JPH09180361A - Disk rotating mechanism applied to disk recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a state of occurrence of distortion to a data surface of a disk and causing distortion in a position of servo information accompanying the progress of the distortion by uniformizing disk holding force in the circumferential direction by a disk pressing member in the disk rotating mechanism particularly of a both end supporting type. SOLUTION: The disk rotating mechanism of the both end supporting type having a fixed shaft 1 fixed to a base body 4 is equipped with a disk pressing member 18 having a push nut part 18a to be fixedly engaged with a hub rising part 2a of a hub 2 supporting plural disks 6 stacked in the axial direction and holding the individual disks 6 by touching the uppermost side disk 6 out of these disks. This disk pressing member 18 has the push nut part 18a formed around a hole in the middle, and this push nut part 18a is engaged with the hub rising part 2a, so as to be fitted into a middle part of the hub 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc rotating mechanism particularly applied to a disc recording / reproducing device such as a hard disc device.

[0002]

2. Description of the Related Art Conventionally, in a disk recording / reproducing apparatus such as a hard disk device (HDD), a disk rotating mechanism (spindle mechanism) for rotating a disk as a recording medium at high speed.
Is provided.

As the disk rotation mechanism of the HDD, a cantilever type in which about two disks are normally mounted and a both-end type in which three or more disks are mounted are well known.
Since the cantilever type mechanism has a structure in which a hub supporting a disc is connected to a fixed shaft and the fixed shaft is driven to rotate, when the number of discs increases, the fixed shaft sways, causing rotational fluctuation. There is a structural problem that causes it.

On the other hand, the double-sided type mechanism has a structure in which the fixed shaft is fixed, and therefore has a structure in which the rotational fluctuation is relatively small even if the number of mounted disks is large. Further, since there are many demands for an HDD having a high storage capacity in which three or more disks are mounted, a double-sided type mechanism is becoming more popular.

As shown in FIG. 9 (A is a plan view, B is a sectional view), the fixed shaft 1 fixed to a base body 4 which is a base of the mechanism is roughly divided into two types of disk rotating mechanisms of both-end holding type.
A spindle hub (hereinafter simply referred to as a hub) 2 which is engaged with the fixed shaft 1 with a bearing mechanism 3 interposed therebetween, and a motor mechanism 5 arranged inside the hub 2. The bearing mechanism 3 has a structure in which two ball bearings are combined, for example.

The hub 2 supports, for example, four discs 6 laminated in the axial direction at the outer peripheral portion thereof, and is rotated about the fixed shaft 1 by the driving force of the motor mechanism 5. The disks 6 are provided in a stacked state with a spacer ring 7 interposed therebetween and at a predetermined interval. The motor mechanism 5 has a so-called in-hub type motor structure, and includes a magnet 5a fixed to the hub 2 and a coil 5b fixed to the base 4 side. That is, the magnet 5a and the coil 5b
Due to the electromagnetic action of and, the hub 2 rotates about the fixed shaft 1.

Further, the disk rotating mechanism is a disk 6
Is provided with a disk pressing member 8 for holding the disk in the axial direction. As shown in FIG. 9 (A), the disc pressing member 8 has a hole 8a formed in the center thereof, and the hole 8a forms a convex portion called a hub rising portion 2a forming an inner peripheral edge of the hub 2. Guided by the parts, radial positioning is performed. The disk pressing member 8 is fastened to four positions of the hub 2 by a plurality of, for example, four small screws 9, and the outer peripheral side 8b is drawn to have a kind of leaf spring structure. This outer peripheral side 8
b contacts the uppermost disc 6 and holds each disc 6 in the axial direction.

[0008]

Conventionally, in a double-sided type disk rotating mechanism used for an HDD, a plurality of disk pressing members 8 are fastened to the hub 2 by, for example, four small screws 9, so that each disk 6 is pressed. Is held in the axial direction. However, in such a mounting structure, the holding force of the disc pressing member 8 in the circumferential direction of the disc 6 is relatively large in the vicinity of the small screw 9 for fastening, and is small in the position away from the small screw 9. Become.

Therefore, when the holding force of the disc 6 by the disc pressing member 8 becomes non-uniform and the temperature environment around the outside of the mechanism changes abruptly, the residual strain of the fastening portion due to the small screw 9 causes the disc 6 to have residual strain. A phenomenon occurs in which the release is uneven in the radial direction. As a result, distortion occurs in the data surface of each disk 6, and in particular, the position of the servo information recorded on the data surface is distorted. In such a situation, in the head positioning control operation for positioning the head at the target position of the disk 6 on the basis of the servo information, the head positioning accuracy is lowered, which causes a read error and a write error.

