JPH01119958A - Disk driving device - Google Patents

Abstract

PURPOSE:To reduce the swing of disks under rotation by supporting a fixed shaft and the disks, fitting simultaneously the shaft into a shaft hole formed on a rotating body and supporting freely rotatably the rotating body in the dynamic pressure action of a fluid arranged in a space between the inner wall of the shaft hole and the opposite outer peripheral part of the fixed shaft. CONSTITUTION:The rotating body 4 is freely rotatably supported at the fixed shaft 1, where the shaft hole 5 with a somewhat larger diameter than pressure receiving parts 3 of the fixed shaft 1 is formed in an axial center part of the rotating body 4. The rotating body 4 is fitted in its shaft hole 5 by the fixed shaft 1, whereas the inner wall of the shaft hole 5 of the rotating body 4 is opposite to the individual pressure receiving parts 3 of the fixed shaft 1. Then, the fluid such as a lubricating oil is arranged in the space between the individual pressure receiving parts 3 of the fixed shaft 1 and the inner wall of the shaft hole 5 of the rotating body 4, and at the time of rotating the rotating body 4, the rotating body 4 is supported by the dynamic pressure of this fluid. By this method, the swing of the disks under rotation can be reduced.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a disk drive device.

(Prior Art) Dynamic pressure bearings are generally known as dynamic pressure bearings, which generate fluid pressure in a gap through relative motion between surfaces, and receive a member by this fluid pressure. Since the bearings maintain a non-contact state, there is no generation of foreign matter such as abrasion particles unlike contact type bearings such as ball bearings.Therefore, for example, if it is applied as a bearing in the drive part of a magnetic disk drive. This has the advantage that the magnetic disk can be placed in an extremely clean environment.

FIG. 6 schematically shows an example of such a disk drive. This disk drive device includes a casing 42 having a space 41 in which a magnetic disk is placed.
A cylindrical part 43 is formed that communicates the inside and outside of the space 41, and a shaft 45 whose base end is connected to the rotor 44 of the electric motor is passed through the cylindrical part 43 from the outside of the casing 42, and the distal end side of the shaft 45 is passed through the cylindrical part 43. is positioned inside the casing 42 protruding from the inner end thereof, and a cup-shaped rotary body 47 that supports the magnetic disk 46 is fixed to the tip thereof, while the inner circumferential portion of the cylindrical portion 43 and the The rotor 44 has a structure in which a fluid (for example, lubricating oil) is arranged in a gap between the outer circumference of the opposing shaft 45.
Dynamic pressure is generated in the fluid by the rotation of the shaft 45 as the shaft 45 rotates, and the shaft 45 is supported by this dynamic pressure.

(Problems to be Solved by the Invention) However, in the above device, since the shaft 45 is supported by the dynamic pressure of the fluid, the shaft 45
, unbalance of weight of rotating body 47, shaft 45
There is a problem in that the shaft 45 oscillates during rotation due to the unbalance of weight that occurs when it is attached to the rotating body 47, and the magnetic disk 46 . . . oscillates accordingly.

Such vibrations of the shaft 45 can be broadly classified into parallel vibrations and conical vibrations. Parallel runout can be explained based on the above device, for example, when the rotating body 4
7, the upper right portion and the lower right portion of the electric motor rotor 44 have a large weight and other parallel imbalances, so the shaft 45 A conical runout refers to a runout in which the center axis of the cylinder rotates around the center axis of the cylinder 43. On the other hand, a conical runout is a runout in which the weight of the upper right portion of the rotating body 47 and the lower left portion of the motor rotor 44 in the figure is large, for example. This is a runout in which the center axis of the shaft 45 rotates around the center axis of the cylindrical portion 43 in a state where the center axis of the cylindrical portion 43 and the center axis of the shaft 45 intersect due to luan balance.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a drive device for a disk that can reduce the occurrence of wobbling of the disk during rotation.

(Means for Solving the Problems) Therefore, in the disk drive device of the present invention, a fixed shaft and a shaft hole formed in a rotating body that supports the disk and is rotationally driven are fitted, and the shaft hole is The rotary body is rotatably supported by the dynamic pressure action of a fluid placed between the inner wall and the outer peripheral portion of the fixed shaft facing the inner wall.

(Function) In the above device, although it is not necessarily theoretically clear, compared to the conventional device, the runout caused by conical unbalance is not much different, but the runout caused by parallel unbalance is significantly reduced. Therefore, if we take advantage of this phenomenon and add weight to the rotating body that causes parallel unbalance, the conical unbalance will be canceled, and as a result, the parallel runout will be reduced. It is possible to prevent the occurrence of conical runout while maintaining the same.

(Example) Next, a specific example of the disk drive device of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

In the figure, reference numeral 1 denotes a fixed shaft, and this fixed shaft 1 projects inside a casing (not shown) in which magnetic disks 2, . . . are arranged. As shown in the figure, this fixed shaft 1 has large-diameter pressure receiving portions 3.3 formed at two positions separated in the axial direction on its outer periphery, which constitute a fluid dynamic pressure receiving surface, which will be described later. There is. On the other hand, a rotating body 4 is rotatably supported on this fixed shaft l. This rotary body 4 is a columnar member whose vertical cross section is approximately H-shaped as shown in the figure, and the length on the inner circumferential side thereof is approximately the length between both pressure receiving portions 3.3 of the fixed shaft 1. - It is designed to meet the A shaft hole 5 having a slightly larger diameter than the pressure receiving portion 3.3 of the fixed shaft l is formed in the axial center of the rotating body 40. The rotating body 4 connects this shaft hole 4 to the fixed shaft 1.
The inner wall of the shaft hole 5 of the rotating body 4 faces each pressure receiving portion 3.3 of the fixed shaft 1.

