindrical sleeve 6 fixed to the center of the motor base 1 as described above.

The motor base 1 is made of aluminum or an aluminum alloy, and the shaft 2 is made of a stainless steel material. Note that the outer peripheral portion of the hub 5 has a structure in which a hard disk (hereinafter, referred to as HD) for recording data can be mounted, although not shown.

Here, the radial dynamic pressure bearing portion will be outlined. A radial dynamic pressure bearing portion that generates a dynamic pressure in the radial direction in the cylindrical sleeve 6 is composed of the shaft 2 and the sleeve 6. On the inner peripheral surface of the sleeve 6,
A shaft 2 which is inserted into this inner peripheral surface and is rotatably supported.
At the upper and lower two positions in the axial direction of the inner peripheral surface that closely faces the outer peripheral surface of
The dynamic pressure groove portions 3 and 4 are formed in an annular shape. Herringbone (fish bone) -shaped dynamic pressure grooves are formed laterally and annularly in the dynamic pressure groove portions 3 and 4, respectively.

On the other hand, on the outer peripheral surface of the shaft 2, two first shaft portions 2a and 2b which closely face and oppose each of the dynamic pressure groove portions 3 and 4, and these two first shaft portions 2a and 2b. And a second shaft portion 2c sandwiched between the first shaft portion 2 and the second shaft portion 2c.
The respective shaft diameters of a, 2b and 2c are as follows: the diameter 2a, 2b of the first shaft portion> the diameter 2 of the second shaft portion 2
It is set to c.

In the sleeve 6, the sleeve 6
A viscous lubricating oil is filled in the gap formed by the inner peripheral surface of the shaft 2 and the outer peripheral surface of the shaft 2. The lubricating oil filled in this gap can flow between the radial dynamic pressure groove portions 3 and 4 and between the thrust dynamic pressure bearings including the above-mentioned flange 8 and thrust plate 7. In the radial dynamic pressure bearing portion having the above-described structure, a dynamic pressure in the radial direction is generated by the dynamic pressure groove portions 3 and 4 of the sleeve 6 and the lubricating oil when the shaft 2 rotates. The dynamic pressure in the radial direction is applied as a uniform pressing force to the entire outer peripheral surface of the shaft 2.

Due to the aforementioned pressing force on the outer peripheral surface of the shaft 2, the shaft 2 can always maintain stable rotation in the sleeve 6. It is needless to say that the dynamic pressure in the radial direction can be generated even if the dynamic pressure groove portions 3 and 4 are not provided in the sleeve 6 but are formed annularly on the outer peripheral surface of the shaft 2 as well. . In FIG. 6, for convenience of explanation, the dynamic pressure groove portions 3 and 4 are illustrated as being formed on the shaft 2.

Next, the thrust dynamic pressure bearing portion will be outlined. One thrust dynamic pressure bearing portion with respect to the radial dynamic pressure bearing portion described above is fixed to the lower end peripheral surface of the shaft 2 or an upper surface 8a of a flange 8 formed integrally with the shaft 2 and an end surface of the sleeve 6 (one step deeper described later). Recessed portion) 6a. Both upper and lower flat surfaces 8a and 8b of the flange 8 described above.
Herringbone-shaped dynamic pressure grooves (not shown) are respectively formed on the top.

On the lower surface of the inner periphery of the sleeve 6, two concentric steps 6a and 6b having different depths are formed. The flange 8 integrated with the shaft 2 is fitted in the recess 6a that is deeper on the inner peripheral side of the step. On the other hand, a thrust plate 7 which constitutes another thrust dynamic pressure bearing portion, which will be described later, is press-fitted into the one-step shallower recessed portion 6b on the outer peripheral side of the step, and the thrust plate 7 causes the lower surface of the inner peripheral surface of the sleeve 6 to be fitted. Seal.

A shaft 2 integrated with a flange 8 is rotatably supported on the lower surface of the inner periphery of the sleeve 6 sealed by the thrust plate 7. On the lower surface of the inner circumference of the sleeve 6 sealed by the thrust plate 7,
Lubricating oil is filled in the gap formed between the flange 8 fixed to the outer peripheral surface of the shaft 2 and the thrust plate 7.