It is an object of the present invention, particularly in a double-sided type disk rotating mechanism, to make the holding force of the disk uniform by the disk pressing member, thereby generating distortion on the data surface of the disk and the position of servo information accompanying it. It is to prevent a situation that causes distortion.

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to a double-end type disk rotating mechanism having a fixed shaft fixed to a base, for a hub supporting a plurality of axially stacked disks, This mechanism has a push nut portion that is fixedly engaged with the hub rising portion, and includes a disc pressing member that holds each disc by contacting the uppermost disc among the discs. That is, the present disc pressing member has a push nut portion around the hole formed in the center without using a screw, and this push nut portion engages with the hub rising portion so that the center portion of the hub is It is a structure that is attached so as to be fitted. Therefore, it becomes possible to make the holding force in the circumferential direction of the disk uniform and prevent the situation where the data surface of the disk is distorted even when the external temperature environment suddenly changes.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are views showing a structure of a disk rotating mechanism relating to the first embodiment, FIG. 1A is a plan view, and FIG. 1B is a sectional view. (Structure of First Embodiment) The disk rotating mechanism of the present embodiment is particularly applied to a small HDD, and is assumed to be a double-sided spindle mechanism that supports and rotates four disks 6, for example. .

That is, as shown in FIG. 1B, in the disk rotating mechanism of this embodiment, a fixed shaft 1 fixed to a base 4 which is the base of the mechanism, and a bearing mechanism 3 interposed on the fixed shaft 1. A hub (spindle hub) 2 engaged with each other and a motor mechanism 5 disposed inside the hub 2. The bearing mechanism 3 has a structure in which two ball bearings are combined, for example.

The hub 2 is made of, for example, a ferritic stainless steel material and supports, for example, four discs 6 laminated in the axial direction at the outer peripheral portion thereof, and is rotated about the fixed shaft 1 by the driving force of the motor mechanism 5. Exercise. Each disk 6
Is made of, for example, a glass material, and is provided in a laminated state with a predetermined interval with a spacer ring 7 interposed. The motor mechanism 5 has a so-called in-hub type motor structure, and includes a magnet 5a fixed to the hub 2 and a coil 5b fixed to the base 4 side. That is, the hub 2 rotates about the fixed shaft 1 by the electromagnetic action of the magnet 5a and the coil 5b.

In such a rotating mechanism, in this embodiment, as the disc pressing member 18 for holding the disc 6 in the axial direction, as shown in FIG. 1 (A), the periphery of the hole formed in the central portion. The push nut portion 18a is used for the above. The material of the disc pressing member 18 is ferritic stainless steel, like the hub 2.

The disc pressing member 18 is positioned so that the claw portion 18c of the push nut portion 18a is engaged with the convex portion called the hub rising portion 2a forming the inner peripheral edge of the hub 2. That is, each peripheral edge portion 18d of the push nut portion 18a is guided by the hub rising portion 2a, and the claw portion 1
It is fixed by 8c. The disc pressing member 18 has a kind of spring structure in which the outer peripheral side 18b is bent, and as shown in FIG. 1 (B), the outer peripheral side 18b comes into contact with the uppermost disc 6 and Hold 6 axially. (Effects of First Embodiment) First, as a basic operation of the HDD, when the device power is turned on, the motor mechanism 5 is rotationally driven. The rotational driving force of the motor mechanism 5 causes the hub 2 to rotate about the fixed shaft 1 with the bearing mechanism 3 interposed therebetween. For example, four disks 6 are supported on the hub 2 by a spacer ring 7 at a predetermined interval.

In the HDD, heads facing the respective data surfaces (front and back surfaces) of the disk 6 are provided within the space defined by the spacer ring 7. That is, H of the present embodiment
In the DD, since it is assumed that the number of disks 6 is 4, eight heads are provided.

The outer peripheral side 18b of each disc 6 is brought into contact with the uppermost disc 6 by the disc pressing member 18 to hold each disc 6 in the axial direction. In the disc pressing member 18 of the present embodiment, the push nut portion 18a at the central portion is guided by the hub rising portion 2a, and the claw portions 18c of the push nut portion 18a are pushed into the hub rising portion 2a so as to be bitten therein. Installed. The dimensional relationship of the disc pressing member 18 is set so that a holding force for the disc 6 is generated by the bending force when the disc pressing member 18 is pushed into a predetermined position guided by the hub rising portion 2a.

