JPH1054419A - Spindle device - Google Patents

Abstract

[PROBLEMS] To provide a spindle device which is compact, has small fluctuation of a non-rotational synchronous component in a radial direction of a mounted disk, and has small startup torque at startup, and has excellent startup / stopping durability. That is the task. A hub having a disk mounted thereon includes a shaft member.
Are rotatably supported via a dynamic pressure bearing A and a ball bearing B. A motor M is interposed between a housing 4 forming a fixed member together with the shaft member 3 and a hub 2 forming a rotating body. The center of gravity of the disk 1 and the axial center P2 of the dynamic pressure bearing A are substantially aligned. Rotor 1 when motor M is not driven
The line of action F of the resultant force of the magnetic attraction generated between the stator 3 and the stator 14 passes through the ball bearing B and reaches the axis of the spindle device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle device for a disk drive used in information / video / audio equipment such as a magnetic disk, a magneto-optical disk, an optical disk, and other precision rotating equipment.

[0002]

2. Description of the Related Art Conventionally, there is a spindle device used in a magnetic disk device, for example, as shown in FIG.

That is, a hub 51 having a disk 50 mounted thereon
Are rotatably supported by a shaft member 54 by two deep groove ball bearings 52, 53, and the two ball bearings 52, 53
A motor 56 is interposed between the hub 51 and the housing 55 supporting the shaft member 54 at a position axially below the hub 51, and the hub 56 and the disk 50 are driven to rotate by the motor 56.

[0004]

However, magnetic disk devices and the like are becoming thinner and higher in recording density, and the spindle device used therein has a low axial height and requires a rotating body. A certain hub 51 and even a disk 50
Is required to be small.

Therefore, the ball bearings 52 and 53 incorporated in a spindle device such as a magnetic disk device are required to have a small non-rotational synchronous component runout. However, the ball bearings 52 and 53 have ball passing vibrations and essential vibrations caused by springs of the bearing parts, and the vibration of the non-rotational synchronous component is reduced to a predetermined value or less even if the machining accuracy is improved. It is difficult to do. Also. According to the study of the inventors, the main cause of the non-rotational synchronous component in the spindle device is that the two ball bearings 52, 52 supporting the rotating body are more likely to be caused than the deflection of the non-rotational synchronous component of the ball bearings 52, 53 alone. It has recently been found that the effect of misalignment due to the assembly error between the 53 is large.

On the other hand, instead of the two ball bearings 52 and 53, a spindle device using a dynamic pressure bearing having a small runout of a non-rotational speed synchronous component as a radial bearing and a thrust bearing has been studied. However, since the bearing surfaces are in contact with each other at rest, there is a disadvantage that the starting torque at the time of starting is large. In particular, when the spindle device is used in a vertical position, there is a problem that the starting torque is increased and the thrust bearing surface is easily damaged or worn due to repeated starting and stopping.

In view of the above problems, the present invention is compact, has a small non-rotational synchronous component fluctuation in the radial direction of a mounted disk, has a small starting torque at the time of starting, and has a durable starting and stopping. It is an object of the present invention to provide a spindle device having excellent performance.

[0008]

In order to solve the above-mentioned problems, a spindle device according to the present invention has a rotating member on which a disk is mounted rotatably supported by a fixed member via a dynamic pressure bearing and a ball bearing. In a spindle device in which a rotor fixed to the rotating body and a stator fixed to a fixed member oppose each other, the rotating body is rotationally driven by a motor, the axial position of the center of gravity of the disk is set between the axial ends of the dynamic pressure bearing. The radial component of the magnetic attraction generated between the rotor and the stator of the motor is more loaded on the ball bearing than on the dynamic pressure bearing.

In the present invention, since the rotating body is supported by the ball bearing and the dynamic pressure bearing, the entire axial load of the rotating body is supported by the ball bearing having a small friction at the time of starting. As a result, even when used vertically, the starting torque is small, the bearing surface of the dynamic pressure bearing is less damaged and worn, and the starting and stopping durability is excellent.

In addition, since the rotating body is supported by the ball bearing and the dynamic pressure bearing, occurrence of non-rotational synchronous components of the spindle device due to misalignment due to an assembly error as in the case of being supported by two ball bearings is avoided. Is done.

