JPH05114102A - Disk fixing device - Google Patents

Abstract

PURPOSE:To increase the attraction force of a hub by a permanent magnet up to the vicinity of an upper limit permitted to a disk by thinning a device itself. CONSTITUTION:A turntable 2 placing a disk 16 having the hub 18 consisting of a magnetic material, the permanent magnet 4 which is loaded on the upper face of the turntable 2 and fixes the disk 16 to the turntable 2 by attracting the hub 18 and a magnetic ring 14 attached to the turntable 2 turnably to the permanent magnet 4 are provided. A part of the lines of magnetic force of the permanent magnet 4 are introduced to the magnetic ring 14 to decrease the lines of magnetic force acting on the hub 18. The number of the lines of magnetic force acting on the hub 18 is adjusted by moving the magnetic ring 14 relative to the permanent magnet 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk fixing device for fixing a disk to a turntable by a magnet clamp.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a conventional disk fixing device. An annular permanent magnet 34, which constitutes a rotor of a motor and is magnetized into a plurality of poles, is attached to a lower surface of a rotor yoke 32 which is a turntable fixed on the shaft 30. The shaft 30 is rotatably supported by a housing 38 by a bearing 36. The permanent magnet 34 is attached to the back yoke 40 so as to face the permanent magnet 34.
A motor for rotating the rotor yoke 32 is formed together with the coil 42 fixed to the housing 38 via. The disk pressing member 44 is made of a ferromagnetic material, and is configured to press and hold the disk 46 against the rotor yoke 32 by the magnetic attraction force of the permanent magnet 34 attached to the rotor yoke 32.

FIG. 9 shows the shape of a plurality of through holes 32a formed in the rotor yoke 32. In this way, the magnetic disc necessary for attracting the disc pressing member 44 through the through hole 32a and holding the disc 46 can be obtained.

As a disk fixing device for fixing a disk such as an optical disk to a turntable, a hub having a magnetic band is attached to the center of the disk because it can handle high-speed rotation and has a simple structure. It is known to fix a magnet with a magnet such as a permanent magnet provided on a turntable.

FIG. 10 shows an example of this type of disk fixing device. The disk 46 has a magnetic band hub 5
0 is centered and adhered to the recording track of the disk 46. On the other hand, an annular permanent magnet 54 is bonded to the lower part of the turntable 52. A shaft 56 is press-fitted in the center of the turntable 52 so that the tip of the shaft 56 projects toward the disk 46. Therefore, in the disk 46, the center hole 58 is centered by the shaft 56, and the hub 50 has the permanent magnet 54.
And is fixed to the turntable 52.

The shaft 56 is rotatably supported by a housing 62 via a bearing 60. The coil 6 is mounted on the housing 62 via a back yoke 64.
6 is fixed so as to face the permanent magnet 54, and constitutes a motor for rotating the turntable 52 together with the permanent magnet 54.

[0007]

When designing such a motor, in order to prevent slippage at the time of starting and stopping the rotation of the disk, it is desirable to make the hub suction force as large as possible within the range allowed by the disk. Due to variations in the magnetization of the permanent magnets, the force with which the permanent magnets attract the hub, that is, the attraction force, may be reduced.

In the former case of the above two conventional examples, although the design value of the attraction force of the disc pressing member 44 can be changed by changing the size and number of the through holes 32a of the rotor yoke 32, the individual permanent magnets can be changed. It is not possible to adjust the variation in the magnetization of 34.

In the latter case, when designing the motor, the permanent magnet 54 must simultaneously satisfy the performance of rotating the turntable 52 and the performance of attracting the hub 50. A magnet having a high magnetic flux density is required to rotate the turntable 52, but such a magnet has an excessively strong attraction force to fix the disk 46, and the gap between the permanent magnet 54 and the hub 50 is increased. I have to take it. For this reason, it becomes an obstacle for making the motor thin, and it becomes a constraint on the design of the permanent magnet 54. Also, as in the former case, the individual permanent magnets 54
It is not possible to adjust the variation in the magnetization of.