In the disk pressing member 18 having such a structure, the fastening portion for the hub 2 is not dispersed in four places by four small screws as in the conventional structure, but the push nut in the central portion is used. The structure is such that the fastening force is concentrated on the portion 18a and the fastening force is made uniform in the circumferential direction. Therefore, when the temperature environment around the outside of the HDD changes abruptly, the residual strain of the disk pressing member 18 is released almost uniformly in the radial direction of the disk 6 even if there are some differences in the thermal expansion coefficients of the components. It

As a result, it is possible to minimize the distortion generated on the data surface of each disk 6. Therefore, in particular, it is possible to suppress the occurrence of distortion with respect to the position of the servo information recorded on the data surface, so that it is possible to prevent a situation in which the accuracy of the head positioning control operation based on the servo information decreases. (Second Embodiment) In the second embodiment, as shown in FIG. 2, the disc pressing member 2 is positioned in the radial direction by the hub rising portion 2a and attached to the surface portion of the hub 2.
8 is a structure held by the push nut member 30. In other words, in the above-described first embodiment, the push nut portion 18 is provided on the periphery of the central hole of the disc pressing member 18.
In the present embodiment, a push nut member 30 independent of the disc pressing member 28 is used.

As shown in FIG. 2B, the disc pressing member 28 is positioned in the radial direction on the surface portion of the hub 2 with the peripheral edge of the center hole thereof being guided by the hub rising portion 2a. Then, as shown in FIG. 3A, the push nut member 30 is attached, and the disc pressing member 28 is held by the peripheral edge portion of the hub rising portion 2a. At this time, the claw portion 30a of the push nut member 30 is attached so as to be engaged with the hub rising portion 2a.

The disc pressing member 28 has a central portion fixed by a push nut member 30 and has an outer peripheral side 28.
b is drawn to have a kind of leaf spring structure.
As shown in (B), the outer peripheral side 28b comes into contact with the uppermost disk 6 and holds each disk 6 in the axial direction.

The operational effects of the other components and the disc pressing member 28 are the same as those of the first embodiment. However, in this embodiment, as compared with the case of the first embodiment, the number of components corresponding to the push nut member 30 is increased, but a push nut portion is provided in the peripheral portion of the central hole with respect to the disc pressing member 28. The step for forming can be eliminated. (Third Embodiment) As shown in FIG. 3, the third embodiment uses a retaining ring member (for example, metal) 40 as a member for holding the disc pressing member 28 on the hub 2. is there. Further, in this embodiment, as shown in FIG.
As shown in (B), a groove 2b for supporting the retaining ring member 40 is formed in the hub rising portion 2a for positioning the disc pressing member 28.

As shown in FIG. 3B, the disc pressing member 28 is positioned in the radial direction on the surface portion of the hub 2 with the peripheral edge of the center hole thereof being guided by the hub rising portion 2a. Then, as shown in FIG. 3A, the retaining ring member 40 is fitted into the groove 2b formed in the hub rising portion 2a in a state where the vicinity of the center hole of the disc pressing member 28 is pressed and bent. At this time, the dimensional relationship is set so that when the retaining ring member 40 is fitted into the groove 2b, a necessary holding force for the disc 6 is generated in the disc pressing member 28.

According to the structure of this embodiment, the disk pressing member 28 is concentrated at the peripheral edge of the hub rising portion 2a, which is the central portion of the hub 2, and the fastening force is made uniform in the circumferential direction. Will be concluded as follows. Therefore, as in the case of the first embodiment described above, when the temperature environment around the outside of the HDD changes abruptly, even if there is some difference in the thermal expansion coefficient of the components, the disc pressing member 28 is The residual strain is released almost uniformly in the radial direction of the disk 6. The operational effects of the other components and the disc pressing member 28 are similar to those of the first embodiment described above. (Fourth Embodiment) As shown in FIG. 4A, the fourth embodiment uses a disc pressing member 38 having a central hole 38a whose center portion is eccentric. The disc pressing member 38 is fitted in the groove 2b formed in the hub rising portion 2a, and is attached in a state where it is positioned in the radial direction on the surface portion of the hub 2.