Further, the axial position of the center of gravity of the disc is
Because the non-rotational synchronous component is set between the axial ends of the dynamic pressure bearing where it is minute or zero, the radial runout of the disk is almost equal to the dynamic pressure bearing runout, and the disk non-rotational The swing of the synchronous component becomes almost zero.

[0012] Also. The radial component of the attractive force generated by the variation of the magnetic attractive force generated between the rotor and the stator when the motor starts and rotates is more loaded on the ball bearing with large load capacity than on the dynamic pressure bearing, and is applied to the dynamic pressure bearing. The radial load applied is reduced, and the load capacity of the dynamic pressure bearing can be designed to be small. In other words, the bearing torque is smaller than when the rotating body is supported only by the dynamic pressure bearing.

[0013]

Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is a spindle device used in a magnetic disk device, an optical disk device, and the like.

First, the structure will be described. As shown in FIG. 1, a hub 2, which is a rotating body on which a disk 1 is mounted,
It is rotatably supported by the shaft member 3 via a dynamic pressure bearing A which is a radial dynamic pressure bearing and a ball bearing B which is separated from the dynamic pressure bearing A in the axial direction. The shaft member 3 is fixed to the housing 4 and forms a fixed member together with the housing 4.

That is, one end (the lower end in FIG. 1) of the shaft member 3 is fixed to the housing 4, and a ball bearing is provided between a lower portion of the insertion hole 2 a provided in the hub 2 and the outer peripheral surface of the shaft member 3. B is inserted, and a dynamic pressure bearing A is formed by the inner peripheral surface of the sleeve 5 and the outer peripheral surface of the shaft member 3 attached to the upper part of the insertion hole 2a. The sleeve 5 for a dynamic pressure bearing is fixed to the upper part of the insertion hole 2a of the hub 2 by press-fitting or bonding.

The sleeve 5 includes an outer cylinder 5a formed in a cylindrical shape, and an inner cylinder 5b formed in a cylindrical shape having an outer diameter capable of being press-fitted into the outer cylinder 5a and pressed into the outer cylinder 5a. A groove 10 for generating dynamic pressure is formed on the inner peripheral surface of the inner cylinder 5b.

The outer cylinder 5a is harder than the inner cylinder 5b and is made of a hard metal such as bearing steel or stainless steel. After cutting, heat treatment and grinding, the inner and outer diameters and both end faces are finished to predetermined dimensional accuracy in advance. The inner cylinder 5b is formed of a soft metal such as a sintered metal (copper or iron), a copper alloy, and an aluminum alloy. The groove 10 is formed by fixing the inner cylinder 5b to the outer cylinder 5a by press-fitting or shrink-fitting.
The inner peripheral surface is grooved by ball rolling, and the bulging of the inner cylindrical surface caused by this is removed by grinding with reference to the outer peripheral surface of the outer cylinder 5a. It is formed by brushing the inner peripheral surface of the cylinder 5b with a brush containing abrasive grains.

In the ball bearing B, the inner ring 6 is fixed coaxially to the shaft member 3, the outer ring 7 is fixed to the hub 2, and a plurality of balls 8 as rolling elements are provided between the inner ring 6 and the outer ring 7. It is interposed and configured.

The inner peripheral surface of the inner race 6 of the ball bearing B and the shaft member 3
Is fixed by bonding or press fitting. Of course, it may be fixed by loose fit. In the case of a loose fit, the inner ring 6 has an annular portion 4a slightly projecting upward from the upper surface of the housing 4.
And is supported in the axial direction.

Similarly, the outer ring 7 may be fixed to the hub 2 by bonding or press-fitting, or may be loosely fitted. The value of the gap at the time of the loose fit is preferably 10 μm or less in terms of runout accuracy. If a loose fit is adopted, it can be assembled simply by inserting the ball bearing B,
Easy assembly. In particular, when the inner ring 6 is used with a loose fit, the assembly is completed only by inserting the hub 2 in which the ball bearing B is incorporated in advance into the shaft member 3, so that the number of assembling steps can be reduced and the cost can be reduced.

When the outer ring 7 is loosely fitted to the hub 2, deformation of the outer ring 7 which is likely to occur at the time of press-fitting or bonding can be prevented, and the deflection accuracy of the ball bearing B can be maintained. A small-diameter portion 20 having a smaller diameter than both ends in the axial direction is provided at an intermediate portion in the axial direction of the insertion hole 2a of the hub.
At 0, the lower end surface of the sleeve 5 and the upper end surface of the outer ring 7 are in contact.