The present invention has been made to solve the above-mentioned conventional problems, and its object is to:
An object of the present invention is to provide a disc fixing device that can make the device itself thin and can raise the suction force of the hub to a value close to the upper limit allowed for the disc.

[0011]

In order to solve such a conventional problem, in a disk fixing device according to the present invention, a disk having a hub made of a magnetic material is placed and is opposed to the disk. A turntable having a first surface and a second surface opposite to the first surface, and mounted on the second surface of the turntable and sucking the hub to fix the disc to the turntable And a magnetic member attached to the first surface so as to be movable with respect to the magnet.

[0012]

[Operation] A magnetic member is provided on the second surface of the turntable,
A part of the magnetic force lines of the permanent magnet is guided to the magnetic member to reduce the magnetic force line acting on the hub, and the magnetic member is moved with respect to the permanent magnet to adjust the number of magnetic force lines acting on the hub.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a circular turntable 2 has a lower portion cut out along the outer circumference. The upper surface of this notch constitutes a second surface, and a ring-shaped permanent magnet 4 for fixing the disk is fixed to this second surface. As shown in FIG. 3, the permanent magnet 4 is magnetized to have, for example, 6 poles on both sides. Further, a vertical hole is formed in the center of the turntable 2, and the main shaft 6 is inserted and fixed in the vertical hole. The main shaft 6 is rotatably supported by a bearing 9 fixed in the housing 8. A coil 10 is fixed on the housing 8 via a back yoke 12 so as to face the permanent magnet 4. The permanent magnet 4 and the coil 10 are
A motor for rotating the turntable 2 is configured.

On the upper part of the turntable 2 is formed a projecting part projecting upward along the outer periphery of the turntable 2. An annular recess is formed inside the protrusion and above the turntable 2. The bottom surface of this recess constitutes the first surface, and the ring-shaped magnetic ring 14 is installed. The magnetic ring 14 is made of a magnetic material and constitutes a magnetic member. The magnetic ring 14 is provided on the bottom surface of the recess so as to be rotatable with respect to the permanent magnet 4 and coaxial with the permanent magnet 4.
As shown in FIG. 4, the magnetic ring 14 is formed with six projecting portions 14 a that project so as to correspond to the six poles of the permanent magnet 4. The magnetic ring 14 is fixed to the turntable 2 after the positional relationship with the permanent magnet 4 is adjusted.

A disc 16 is placed on the upper surface of the projecting portion of the turntable 2. This state is shown in FIG. Hub 18 made of magnetic material fixed to disk 16
The center hole 20 is centered on the main shaft 6, is attracted by the permanent magnet 4, and is fixed to the turntable 2. In this state, the disk 16 integrated with the turntable 2 is rotationally driven by the motor formed by the permanent magnet 4 and the coil 10.

FIG. 5 and FIG. 6 show the case where the magnetic field lines reaching the hub 18 fixed to the disk 16 are the most and the least when the relative positions of the protrusions 14a of the magnetic ring 14 and the magnetizing pattern of the permanent magnets 20. Indicates.

As shown in FIG. 5, the protrusion 1 of the magnetic ring 14 is formed.
When 2a corresponds to the N pole and the S pole of the magnetization pattern of the permanent magnet 20, respectively, the number of magnetic lines of force reaching the hub 18 is the largest, and the force of the permanent magnet 4 attracting the hub 18 is maximum. When the protrusion 14a of the magnetic ring 14 straddles the N and S poles of the magnetization pattern of the permanent magnet 20 as shown in FIG. 6, most of the magnetic force lines are bypassed through the protrusion 14a and reach the hub 18. The lines of magnetic force are the smallest, and the force with which the permanent magnet 4 attracts the hub 18 is minimized.