Further, the disc pressing member 38 has a structure shown in FIG.
As shown in (B), a diaphragm 38c provided with a screw hole for fastening is provided. The screw hole of this diaphragm 38c
The disc pressing member 38 is arranged at a position matching the screw hole 9a provided in the hub 2. The disc pressing member 38 is fastened to the surface portion of the hub 2 by the fastening screw 9.

At this time, the vicinity of the central hole 38a of the disc pressing member 38 is pushed and bent, and the diaphragm 38c is slid in the direction to be pushed out, so that the peripheral edge of the central hole 38a is formed in the hub rising portion 2a. It is fitted in the groove 2b.
The dimensional relationship is set so that the fastening force of the disc 6 is generated in the disc pressing member 38 by fastening the fastening screw 9 in this state.

In other words, an eccentric center hole 38a is formed in order to slide the disc pressing member 38 to position it with respect to the hub rising portion 2a. In addition, in order to improve the rigidity of the fastening portion by the screw 9, the diaphragm 38
Although c is formed, it is unnecessary if sufficient rigidity can be obtained without the diaphragm 38c.

As described above, the disc pressing member 38 is
As shown in FIG. 4B, the outer peripheral side 38b of the groove 2b formed in the hub rising portion 2a and the one screw 9 are in contact with the uppermost disk 6, and The disk 6 will be held in the axial direction. This outer peripheral side 38
b is drawn to form a kind of leaf spring structure.
Therefore, even if there is some difference in the thermal expansion coefficient of the components when the temperature environment around the outside of the HDD fluctuates rapidly,
Since there is only one fastening portion by the screw 9, the residual strain of the disc pressing member 38 is released substantially uniformly in the radial direction of the disc 6. The operational effects of the other components and the disc pressing member 38 are similar to those of the first embodiment described above. (Fifth Embodiment) As shown in FIG. 5, in the fifth embodiment, the disc pressing member 2 is positioned in the radial direction by the hub rising portion 2a and attached to the surface portion of the hub 2.
8 is a structure held by the nut member 50b.
The nut member 50b is fitted to the male screw portion 50a formed on the hub rising portion 2a and holds the disc pressing member 28 positioned by the hub rising portion 2a.

That is, as shown in FIG. 5 (B), the disk pressing member 28 has the hub rising portion 2a at the periphery of the central hole thereof.
And is positioned in the radial direction on the surface portion of the hub 2. Then, as shown in FIG. 3A, the nut member 50b is fitted so as to mesh with the male screw portion 50a formed on the outer circumference of the hub rising portion 2a. At this time,
The dimensional relationship is set so that when the nut member 50b is screwed to a predetermined position, the disc pressing member 28 bends and a necessary holding force for the disc 6 is generated.

The male screw portion 5 of the hub rising portion 2a as described above.
0a and the nut member 50b, the disk pressing member 28
Has a kind of leaf spring structure in which the outer peripheral side 28b is drawn while being fixed to the surface portion of the hub 2, and the outer peripheral side 28b is the uppermost disc 6 as shown in FIG. 5B. To hold each disk 6 in the axial direction. The operational effects of the other components and the disc pressing member 28 are similar to those of the first embodiment described above. (Sixth Embodiment) In the sixth embodiment, as shown in FIG. 6, the disc pressing member 6 is radially positioned by the hub rising portion 2a and attached to the surface portion of the hub 2.
0 is a nut portion 60a formed in the peripheral portion of the central hole
Is a structure in which it is fitted and held in a male screw portion formed in the hub rising portion 2a.

That is, as shown in FIG. 6A, a nut portion 60a is formed on the peripheral portion of the central hole of the disc pressing member 60 by burring. On the other hand, a male screw portion that fits with the nut portion 60a is formed on the peripheral portion of the hub rising portion 2a.

As shown in FIG. 6B, in the disc pressing member 60, the peripheral edge of the central hole in which the nut portion 60a is formed is guided by the hub rising portion 2a so that the surface of the hub 2 is radially moved. Positioned. Here, the fastening hole 60c formed in advance on the surface of the disc pressing member 60 is set as, for example, a mounting jig, and the mounting jig is used to
The nut portion 60a of the disc pressing member 60 is fitted so as to be screwed into the male screw portion of the hub rising portion 2a. In addition,
Instead of the fastening hole 60c, a cutout portion may be formed in the outer peripheral portion of the disc pressing member 60, and the cutout portion may be set as a mounting jig.

