JPH05234327A - Small size magnetic disk device - Google Patents

Abstract

PURPOSE:To reduce vibration of a magnetic disk in a small size magnetic disk devices which ensures a large capacity and high speed rotation of disks. CONSTITUTION:Projection areas are provided to the portions of a cover 1 and a base 9 provided opposed to magnetic disks 4a, 4b and a gap between the projected portions and magnetic disks 4a, 4b is kept at 3mm or lower. The part where a gap between the magnetic disk and cover or base is kept at 3mm or less is provided to the cover and base. Thereby, disturbance of air flow on the magnetic disks due to high speed rotation thereof can be reduced and accordingly vibration of magnetic disks can be lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small magnetic disk device.

[0002]

2. Description of the Related Art FIG. 3 is a schematic view of a 5.25-inch small magnetic disk drive. Eight magnetic disks 4 having a diameter of 5.25 inches and a plate thickness of 1.91 mm are stacked on a spindle 3 having a built-in motor, and are rotationally driven at 3600 rpm. The magnetic head 6 is provided so as to face both sides of the magnetic disk 4, and is positioned on each data track on the magnetic disk 4 by the voice coil motor 8. The magnetic head 6 floats on the magnetic disk 4 in a non-contact manner while maintaining a submicron flying height by a fluid force generated as the magnetic head 4 rotates. In this state, reading and writing of information from the magnetic disk 4 is performed. It is carried out.

In the magnetic disk device, it is an important development item to increase the storage capacity and increase the throughput. The increase in storage capacity is realized by increasing the storage density (linear density and track density) and increasing the number of magnetic disks per magnetic disk device. For higher throughput, there is a tendency to increase the rotation speed and increase the data transfer rate. In order to increase the linear density, it is necessary to reduce the flying height of the magnetic head. In order to mount the magnetic disks at a high density, the plate thickness of the magnetic disks is reduced and many magnetic disks are stacked. On the other hand, the greatest problem of the magnetic disk device is destruction of information (head crash) due to collision between the magnetic head and the magnetic disk. A rotating disk such as a magnetic disk tends to have large vibrations in proportion to the cube of its rotation speed. Similarly, the amplitude of the disk vibration increases in inverse proportion to the plate thickness.

In particular, this tendency is remarkable for the two outermost disks of the stacked disks. This is because the disk vibration is caused by the turbulence of the air flow accompanying the rotation of the disk, and the flows on the two outer disks are strongly affected by the cover and base, respectively, and are more turbulent than the other disks. It is thought to be because. FIG. 4 shows the result of measuring how the actual disc vibration varies depending on the disc. It can be seen that the vibration of the disk facing the cover of the device and the disk corresponding to the base are larger than those of the other disks. From the above, it is expected that the model that lowers the flying height and rotates at high speed with a thin plate will have a greater tendency of head crash than the conventional model, especially when two layers on the outer side are stacked. Discs are expected to be the most dangerous.

In the conventional small-sized magnetic disk device, almost no measures have been taken against this problem. This is because the disk diameter was smaller than that of a large-sized disk device (disk diameter of 5.25 inches or more), and the influence of this factor on the fluctuation of the flying height was not so large.

[0006] In a large disk device
It has been proposed in Japanese Patent No. 6683 to increase the disk thickness of only the two outer disks to suppress vibration.
Japanese Patent Laid-Open No. 53-57009 proposes a structure in which a flow plate is provided around the disk to regulate the flow on the disk and suppress disk vibration.

[0007]

The above method proposed for a large magnetic disk has a problem when applied to a small magnetic disk. The difference between a small magnetic disk and a large magnetic disk is that reliability is a major consideration for a large magnetic disk, while reliability and cost and power consumption must be considered for a small magnetic disk. This is a restriction derived from the fact that small magnetic disks are used in personal level devices such as personal computers and workstations.

The method of using only two thick disks on the outside of Japanese Utility Model Laid-Open No. 2-96683 has a problem in terms of cost because two kinds of disks are required and assembly is complicated. ..

The structure provided with the current plate increases the rotational load, increases the number of parts, and increases the complexity of assembly. In the case of a small magnetic disk, its size is limited,
It is difficult to provide the member outside the disc.

The present invention proposes an effective method of reducing the vibration of the disk due to the interaction between the magnetic disk and the cover rotating at high speed or the magnetic disk and the base without increasing the cost and power consumption.

[0011]

Detailed experiments have revealed that disk vibration can be effectively reduced by performing the following configuration.

In order to solve the above-mentioned problems, the cover or the base is constructed so as to have a portion whose distance from the magnetic surface of the magnetic disk is 3 mm or less. Alternatively, a member is attached to the cover or the base so that the distance between the member and the magnetic surface of the magnetic disk is 3 mm or less.

[0013]

It is considered that the cause of the disk vibration is that the airflow accompanying the rotation on the disk is disturbed on the disk surface perpendicularly to the disk surface. When discs are stacked, the inner discs are sandwiched between the discs that rotate at the same speed, so it is difficult for the discs to distort, but the two outer discs face the stationary cover and base, respectively. .. Therefore, the disc surface is likely to be disturbed and the disc vibration is increased. Here, as the characteristics of the fluid, the occurrence of turbulence depends on the flow velocity V and the representative length L.
(Here, the gap between the disc and the cover or the disc and the base) and the Reynolds (Re) number (Re = V * L / u) expressed by the kinematic viscosity u of the fluid, and the Re number occurs above a certain size However, there is a property that it does not occur below that. In the case of a magnetic disk, the flow velocity is fixed because the rotation speed is constant, and the kinematic viscosity is also constant, so the Re number is determined by the gap. Therefore, if the gap is made smaller, there is a condition that turbulence does not occur below a certain gap. Basically, it is sufficient to make the gap as small as possible, but in reality, it is an important problem to find out this condition because it is related to the assembly error of the cover and the disk and the processing accuracy.

