JP2001227534A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid bearing spindle motor having high moment yield strength at rocking time even in a limited height dimension, being excellent in reliability and impact resistance and reducing electric power consumption. SOLUTION: In this spindle motor having a shaft 13 having a flange part 16 on one end and a sleeve 12 opposed to the shaft via radial fluid bearing clearance ΔR and arranging a thrust fluid bearing S between at least one plane of the flange part and a mating member 17 opposed to this, when a diameter of the shaft 13 is (d) and a diameter of the flange part 16 is D, the relationship of 1.5d<=D<=2.0d is satisfied, and when radial clearance of a radial fluid bearing R is ΔR and shaft directional clearance of the thrust fluid bearing formed between the flange part and the mating member in the thrust fluid bearing is A, the relationship of ΔR<=A<=10 ΔR is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to information equipment, sound and
The present invention relates to a spindle motor for video equipment and office machines, and more particularly to a spindle motor excellent in durability and reliability which is optimal for a magnetic disk device (HDD), an optical disk device, and the like.

[0002]

2. Description of the Related Art As a conventional spindle motor of this type, for example, there is a spindle motor for an HDD as shown in FIG. In this device, a sleeve 2 is fixed to a base 1, and a shaft 3 is rotatably inserted through the sleeve 2,
A hub 4 is integrally attached to the shaft 3.

[0003] The lower end surface of the shaft 3 is a thrust receiving surface 3s,
A counter plate 6 having a thrust bearing surface 6s opposed to the thrust receiving surface 3s is fixed to the base 1. At least one of the thrust receiving surface 3s and the thrust bearing surface 6s has a spiral dynamic pressure generating groove 7, for example. And the thrust fluid bearing S is configured. On the other hand, a pair of upper and lower radial receiving surfaces 3r are formed on the outer peripheral surface of the shaft 3 at an interval in the axial direction, and a radial bearing surface 2r facing the radial receiving surface 3r is formed on the inner peripheral surface of the sleeve 2. Radial receiving surface 3r and radial bearing surface 2r
A radial fluid bearing R is provided with at least one of them having, for example, a herringbone-shaped dynamic pressure generating groove 8.

The shaft 3 and the hub 4 are integrally rotated by a motor M composed of a stator 9 fixed to the outer periphery of the base 1 and a rotor magnet 10 fixed to the inner surface of the hub 4. . When the shaft 3 rotates, a dynamic pressure is generated in the lubricant between the bearings by the pumping action of the dynamic pressure generating grooves 7, 8 of the thrust fluid bearing S and the radial fluid bearing R. No contact with 6 and it is supported.

[0005]

A spindle motor for an HDD employing such a fluid bearing as a bearing has a limited height, especially for an HDD mounted on a portable device such as a notebook computer. While satisfying strict conditions such as dimensions (for example, 9.5 mm or less) and low power consumption, the fluid bearing portion hardly contacts during operation even when used in a oscillating train or car. In addition, a highly reliable hydrodynamic bearing spindle motor has been demanded for a long time.

In addition, since a large external impact of up to 1000 G may act due to carelessness when the portable device is carried or handled, the lubricant held in the lubricant pool is
There is also a need for a hydrodynamic bearing spindle motor that is less likely to scatter and flow outside even when an external impact is applied. Therefore, an object of the present invention is to provide a hydrodynamic bearing spindle motor that has high moment resistance during swinging even in the limited height dimensions exemplified above, and has excellent reliability and impact resistance. .

[0007]

In order to achieve the above object, the present invention comprises a shaft having a flange at one end, and a sleeve opposed to the shaft via a radial fluid bearing gap. In a spindle motor in which a thrust fluid bearing is provided between at least one flat surface of the portion and a mating member opposed thereto, when the diameter of the shaft is d and the diameter of the flange is D, 1.5d ≤D
≤2.0d, and the radial clearance of the radial fluid bearing is ΔR, and the axial clearance of the thrust fluid bearing formed between the flange portion and the mating member in the thrust fluid bearing is A. When ΔR ≦
It is assumed that the relationship of A ≦ 10ΔR is satisfied.