In such a structure, when the disc pressing member 60 is screwed to a predetermined position by the nut portion 60a, the disc pressing member 60 is bent and a necessary holding force for the disc 6 is generated. Is set. The disc pressing member 60 has a kind of leaf spring structure in which the outer peripheral side 60b is drawn in a state of being fixed to the surface part of the hub 2, and as shown in FIG.
0b comes into contact with the uppermost disc 6 to hold each disc 6 in the axial direction.

Therefore, the fastening force can be increased by fitting the disc pressing member 60 to the male screw portion of the hub rising portion 2a, which is the central portion of the hub, without using a plurality of fastening screws as in the prior art. The disc pressing member 60 can be fixed so as to be uniform in the circumferential direction. Therefore, when the temperature environment around the outside of the HDD changes abruptly, the residual strain of the disk pressing member 60 is released almost uniformly in the radial direction of the disk 6 even if there is a slight difference in the coefficient of thermal expansion of the components. It
The operational effects of the other components and the disc pressing member 60 are similar to those of the first embodiment described above. (Seventh Embodiment) In the seventh embodiment, as shown in FIG. 7C, a retaining ring member (for example, metal) 70 is used as a member for holding the disc pressing member 28 on the hub 2. It is a structure. The retaining ring member 70 is provided with protrusions (projections) 70a on the inner peripheral side at predetermined intervals. on the other hand,
At the hub rising portion 2a for positioning the disc pressing member 28, as shown in FIG.
A notch (L-shaped notch) 2c for engaging with the protrusion 70a is formed.

As shown in FIG. 7B, the disc pressing member 28 is positioned in the radial direction on the surface portion of the hub 2 with the peripheral edge of the center hole thereof being guided by the hub rising portion 2a. Then, as shown in FIG. 7 (A), the protrusion 70a of the retaining ring member 70 is engaged with the notch 2c of the hub rising portion 2a in a state where the vicinity of the central hole of the disc pressing member 28 is pressed and bent. Fit them together. At this time, the protruding portion 70a of the retaining ring member 70 is attached to the hub rising portion 2a.
The dimensional relationship is set so that the disc pressing member 28 bends at the time when the discs are engaged with each other at a predetermined position to generate a necessary holding force for the disc 6.

According to the structure of this embodiment, the disc pressing member 28 is concentrated by the snap ring member 70 at the periphery of the hub rising portion 2a, which is the central portion of the hub 2, and the fastening force is distributed. It will be fastened so as to be uniform in the direction. Therefore, as in the case of the first embodiment described above, when the temperature environment around the outside of the HDD changes abruptly, even if there is some difference in the thermal expansion coefficient of the components, the disc pressing member 28 is The residual strain is released almost uniformly in the radial direction of the disk 6. The operational effects of the other components and the disc pressing member 28 are similar to those of the first embodiment described above. (Eighth Embodiment) The eighth embodiment is shown in FIG.
As shown in (D), the protrusion 80a formed in the peripheral portion of the central hole of the disc pressing member 80 is provided with the hub rising portion 2a.
The disc pressing member 80 is held by being engaged with the notch portion (L-shaped notch portion) 2c formed in the.

As shown in FIG. 8B, the disk pressing member 80 is positioned in the radial direction on the surface portion of the hub 2 with the peripheral edge of the central hole being guided by the hub rising portion 2a. Here, the fastening hole 80c formed on the surface of the disc pressing member 80 in advance is set as, for example, a mounting jig, and the projecting portion 80a of the disc pressing member 80 is set to the hub standing position by using this mounting jig. The notch portion 2c of the raising portion 2a is engaged with the notch portion 2c so as to mesh with each other.

In such a structure, when the disc pressing member 80 is engaged with the projection 80a at a predetermined position, the disc pressing member 80 is bent and a necessary holding force for the disc 6 is generated. Is set. The disk pressing member 80 has a kind of leaf spring structure in which the outer peripheral side 80b is drawn in a state of being fixed to the surface portion of the hub 2, and as shown in FIG.
0b comes into contact with the uppermost disc 6 to hold each disc 6 in the axial direction.