FIG. 5 shows the results of measuring the relationship between the disc vibration and the gap between the cover and the disc provided with a member whose disc space can be changed arbitrarily. As can be seen from FIG. 5, when the distance between the member and the disc is 3 mm or less, the disc vibration sharply decreases.
Therefore, this value is the condition under which the turbulence described above occurs.

[0015]

FIG. 1 shows a first embodiment of the present invention. Eight magnetic disks 4 having a diameter of 5.25 inches or less and a plate thickness of less than 0.075 inches are stacked on the spindle 3 at predetermined intervals by spacers 10 and fixed by the clamp 2.
The magnetic disk 4 is rotationally driven by a motor built in the spindle 3 at a predetermined rotation speed of 5400 rpm or more. The magnetic heads 6 are provided so as to face both sides of the magnetic disk 4, and are floated at a submicron height from the magnetic disk 4 by the hydrodynamic force generated by the rotation of the magnetic disk 4 to read / write information from / to the magnetic disk 4. .. The magnetic head 6 is supported by the carriage arm 5, and the shaft 7
Is swingably driven by a voice coil motor 8 to read and write information on an arbitrary information track on the magnetic disk 4. The center fixing shaft of the spindle 3 and the shaft 7 are fixed to the cover 1 and the base 9, and fix the geometrical positions of the rotation centers of the magnetic disk 4 and the magnetic head 6.

A portion of the cover 1 facing the magnetic disk 4a is provided with a convex portion with respect to the magnetic disk 4a within a range that does not hinder the movement of the carriage arm 5 and the magnetic head 6. The gap distance Δt between the lower surface of the convex portion and the magnetic disk 4a is 0.
It is configured to have a thickness of 3 mm or less, thereby suppressing the vibration of the magnetic disk 4a. FIG. 2 shows this convex portion in an enlarged manner. The portion of the base 9 facing the magnetic disk 4b is thick within a range that does not hinder the movement of the carriage arm 5 and the magnetic head 6, and the gap distance Δt between the upper surface of the thick portion and the magnetic disk 4b is 0.3 mm. The vibration of the magnetic disk 4b is suppressed by the following configuration.

FIG. 7 shows a second embodiment of the present invention. The support member 1 is provided on the portion of the cover 1 facing the magnetic disk 4a.
The vibration damping plate 12 is configured through the structure 1. Damper 12
The gap Δt between the magnetic disk 4a and the magnetic disk 4a is configured to be 0.3 mm or less.
The turbulence of the upper air flow is suppressed, and the vibration of the magnetic disk 4a is reduced. FIG. 8 shows the above portion in an enlarged manner. Base 9
Similarly to the cover 1, a damping plate 12 is provided to suppress the vibration of the magnetic disk 4b.

FIG. 9 shows a third embodiment of the present invention. Inside the cover 1 and the base 9, there are provided concentric or radial ribs 13 as shown in FIG. This rib 1
The gap distance Δt between the end surface of No. 3 and the magnetic disks 4a and 4b is set to 0.3 mm or less, and it has the effect of reducing the vibration of the magnetic disk 4 as in the first and second embodiments. ..

The same effects can be expected even if the first to third embodiments described above are separately combined with the cover 1 and the base 9.

FIG. 6 is a comparison of how the vibration of the disk changes between the conventional method and the present invention. Compared with the conventional configuration, the vibration is 1/3 at the top disc and 1/5 at the bottom disc. Also,
It can be seen that not only the outer two discs but also the second and third discs have a damping effect.

[0021]

According to the present invention, the vibration of the disk can be effectively suppressed without increasing the cost and the power consumption. Therefore, it is possible to reduce the risk of head crash due to disk vibration of a small-sized magnetic disk device that performs high-speed recording at high speed.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is an enlarged view of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a magnetic disk device.

FIG. 4 is an actual measurement diagram showing a difference in vibration between the stacked disks.

FIG. 5 is an actual measurement diagram showing a relationship between a cover, a top disc, a gap, and a top disc vibration.

FIG. 6 is an explanatory diagram of a comparison between the conventional configuration and the effect of the present invention.

FIG. 7 is a sectional view of the second embodiment of the present invention.

FIG. 8 is an enlarged view of the second embodiment of the present invention.

FIG. 9 is a sectional view of a third embodiment of the present invention.

FIG. 10 is a side view of the third embodiment of the present invention.

[Explanation of symbols]

1 ... Cover, 2 ... Clamp, 3 ... Spindle, 4 ... Magnetic disk, 4a ... Top disk, 4b ... Bottom disk,
5 ... Carriage arm, 6 ... Magnetic head, 7 ... Shaft,
8 ... Voice coil motor, 9 ... Base, 10 ... Spacer, 11 ... Support member, 12 ... Damping plate, 13 ... Rib.

Claims (1)

[Claims] 1. One or more magnetic disks having a diameter of 5.25 inches or less and a plate thickness of less than 0.075 inches,
A motor that rotationally drives this, a magnetic head that reads and writes magnetic information on the magnetic disk, an actuator that supports the motor and moves and positions it to an arbitrary position on the magnetic disk, and protects the above-mentioned components, In a small-sized magnetic disk device comprising a cover and a base arranged in the above-mentioned positional relationship, and the number of revolutions of the magnetic disk is 5400 rpm or more, the distance between the cover or the base facing the magnetic surface of the magnetic disk and the magnetic disk is 3 mm or less. A small magnetic disk drive characterized in that such a portion is formed on the cover or the base.