JPH046667A - Rotary equipment and motor or its bearing component - Google Patents

Abstract

PURPOSE:To enhance support stiffness of a rotating body, to attain positioning with high precision, to ensure fluid lubrication and to prevent scattering of magnetic fluid by arranging permanent magnets on a shaft, magnetizing the magnetic fluid on a radial bearing slide face to support the fluid on the shaft securely and forming a thrust bearing with the permanent magnets arranged opposite to each other. CONSTITUTION:Since permanent magnets 4a, 4b are arranged in a hollow of a shaft 1 opposite to a slide face of radial bearing 2a, 2b, magnetic fluid 3a(3b) of the sliding face of the bearings 2a, 2b is magnetized and supported on the surface of the shaft strongly. Thus, sure fluid lubrication is ensured and the fluid is not scattered by rotation of the shaft. Moreover, thrust bearing components 5a, 5b, 15a, 15b utilize the magnetic force of the permanent magnets to balance the magnetic forces of two sets of permanent magnets 5a, 5b, 15a, 15b to support the shaft 1 in noncontact state. Thus, the gap between opposed faces of the magnets is made narrow to increase the magnetic force thereby position the shaft 1 in the axial direction with high precision. Thus, flowout or scattering of the magnetic fluid is not caused and the smooth and highly precise rotation is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotating device and a bearing assembly used in information equipment such as magnetic disk drives and office automation equipment.

[Conventional technology]

In order to increase the recording density of magnetic disk devices, it is necessary to improve the rotation accuracy of the magnetic disk drive system. As shown in FIG. 9, the basic configuration of a magnetic disk device is as follows: a magnetic disk 7 attached to a shaft 1 via a hub 6; a motor 12 that drives the magnetic disk; a ball bearing 28 that rotatably supports the shaft 1; A magnetic head 30 for reading and writing. It consists of a voice coil motor 31 that drives this. 12A is a stator of the motor 12, and 12B is a rotor. The magnetic disk 7 is rotated at a constant speed of 3600 revolutions per minute. Conventionally, in order to maintain rotation accuracy of the magnetic disk 7, both ends of the shaft 1 are supported by ball bearings 28, and preload is applied to the ball bearings 28 to ensure positioning in the radial and thrust directions. Further, if the surface of the magnetic disk becomes contaminated by adhesion of surrounding dust, oil vapor, etc., information cannot be read or written, so the magnetic disk drive is constructed in a sealed container. For this reason, a magnetic fluid seal 29 is incorporated into the end bracket 25 in order to prevent the lubricating grease sealed in the ball bearing 28 from scattering. This sealing mechanism is an essential component of magnetic disk drives. When rotating a magnetic disk drive configured in this way and using ball bearings, even slight damage to the rolling elements or track surfaces will cause irregular vibrations related to ball transfer to occur and grow, resulting in decreased rotational accuracy. becomes unsustainable. Therefore, in order to increase the recording density and solve the above-mentioned problems, a system has been proposed in which fluid bearings are used as bearings in place of ball bearings to maintain smooth rotation and precisely rotate the bearings.

In Japanese Patent Application Laid-Open No. 60-88223, the magnetic fluid is used for both lubrication and sealing, and the swaged bearing structure contains the magnetic fluid to lubricate the radial bearing and the thrust bearing to ensure smooth rotation. In JP-A-58-137617, permanent magnets are used as the bearing material, magnetic fluid is held on the bearing sliding surface by magnetic force, and fluid lubrication is used to ensure smooth rotation. Further, Japanese Patent Application Laid-open No. 147117/1984 discloses various bearing structures in which a fluid bearing is constructed in a magnetic fluid seal. In addition, since oil leakage from the bearings of motors used in copying machines and the like is not allowed, various improvements have been made to the shaft seals.

