JPH08186953A - Spindle equipment - Google Patents

Abstract

PURPOSE: To prevent dusting and perform high-speed, high-precision rotation. CONSTITUTION: A rotating shaft 24 equipped with a hard disk 22 at the top end is supported in a noncontact state in the axial direction by magnetic levitation of a bearing disk 26. Also, the rotating shaft 24 is supported by a magnetic force in radial direction by the magnetic bearing functions of a magnetic bearing composite motor 34 and is driven to rotation by the motor function of the magnetic bearing composite motor 34.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle device, and more particularly to a small spindle device used in a printing device such as a laser printer or a hard disk drive.

2. Description of the Related Art In a hard disk drive of a computer, it is necessary to rotate the disk with high precision in order to increase the recording density, and in a digital copying machine, a laser printer, etc., high-speed printing with high quality is required. It is necessary to rotate the mirror at high speed and with high precision. Therefore, as a spindle device for rotating and driving these hard disks and polygon mirrors, one that enables extremely high-speed and highly accurate rotation is used, and as the bearing thereof, a rolling bearing or an air bearing is generally used. Target. FIG. 4 shows an example of a bearing portion in a spindle device for driving a hard disk. As shown in this figure, the rotating shaft 10 is rotatably supported by a ball bearing 12 with respect to a bracket 14.
A hub 16 is attached to the upper end of the rotary shaft 10, and the hard disk is attached to the outer peripheral surface of the hub 16 (not shown). This spindle device is driven,
When the rotating shaft 10 rotates at high speed, dust, dust, etc. are generated from the ball bearing 12. Since this dust may adversely affect the hard disk, magnetic head, etc., in the conventional spindle device, a shaft seal using magnetic fluid is used to prevent the generated dust, etc. from entering the hard disk or magnetic head side. 18 (magnetic fluid seal) was provided.

However, even if the magnetic fluid seal 18 is used, dust and the like cannot be completely prevented because dust is also generated from the seal. Further, in the related art, since the motor portion (not shown) that applies the rotational force to the rotating shaft 10 and the bearing portion are separate, the rotating shaft 10 is relatively long and vibration is likely to occur. Therefore, it has been difficult to achieve high-speed rotation and high-precision rotation. Further, in recent years, hard disk drives, laser printers and the like have been downsized, so downsizing of the spindle device has become an important issue. Therefore, an object of the present invention is to provide a spindle device capable of preventing dust generation and rotating at high speed and with high accuracy.

According to a first aspect of the present invention, there is provided a rotary shaft having a hard disk attached thereto, a thrust magnetic bearing for axially supporting the rotary shaft by a magnetic force, and a radial direction for the rotary shaft by a magnetic force. The above-described object is achieved by providing a spindle device with a magnetic bearing composite motor having a magnetic bearing function of supporting the above and a motor function of applying a rotational force to the rotating shaft. According to a second aspect of the present invention, a rotary shaft to which a polygon mirror is attached, a thrust magnetic bearing that axially supports the rotary shaft by magnetic force, a magnetic bearing function that radially supports the rotary shaft by magnetic force, and The above object is achieved by providing a spindle device with a magnetic bearing composite motor having a motor function of applying a rotational force to a rotating shaft.