In the thrust dynamic pressure bearing portion having the above-mentioned structure, when the shaft 2 rotates, it is provided on the inner peripheral surface 6a of the sleeve 6 which closely faces the flange 8 and the upper and lower flat surfaces 8a and 8b of the flange 8. The dynamic pressure in the thrust direction is generated by the two herringbone dynamic pressure grooves (not shown), the upper surface of the thrust plate 7, and the lubricating oil.
As a result, when the shaft 2 does not rotate, the lower end of the shaft 2 and the lower surface 8b of the flange 8 are abutted and locked to the upper surface of the thrust plate 7, and when the shaft 2 is rotating, the shaft 2 Lower end and lower surface 8 of flange 8
b is separated from the upper surface of the thrust plate 7.

The dynamic pressure in the thrust direction is applied to the upper and lower flat surfaces 8a and 8b of the flange 8 integrated with the shaft 2 in different pressing directions and as uniform pressing forces.

Specifically, the dynamic pressure in the thrust direction is
The rotor 16 is formed by the dynamic pressure groove on the upper surface 8a of the flange 8.
Due to the dynamic pressure generated in the direction of pushing down the (shaft 2) and the dynamic pressure groove on the lower surface 8b of the flange 8, the rotor 1
The rotor 16 is rotatably supported by the shaft 2 in the thrust direction by balancing the dynamic pressure generated in the direction of pushing the rotor 6 upward.

[0023]

By the way, as described above, the radial dynamic pressure bearing portion and the thrust dynamic pressure bearing portion in the HDD spindle motor 30 shown in FIG. 6 are provided with dynamic pressures in the radial direction and the thrust direction, respectively. Lubricating oil having a viscosity necessary to generate each is filled in a required amount in each dynamic pressure bearing portion. The lubricating oil remains in each dynamic pressure bearing portion when the shaft 2 does not rotate, but when the shaft 2 rotates, the lubricating oil flows and springs to the open end portion above the sleeve 6.

This phenomenon is generally called a pump-out state. In this pump-out state, the rotation of the rotor 16 causes the lubricating oil to flow out to the outer peripheral portion of the rotor, which causes
There is a risk that it will adhere to the surface of the HD mounted on the hub 5 of No. 6 and hinder the recording and reproduction of data. Further, due to the outflow of the lubricating oil, the amount of the lubricating oil filled in each of the dynamic pressure bearing portions becomes insufficient, and the dynamic pressures in the radial direction and the thrust direction generated by each dynamic pressure bearing portion are effectively It doesn't work.

As a result, the rotor 16 can no longer rotate at the specified number of rotations, so that the spindle motor 30 for the HDD cannot obtain the original function as the spindle motor for the HDD, and there is a risk that the rotation performance will be defective. was there.
On the contrary, the state in which the lubricating oil is retained in the dynamic pressure bearing is called pump-in.

Normally, for example, the dynamic pressure groove portion 3 in FIG. 6 is machined with a = b, but sometimes b> a or pumping out due to machining error in cylindricity or roundness. It may happen. In such a case, in order to prevent the lubricating oil from flowing out of the sleeve 6, the shaft 2 which is the open end portion of the sleeve 6 and the inner peripheral upper portion of the sleeve 6 are formed into a taper portion 17 (angle θ) so that the sealing (sealing) is performed. However, this means alone was not sufficient as a sealing effect.

The present invention has been made in view of the above problems, and an object thereof is to prevent lubricant from leaking out and contaminating the space outside the motor, and
An object of the present invention is to provide a spindle motor that can be effectively prevented without impairing miniaturization of the motor.

[0028]

In order to solve the above-mentioned problems, the present invention comprises, as claim 1, a lubricant interposed between a shaft 2 and a sleeve 6 into which the shaft 2 is inserted. The radial dynamic pressure bearings 3 and 4, the thrust dynamic pressure bearing configured by interposing a lubricant between the flange 8 integrally fixed to one side of the shaft 2 and the end surface of the sleeve 6, and On the lower end side of the flange 8 and
The thrust plate 7 attached to the lower end of the sleeve 6, the hub 5 in which the shaft 2 is fixed to the through hole 5a in the central portion, the radial dynamic pressure bearings 3 and 4 and the thrust dynamic pressure bearing are included in the hub 5 In the spindle motor 20 installed at a predetermined position in the inside, the radial dynamic pressure bearings 3 and 4 and the thrust dynamic pressure bearing are in a state in which the open end of the sleeve 6 is inside the hub 5 in the one state. The floating height of the shaft 2 when installed and rotated at the rated speed is t1, and the radial dynamic pressure bearings 3 and 4 and the thrust dynamic pressure bearing are inside the hub 5 and the open end of the sleeve 6 is provided. Is set to be 180 ° opposite to the one state with the upper side as the upper side, and when the flying height of the shaft 2 when rotated at the rated speed is t2, t1> t2 is set. To do.

