JP2001325782A - Method for manufacturing center core of magnetic disk cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a center core which can avert the adverse influence of the burrs of the center core of a magnetic disk cartridge formed by rotatably housing magnetic disk media into a flat cartridge case and fixing the center core concentrically provided with a flange, whose one surface is formed as a surface to be stuck to the magnetic disk media, to the central position of the magnetic disk media. SOLUTION: A step part 67c lower on the outer side is concentrically pressed and formed by forging of a plate member in a position slightly deviating to the inner side from a position corresponding to the outer peripheral edge of a flange 67 on the surface 67a side to be stuck with the magnetic disk media and thereafter, the flange 67 is formed by blanking through from the opposite surface side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-small magnetic disk cartridge containing a disk-shaped magnetic disk medium in a flat cartridge case and having a large recording capacity, the center core being fixed to the center position of the magnetic disk medium. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a magnetic disk medium (a so-called floppy disk) in which a magnetic layer is provided on both sides of a disk-shaped base made of a flexible polyester sheet or the like and magnetically recorded on the magnetic layer by a magnetic head while being driven to rotate. (Registered trademark) disk) is provided in a flat case, and is mainly used as a recording medium for a computer because of its advantages such as easy handling and low cost.

In such a magnetic disk cartridge, a center core concentrically provided with a spindle hole into which a spindle of a drive device is inserted and a flange having one surface as a sticking surface of the magnetic disk medium is provided on a center core of the magnetic disk medium. It is fixed at the center position. In a conventional floppy disk, the center core is formed by drawing a metal plate, and the center core is formed by being pulled out on the outer periphery of the flange.

By the way, the miniaturization of the computer using the above-mentioned magnetic disk cartridge has progressed, and the notebook type personal computer has become widespread. An external system without a built-in disk drive device is now being sold. The adoption of this external method is excellent in terms of portability of small personal computers.However, for example, there is a problem that a large amount of data cannot be recorded and reproduced because magnetic disk cartridges cannot be used at the carrying destination of small personal computers. This causes a problem that data cannot be recorded on a plurality of magnetic disk cartridges.

[0005] From these points, some small personal computers have a PC card slot (conforming to the PCMCIA specification) in which a PC card is mounted to support an external interface and additional memory. It has been proposed to configure an external storage device using a magnetic disk cartridge.

A PC that can be inserted into the PC card slot
The specifications of the card are type II, the thickness is 5.0 mm, and the magnetic disk cartridge and the disk drive are intended to be included in this thickness. Therefore, the thickness of the magnetic disk cartridge is about 2 to 3 mm. It must be made ultra-thin.

[0007] Even when the above-mentioned ultra-small magnetic disk cartridge is constructed, a large recording capacity is required as a recording medium. However, if the recording density is increased to secure the maximum recording capacity, the transfer rate is reduced. Since it is necessary to rotate the magnetic disk medium at a high speed in order to increase the height, a high-accuracy center core is required.

[0008]

However, as described above, when the center core is formed by drawing a metal plate and is finally formed by being pulled out on the outer periphery of the flange, the center core must be formed on the outer peripheral edge of the flange. “Punching burrs” occur.

[0009] This pulling burr is, depending on the pulling direction,
The magnetic disk media will remain on either the sticking surface of the magnetic disk media or the surface on the opposite side. The burrs deform the magnetic disk medium at the outer peripheral portion of the flange, which causes so-called “surface runout deterioration”.

On the other hand, if the burrs are left on the surface opposite to the sticking surface of the magnetic disk medium, the magnetic disk media will not be deformed, but there is a risk that the burrs come into contact with the inner surface of the cartridge shell. Yes, in that case, "shell shaving" may occur, causing dust to generate an error.

For this reason, barrel processing, processing for turning the burrs in the radial direction by pressing the flange again, and the like are performed. In the former barrel processing, the center core contacts the barrel compound, or the center cores contact each other. The contact may cause scratches or impair the surface accuracy. Further, in the latter processing of turning the punched burrs in the radial direction, there is a risk that the burrs may be mutually damaged in the process, and in an extreme case, the burrs may fall off from the outer peripheral edge of the flange of the center core.

In view of such circumstances, the present invention provides a method of manufacturing a center core which does not require the above-described barrel processing even if the flange is pulled out on the outer periphery of the flange or the processing of pressing the flange again to turn the burr in the radial direction. It is intended to provide.