In the spindle device according to the first and second aspects, the thrust magnetic bearing supports the rotating shaft in the axial direction by the magnetic force. The magnetic bearing composite motor supports the rotating shaft in the radial direction by magnetic force by the magnetic bearing function, and also applies the rotating force to the rotating shaft by the motor function. As a result, the rotating shaft rotates in a magnetically levitated state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the spindle device of the present invention will be described in detail below with reference to FIGS. FIG.
Shows the spindle device according to the first embodiment. As shown in this figure, the spindle device 20 of this embodiment has a hard disk 2 at one end (upper end in FIG. 1).
2 is equipped with a rotary shaft 24 attached thereto. The rotating shaft 24 is provided with a bearing disk 26 made of a ferromagnetic material, and two axial electromagnets 28a and 28b are arranged so as to sandwich the bearing disk 26 in the upper and lower sides in FIG. ing. Each of the axial electromagnets 28a and 28b is a coil wound in a ring shape, and is energized to apply a magnetic attraction force to the bearing disk 26 in the axial direction. Although not shown, the spindle device 20
Has an axial sensor that detects the displacement of the rotary shaft 24 in the axial direction, and the respective exciting currents of the axial electromagnets 28a and 28b correspond to the detection values of the axial sensor (not shown).
Feedback control is performed by the magnetic bearing control circuit A. That is, in this embodiment, the magnetic bearing control circuit A, the axial electromagnets 28a, 28b, etc. constitute a thrust magnetic bearing for axially supporting the rotary shaft 24. In addition, the axial electromagnets 28a and 28b
Is fixed to the housing 32 via the fixing member 30. A magnetic bearing composite motor 34 is arranged below the axial electromagnets 28a and 28b in FIG. 1 so as to surround the rotary shaft 24. This magnetic bearing composite motor 3
A motor 4 has both a magnetic bearing function of supporting the rotating shaft 24 in the radial direction by magnetic force and a motor function of applying a rotating force to the rotating shaft 24 by generating a rotating magnetic field. In the magnetic bearing composite motor 34 in this embodiment,
A bearing winding for generating a magnetic force for supporting the rotating shaft 24 and a motor winding for generating a rotating magnetic field are wound around the same iron core. Each winding is connected to the magnetic bearing function control circuit B1 and the motor function control circuit B2 of the magnetic bearing composite motor control unit B, respectively. The magnetic bearing function control circuit B1 controls the position of the rotary shaft 24 in the radial direction by controlling the current of the bearing winding. That is,
Although not shown in FIG. 1, the spindle device 20 includes a radial sensor that detects a radial displacement of the rotary shaft 24, and the magnetic bearing function control circuit B1 includes a detection value of a radial sensor (not shown). Is fed back to control the current of the bearing winding so that the rotary shaft 24 is held at a predetermined floating position. On the other hand, the motor function control circuit B2 controls the current of the motor winding to rotate the rotary shaft 24 at a predetermined rotation speed. Next, the operation of the embodiment thus configured will be described. First, when the axial electromagnets 28a and 28b are energized, the rotary shaft 24 is magnetically levitated in the axial direction, and the bearing windings of the magnetic bearing composite motor 34 are energized to be magnetically levitated in the radial direction. It At this time, the axial electromagnet 2
The magnetic bearing control circuit A performs feedback control of the exciting currents 8a and 28b in accordance with the detection value of the axial direction sensor (not shown), thereby controlling the axial position of the rotary shaft 24. Further, the current in the bearing winding of the magnetic bearing composite motor 34 is feedback-controlled by the magnetic bearing function control circuit B1 according to the detection value of a radial sensor (not shown), so that the radial position of the rotary shaft 24 is increased. Control is performed. Then, the motor function control circuit B2 energizes the motor winding of the magnetic bearing composite motor 34, and the rotating shaft 2
By generating a rotating magnetic field with respect to No. 4, the rotating shaft 24 rotates. That is, the hard disk 22 rotates. As described above, in the present embodiment, the rotating shaft 24 is supported in a non-contact manner by the magnetic bearing function of the axial electromagnets 28a and 28b and the magnetic bearing combined motor 34, so that no dust or dust is generated. . Therefore, it is possible to prevent the hard disk 22 from being adversely affected by dust or the like. Also,
Since the magnetic bearing composite motor 34 has not only a motor function but also a magnetic bearing function for supporting the rotating shaft 24 by magnetic force, the conventional spindle device in which the bearings are provided separately from the motor in the axial direction is provided. In comparison, the axial length of the rotary shaft 24 can be shortened. Therefore, the entire device can be downsized, and since the rotating shaft 24 is less likely to vibrate due to the reduced axial length, it is possible to perform higher-speed rotation and highly accurate rotation without shake. That is, in the hard disk drive, since the track pitch can be narrowed, higher density recording can be performed. Furthermore, compared to the conventional spindle device shown in FIG.
Since there is no magnetic fluid seal 18, the structure can be simplified. Further, in the conventional spindle device (see FIG. 4), the rotation speed is limited due to the magnetic fluid seal 18,
Although the limit was about 20,000 revolutions per minute, the spindle device 20 of this embodiment does not require a sealing material,
Higher speed rotation is possible. Next, a second embodiment will be described. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be appropriately omitted. FIG. 2 shows a spindle device according to the second embodiment. In the spindle device 40 according to the present embodiment, the axial electromagnets 28a and 28b and the magnetic bearing combined motor 34 are fixed to a cylindrical case 42, and the rotating shaft 24 has a bottom surface at the upper end in FIG. A shaped hub 44 is attached. In this embodiment, the case 42 and the axial electromagnets 28a, 28b,
The magnetic bearing composite motor 34 and the like are housed in the hub 44, and the hard disk 46 is attached to the outer peripheral surface of the hub 44. Other configurations, operations and effects are
This is the same as the embodiment. Next, a third embodiment will be described. The same components as those in the first and second embodiments are designated by the same reference numerals, and detailed description thereof will be appropriately omitted. FIG. 3 shows a spindle device according to a third embodiment. Spindle device 5 of this embodiment
In No. 0, the thrust bearing is not a control type magnetic bearing using an electromagnet but a magnetic bearing using a permanent magnet. That is, the rotating shaft 52 is provided with a bearing disk 56 to which a ring-shaped permanent magnet 54 is attached, and faces the ring-shaped fixed permanent magnet 58 attached to the upper part of the housing 62 in FIG. There is. The two permanent magnets 54, 58 have the same poles on the surfaces facing each other, and a magnetic repulsive force acts between the permanent magnets 54, 58 in the axial direction. This magnetic repulsive force is due to the gap between the permanent magnets 54 and 58 being equal to or less than a predetermined distance,
The gravity is larger than the gravity of the entire rotating body including the rotating shaft 52, the hard disk 22 attached to the upper end of the rotating shaft 52, the bearing disk 56, and the like. Therefore, as shown in FIG.
It is magnetically levitated at a position where the magnetic repulsive force between 8 and gravity balance each other. Further, the rotary shaft 52 has a small diameter portion 52a formed to have a small diameter, and a cylindrical radial bearing permanent magnet 60 is fitted into the small diameter portion 52a. This radial bearing permanent magnet 60 has an inner peripheral surface of the fixed permanent magnet 58 fixed to the housing 62 side when the rotary shaft 52 is inserted into the housing 62 and is magnetically levitated as shown in FIG. Is facing. The outer peripheral portion of the radial bearing permanent magnet 60 and the inner peripheral portion of the fixed permanent magnet 58, which are opposed to each other, have the same pole, and a magnetic repulsive force acts between them in the radial direction. There is. Therefore, the rotating shaft 52 is supported by the radial magnetic repulsion force substantially on the central axis of the fixed permanent magnet 58 in a non-contact manner. That is, the permanent magnets 58 and 60 form a radial magnetic bearing. Other configurations and operations are similar to those of the first embodiment. In the present embodiment, the rotary shaft 52 is radially supported by the radial magnetic bearing composed of the permanent magnets 58, 60 and the radial magnetic bearing having the magnetic bearing function of the magnetic bearing composite motor 34, and the permanent magnets 54, 58. Is supported in the axial direction by a thrust magnetic bearing composed of. Then, the motor function of the magnetic bearing composite motor 34 causes a rotating magnetic field to be generated to rotate the motor. As described above, in the spindle device 50 of this embodiment, the rotary shaft 52 has the permanent magnets 58, 6
Since the radial magnetic bearing configured by 0 and the radial magnetic bearing having the magnetic bearing function of the magnetic bearing composite motor 34 are supported at two upper and lower positions, the bearing rigidity is higher than in the first and second embodiments. . Therefore, since the rotating shaft 52 is less likely to vibrate, more accurate and high speed rotation can be performed. In each of the above embodiments, the hard disks 22 and 46 are attached to the rotary shafts 24 and 52, but instead of these, a polygon mirror is attached and the spindle devices 20, 40 and 50 are used as recording devices such as laser printers. May be used for. In this case, the spindle devices 20, 40,
As described above, the 50 can rotate at high speed and with high precision, so that high quality printing can be performed at high speed. Further, in each of the above embodiments, in the magnetic bearing composite motor 34, the bearing winding and the motor winding constitute independent circuits, but one winding has a current for the magnetic bearing. It is also possible to use a magnetic bearing composite motor of the type which simultaneously supplies the electric current for the motor and the electric current for the motor.