That is, the portion of the inner wall of the shaft hole 5 that faces the pressure receiving portion 3.3 constitutes a fluid pressure receiving surface, as will be described later. A fluid such as lubricating oil is disposed in the gap between each pressure receiving part 3.3 of the fixed shaft 1 and the inner wall of the shaft hole 5 of the rotary body 4, so that fluid such as lubricating oil is generated in this fluid when the rotary body 4 rotates. The rotating body 4 is supported by dynamic pressure. Note that the axial support of the rotating body 4 and the sealing of lubricating oil are provided by appropriate means, although not shown.

Figure 2 shows the results of measuring the unbalance vibration response between the parallel unbalance and conical unbalance of the disk drive device with the above configuration and comparing it with the unbalance vibration response of the conventional disk drive device described above. is shown in a graph. The figure shows the bearing radius clearance (pressure receiving part 3.3) on the horizontal axis.
and the inner wall of the shaft hole 5, or the gap between the outer periphery of the shaft 45 and the inner periphery of the cylindrical part 43. It shows changes in the unbalanced vibration response of the field when the damping coefficient is taken and the bearing radius clearance is changed.

As shown in the figure, the unbalance vibration response to a parallel unbalance of a fixed shaft type is significantly smaller than the unbalance vibration response to a parallel unbalance of a rotating shaft type. Further, the response to a conical unbalance of a fixed shaft type is also smaller than the vibration response to a conical unbalance of a rotating shaft type. Therefore, in the above device, if conical imbalance is prevented from occurring by actively generating parallel imbalance, the vibration response due to unbalance can be significantly reduced. That is, at one end of the outer circumferential portion of the rotating body 4 (lower end in the figure), there is a collar-shaped portion 6 that expands outward in the radial direction.
is formed, a plurality of magnetic disks 2 and annular spacers 7 are inserted alternately, and an annular tightening member 8 and a collar portion 6 are inserted.
The magnetic disks 2 and the spacer 7 are fixed eccentrically to one side, and thereby the parallel antenna It creates balance.

In this case, the magnetic disk 2... and the spacer 7...
are fitted with the rotating body 4 lying on its side, tightened and fixed, and each magnetic disk 2... and spacer 7...
It is preferable to have a configuration in which, by their own weight, they are gathered to one side, and a parallel imbalance is actively generated. As a result, the conical unbalance of the rotating body 4 itself is canceled out, and as a result, the conical runout can be eliminated while the parallel runout is kept small. As a result, it is possible to reduce the vibration of the magnetic disk 2.

Furthermore, in the above embodiment, since the vicinity of both the upper and lower ends of the rotating body 4 is supported, the conical vibration that occurs in the rotating body 4 can also be reduced, and in this respect as well, the magnetic disk 2... It is possible to reduce vibration.

Further, in the embodiment described above, it is possible to directly connect the rotor of the electric motor to the rotating body 4, and therefore it is also possible to configure the device compactly in the axial direction.

On the other hand, FIGS. 3 and 4 show models for calculating the natural frequencies of each parallel mode and conical mode of a fixed shaft type disk drive device and a shaft rotating type disk drive device. In the model shown in FIG. 3, a beam 11 having a weight 13 in the center is used as a rotating body, and both ends of the beam 11 are supported by springs 12 and 12 which function as bearing rigidity. Also, in the model shown in Figure 4,
A weight 49 as a rotor 44 and a weight 5 as a rotating body 47 are attached to both ends of a beam 48 as a rotating shaft 45, respectively.
0 is attached, and the two weights 49 and 50 are supported by springs 51 and 51 each having a function as bearing rigidity. Using these models, the natural frequencies of the parallel mode and conical mode were determined, and the results are shown in FIG. The figure shows the bearing stiffness on the horizontal axis and the natural frequency on the vertical axis. From the figure, it can be seen that the natural frequency of the conical mode of the fixed shaft type is extremely higher than the natural frequencies of other modes. I understand. In other words, by using a fixed shaft type, it is possible to more effectively avoid the risk of damage to the device due to resonance.

Although the embodiment of the disk drive device of the present invention has been described above, the fluid disposed in the gap between the pressure receiving part 3 and the inner wall of the shaft hole 5 may be any fluid that can function as a dynamic pressure bearing. For example, it is possible to use a variety of fluids.

(Effects of the Invention) As described above, since the disk drive device of the present invention has the above-described configuration, it is possible to reduce the occurrence of wobbling of the disk during rotation.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the disk drive device of the present invention, FIG. 2 is a graph showing the relationship between bearing radial clearance and unbalanced vibration response, etc., and FIGS. 3 and 4 are shafts, respectively. Models of fixed type and shaft rotating type disk drive devices. Figure 5 is a graph showing the relationship between each natural frequency of parallel mode and conical mode and bearing rigidity determined based on the above model, and Figure 6 is FIG. 2 is an explanatory diagram of a conventional disk drive device. ■...Fixed shaft, 2...Magnetic disk, 4...
・Rotating body, 5... shaft hole. Patent applicant Nippon Ferrofluidics Co., Ltd.

Claims (1)

[Claims] 1. A fixed shaft is fitted into a shaft hole formed in a rotary body that supports a disk and is rotationally driven, and is disposed between an inner wall of the shaft hole and an outer peripheral portion of the fixed shaft facing thereto. 1. A disk drive device, wherein the rotating body is rotatably supported by the dynamic pressure action of the fluid.