Therefore, without using a plurality of fastening screws as in the conventional case, the disc pressing member 80 is fitted into the cutout portion 2c of the hub rising portion 2a which is the central portion of the hub 2 so that the fastening can be achieved. The disc pressing member 80 can be fixed so that the force is uniformized in the circumferential direction. Therefore, when the temperature environment around the outside of the HDD changes abruptly, the residual strain of the disk pressing member 80 is released almost uniformly in the radial direction of the disk 6 even if there is a slight difference in the coefficient of thermal expansion of the components. It The other components and the disc pressing member 80
The function and effect regarding are the same as those of the above-described seventh embodiment. Here, as compared with the seventh embodiment, a process for forming the protrusion 80a on the disc pressing member 80 is required, but the retaining ring member 70 which is an independent member is not necessary, and therefore the configuration It is possible to reduce the number of parts.

[0041]

As described above in detail, according to the present invention, in a double-end type disk rotating mechanism particularly applied to an HDD, the fastening portion of the disc pressing member with respect to the hub member is concentrated at a substantially central portion or one location. With such a mounting structure, the holding force of the disk can be made uniform in the circumferential direction. Therefore, it is possible to uniformly release the residual strain of the fastening portion of the disc pressing member due to the abrupt change of the external temperature environment in the radial direction of the disc. This makes it possible to prevent the occurrence of distortion on the data surface of the disk and the accompanying distortion of the servo information position.

[Brief description of the drawings]

1A and 1B are views showing a structure of a disk rotating mechanism relating to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a sectional view.

2A and 2B are views showing the structure of a disk rotating mechanism relating to the second embodiment, where FIG. 2A is a plan view and FIG.
Is a sectional view.

3A and 3B are views showing a structure of a disk rotating mechanism relating to a third embodiment, where FIG. 3A is a plan view and FIG.
Is a sectional view.

4A and 4B are views showing a structure of a disk rotating mechanism relating to a fourth embodiment, where FIG. 4A is a plan view and FIG.
Is a sectional view.

5A and 5B are views showing a structure of a disk rotation mechanism relating to a fifth embodiment, where FIG. 5A is a plan view and FIG.
Is a sectional view.

6A and 6B are views showing a structure of a disk rotating mechanism relating to a sixth embodiment, where FIG. 6A is a plan view and FIG.
Is a sectional view.

7A and 7B are views showing the structure of a disk rotating mechanism relating to a seventh embodiment, in which FIG. 7A and FIG. 7C are plan views, and FIG. 7B and FIG. Sectional view.

8A and 8B are views showing a structure of a disk rotating mechanism relating to an eighth embodiment, wherein FIG. 8A and FIG. 8C are plan views, and FIG. 8B and FIG. Sectional view.

FIG. 9 is a diagram showing a structure of a conventional HDD spindle mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fixed shaft 2 ... Hub (spindle hub) 2a ... Hub rising part 3 ... Bearing structure 4 ... Base body 5 ... Motor mechanism 5a ... Magnet 5b ... Coil 6 ... Disk 7 ... Spacer ring 8 ... Disk pressing member 9 ... Small screw 18 ... Disc retaining member 18a ... Push nut part 28 ... Disc retaining member 30 ... Push nut member 38 ... Disc retaining member 40 ... Retaining ring member 50b ... Nut member 60 ... Disc retaining member 70 ... Retaining ring member 80 ... Disc retaining member 80a …protrusion

Claims (8)