According to the spindle device of the present invention, it is possible to prevent dust generation and perform high-speed and high-precision rotation.

[Brief description of drawings]

FIG. 1 is a sectional view showing a spindle device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a spindle device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a spindle device according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional spindle device.

[Explanation of symbols]

 20, 40, 50 Spindle device 22, 46 Hard disk 24, 52 Rotating shaft 26, 56 Bearing disk 28a, 28b Axial electromagnet 30 Fixing member 32, 62 Housing 34 Magnetic bearing composite motor 42 Case 44 Hub 54 Permanent magnet 58 Fixed side Permanent magnet 60 Permanent magnet for radial bearing A Magnetic bearing control circuit B Magnetic bearing composite motor control unit B1 Magnetic bearing function control circuit B2 Motor function control circuit

Claims (2)

[Claims] 1. A rotary shaft to which a hard disk is attached, a thrust magnetic bearing that axially supports the rotary shaft by magnetic force, a magnetic bearing function that radially supports the rotary shaft by magnetic force, and a rotary shaft on the rotary shaft. A magnetic bearing composite motor having a motor function of giving a rotational force, and a spindle device. 2. A rotary shaft to which a polygon mirror is attached, a thrust magnetic bearing that axially supports the rotary shaft by magnetic force, a magnetic bearing function that radially supports the rotary shaft by magnetic force, and the rotary shaft. And a magnetic bearing composite motor having a motor function of applying a rotational force to the spindle device.