Since the relationship between the diameter d of the shaft and the diameter D of the flange, and the relationship between the radial clearance ΔR of the radial fluid bearing and the axial clearance A of the thrust fluid bearing are all as described above, the height dimension and Even when bearing torque is restricted, H
Moment resistance of the hydrodynamic bearing spindle motor required at the time of swinging of a device such as a DD is improved. That is, when the diameter D of the flange is less than 1.5 times the diameter d of the shaft, the area of the flange is not sufficient, so that the thrust load capacity is reduced, and the rising start rotation speed at the time of startup is high. Since the required time is long, there is a problem that damage due to wear of the thrust fluid bearing increases. On the other hand, when the diameter D of the flange exceeds 2.0 times the diameter d of the shaft, the bearing torque of the thrust fluid bearing portion increases, which causes a problem that power consumption increases. Therefore, 1.5d ≦ D ≦
It is necessary to satisfy the relationship of 2.0d.

If the axial clearance A of the thrust fluid bearing is smaller than the radial clearance ΔR of the radial fluid bearing,
At the time of startup, instead of the shaft sliding on the radial bearing surface having a low peripheral speed, the shaft comes into sliding contact with the mating member on the outer peripheral edge of the flange having a high peripheral speed, and there is a problem that damage due to wear becomes large, and If the clearance A exceeds 10 times the clearance ΔR, the damping due to the squeeze film action of the oil film when the HDD or the like swings is small, so that a predetermined moment resistance cannot be secured. Therefore, ΔR
It is necessary to satisfy the relationship of ≦ A ≦ 10ΔR.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an embodiment of the spindle motor of the present invention. First, the configuration will be described. A cylindrical portion 11a erected at the center of the base 11 is described.
, A flanged cylindrical sleeve 12 is inserted and fixed integrally.

A hollow shaft 13 having an outer diameter d is inserted through the sleeve 12. The hollow shaft 13 has a female screw 13f on the inner peripheral surface.
And a shallow inverted cup-shaped hub 1 at the upper end.
4 are integrally fixed. A disk-shaped thrust plate 16 as a flange having an outer diameter D is integrally fixed to a shaft lower end protruding from the lower end of the sleeve 12. In the case of this embodiment, the thrust plate 16
Is set by screwing a set screw B to a female screw 13f on the inner peripheral surface of the hollow shaft 13. The lower end surface of the thrust plate 16 is opposed to the upper surface of a counter plate 17 which is a mating member attached to the base 11, and the two opposing surfaces are in contact with each other when stopped.

Both upper and lower planes of the thrust plate 16 are a thrust receiving surface 16s. On the other hand, a lower end surface of the sleeve 12 and a lower surface thrust receiving surface 16s which are mating members opposing the upper surface thrust receiving surface 16s are opposed to each other. The counter plate 17 is a thrust bearing surface 12s and 17s, respectively, and at least one of the opposed thrust receiving surface and the thrust bearing surface is provided with a herringbone-shaped dynamic pressure generating groove, for example. The fluid bearing S is configured. As shown in FIG. 2, the herringbone-shaped thrust dynamic pressure generating groove has a radially outward groove length lb from the groove top P that is shorter than a groove length la from the groove top P to the inner circumferential side. Since the pump action generated by the rotation drive is smaller on the outer peripheral side from the groove top P than on the inner peripheral side, the lubricant is sent from the central part toward the outer peripheral part.

A pair of radial receiving surfaces 13r are formed vertically on the outer peripheral surface of the shaft 13 with an interval in the axial direction, and a radial bearing surface 12r facing the radial receiving surface 13r is formed on the inner peripheral surface of the sleeve 12. A radial fluid bearing R is provided on at least one of the radial receiving surface and the radial bearing surface, for example, with a herringbone-shaped groove 18 for generating dynamic pressure. This radial fluid bearing R
By forming the dynamic pressure generating groove 18 in an inward asymmetric groove pattern in which the groove length is slightly shorter on the inner side than on the outer side, the phenomenon that the lubricant in the bearing gap flows out to the outside during rotation can be prevented. .