[Claims] 1. A disk rotating mechanism, which is applied to a disk recording / reproducing apparatus for fixedly holding a plurality of disks as recording media and rotationally driving each of the disks, comprising: a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. And a hub member having a positioning hub rising portion disposed around the upper side of the fixed shaft, and a motor mechanism provided at a position corresponding to the inside of the hub member and rotationally driving the hub member. And a push nut portion that is attached to the surface portion of the hub member and fixedly engages with the hub rising portion, and is the uppermost disc among the respective discs supported by the hub member. To Disk rotating mechanism, characterized by comprising a disk pressing member for holding the respective disks touch. 2. A disk rotating mechanism which is applied to a disk recording / reproducing apparatus for fixedly holding a plurality of disks which are recording media and rotationally driving each of the disks, comprising a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. And a hub member having a positioning hub rising portion disposed around the upper side of the fixed shaft, and a motor mechanism provided at a position corresponding to the inside of the hub member and rotationally driving the hub member. Of the discs mounted on the surface of the hub member and supported by the hub member in a state of being positioned by the hub rising portion, the discs come into contact with the uppermost disc. And a push nut member for fixedly engaging the hub rising portion and holding the disc pressing member on the surface portion of the hub member. Disk rotation mechanism. 3. A disk rotating mechanism, which is applied to a disk recording / reproducing apparatus for fixedly holding a plurality of disks which are recording media and rotationally driving each of the disks, comprising a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. And a hub member having a positioning hub rising portion disposed around the upper side of the fixed shaft, and a motor mechanism provided at a position corresponding to the inside of the hub member and rotationally driving the hub member. Of the discs mounted on the surface of the hub member and supported by the hub member in a state of being positioned by the hub rising portion, the discs come into contact with the uppermost disc. And a retaining ring member for engaging the groove formed in the hub rising portion to retain the disc pressing member on the surface portion of the hub member. And a disk rotation mechanism. 4. A disk rotation mechanism applied to a disk recording / reproducing apparatus for fixedly holding a plurality of disks which are recording media and rotationally driving each of the disks, comprising a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. And a hub member having a positioning hub rising portion disposed around the upper side of the fixed shaft, and a motor mechanism provided at a position corresponding to the inside of the hub member and rotationally driving the hub member. And a central hole attached to the surface portion of the hub member and eccentric to engage with the groove of the hub rising portion, and the central hole engages with the groove of the hub rising portion. Screw on the hub member By being engaged, the disk rotating mechanism, characterized by comprising a disk pressing member for holding the respective disk in contact with the uppermost disk in each disk that is supported by the hub member. 5. A disk rotation mechanism applied to a disk recording / reproducing apparatus for fixedly holding a plurality of disks as recording media and rotationally driving each disk, comprising a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. A hub member having a positioning hub rising portion arranged around the upper side of the fixed shaft and having a screw structure formed around the fixed shaft, and provided at a position corresponding to the inside of the hub member, A motor mechanism that drives the hub member to rotate, and a motor mechanism that is attached to a surface portion of the hub member and is supported by the hub member in a state of being positioned by the hub rising portion. De A disk pressing member that holds the disks by contacting the disk, and a nut member that is fitted to the screw structure portion of the hub rising portion and holds the disk pressing member on the surface portion of the hub member. A disk rotation mechanism comprising: 6. A disk rotation mechanism applied to a disk recording / reproducing apparatus for holding a plurality of disks as recording media in a fixed manner and rotationally driving each disk, comprising a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. A hub member having a positioning hub rising portion arranged around the upper side of the fixed shaft and having a screw structure formed around the fixed shaft, and provided at a position corresponding to the inside of the hub member, A motor mechanism for rotationally driving the hub member, and a nut portion that is attached to a surface portion of the hub member and that fits into the screw structure portion of the hub rising portion, and is positioned on the hub rising portion. In the state Disk rotating mechanism, characterized in that serial in contact with the uppermost disk in said each disk supported by the hub member; and a disc pressing member for holding the respective discs. 7. A disk rotation mechanism applied to a disk recording / reproducing apparatus for holding a plurality of disks as recording media in a fixed manner and rotationally driving each disk, comprising a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. And a hub member having a positioning hub rising portion disposed around the upper side of the fixed shaft, and a motor mechanism provided at a position corresponding to the inside of the hub member and rotationally driving the hub member. Of the discs mounted on the surface of the hub member and supported by the hub member in a state of being positioned by the hub rising portion, the discs come into contact with the uppermost disc. And a disc pressing member for holding the disc pressing member, and a protrusion that engages with a notch formed around the hub rising portion, and the protrusion is fitted into the notch so that the disc pressing member is A disc rotating mechanism comprising: a retaining ring member for holding the hub member on the surface thereof. 8. A disk rotation mechanism applied to a disk recording / reproducing apparatus for fixedly holding a plurality of disks as recording media and rotationally driving each of the disks, comprising a fixed shaft fixed to a base body. A surface rotatably provided on the fixed shaft with a bearing mechanism interposed therebetween to support the disks stacked at a predetermined interval in the axial direction at an outer peripheral portion and to be coupled to the base body as a lower side. A hub member having a positioning hub rising portion that is arranged around the upper side of the fixed shaft and has a cutout portion formed around the fixed shaft, and is provided at a position corresponding to the inside of the hub member, A motor mechanism for rotationally driving the hub member, and a protrusion that is attached to a surface portion of the hub member and that fits into the cutout portion of the hub rising portion, and is positioned on the hub rising portion. In front Disk rotating mechanism, characterized in that said is supported by the hub member in contact with the uppermost disk within each disk was and a disc pressing member for holding the respective disk.