In the dynamic pressure bearing A, one of the cylindrical radial bearing surfaces formed on the outer peripheral surface of the shaft member 3 and the other radial bearing surface formed on the sleeve 5 have a predetermined diameter in the radial direction. The bearings are opposed to each other with a bearing gap therebetween, and the bearing gap is filled with a lubricating fluid.

Tapered surfaces are formed at both axial ends of the other radial bearing surface provided on the sleeve 5. That is, the other radial bearing surface includes two tapered surfaces provided at both ends in the axial direction, and a cylindrical bearing surface main body formed between the two tapered surfaces.

Each of the tapered surfaces holds the lubricating fluid by surface tension, and is inclined so as to become farther away from one of the radial bearing surfaces provided on the shaft member 3 as it goes away from the bearing surface body.

Here, it is preferable that each inclination angle from the axis of each tapered surface is selected in a range of about 2 ° to 40 °. When the angle of inclination of the tapered surface is smaller than 2 °, the amount of lubricating fluid that can be held by the tapered surface becomes unnecessarily small, and when it is larger than 40 °, the centrifugal force during rotation of the hub 2 as a rotating body. Thereby, the lubricating fluid is easily scattered. When the rotation speed of the hub 2 is higher than 3600 rpm, the inclination angle of the tapered surface is designed to be 30 ° or less, thereby preventing the lubricating fluid from scattering and providing a more reliable bearing device. it can.

The bearing surface body of the sleeve 5 includes:
A so-called herringbone-shaped or spiral-shaped groove 10 for generating dynamic pressure is formed. Of course, the groove 10 for generating dynamic pressure may be provided on one radial bearing surface of the shaft member 3, or may be provided on both bearing surfaces of the shaft member 3 and the sleeve 5.

As the lubricating fluid to be filled in the bearing gap, for example, oil, grease, magnetic fluid or the like is used. A shield plate 11 is fixed to a portion of the insertion hole 2a above the sleeve 5 by a known means such as caulking.
The shield plate 11 is attached after injecting the lubricating fluid. Even if the lubricating fluid adheres to the outer peripheral surface of the shaft member 3 or the upper end surface of the sleeve 5 when the lubricating fluid is injected, the upper end surfaces of the shield plate 11 and the sleeve 5 The lubricating fluid is held in the gap S in the axial direction between the lubricating fluid and the lubricating fluid is prevented from scattering into the magnetic disk 1 device.

The width of the axial gap S between the shield plate 11 and the upper end surface of the sleeve 5 is preferably about 5 to 300 μm. When it is less than 5 μm, the lubricating fluid in the bearing gap is sucked into the axial gap S by capillary action due to the surface tension of the lubricating fluid because the lubricating fluid becomes smaller than the bearing gap of the dynamic pressure bearing A. When the gap exceeds 300 μm, the capillary force due to the surface tension of the lubricating fluid decreases,
Poor retention of lubricating fluid.

When the hub 2 rotates as in the present embodiment, a centrifugal force acts on the lubricating fluid, so that the shield plate 11 is not fixed only by caulking, but is closely attached by using an adhesive or the like. It is preferable to improve the properties.

If a lid is attached to the hub 2 instead of the shield plate 11, it is possible to further prevent the lubricating fluid from scattering inside the magnetic disk device. However, since the upper end surface of the shaft member 3 is covered with the lid, the upper end portion of the shaft member 3 is limited to a free end, and both ends in the axial direction of the shaft member 3 cannot be supported by the fixing member.

With the above configuration, the hub 2 on which the disk 1 is mounted is rotatably supported by the shaft member 3 via the ball bearing B and the dynamic pressure bearing A. A motor M is provided between the hub 2 and the housing 4 and radially outward of the ball bearing B at a position concentric with the ball bearing B.

That is, an annular rotor 13 is fixed to a portion of the hub 2 on the housing 4 side, and a stator 14 is disposed concentrically with the rotor 13 on the inner peripheral side of the rotor 13 with a predetermined gap. Then, the stator 14 is fixed to the housing 4. The rotor 13 includes a magnet 13a provided on an inner peripheral portion facing the stator 14 and a back yoke 13b fixed to an outer peripheral surface of the magnet 13a. The back yoke 13b is for reducing magnetic flux leakage to the outside.