The axial clearance A of the thrust fluid bearing of the thrust fluid bearing S is defined by thrust bearing surfaces 12s and 17s.
This is a dimension obtained by subtracting the thickness dimension of the thrust plate 16 from the dimension between s, and the gap A satisfies the relationship of ΔR ≦ A ≦ 10ΔR in relation to the radial gap ΔR of the radial fluid bearing R. Since the axial clearance A of the thrust fluid bearing portion is equal to or greater than the radial clearance ΔR of the radial fluid bearing, the outer peripheral edge of the flange having a high peripheral speed at the time of startup is less likely to be in sliding contact with the mating member, and therefore damage due to wear of the thrust plate 16 is reduced. Reduce as much as possible. Further, since the gap A is 10 times or less of the gap ΔR, HD
Damping due to the squeeze film action of the oil film when the device such as D swings increases, and a predetermined moment resistance can be secured.

The relationship between the diameter D of the thrust plate 16 and the diameter d of the shaft 13 is 1.5d ≦ D ≦ 2.0d. Since the diameter D is at least 1.5 times the diameter d, the area of the thrust plate 16 is sufficient, and the thrust load capacity of the thrust bearing S is large. The time is shortened, and the damage due to wear of the thrust fluid bearing S is reduced.
On the other hand, since the diameter D of the thrust plate 16 is not more than 2.0 times the diameter d of the shaft 13, the bearing torque of the thrust fluid bearing S is suppressed, and power consumption is reduced.

Further, an annular gap is interposed between the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the cylindrical portion 11a raised on the base 11 as a mating member. The gap forms a lubricant reservoir 19. Above the lubricant reservoir 19, an air passage 20 communicating with the outside air is opened. The ventilation path 20 initially has a bent portion 21 extending horizontally from the uppermost portion of the lubricant reservoir 19 and rising vertically to the joint surface with the base cylindrical portion 11a, as shown in FIG. It is open at the upper end surface of the joint between the base 12 and the base cylindrical portion 11a. Since the ventilation path 20 has such a bent shape, even if a large external impact is applied, the lubricant in the lubricant reservoir 19 is unlikely to scatter and flow directly from the ventilation path 20 to the outside.

The outer peripheral surface of the sleeve 12, which forms the inner peripheral surface of the lubricant reservoir 19, has a lower thrust fluid bearing S
The taper surface 12t is such that the gap becomes narrower toward. However, the tapered surface 12t is not necessarily the sleeve 12
The outer peripheral surface of the sleeve 12 may be formed on the inner peripheral surface of the base cylindrical portion 11a which is the mating side, or may be formed on both the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the base cylindrical portion 11a. May be.

The portion of the lower portion of the lubricant reservoir 19 which communicates with the fluid bearing in the vicinity thereof is equal to the bearing clearance,
Alternatively, a lubricant supply passage 22 having a slightly larger gap is provided so that the lubricant can be easily held by capillary action based on surface tension. In order to reduce the torque of the spindle motor, two upper and lower radial fluid bearings R,
The inner peripheral surface of the sleeve 12 sandwiched between R (or the outer peripheral surface of the shaft 13 or both the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft).
A relief groove 24 formed of a tapered peripheral groove having a narrower clearance toward the bearing clearance of the radial fluid bearing R is provided. However, if the depth of the escape groove 24 is increased, the air can be easily entrained.
An air vent hole 25 is provided in the sleeve 12 for communicating the lubricant reservoir 4 with the lubricant reservoir 19.

The thrust plate 16 is also provided with a flow hole 26 for letting out the air bubbles remaining in the bearing gap as a through hole in the thickness direction.
7 is also provided with a through hole 27 formed of a through hole in the thickness direction at the center. A stator 9 fixed to the outer periphery of the cylindrical portion 11a of the base 11 to rotationally drive a hub 14 for mounting a magnetic disk (not shown) on the outer periphery, which is a rotating body;
A motor M composed of the rotor magnet 10 fixed to the inner diameter surface of the hub 14 is provided between the inner periphery of the hub 14 and the cylindrical portion 11a.
It is mounted between the outside.