In the second aspect, the radial dynamic pressure bearings 3 and 4 formed by interposing a lubricant between the shaft 2 and the sleeve 6 into which the shaft 2 is inserted, and the radial dynamic pressure bearings 3 and 4 integrally formed on one side of the shaft 2. The flange 8 and the sleeve 6 fixed to the
A thrust dynamic pressure bearing formed by interposing a lubricant between the end plate and the end face, the thrust plate 7 attached to the lower end side of the flange 8 and to the lower end of the sleeve 6, and the through hole 5a in the central portion. In the spindle motor 20 in which the hub 5 to which the shaft 2 is fixed, the radial dynamic pressure bearings 3 and 4, and the thrust dynamic pressure bearing are installed at predetermined positions in the hub 5, the hub 5 is integrally fixed. A lubricating oil holding portion 9 is recessed at the end of the shaft 2 on the thrust dynamic pressure bearing side, and the lubricating oil holding portion 9 has a volume of lubricating oil stored in the lubricating oil holding portion 9 of Sa. , 5% ≦ Sa / S ≦ 20%, where S is the volume of lubricating oil held in the entire radial dynamic pressure bearing and the thrust dynamic pressure bearing
The volume is set so that

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. In addition, since the examples described below are preferable specific examples of the present invention, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless stated otherwise, the present invention is not limited to these embodiments.

An embodiment of the spindle motor according to the present invention will be sequentially described below with reference to FIGS. In addition,
The same reference numerals are used for the same components as the conventional one, and detailed description thereof will be omitted.

FIG. 1 is a cross-sectional view of an embodiment in which the hydrodynamic bearing portion applied to the spindle motor according to the present embodiment is installed in the hub in one state with the open end of the sleeve facing upward. FIG. 2 and FIG. 2 are for one state in which the dynamic pressure bearing portion of FIG. 1 has the open end of the sleeve as the upper side in the hub.
FIG. 3 is a vertical sectional view of an embodiment of the spindle motor according to the present embodiment, and FIG. 4 is a spindle motor according to another embodiment. FIG. 5 is a vertical cross-sectional view of one example, and FIG. 5 is a graph showing the relationship between the lubricating oil holding capacity and the holding force.

In FIG. 1, reference numeral 2A denotes a tip portion of the shaft 2 which constitutes a dynamic pressure bearing portion 40 and is inserted into a sleeve 6A described later, 6A denotes a sleeve, 7a denotes an upper surface portion of the thrust plate 7, and 9 denotes A lubricating oil holding portion 14 is provided at a lower end portion of the shaft 2 and an oil barrier holding portion 14 is formed between an upper end portion 2e of the shaft 2 and a tip portion 2A of the shaft 2.

Here, in the state of FIG. 1, the shaft 2
The flying height (amount) t1 of the shaft 2 when the tip portion 2A of the shaft 2 is rotated from the outside at a rated rotation speed, for example, via a belt (not shown), is the thrust bearing portion from the upper surface 7a of the thrust plate 7 ( It means the distance to the lower surface 8b of the flange 8). The state of FIG. 2 is a state in which FIG. 1 is installed upside down as described above.
The flying height (amount) t2 of the above means the distance between the upper end surface 6a of the sleeve 6A and the upper surface 8a of the flange 8. For convenience of explanation, in the states of FIGS. 1 and 2, the shaft 2 is shown as being in a floating state.

The HDD spindle motors 20 and 20A in FIGS. 3 and 4 are often used in the installation state shown therein, but are not necessarily limited to this installation state in the actual use state. It may be in any installation state. Further, the dynamic pressure groove portions 3 and 4 in FIGS. 1 to 4 are schematically drawn in a plan view.

Next, referring to FIGS. 1 to 3, the specific operation of the sealing effect for preventing the lubricating oil held in the first dynamic pressure groove portion 3 from flowing out of the sleeve 6A will be described. explain.