In this way, the motor M whose rotor 13 and stator 14 face each other in the radial direction is positioned concentrically with the ball bearing B on the radially outer periphery of the ball bearing B. Then, the set position of the rotor 13 of the motor M is shifted slightly above the stator 14, and a preload is applied to the ball bearing B by an axial suction force generated between the rotor 13 and the stator 14. Since the intersection (point of action) of the contact angle of the ball bearing B is located on the side opposite to the dynamic pressure bearing A with respect to the axial center P1 of the ball bearing, the moment rigidity of the entire spindle device can be increased. The line of action F of the resultant force of the magnetic attraction force generated between the rotor 13 and the stator 14 when the motor M is not driven.
Passes through the outer raceway of the ball bearing B and the center of the ball 8 to reach the axis of the spindle device. Therefore, most of the radial components of the magnetic attraction generated between the rotor 13 and the stator 14 at the time of startup and rotation are loaded on the ball bearing B,
The thrust component is applied to the ball bearing B.

The preload applied to the ball bearing B may be the attraction or repulsion of a plurality of separately provided permanent magnets, or the attraction acting between the permanent magnet and the ferromagnetic material.
Further, both may be used in combination. In addition, almost all the thrust load applied to the rotating body is supported by the ball bearing B.

In the above configuration, the rotating body is formed by the hub 2, the sleeve 5 attached to the hub 2, and the like. Then, the disk mounting surface 2b is set so that the center of gravity of the disk 1 and the axial center P2 of the dynamic pressure bearing A substantially coincide with each other.
Is provided on the hub 2, and the disk 1 is mounted on the mounting surface 2b.

Next, the operation, operation, effects and the like of the spindle device having the above configuration will be described. In the above device, the hub 2
Is rotatably supported on the shaft member 3 by the ball bearings B and the dynamic pressure bearings A. When the motor M is driven, the rotor rotates around the shaft member 3.

At this time, the dynamic pressure bearing A is a bearing in which one radial bearing surface and the other radial bearing surface are not in contact with each other when the hub 2 rotates, and the runout of the non-rotation synchronous component is almost zero. On the other hand, the ball bearing B is essentially a ball 8 passing vibration and a ball 8
Since there is a vibration that is not synchronized with the rotation speed due to the spring due to the elastic deformation of the contact portion, it has a non-rotationally synchronized component that is not synchronized with the rotation speed.

That is, in the portion of the rotating body of the spindle device in the axial position equal to the axial position of the dynamic pressure bearing A, the non-rotational synchronous component swings at almost zero, and is equal to the axial position of the ball bearing B. In the portion at the axial position, the ball bearing B rotates in a state where there is a runout of a non-rotational synchronous component inherent to the ball bearing B.

In the present embodiment, since the axial position of the center of gravity of the disk 1 and the axial center P2 of the dynamic pressure bearing A are substantially aligned, the radial deflection of the disk 1 is reduced by the dynamic pressure bearing A. And the deflection of the non-rotational synchronous component of the disk 1 in the radial direction can be made substantially zero. As a result, it is possible to cope with higher recording density.

Here, the spindle device of the present embodiment is free from the influence of inclination due to an assembling error of the two ball bearings. Smaller than the spindle device.

The axial position of the center of gravity of the disk 1 is
It is not necessary to match with the axial position P2 of the dynamic pressure bearing A,
Almost the same effect can be obtained if it is located between the axial ends of the dynamic pressure bearing and at the axis of the dynamic pressure bearing.

Further, the line of action F of the resultant force of the magnetic attraction generated between the rotor 13 and the stator 14 when the motor M is not driven passes through the ball bearing B and reaches the axis of the spindle device. Most of the radial attractive force generated by the variation of the magnetic attractive force generated between the rotor 13 and the stator 14 at the time of startup and rotation is received by the ball bearing B having a large load capacity. That is, when the load capacity of the dynamic pressure bearing A is designed to be large, the dynamic torque is also increased. However, since the radial load applied to the radial dynamic pressure bearing A can be reduced as described above,
The load capacity of the radial dynamic pressure bearing A can be designed to be small.