The injection of the lubricant into the spindle motor is performed by using a dispenser. Then, after assembling the whole, it is injected through a through hole 27 provided in the counter plate 17. The injected lubricant fills the respective clearances of the thrust fluid bearing S and the radial fluid bearing R by the surface tension, and the excess lubricant is accumulated in the lubricant reservoir 19, and the tapered surface 12t has a capillary based on the surface tension. Maintained by the phenomenon. Therefore, even if the spindle motor is inverted during transportation or use,
The lubricant in the lubricant reservoir 19 does not flow out.

At the time of this injection, the air in the escape groove 24 in the radial fluid bearing R is pushed out through the air vent hole 25 into the lubricant reservoir 19 having a larger volume, and is discharged from the upper ventilation path 20 to the outside. Therefore, the entrapment of air bubbles in the lubricant is small. Even if it gets caught, it is discharged to the outside from above the radial fluid bearing R, and most is separated in the lubricant reservoir 19 and discharged to the outside from the upper air passage 20. That is, since the lubricant reservoir 19 has a tapered shape, the lubricant is sucked toward the narrower gap by the surface tension. On the other hand, the entrained residual air bubbles are separated and discharged to the larger gap. Therefore, it is possible to prevent the bubbles in the lubricant from expanding during transportation or use of the spindle motor to push out the lubricant in the bearing gap to the outside, thereby preventing shortage of the lubricant.

In the state where the lubricant is filled, even if a large external impact of up to 1000 G may act due to carelessness during transportation or handling, the bent portion is formed in the air passage 20 above the lubricant reservoir 19. Because of the provision of the seal 21, there is little possibility that the lubricant in the lubricant pool 19 will scatter and flow out of the air passage 20 to the outside due to such an external impact. In addition, since the size of the gap of the lubricant reservoir 19 is reduced toward the lower lubricant supply passage 22 by the tapered surface 12t, the lubricant scattered by the external impact is also used as long as it does not flow out. Lubricant supply path 22 with a narrow gap in reservoir 19
It is naturally collected toward.

When the shaft 13 and the hub 14 are integrally rotated by the motor M, the lubricant filled in the bearing gaps of the thrust fluid bearing S and the radial fluid bearing R is filled with the dynamic pressure generating groove. Dynamic pressure is generated by the pumping action,
The shaft 13 and the hub 14 are supported without contact with the sleeve 12 and the counter plate 17. Even if there are bubbles remaining in the bearing gap due to the rotation, the air vent hole 25 provided between the radial fluid bearings R, the circulation hole 26 provided in the thrust plate 16, the through hole 27 provided in the counter plate 17, the lubrication Ventilation path 20 provided in agent pool 19
Immediately released to the outside air via.

Further, since both sides of the bearing are opened to the same atmospheric pressure as the outside air by the air vent hole 25 and the circulation hole 26, the lubricant held between the bearing gaps of the radial fluid bearing R and the thrust fluid bearing S is rotated. Are pushed into the bearing gaps and do not flow with each other. Therefore, if the herringbone groove of the radial fluid bearing R is a slightly inward asymmetric groove pattern, the lubricant does not flow out from the bearing gap during rotation.

If the lubricant retained in the bearing gap gradually evaporates or scatters and runs short over a long period of operation, the lubricant is retained in the lubricant reservoir 19 by capillary action based on surface tension. The lubricating oil is sucked into the narrower gap while being guided by the tapered surface 12t according to the shortage, and is replenished until the lubricant is filled in the bearing gap. That is, as the lubricant in the bearing gap decreases, the lubricant is sucked by the capillary action in the narrow bearing gap via the lubricant supply passage 22, and the tapered surface 12 of the lubricant reservoir 19 is reduced.
It is stabilized at a position where the surface tension of t is balanced. Thus, the lubricant is automatically replenished by the reduced amount of the lubricant.

According to the present embodiment, since the gap of the lubricant reservoir 19 is tapered, the lubricant is sucked into the narrower gap by the surface tension, while the residual air bubbles entrained during assembly are large. Is discharged separately. Therefore, a lubricant free of air bubbles is automatically and reliably supplied to each bearing gap, communicates with the lubricant reservoir 19, and is always filled with the lubricant. A spindle motor with excellent performance can be obtained.