[0013]

According to the present invention, there is provided a center core having a flat cartridge case in which a magnetic disk medium is rotatably accommodated, and a center concentrically provided with a flange having one surface as an attaching surface of the magnetic disk medium. Is a method of manufacturing a center core in a magnetic disk cartridge fixed to a center position of a magnetic disk medium,
By forging the plate member, a step portion having a lower outside is concentrically pressed and formed at a position slightly inward from a position corresponding to the outer peripheral edge of the flange on the magnetic disk medium sticking surface side, and then the opposite is performed. The flange is formed by being dropped from the surface side.

[0014]

According to the method of manufacturing the center core of the present invention, the flange is pulled out from the opposite side of the magnetic disk medium to the sticking surface, so that the burrs remain on the magnetic disk medium to the sticking surface. Since the outer peripheral edge of the flange on the magnetic disk medium attaching surface side is lower than the magnetic disk medium attaching surface by the formation of the portion, there is no possibility that the tip of the punched burr comes into contact with the magnetic disk medium, and therefore, The deformation of the magnetic disk medium due to the burrs can be completely eliminated.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

1 to 4 show an embodiment of a magnetic disk cartridge provided with a center core manufactured according to the present invention, and FIG. 1 shows a state in which a window for inserting a magnetic head is closed by a shutter member. It is the perspective view seen from the upper surface side. FIG. 2 is a perspective view of a state in which the magnetic head insertion window is opened as viewed from the lower surface side. FIG. 3 is an exploded perspective view of the magnetic disk cartridge. Further, FIG. 4A is an enlarged sectional view of a central portion, and FIG. 4B is an enlarged sectional view of a central portion of the center core. In addition, in order to clarify the structure, the thickness and the like of each part in the drawings are shown in proportions different from actual dimensions.

The magnetic disk cartridge 1 has a disk-shaped magnetic disk medium 10 (see FIG. 3) rotatably housed in a flat cartridge case C.
The cartridge case C includes a base plate 2 serving as a central member.
And a substantially planar upper cover case 3 and a lower cover case 4 attached to the top and bottom of the base plate 2. The magnetic disk medium 10 has a disk-shaped base made of a flexible polyester sheet or the like provided with magnetic layers on both sides, and has a metal center core 11 fixedly integrated at the center.

Base plate 2 of cartridge case C
The annular portion 66 of the center core 11 (FIG. 4)
(A)) is provided, and the lower cover case 4 is provided with a hole 2 at a position overlapping the hole 27.
The magnetic disk medium 10 is housed in the cartridge case C such that a hole 7 having a size substantially equal to that of the hole 7 is formed, and the bottom surface of the hub 66 of the center core 11 faces the outside from the hole 7.

A window 8 is formed at the front end of the cartridge case C with respect to the insertion direction D (arrow in FIG. 1) with respect to the drive device so that the recording / reproducing magnetic head can be accessed. The window 8 is vertically penetrated and opened from the front end faces of the base plate 2 and the upper and lower cover cases 3 and 4 toward the center thereof in a rectangular shape (see FIG. 2). A shutter member 5 for opening and closing the portion 8 is built inside the upper and lower cover cases 3 and 4 so as to be slidable in the left-right direction.

With such a structure of the window 8, the recording / reproducing magnetic head can be inserted into the window 8 from the front end side of the cartridge case C without opening and closing greatly up and down.
Moreover, the adoption of the built-in shutter member 5 prevents the shutter member 5 from coming off due to insufficient strength due to miniaturization, becomes strong against dropping, etc., and has good assemblability.

Next, the structure of each component will be specifically described with reference to FIG.

First, the base plate 2 is made of a synthetic resin such as acrylonitrile-butadiene-styrene copolymer (ABS resin) or POM resin, and has a substantially rectangular flat plate shape. A circular recess 21 for accommodating the disk medium 10 is formed, and a circular hub accommodation hole 27 is opened at the center of the thin bottom plate of the recess 21. In addition, the front end portion of the bottom plate of the concave portion 21 is cut into a substantially rectangular shape, and the shutter member 5
Space 2 into which a lower plate 52 to be described later is movably inserted.
2, the central portion of the front end portion of the base plate 2 is removed in the front-rear direction, and the window portion 8 is opened vertically. The front surface of the front wall on one side (the right side in FIG. 3) of the window 8 of the base plate 2 is on the other side (the left side in FIG. 3).
A spring housing 23 is formed to retreat from the front surface of the front wall, and a shutter spring 6 described later is arranged in this portion.