[Problem to be solved by the invention] In the structure of the fluid bearing using the magnetic fluid described above, the volume of the magnetic fluid expands due to the heat generated by the bearing, motor, etc., the magnetic fluid overflows, and centrifugation occurs due to the rotation of the shaft. There is a risk of magnetic fluid scattering due to force. However, no consideration was given to temperature rise, and there was a problem that the magnetic fluid would scatter during high-speed rotation. In addition, in magnetic disk drives, it is necessary to increase the bearing support rigidity of radial and thrust bearings and maintain reliable positioning and rotational accuracy with high precision, but thrust bearings have not been considered, and conventional fluid It has not been possible to improve the rotational accuracy of the bearing structure of the bearing.

The present invention uses a magnetic fluid bearing that has a simple structure and is free from contamination by magnetic fluid, provides a bearing assembly that can reliably position a rotating body such as a magnetic disk, and achieves cleanliness and high-precision rotation of a single-rotation device. Another object of the present invention is to provide a motor and a magnetic disk device suitable for applying the present invention.

[Means to solve the problem]

In order to achieve the above objective, the radial bearing, which is the first bearing structure, is made up of a shaft and a bearing, with a hollow shaft facing the radial bearing sliding part and a ring-shaped permanent magnet placed in the hollow part. A radial bearing is constructed by sealing a magnetic fluid in the gap between the sliding surfaces of the bearing and firmly holding it on the shaft surface using the magnetic force of a permanent magnet. Additionally, grooves are provided at both ends of the bearing to prevent the magnetic fluid from flowing out or scattering due to temperature rise. Furthermore, there is a risk that the magnetic fluid may flow out and scatter due to the volumetric expansion of the air within the device, but a pressure balance mechanism is provided to prevent the internal pressure from increasing. The thrust bearing, which is the second bearing structure, has a rotating member and a stationary member arranged with ring-shaped permanent magnets facing each other.The thrust bearing is configured by a combination of two sets of facing permanent magnets, and the magnetic disk is The rotation accuracy is increased by positioning the shaft in the axial direction.

[Effect]

The structure of the magnetic fluid bearing according to the present invention has a permanent magnet arranged in the hollow part of the shaft facing the radial bearing sliding surface, so the magnetic fluid on the bearing sliding surface is magnetized and firmly held on the surface of the shaft. . Therefore, reliable fluid lubrication is ensured, and even during rotation, the magnetic fluid is held on the shaft by magnetic force, so it does not scatter. Furthermore, although the magnetic fluid expands in volume due to the heat generated by the sliding surface, the magnetic fluid does not scatter even when the bearing rotates because a circumferential groove is provided at the end of the bearing. Furthermore, due to rotation, the bearing and motor generate heat, and the air inside the device expands in volume, increasing the internal pressure and forcing the magnetic fluid sealed in the radial bearing out of the bearing. Since the pressure is balanced with atmospheric pressure, the magnetic fluid will not flow out even if the temperature inside the device rises. The thrust bearing structure uses the magnetic force of the permanent magnets to balance the magnetic forces of two opposing sets of permanent magnets and supports the rotating body in a non-contact state. Therefore, by setting a narrow gap between the facing surfaces of the magnets and increasing the magnetic force, the rotating body can be positioned with high accuracy in the axial direction.

Therefore, in the rotating device using the bearing structure according to the present invention, there is no outflow or scattering of the magnetic fluid, and smooth and highly accurate rotation can be maintained.

〔Example〕

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

FIG. 1 shows a magnetic disk drive using a bearing structure according to the present invention. The magnetic disk 7 is fixed to the hub 6 with a spacer ring 9 and a clamp 8, and the hub 6 is supported by radial bearings 2a and 2b mounted on a collar 17 so as to be rotatable about the shaft l. Also, hub 6
radial bearings 2a, 2b, holder 10 and support body 14
Ring-shaped permanent magnets 5a, 5b and 15a fixed to
.

It is supported in the axial direction in a non-contact state using the magnetic force of the thrust bearing formed by the bearing 15b. The magnetic disk is driven by the motor stator 12 and motor rotor 11 that generate a rotating magnetic field.