As a result, it is possible to set a small bearing torque which is a problem in the dynamic pressure bearing A. The radial component of the magnetic attraction generated between the rotor 13 and the stator 14 may be applied to the ball bearing B more than the dynamic pressure bearing A.

The line of action F of the resultant force of the magnetic attraction generated between the rotor 13 and the stator 14 when the motor M is not driven preferably passes through the ball bearing B and reaches the axis of the spindle device. However, it is more preferable to pass through the outer raceway of the ball bearing B to reach the axis of the spindle device, and more preferably to pass through the center of the ball 8 of the ball bearing B to reach the axis of the spindle device.

The disk 1 attached to the hub 2 is 2
More than one sheet may be used. For example, when two or more disks are mounted, the axial position of one center of gravity formed by combining two or more disks is located between the axial ends of the radial dynamic pressure bearing A and the dynamic pressure bearing A In this case, the deflection of the non-rotational synchronous component in the radial direction of each disk can be reduced to the same size as when the rotating body is supported only by the dynamic pressure bearing. It is desirable that the position of the center of gravity of each disk in the axial direction be located between both ends in the axial direction of the dynamic pressure bearing A and at the axis of the dynamic pressure bearing.

The ball bearing B which is a rolling bearing is not limited to a deep groove ball bearing, but may be an angular ball bearing, a four-point contact ball bearing or the like. When a four-point contact ball bearing is used as the ball bearing B, moment rigidity can be obtained by the four-point contact ball bearing alone, so that the moment rigidity of the entire bearing device can be improved. When a four-point contact ball bearing is used, a preload is applied inside the bearing with the bearing gap as a negative gap, so that a mechanism for applying a preload to the ball bearing B, such as a magnet for attraction, can be eliminated.

In the above description, the structure in which the shaft member 3 is fixed has been described, but a structure in which the shaft member 3 side rotates may be used. Further, the sleeve 5 may be configured by integrating the outer cylinder 5A and the inner cylinder 5B from one member.

[0048]

As described above, in the spindle device according to the present invention, the rotating body is supported by the ball bearing and the dynamic pressure bearing, and the entire axial load of the rotating body is supported by the ball bearing. Even when used, the starting torque is small, the damage and wear of the dynamic pressure bearing surface is small, and the starting and stopping durability is excellent.

Further, the radial attractive force generated by the variation of the magnetic attractive force generated between the rotor and the stator of the motor at the time of start-up and rotation is larger on the ball bearing having a large load capacity than on the dynamic pressure bearing. Thus, the radial load applied to the dynamic pressure bearing is reduced. As a result, it is possible to design the load capacity of the dynamic pressure bearing small,
The bearing torque can be reduced as compared with the case where the rotating body is supported only by the dynamic pressure bearing. Therefore, the height of the device in the axial direction can be reduced.

In addition, since there is only one ball bearing for supporting the rotating body and the axial position of the center of gravity of the disk is located between both ends of the dynamic pressure bearing in the axial direction, the radial runout of the disk can be reduced. As a result, the vibration of the non-rotational synchronous component in the radial direction of the disk can be made substantially zero. As a result, it is possible to cope with higher recording density.

[Brief description of the drawings]

FIG. 1 is a diagram showing a spindle device according to an embodiment of the present invention.

FIG. 2 is a view for explaining a conventional spindle device.

[Explanation of symbols]

 A dynamic pressure bearing B ball bearing M motor P1 axial center of ball bearing P2 axial center of dynamic pressure bearing 1 disk 2 hub (rotating member) 3 shaft member (fixing member) 4 housing (fixing member) 5 sleeve (rotating member) 6) Inner ring 7 Outer ring 8 Ball 13 Rotor 14 Stator

Claims (1)

[Claims] 1. A motor in which a rotating body on which a disk is mounted is rotatably supported by a fixed member via a dynamic pressure bearing and a ball bearing, and a rotor fixed to the rotating body and a stator fixed to the fixed member face each other. In a spindle device in which a rotating body is driven to rotate, an axial position of a center of gravity of the disk is located between axial ends of a dynamic pressure bearing, and a magnetic attraction force generated between a rotor and a stator of the motor is generated. A spindle device wherein a radial component is loaded more on a ball bearing than on a dynamic pressure bearing.