Further, the corner portions 25 of the four corners of the base plate 2 are formed so as to protrude in the vertical direction and have a large thickness and project outward, and the four corner portions of the upper and lower cover cases 3 and 4 correspond to the corner portions. When the upper and lower cover cases 3 and 4 are fitted to the base plate 2, the corner portions 25 of the base plate 2 are exposed to the outside. Each corner portion 25 is provided in a shape in which the surface protrudes flush or outward with the surface of the upper and lower cover cases 3 and 4.

By exposing the corner portion 25 of the base plate 2 to the outside as described above, when a shock or the like at the time of drop acts, the corner portion 25 can absorb the shock, and can be inserted into the drive device and inserted. At the time of unloading operation, it is prevented from getting stuck and stable operation is ensured. In each corner 25, a hole 26 penetrating in the vertical direction (a hole having an intermediate depth without penetrating) may be used.
Is provided so as to obtain a larger buffering action at the time of a drop impact. The base plate 2 has a strength that allows a deformation that does not hinder the recording and reproduction of the magnetic disk medium 10. However, from the viewpoint of shock absorption, the base plate 2 is preferably made of an elastic plastic. In addition, a material containing a lubricant is preferable in terms of sliding with respect to the shutter member 5, and a material containing a filler material is used in order to improve dimensional accuracy and improve assemblability with the cover cases 3 and 4. Is good.

Further, as shown in FIG. 1, a notch-shaped concave portion 15 is formed on the side surface of the corner portion 25 on both sides of the front portion of the base plate 2.
The concave portion 15 is provided for positioning when loaded in the drive device, or for preventing erroneous insertion in the front-back direction or the front-back direction. The recess 15 may be provided only on one side surface or on the side surface of the rear corner portion 25. In the case of the present embodiment, the corner of one of the front corners 25 is notched diagonally to form the erroneous insertion prevention part 16.

Further, on the side surface of the cartridge case C, at a position different from the recess 15, for example, as shown in FIG.
Although the discrimination unit 17 for disc type (for example, the type of recording capacity) is provided on the side wall of No. 4, a write protector unit may be provided here. Furthermore, the identification section 17 may be provided with an identification piece that enables the detection function to be turned on / off so as to be able to be inserted or inserted / extracted. By forming the concave portion 15 and the identification portion 17 on the side surface, a drive-side detection mechanism or the like having no installation space in the vertical direction can be arranged on the side.

The upper and lower cover cases 3 and 4 are formed of a high-strength material such as a pressed stainless steel plate. The upper cover case 3 and the lower cover case 4 have a substantially symmetrical shape, and the four corners are rectangular. It is removed, a flat rectangular window 8 is opened in the center of the front part, and the front, rear, left and right edges are bent at right angles, and the front walls 31, 41, both side walls 32, 42, respectively.
The rear wall portions 33 and 43 are configured. The front wall portion 3 on one side (the left side in FIGS. 1 and 3 and the right side in FIG. 2) with respect to the window portion 8.
The slits 18 (see FIGS. 1 and 2) are formed between the upper and lower front wall portions 31 and 41 when the upper and lower cover cases 3 and 4 are attached to the base plate 2. It is supposed to be. Then, the shutter opening / closing member on the drive device side is inserted into the slit 18,
The shutter member 5 is moved along the slit 18 to open the shutter member 5. The front wall 3 on the opposite side of the window 8 (the right side in FIGS. 1 and 3 and the left side in FIG. 2).
1, 41, that is, a notch is formed at the end side of the portion located in front of the spring storage portion 23, and a rectangular spring is formed in a state where the front wall portions 31, 41 of the upper and lower cover cases 3, 4 are fitted together. An insertion opening 19 (see FIGS. 1 and 2) is formed and used for mounting the shutter spring 6.

