JPH0333984Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a magnetic disk housed in a magnetic disk jacket constituting a magnetic disk cassette.

[Background technology and its problems]

Since the magnetic sheet is repeatedly attached to the rotating shaft of the magnetic recording/reproducing device, it is preferable to attach it to a metal hub having a center core and a reference surface using an elastic body, a magnetic sheet holder, etc., and then position and attach it.

Fig. 1 is a cross-sectional view of a conventional magnetic disk.A magnetic disk D is made by molding a center core 2 by outsert on an annular metal hub 1 having reference surfaces on the top and bottom, and then forming an annular magnetic disk on top of the metal hub 1. The sheet 3, the annular elastic body 4, and the annular magnetic sheet presser 5 are sequentially laminated, and the center core 2 and the magnetic sheet presser 5 are fixed by welding or the like. Therefore, the magnetic sheet 3 is pressed and fixed to the reference surface of the metal hub 1 by the magnetic sheet presser 5 via the elastic body 4. Note that the diameter of the metal hub 1 is smaller than the diameter of the hole H provided in the magnetic disk jacket J shown by the two-dot chain line.
The reason why the outer diameter of the metal hub 1 is large is to prevent the thin magnetic sheet 3 from being damaged by the metal hub 1 slipping out of the hole H.

Conventional magnetic disk D configured as above
Since the metal hub 1 and the magnetic sheet 3 are in contact with each other up to the outermost periphery of the metal hub 1, if the temperature changes due to the difference in the coefficient of expansion between the metal hub 1 and the magnetic sheet 3, the recording on the magnetic sheet 3 will be There is a problem in that wrinkles occur in the innermost circumferential portion (hereinafter simply referred to as the innermost circumferential portion) in the possible region A. In addition, since the diameter of the metal hub 1 is larger than the range in which the magnetic sheet 3 is fixed to the metal hub 1 by the elastic body 4, and the magnetic sheet 3 is in contact with the outermost periphery of the metal hub 1, the innermost periphery of the magnetic sheet 3 is There is a problem in that the portion is susceptible to surface runout of the metal hub 1. Therefore, stable head touch of the magnetic head cannot be obtained in the innermost circumferential portion of the magnetic sheet 3, and the recording area A of the magnetic sheet 3
cannot be used effectively.

Therefore, the outer diameter of the metal hub 1 can be made smaller, but as mentioned above, the metal hub 1 will fall out from the magnetic disk jacket J and damage the magnetic sheet 3. It cannot be smaller than the dimensions.

[Purpose of invention]

This invention was made in view of the above points, and is intended to provide a magnetic disk in which stable head touch of the magnetic head can be obtained up to the innermost circumferential portion of the magnetic sheet, and the recording area of the magnetic sheet can be used effectively. be.

[Summary of the idea]

In order to achieve the above object, this invention presses and fixes the magnetic sheet on the inner circumference of the metal hub via a synthetic resin washer, thereby separating the outer circumference of the metal hub from the magnetic sheet. With this structure, stable head touch of the magnetic head can be obtained up to the innermost circumferential portion of the magnetic sheet, and the recording area of the magnetic sheet can be used effectively.

〔Example〕

Figure 2 is a sectional view showing an embodiment of this invention.
Reference numeral 6 denotes an annular washer made of synthetic resin such as polyester to a thickness of 100 μm, and its outer diameter is smaller than the outer diameter of the metal hub 1. Note that other symbols indicate the same parts as in FIG.

The magnetic disk D of this invention is shown in Figure 2.
Since the washer 6 is inserted between the metal hub 1 and the magnetic sheet 3, the magnetic sheet 3 is inserted between the inner peripheral part of the metal hub 1, that is, the part where the washer 6 contacts, and the magnetic sheet presser 5 via the elastic body 4. is pressed and fixed, and the outer peripheral portion of the metal hub 1 is in a state separated from the magnetic sheet 3. Therefore, since the inside of the innermost circumferential portion of the magnetic sheet 3 is separated from the metal hub 1, wrinkles are less likely to occur in the innermost circumferential portion of the magnetic sheet 3 due to the difference in expansion coefficients as described above. Moreover, since the washer 6 made of synthetic resin is interposed between the metal hub 1 and the magnetic sheet 3, the generation of wrinkles can be more effectively prevented. That is, since the magnetic sheet 3 is usually formed by magnetically coating a resin sheet, there is almost no difference in expansion coefficient between the magnetic sheet 3 and the washer 6, and the washer 6 and the metal The difference in expansion rate that occurs between the washer 6 and the metal hub 1 is due to the small contact area, and the strain that occurs between the washer 6 and the metal hub 1 is absorbed by the washer 6, resulting in magnetic Since there is almost no possibility that it will affect the magnetic sheet 3, it is especially important to use the washer 6 made of synthetic resin.
This is a more effective means for preventing wrinkles in the skin.

In this way, since the generation of wrinkles on the magnetic sheet 3 can be prevented, a stable head touch can be obtained, and the recording area A of the magnetic sheet 3 can be used effectively. Further, since the part that presses and fixes the magnetic sheet 3 is the inner peripheral part of the metal hub 1, and the outer peripheral part is separated from the magnetic sheet 3, the influence of surface runout of the metal hub 1 does not appear on the magnetic sheet 3.

Note that the surface runout of the metal hub 1 will not appear on the magnetic sheet 3 as the fixing width w becomes smaller, but if it is too small, the magnetic sheet 3 will not be able to be fixed and will slip, so the width w that can be fixed should be 50% or more. Setting it to around 70% will satisfy both conditions.

[Effect of idea]

As explained above, the magnetic disk of this invention has a configuration in which a magnetic sheet is pressed and fixed on the inner circumference of a metal hub via a synthetic resin washer having an outer diameter smaller than the outer diameter of the metal hub. Therefore, the outer peripheral part of the metal hub is separated from the magnetic sheet, and the magnetic sheet is fixed in contact with the washer, which has almost no difference in expansion coefficient, so the difference in expansion coefficient between the metal hub and the magnetic sheet is As a result, wrinkles generated on the magnetic sheet can be more effectively prevented, and furthermore, the influence of surface runout of the metal hub no longer appears on the magnetic sheet. Therefore, stable head touch of the magnetic head can be obtained up to the innermost portion of the magnetic sheet, and there is an advantage that the recording area of the magnetic sheet can be used effectively.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional magnetic disk, and FIG. 2 is a sectional view showing an embodiment of this invention. In the figure, D is a magnetic disk, 1 and 7 are metal hubs,
2 is a center core, 3 is a magnetic sheet, 4 is an elastic body,
5 is a magnetic sheet presser, 6 is a washer, and J is a magnetic disk jacket.

Claims (1)

[Scope of utility model registration request] In a magnetic disk having a structure in which a magnetic sheet is attached to a reference surface of a metal hub having predetermined dimensions, a washer made of synthetic resin having an outer diameter smaller than the outer diameter of the metal hub is provided, and this washer is connected to the metal hub. 1. A magnetic disk characterized by having a structure in which the magnetic sheet is interposed between the magnetic sheet and the metal hub and the magnetic sheet is pressed and fixed to the metal hub by a magnetic sheet presser.