The radial dynamic pressure bearing 3 constituting the above-mentioned first dynamic pressure groove portion includes the sleeve 6A and the tip portion 2 of the shaft 2.
Due to the combination of processing accuracy such as cylindricity and roundness of A, it is not possible to judge whether it is pump-in or pump-out unless it is rotated in the assembled state. When the widths a and b of the dynamic pressure generating portion of the radial dynamic pressure generating groove 3 are set to be a> b, a
Since the dynamic pressure generating force is larger on the side, the pump-in state does not flow out the lubricating oil. On the other hand, when a <b, the lubricating oil is pumped out from the upper side. Therefore, if the portion b side is too large, the lubricating oil does not flow sufficiently to the portion a, and the function of the dynamic pressure bearing is not fulfilled.

In this embodiment, for example, the shaft 2 has a diameter of 4.5 mm, the rotation speed is 7200 r / min, and a + b =
1.8 mm, ab = 10 μm ± 5 μm. As a result, the lubricating oil of the dynamic pressure bearing is pumped in.
The flying height of the shaft 2 at this time is t1 = 5 μm, t2 =
It is 4 μm. When t1> t2 in the installation method shown in FIGS. 1 and 2, pump-in is performed, and when t1 <t2, pump-out is performed. Therefore, if the shaft floating amount of the dynamic pressure bearing is set to t1> t2, it is possible to obtain a highly reliable spindle motor 20 for hard disk in which lubricating oil does not flow out.

In this embodiment, an oil barrier holding portion 14 is provided between the tip portion 2A of the shaft 2 and the upper end portion 2e of the shaft 2 which are in contact with the inner peripheral portion of the hub to prevent the lubricating oil from flowing out. Specifically, 0.2 m from the surface of the shaft 2.
The groove of m is formed with a width of 1 mm, and this is the oil barrier holding portion 14. The oil barrier holding portion 14 is coated with an oil repellent (for example, a fluoropolymer) to prevent the lubricating oil from flowing out. The oil-repellent agent is wiped off after being applied to the shaft 2, but the oil-repellent agent applied to the groove is retained without being wiped off, so that the effect of eliminating the lubricating oil is maintained.

In the above description, the shaft 2 is fixed to the rotor 16 and the thrust dynamic pressure bearing functions between the shaft 2 and the stator 15 in FIG. However, the embodiment of the present invention is not limited to the above configuration. For example, a spindle motor 20A according to another embodiment shown in FIG.
B is fixed to the stator 15A, and the radial dynamic pressure bearing functions between the shaft 2B and the rotor 16A, and the same effect is exhibited.

Here, the configuration of FIG. 4 will be outlined. As shown in FIG. 4, a motor base (hereinafter,
A shaft 2B, which is fixed to a base portion 1 and has its axis centered vertically, is inserted through an insertion hole of a sleeve 6B forming a bearing member, and has a structure in which the sleeve 6B side rotates.

That is, the outer peripheral surface of the shaft 2B and the inner peripheral surface of the sleeve 6B form two radial dynamic pressure bearings 3A and 4A of a dynamic pressure bearing, and the shaft 2B is provided above the shaft 2B. A thrust bearing portion (flange) 8 having a diameter larger than the shaft diameter is provided. And the sleeve 6B
Upper end surface portion 6a of the thrust bearing portion 8 and the lower end surface portion 8a of the thrust bearing portion 8
And a thrust dynamic pressure bearing between the upper surface of the thrust bearing portion 8 and the lower surface of the bush 18. By thus providing the radial dynamic pressure bearings 3A, 4A and the thrust bearing 8, the sleeve 6B is rotatably supported by the shaft 2B. As described above, the thrust bearing portion 8 has a larger diameter than the shaft diameter of the shaft 2B, so that the thrust bearing portion 8 also serves to prevent the shaft 2B from coming off in the vertical direction.

Reference numeral 5A is a hub integrally formed with the sleeve 6B. The hub 5A has a rotor yoke 13 to which a ring-shaped magnet 12 is fixedly fixed therein. On the other hand, on the base 1, the core 10 having the coil 11 wound concentrically on the shaft 2B is provided with the ring-shaped magnet 12 described above.
It is fixed with a predetermined gap. The sleeve 6B is rotationally driven at a high speed by the rotor portion such as the rotor yoke 13 and the stator portion such as the coil 11 described above. The lead wire 19 at the end of the coil 11 is connected to the pattern of the flexible substrate 21 through a hole provided in the base 1 by, for example, soldering.