The lubricant reservoir 1 is provided around the outer periphery of the sleeve 12.
The provision of 9 has a great practical advantage that the overall height of the spindle motor can be reduced. In particular, according to this embodiment, the axial clearance A of the thrust fluid bearing S is set to ΔR ≦ A ≦ 10ΔR in relation to the radial clearance ΔR of the radial fluid bearing R. The outer peripheral edge of the plate 16 is less likely to be in sliding contact with the mating member, that is, the sleeve 12 and / or the counter plate 17, so that damage due to abrasion of the thrust plate 16 is reduced as much as possible, while rocking of a device such as an HDD. Occasionally, the damping due to the squeeze film action of the oil film increases, and a predetermined moment proof stress can be secured.

The relationship between the diameter D of the thrust plate 16 and the diameter d of the shaft 13 is 1.5d ≦ D ≦ 2.0d. As a result, the damage due to wear of the thrust fluid bearing S is reduced, and the bearing torque of the thrust fluid bearing S is suppressed, so that power consumption is reduced. The inventors set the diameters d and D and the gap ΔR and a in Example 1 in Table 1.
-3 and comparative examples 4-6, prototypes of spindle motors (having a height of 9.5 mm or less) were prototyped, and the rotational speed was 4200 r.
The abrasion resistance and moment resistance of the thrust fluid bearing S were tested by rotating the bearing at pm. The results are shown in Table 1.
Was as described in the judgment column.

[0029]

[Table 1]

The detailed structure of the spindle motor of the present invention, the presence or absence of air vent holes, flow holes and through holes, groove patterns, and the like are not limited to the above-described embodiment, and may be appropriately determined as necessary. Can be changed.

[0031]

As described above, according to the present invention, since the diameter D of the flange is 1.5 or more of the diameter d of the shaft, the area of the flange is sufficient, the thrust load capacity is increased, and the start-up is started. In this case, the number of revolutions at which the ascending start of the ascent is low, and thus the time required for ascending is reduced, so that the thrust fluid bearing is less likely to be damaged by wear. On the other hand, since the diameter D of the flange is not more than 2.0 times the diameter d of the shaft, the bearing torque of the thrust fluid bearing portion is reduced, so that power consumption is reduced.

Further, since the axial clearance A of the thrust fluid bearing portion is equal to or larger than the radial clearance ΔR of the radial fluid bearing, the outer peripheral edge of the flange having a high peripheral speed at the time of start-up does not or does not come into sliding contact with the mating member, thereby reducing wear. Since the resulting damage is reduced and the clearance A is 10 times or less of the clearance ΔR, the damping by the squeeze film action of the oil film becomes sufficient at the time of swinging of a device such as an HDD, so that a predetermined moment proof stress is secured. There is also an effect that can be done.

Thus, according to the present invention, it is possible to provide a fluid bearing spindle motor having high moment resistance during swinging, having excellent reliability and impact resistance, and having low power consumption even with a limited height. .

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a spindle motor according to the present invention.

FIG. 2 is a schematic view of a groove pattern of the thrust fluid bearing S shown in FIG.

FIG. 3 is a plan view of an end face of a sleeve of FIG. 1;

FIG. 4 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 12 sleeve 13 shaft 14 hub 16 flange (thrust plate) 17 mating member (counter plate) D diameter of flange (thrust plate) d diameter of shaft ΔR radius clearance A axial clearance R radial fluid bearing S thrust fluid bearing

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsuhiko Tanaka 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3J011 AA04 BA05 CA02 CA04 JA02 MA24 5H605 BB05 BB19 CC02 CC03 CC04 CC05 CC10 EA07 EB06 EB08 EB17 5H607 BB01 BB14 BB17 DD05 DD15 FF12 GG07 GG12

Claims (1)

[Claims] A shaft having a flange at one end, and a sleeve opposed to the shaft via a radial fluid bearing gap, between at least one flat surface of the flange and a mating member opposed thereto. In a spindle motor provided with a thrust fluid bearing, the diameter of the shaft is d,
When the diameter of the flange portion is D, 1.5d ≦ D ≦
2.0d, and the radial clearance of the radial fluid bearing is ΔR, and the axial clearance of the thrust fluid bearing formed between the flange portion and the mating member in the thrust fluid bearing is A. When ΔR ≦ A
A spindle motor characterized by satisfying a relationship of ≦ 10ΔR.