On the upper surface of the central portion of the upper cover case 3,
A concave portion 35 serving as a label attaching portion is formed, and a bottom surface of the concave portion 35 projects downward. The recess 35 is provided in the rotation area of the magnetic disk medium 10 in an assembled state. The depth of the concave portion 35 is set at the center of the space between the lower surface of the concave portion 35 facing the bottom surface of the circular concave portion 21 of the base plate 2 and the bottom surface of the circular concave portion 21 in the thickness direction of the base plate 2. 10 is set to be located. That is, the magnetic disk medium 1 located at the center in the thickness direction of the base plate 2
0 so that the upper and lower clearances are substantially equal.
By setting the depth, the rotational stability of the magnetic disk medium 10 is improved, and the presence of the concave portion 35 improves the strength of the upper cover case 3.

The shutter member 5 is inserted between the base plate 2 and the upper and lower cover cases 3 and 4 and into the sliding space 22 opened to the base plate 2 on the lower surface side, and is slidably mounted in the left and right opening and closing directions. You. The shutter member 5 is made of metal, for example, formed in a substantially U-shaped cross section from a stainless steel plate or an aluminum plate. The upper plate portion 51 and the lower plate portion 52 are connected by a connecting portion 53 at the front end. The height of 53 is substantially equal to the thickness of the front part of the base plate 2. Then, a shutter window 54 is formed by being cut out in a substantially rectangular shape from the connecting portion 53 to the upper surface plate portion 51 and the lower surface plate portion 52. The shutter window 54 has a size substantially corresponding to the window 8 of the cartridge case C, and is communicated with the shutter window 54 during the opening operation. The shutter window 54 is provided at a position deviated from the center of the shutter member 5, and together with the connecting portion 53, the cartridge case C
A closing area for closing the window 8 is formed adjacent to the shutter window 54.

A spring receiving projection 55 bent from the connecting portion 53 of the shutter member 5 is provided on the inner surface of the front end of the shutter window portion 54 on the side of the closed area, and the shutter spring 6 formed of a coil spring in the opening and closing direction is provided on the back thereof. When contracted, the shutter member 5 is urged in the closing direction. Although not shown, at least one of the upper surface plate portion 51 and the lower surface plate portion 52 is cut and raised, and is engaged with a guide groove extending in the left and right direction on the base plate 2 so as to be assembled. It is useful for preventing the coming off. Reinforcing ribs 56 are formed on the upper plate portion 51 and the lower plate portion 52 of the shutter member 5 to prevent deformation during the opening operation. The reinforcing rib 56 is formed in a protruding shape protruding outward to suppress the generation of abrasion powder and the like due to the sliding of the tips of the upper and lower plate portions 51 and 52 contacting the upper and lower cover cases 3 and 4. It also has the effect of reducing the frictional resistance of the device and ensuring the stability of the opening and closing operation.

On the upper and lower sides of the magnetic disk medium 10, protective sheets 12 made of a plastic sheet or the like having a PET sheet surface subjected to a sliding process (Teflon (registered trademark) process) are interposed. The protective sheet 12 has a portion corresponding to the window portion 8 removed in the radial direction to form a substantially C-shape, and an opening 12a is formed in a portion opposite to the window portion 8, and a cleaning member 13 is provided in this portion. The cleaning member 1 is fixed to the inner surface of the upper cover case 3 and the bottom surface of the base plate 2 from the magnetic disk medium 10 side.
At the same time, the protection sheet 12 is fixed by the fixation of the protective sheet 3.
The cleaning member 13 is brushed on the side facing the magnetic disk medium 10 and comes into contact with the surface of the magnetic disk medium 10 to remove dust on the surface. An adhesive is applied to the opposite surface of the cleaning member 13.

To assemble the magnetic disk cartridge 1, the protective sheet 12 is fixed to the circular concave portion 21 of the base plate 2 and the lower surface of the upper cover case 3 by fixing the cleaning member 13 in advance. After the magnetic disk medium 10 is set in the shutter member 5, the shutter member 5 is mounted from the front. Subsequently, the upper cover case 3 is fitted to the base plate 2 from above and the lower cover case 4 is fitted and held from below to form an integral unit. 4 is spot-welded. As a result, the upper surface of the circular recess 21 of the base plate 2 is covered with the upper cover case 3, and the flat space defined by the bottom surface of the upper cover case 3 and the upper surface of the circular recess 21 becomes a storage space for the magnetic disk medium 10. The magnetic disk medium 10 is rotatably stored. Thereafter, the coil-shaped shutter spring 6 is bent from the spring insertion port 19 in the front wall portion of the upper and lower cover cases 3 and 4 while the inner spring housing 2 is being bent.
3 and the front end thereof is brought into contact with the spring receiving projection 55 of the shutter member 5, and the rear end is pressed into the storage portion 23 while being contracted, thereby completing the assembly. In addition, the spring insertion port 1
9, the shutter spring 6 assembled
Is locked out.