The radial dynamic pressure bearings 3A and 4A include a radial dynamic pressure bearing portion (not shown) provided on the outer peripheral surface of the shaft 2B and a radial dynamic pressure receiving portion (not shown) provided on the inner peripheral surface of the sleeve 6B. It is configured to face the surface with a predetermined bearing gap.

Further, a lubricating fluid is filled between the above-mentioned not-shown radial receiving surface of the sleeve 6B and the above-mentioned not-shown radial dynamic bearing portion of the shaft 2B. As the lubricating fluid, for example, oil or grease is used. Further, a so-called herringbone-shaped dynamic pressure groove is formed in the radial dynamic pressure bearing portion (not shown) of the shaft 2B. By this dynamic pressure groove, when the sleeve 6B is rotated, the lubricating fluid is respectively pumped toward the center of the dynamic pressure groove, and the necessary lubricating fluid is provided between the radial dynamic pressure bearing portion and the radial dynamic pressure receiving surface. It is supplied to the gap.

Here, returning to FIG. 3 again, the prevention of the outflow of the lubricating oil will be explained again. FIG. 3 shows a spindle motor 2 in which a radial bearing and a thrust bearing are dynamic pressure bearings.
It is a structure sectional view of 0. A lubricating oil holding portion 9 is provided on the end surface of the shaft 2 on the thrust plate 7 side, and a state in which lubricating oil (not shown) is held is shown. The lubricating oil held in the lubricating oil holding portion 9 must be assembled so as not to contain bubbles. In this way, by providing the lubricating oil holding portion 9 in the above-mentioned portion, it is possible to prevent the lubricating oil from flowing out when the dynamic pressure bearing 3 is in the pump-out state, as described in detail below. It is a thing.

Here, when the lubricating oil capacity held in the thrust dynamic pressure bearing 8 and the radial dynamic pressure bearings 3 and 4 is S and the holding capacity held in the lubricating oil holding portion 9 is Sa,
A graph showing the dimensional difference and the capacity ratio of the dynamic pressure generating portion as shown in FIG. 5 is obtained. From FIG. 5, it is understood that the lubricating oil holding capacity (product) amount is preferably 5% ≦ Sa / S ≦ 20%. This means that if Sa / S is 5% or less, it is meaningless to provide a lubricating oil holding portion, and if it exceeds 30%, the radial dynamic pressure portion 4 cannot sufficiently suck (pump in) the lubricating oil. ing.

Therefore, the volume of the lubricating oil holding portion 9 should be 5% ≦ S.
By setting a / S ≦ 20%, the dynamic pressure groove of the radial dynamic pressure bearing 4 on the thrust bearing side can be made into a pump-in configuration, so that the lubricant oil retained in the lubricant oil retaining portion 9 is radial. The effect of being sucked to the bearing side and circulating in the dynamic pressure portion is obtained. In the example, S = 27 μl (microliter) and Sa = 3 μl.

[0049]

As described in detail above, according to the first aspect of the invention, a radial dynamic pressure bearing formed by interposing a lubricant between a shaft and a sleeve into which the shaft is inserted, and the shaft. A thrust dynamic pressure bearing formed by interposing a lubricant between the flange integrally fixed to one side and the end surface of the sleeve, and the lower end side of the flange,
Further, the thrust plate attached to the lower end of the sleeve, the hub having the shaft fixed in the through hole in the central portion, the radial dynamic pressure bearing and the thrust dynamic pressure bearing are installed at predetermined positions in the hub. In the spindle motor configured as above, the radial dynamic pressure bearing and the thrust dynamic pressure bearing are installed in the hub in one state with the open end of the sleeve as an upper side, and the radial dynamic pressure bearing and the thrust dynamic pressure bearing are rotated at a rated speed. The floating height of the shaft is t1, and the radial dynamic pressure bearing and the thrust dynamic pressure bearing are installed in the hub in a state of being 180 ° opposite to the state in which the open end of the sleeve is on the upper side, and rated. When the flying height of the shaft when rotated at the number of revolutions is t2, by setting t1> t2, the lubricating oil is pumped in and the lubricating oil is prevented from flowing out. Since it is Rukoto, it is possible to provide a highly reliable spindle motor.