Covers 19 and 20 are attached to the magnetic disk 7 to prevent dust from adhering to it from the outside. The radial bearings 2a and 2b have magnetic fluids 3a and 3b sealed in the gap formed by the shaft 1, and in order to ensure that the magnetic fluid is held in this gap, the shaft 1 is located opposite the radial bearing sliding surface. This portion is hollow, and ring-shaped permanent magnets 4a and 4b are fixed therein. 18a, 1
8b is a member for fixing the magnet, and the inside and outside of the device are communicated through holes 13 and 25 provided in the shaft l.

FIG. 2 is a partial sectional view showing the configuration of a radial bearing and a thrust bearing. A rare earth ferromagnetic permanent magnet 4a fixed in the hollow part of the shaft 1 is magnetized in the axial direction (or may be magnetized radially), and a magnetic fluid 3a is sealed in the gap between it and the radial bearing 2a. constitutes a magnetic circuit as shown, and holds the magnetic fluid 3a on the surface of the shaft 1. In this case, it is better to use a non-magnetic material for the shaft 1 in order to strengthen the magnetization of the magnetic fluid 3a. In addition, in the magnetic disk drive shown in FIG. 1, the shaft 1 is fixed and the radial bearing 2a rotates, so that the magnetic fluid adhering to the end of the radial bearing 2a is scattered by centrifugal force, so the radial bearing 2a Grooves 21 are provided at both ends to prevent the magnetic fluid from scattering. When the rotation stops, the magnetic fluid attached to the groove 21 due to rotation is attracted by the magnet and returns to its original state.

The thrust bearing is composed of a ring-shaped permanent magnet 5a fixed to the end of the radial bearing 2a and a permanent magnet 5b fixed to the stationary side holder 10 opposite to the ring-shaped permanent magnet 5a. The magnets are placed opposite each other. Therefore, the rotating body is supported without contact with the stationary body by this magnetic repulsive force, but since the magnetic disk 7 cannot be reliably positioned in this state, a similar Permanent magnets 15a and 15b are arranged facing each other so that a magnetic attraction force is generated in this combination, and the magnetic disk 7 is supported in a non-contact manner by balancing the magnetic repulsion force and the magnetic attraction force. There is.

In this case, if the magnetic attractive force is larger than the repulsive force, non-contact support will not be possible, so the maximum value of the magnetic repulsive force is set to be larger than the maximum value of the magnetic attractive force. In this way, the rotating body can be positioned in the axial direction without contact using the magnetic repulsion and attraction forces, but this magnetic force becomes stronger as the gap between the facing surfaces of the magnets is narrowed, so it is possible to increase the rigidity in the axial direction. , the magnetic disk 7 can be reliably positioned. When a magnetic disk device configured in this manner is rotated, the air between the radial bearings expands in volume due to the heat generated by the radial bearings and the motor, but the holes 13 and 25 in the shaft 1 allow communication between the inside and outside of the device. The pressure is always balanced with the atmospheric pressure, and the magnetic fluids 3a and 3b are not pushed out in the axial direction and do not flow out even if the temperature inside the device increases.

Fig. 3 shows another embodiment of the radial bearing. The basic structure of the radial bearing is the same as Fig. 2, but the difference is that a groove 22 for generating dynamic pressure is provided on the surface of the shaft 1. In addition to increasing the rigidity of the radial bearing, the grooves 22 more reliably hold the magnetic fluid 3a on the bearing sliding surface.

That is, the magnetic fluid at the end of the radial bearing 2a is scraped off at the end of the groove 22 by rotation and carried into the sliding surface, so that the magnetic fluid does not scatter from the bearing end, and furthermore, dynamic pressure is not generated. Since the grooves 22 can increase the rigidity of the lubricating film on the sliding surface, reliable fluid lubrication is ensured.

FIG. 4 shows another embodiment of the radial bearing. The basic structure of the radial bearing is the same as the embodiment described above, but the difference is that the sliding part of the radial bearing 2a has a porous sliding part. The point is that a moving member 24 is provided and impregnated with a warm magnetic fluid to replenish the magnetic fluid. In addition, in this configuration, an oil cover 23 is attached to the porous sliding member 24, and grooves 2 for preventing magnetic fluid scattering are provided at both ends of the bearing as in the above embodiment.
1 is provided. In this embodiment, the impregnated magnetic fluid expands in volume due to the heat generation of the sliding surface, and has the effect of supplying the magnetic fluid 3a into the gap between the sliding surfaces.