In this way, the magnetic ring 14 is rotated about the main shaft 6 with respect to the permanent magnet 4, the number of magnetic lines of force reaching the hub 18 is changed, and the force for attracting the hub 18 is optimally adjusted. The magnetic ring 14 is adhesively fixed to the turntable 2 after the suction force of the hub 18 is adjusted. The present invention is not limited to the above-mentioned embodiments, but various embodiments and modifications are possible.

For example, the first surface and the second surface of the turntable are formed by forming the recesses and the notches and the bottom surface and the upper surface thereof, but it is not necessary to form the recesses or the notches. good.

The magnetic ring may be constructed as shown in FIG. The magnetic ring 22 is formed of an annular thin plate. The magnetic ring 22 includes a thick portion 22a and a thin portion 22 which are alternately arranged in the circumferential direction.
b. Thick portion 26a and thin portion 22b
Are the same as the number of poles of the permanent magnets, and are arranged concentrically with the permanent magnets 4 with respect to the turntable 2 like the magnetic ring 14 shown in FIG. In this case, the thick portion 22a corresponds to the protrusion 14a of the magnetic ring 14 in FIG. When the thick portion 22a corresponds to the north and south poles of the permanent magnet 4, the force of attracting the hub is maximum, and when the thick portion 22a straddles the north and south poles, it is minimum.

[0022]

According to the present invention, even if a strong magnet is used to drive the disc to rotate, the force for attracting the hub can be optimized, so that the gap between the hub and the magnet can be small. As a result, the motor can be made thinner. In addition, since it is possible to suppress variations in hub attraction due to variations in coercive force, it is possible to increase attraction near the upper limit of hub attraction determined by disc standards, etc., and prevent disc slippage. I can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a disk fixing device according to the present invention.

FIG. 2 is a cross-sectional view showing a state where the disc is fixed.

FIG. 3 is a top view showing a magnetization direction of a permanent magnet.

FIG. 4 is a top view showing a magnetic ring fixed to a turntable.

FIG. 5 is a side view showing a positional relationship between a magnetic ring and a permanent magnet, showing a case where the number of magnetic field lines extending to the hub of the disk is maximum.

FIG. 6 is a side view showing a positional relationship between a magnetic ring and a permanent magnet, showing a case where the number of magnetic lines of force reaching a hub of a disc is minimum.

FIG. 7 is a top view showing a modified example of the magnetic ring.

FIG. 8 is a cross-sectional view showing a conventional disk fixing device.

9 is a perspective view showing a rotor yoke of the disk fixing device in FIG.

FIG. 10 is a sectional view showing another conventional disk fixing device.

[Explanation of symbols]

2 ... turntable, 4 ... permanent magnet, 14 ... magnetic ring, 16 ... disk, 18 ... hub.

[Procedure amendment]

[Submission date] June 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

The magnetic ring may be constructed as shown in FIG. The magnetic ring 22 is formed of an annular thin plate. The magnetic ring 22 includes a thick portion 22a and a thin portion 22 which are alternately arranged in the circumferential direction.
b. Thick portion 26a and thin portion 22b
Are the same as the number of poles of the permanent magnets, and are arranged concentrically with the permanent magnets 4 with respect to the turntable 2 like the magnetic ring 14 shown in FIG. In this case, the thick portion 22a corresponds to the protrusion 14a of the magnetic ring 14 in FIG. When the thick portion 22a corresponds to the north and south poles of the permanent magnet 4, the force of attracting the hub 18 is maximum, and when it spans the north and south poles, it is minimum.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Claims (1)

[Claims] 1. A disk having a hub made of a magnetic material is placed, and a first surface facing the disk and the first surface.
A turntable having a second surface opposite to the surface of the turntable, a magnet mounted on the second surface of the turntable for attracting the hub and fixing the disc to the turntable, and A disk fixing device comprising: a magnetic member movably attached to the first surface.