According to the second aspect of the present invention, a radial dynamic pressure bearing formed by interposing a lubricant between the shaft and a sleeve through which the shaft is inserted, and integrally fixed to one side of the shaft. Thrust dynamic pressure bearing formed by interposing a lubricant between the formed flange and the end surface of the sleeve, a thrust plate attached to the lower end side of the flange and to the lower end of the sleeve, and a central portion In a spindle motor in which a hub having the shaft fixed in a through hole, the radial dynamic pressure bearing and the thrust dynamic pressure bearing are installed at predetermined positions in the hub, the integrally fixed thrust dynamic pressure bearing side A lubricating oil holding portion is provided at the end of the shaft, and the lubricating oil holding portion has a volume of lubricating oil accommodated in the lubricating oil holding portion of Sa,
Assuming that the volume of the lubricating oil held in the entire radial dynamic pressure bearing and the thrust dynamic pressure bearing is S, 5% ≦ Sa
By setting the volume so that / S ≦ 20%, the lubricating oil in the lubricating oil holding portion can be effectively sucked and distributed to the dynamic pressure portion, so that a highly reliable spindle motor is provided. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment in which a dynamic pressure bearing portion applied to a spindle motor according to the present invention is installed in a hub in one state with an open end portion of the sleeve facing upward. .

FIG. 2 is a cross-sectional view showing a case where the dynamic pressure bearing unit of FIG. 1 is installed in the hub 180 ° opposite to the state in which the open end of the sleeve is on the upper side, that is, when installed upside down.

FIG. 3 is a vertical sectional view of an embodiment of a spindle motor according to the present invention.

FIG. 4 is a sectional view of another embodiment of the spindle motor according to the present invention.

FIG. 5 is a graph showing a relationship between a lubricating oil holding capacity and a holding force.

FIG. 6 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

1 Motor base, base 2, 2B shaft 2A tip 2a, 2b First shaft portion 2c Second shaft part 3, 4 dynamic pressure groove, dynamic pressure bearing 3A, 4A dynamic pressure bearing 5, 5A hub 6, 6A, 6B, 6a sleeve 7 Thrust plate 7a upper surface 8 Flange, thrust bearing 8a upper surface 8b lower surface 9 Lubricant holding section 10 cores 11 coils 12 ring magnet 13 York 14 Oil barrier holder 15, 15A stator 16, 16A rotor 17 Tapered part 18 bush 19 Lead line 20, 20A spindle motor 21 Flexible substrate 30 HDD spindle motor 40 Dynamic bearing

Claims (2)

[Claims] 1. A radial dynamic bearing formed by interposing a lubricant between a shaft and a sleeve in which the shaft is inserted, a flange integrally fixed to one side of the shaft, and an end surface of the sleeve. A thrust dynamic pressure bearing formed by interposing a lubricant between the shaft and the thrust plate attached to the lower end of the flange and to the lower end of the sleeve, and the shaft fixed to the through hole in the central portion. A hub, the radial dynamic pressure bearing and the thrust dynamic pressure bearing are installed at predetermined positions in the hub, wherein the radial dynamic pressure bearing and the thrust dynamic pressure bearing have the sleeve in the hub. Is installed with the open end of the shaft up, and the floating height of the shaft when rotated at the rated speed is t1, the radial dynamic pressure bearing and the thrust. The dynamic pressure bearing is installed in the hub in a state of 180 ° opposite to the one in which the open end of the sleeve is on the upper side, and the floating height of the shaft when rotated at the rated speed is t2. The spindle motor is characterized by setting t1> t2. 2. A radial dynamic pressure bearing formed by interposing a lubricant between a shaft and a sleeve through which the shaft is inserted, a flange integrally fixed to one side of the shaft, and an end surface of the sleeve. A thrust dynamic pressure bearing formed by interposing a lubricant between the shaft and the thrust plate attached to the lower end of the flange and to the lower end of the sleeve, and the shaft fixed to the through hole in the central portion. A hub, the radial dynamic pressure bearing and the thrust dynamic pressure bearing are installed at predetermined positions in the hub, and the end of the shaft on the thrust dynamic pressure bearing side that is integrally fixed is lubricated. An oil holding portion is provided as a recess, and the lubricating oil holding portion has a volume of lubricating oil accommodated in the lubricating oil holding portion of Sa, the radial dynamic pressure bearing and the thrust dynamic pressure. When the volume of the lubricating oil is S held in 受全 body, a spindle motor, characterized in so that it has set the volume to be 5% ≦ Sa / S ≦ 20%.