When the magnetic disk cartridge 1 is loaded in the drive device, the pawl of the opening / closing mechanism is inserted into the slit 18 at the front end, engages with the end of the shutter member 5, and moves it in the opening direction. Manipulate. Accordingly, the window 8 of the base plate 2 is opened, and the hub receiving hole 27 of the base plate 2 is opened.
The bottom of 1 is exposed to the outside through the hole 7 of the lower cover case,
The state shown in FIG. 2 is obtained.

As shown in FIG. 4 (a), the center core 11 has a disc-shaped portion 62 provided at the center with a spindle hole 61 penetrating between the parallel upper and lower surfaces 62a and 62b, and a periphery of the disc-shaped portion 62. , Annular portions 65 and 66 formed coaxially with the spindle hole 61 and a flange 67 having an upper surface with an attachment surface 67a of the magnetic disk medium 10.
It is composed of The spindle 70 of the drive device has a small cylindrical portion 7 inserted into the spindle hole 61 of the center core 11 at the center of the flat upper surface 70a.
1 is coaxially provided, and the lower surface 62b of the disc-shaped portion 62 of the center core 11 is magnetically attracted to the flat upper surface 70a.

The flange 67 is concentrically formed with a stepped portion 67c whose height is lower outwardly from the outer periphery of the flange 67, so that the surface 67a of the flange 67 on which the magnetic disk medium 10 is stuck is formed. Outer circumference is flange 6
7 is closer to the inside than the outer circumference.

The inner wall surface of the spindle hole 61 is shown in FIG.
As shown in the figure, a cylindrical wall surface portion 61a occupying a central portion of the spindle hole 61 in the direction of the axis L, and diameters are expanded from upper and lower ends of the cylindrical wall surface portion 61a toward upper and lower surfaces 62a and 62b, respectively. inclined wall portion 61b which is inclined by an angle theta ₁ with respect to L, consisting of 61c. The cylindrical wall surface portion 61a of the spindle hole 61 is parallel to the outer wall surface 71b of the cylindrical small diameter portion 71 of the center core 11, and its axis L
The dimension in the direction is set in the range of 0.3 to 0.6 mm.

Further, the inclined wall portion 61b, the inclination angle theta ₁ of 61c, when the magnetic disk cartridge 1 is chucked by the drive device, the initial spindle 70 is inserted from the bottom surface of the cartridge 1 to the spindle hole 61 It is set to be equal to or greater than the movement angle of the cartridge from the stage to chucking.
By setting the inclined wall portion 61b, the inclination angle theta ₁ of 61c in this way, reliable chucking is ensured.

Next, a method of manufacturing the center core 11 having the above configuration will be described with reference to FIG.

First, as shown in FIG. 5A, a plate member is pressed from both sides by forging to form a disk-shaped portion 62 and annular portions 65 and 66, and a magnetic disk medium of a flange 67 is formed. A step 67c is formed concentrically at a position slightly inward from a position corresponding to the outer peripheral edge of the surface on the side of the attaching surface 67a, and the surface 67d outward from the step 67c is attached to the magnetic disk medium attaching surface 67a. Lower than

The upper and lower surfaces 62a and 62a are formed in such a manner that a thin portion 62e is left at a central portion of the disk-shaped portion 62 corresponding to the spindle hole 61 in the thickness direction of the disk-shaped portion 62.
By forming the tapered recesses 62c and 62d coaxially in 62b, the inclined wall surfaces 61b and 61c of the spindle hole 61 in FIG. 4B are formed in advance.

Next, as shown by an arrow in FIG. 5A, a step 67c is provided as shown in FIG. 5B by dropping it from the surface 67b opposite to the magnetic disk medium attaching surface 67a. The flange 67 is formed and the disc-shaped portion 62 is formed.
The cylindrical thin wall portion 61e of the spindle hole 61 in FIG. 4B is formed by subjecting the thin portion 62e at the center of the cylinder hole to a cylindrical shape from the same direction (spindle insertion direction). 61 is completed.

The height of the stepped portion 67c is appropriately selected according to the thickness of the flange 67 because the height of the burrs 67e generated varies depending on the thickness of the flange 67. From, generally 0.1-0.3m
m.

As is apparent from the above description, in the manufacturing method of the center core 11 in the present embodiment, the flange 67 is finally formed by dropping from the side opposite to the magnetic disk medium attaching surface 67a side. Therefore, the burrs 67 as shown in FIG.
Although e occurs, a stepped portion 67c whose outside is lowered is formed concentrically in advance at a position slightly inward from a position corresponding to the outer peripheral edge of the flange 67 on the magnetic disk medium attaching surface 67a side. As a result, the surface 67d outward from the step 67 is lower than the magnetic disk medium attaching surface 67a. As is apparent from FIG. 5C, there is a possibility that the tip of the punch burr 67e reaches the magnetic disk medium 10. Absent. Therefore, there is no need for barrel treatment or treatment for pressing the flange again to remove the burrs in the radial direction, so that the surface of the center core is scratched, the surface accuracy is impaired, or the burrs are formed on the outer peripheral edge of the center core flange. The danger of peeling off from the object is avoided.

In the present embodiment, the inner wall surface of the spindle hole 61 of the center core 11 is
By providing the cylindrical wall portion 61a having a wall surface parallel to the axis L at the center of the first axis L direction, a highly accurate fitting state with the spindle 70 is obtained, and the cylindrical wall portion 61a is Inclined wall portions 61b, 61c whose diameters are increased outward from the upper and lower ends, respectively, in the direction of the axis L.
When the cartridge 1 is mounted on the drive device, even if the axis L of the center core 11 is inclined with respect to the axis of the cartridge 1, the small-diameter portion 71 of the spindle 70 is inserted into the spindle hole 61. It has the advantage of being easily inserted.

Further, since the center core 11 is formed by forging, a high-accuracy center core 11 can be manufactured at low cost without the risk of deterioration of magnetic properties as in cutting.

Further, the thin portion 62 formed by forging
The cylindrical wall surface portion 61a of the spindle hole 61 is formed by subjecting e to a cylindrical process of pulling it out from the insertion direction of the spindle 70, so that the spindle hole 61 with high precision can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of a magnetic disk cartridge having a center core manufactured according to the present invention, showing a state in which a window for inserting a magnetic head is closed by a shutter member, as viewed from above.

FIG. 2 is a perspective view of the magnetic disk cartridge shown in FIG. 1, showing a state in which a window for inserting a magnetic head is opened, as viewed from a lower surface side;

FIG. 3 is an exploded perspective view of the magnetic disk cartridge shown in FIGS. 1 and 2;

FIG. 4A is an enlarged sectional view of a main part of a magnetic disk cartridge, and FIG. 4B is an enlarged sectional view of a central portion of a center core.

5 (a) and 5 (b) are illustrations of a method of manufacturing a center core according to the present invention, and FIG. 5 (c) is an enlarged sectional view of an outer peripheral edge of a flange of the center core manufactured according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic disk cartridge C cartridge case 2 Base plate 3 Upper cover case 4 Lower cover case 5 Shutter member 6 Shutter spring 8 Window part for magnetic head insertion 10 Magnetic disk media 11 Center core 12 Protective sheet 13 Cleaning member 19 Spring insertion opening 21 Circular recess 23 Spring storing part 25 Corner part 27 Hub receiving hole 35 Depression 61 Center core spindle hole 67 Center core flange 67a Magnetic disk media attaching surface 67c Step 67e

Claims (1)

[Claims] 1. A magnetic disk medium is rotatably accommodated in a flat cartridge case, and a center core concentrically provided with a flange having one surface as an attachment surface of the magnetic disk medium is provided at a center position of the magnetic disk medium. A method for manufacturing the center core in a magnetic disk cartridge fixed to the magnetic disk cartridge, wherein a forging process is performed on a plate member to a position slightly inward from a position corresponding to an outer peripheral edge of the flange on the magnetic disk medium attaching surface side. And a step of concentrically pressing and forming a step portion having a lower outside, and then forming the flange by pulling out from an opposite surface side.