That is, if the sliding member 24 is provided with such a magnetic fluid replenishment function, even if the magnetic fluid 3a is insufficient for some reason, the impregnated magnetic fluid will seep into the sliding part when the temperature rises due to rotation. This has the advantage of not causing poor lubrication.

When the rotation stops and the temperature drops, the magnetic fluid is absorbed into the sliding member 24 again, so that the magnetic fluid does not become consumed.

FIG. 5 is a diagram showing another embodiment according to the present invention. In this embodiment, a hub 6 is fixed to a shaft 1, and the shaft 1 is rotatably supported by radial bearings 2a and 2b arranged on a stationary body. The configuration of the magnetic disk device is the same as that shown in FIG.

Radial bearings 2a and 2b are fixed to end brackets 25 and 26 that are stationary bodies, a motor rotor 11 is attached to the shaft 1, and the shaft 1 is driven by a motor stator 12. The radial and thrust bearing structure according to the present invention can also be applied to a shaft-rotating magnetic disk device as shown in this embodiment, and can provide the same effect as the above-mentioned fixed-shaft magnetic disk device. can.

FIG. 6 shows another embodiment according to the present invention. In this configuration, a thrust bearing is constituted by a permanent magnet 4b fixed to the end of the shaft 1 and a permanent magnet 27 on the oil cover 23b, and the radial bearing part This figure shows an embodiment in which the permanent magnet of 2 is also used as a permanent magnet of a thrust bearing. Therefore, there is an advantage that the structure is simpler and the number of parts is smaller than the above-mentioned embodiments.

FIG. 7 shows another embodiment of the present invention, which differs from the above embodiment in that the thrust bearing supports the rotating body in the axial direction by magnetic repulsion. In this embodiment, ring-shaped permanent magnets 5a, 5b and 15a, 15b are arranged opposite to each other on the end brackets 14 and 25 and the hub 6,
Both are combined so that magnetic repulsion is generated on the opposing surfaces of the permanent magnets. Even if the thrust bearing is configured using magnetic repulsion as in this embodiment, the support rigidity in the axial direction can be increased as in the above embodiment, and thus the magnetic disk can be positioned with high precision.

Although the above-described embodiment is an example of a configuration for a magnetic disk device, FIG. 8 shows an embodiment in which a radial bearing structure according to the present invention is applied to a motor used for a drum, a fan, etc. of a copying machine. A motor rotor 11 is attached to the shaft 1, and both ends of the shaft 1 are rotatably supported by radial bearings 2a and 2b arranged in a frame 32, and the motor is driven by the rotating magnetic field of the motor stator 12. . The radial bearing structure has the same structure as shown in FIG. 2, and dust-proof covers 33 and 34 are attached to the ends of the radial bearing, but it goes without saying that the same effects as in the previous embodiment can be achieved. In addition, although this type of motor used an oil-impregnated bearing and was equipped with a sealing mechanism to prevent oil leakage, there were cases where a sufficient seal could not be achieved.However, by applying the radial bearing structure of the present invention, Even without providing a mechanism, the bearing part has a sealing function, so a reliable seal can be achieved. Furthermore, by using a porous material for the radial bearings, the thrust bearings 35a, 35b can be lubricated by the magnetic fluid impregnated in the radial bearings 2a, 2b without the need to apply lubricating fluid, which eliminates the need for oil lubrication, which is conventionally used. It has advantages such as a simpler structure compared to the bearing structure made by the conventional method.

〔Effect of the invention〕

According to the present invention, by arranging a permanent magnet on the shaft as described above, the magnetic fluid on the radial bearing sliding surface can be magnetized and firmly held.

Ensures fluid lubrication and prevents magnetic fluid from scattering.

In addition, by using a porous material as a sliding material for the bearing, it is possible to replenish the magnetic fluid, ensuring reliable lubrication.Furthermore, by providing grooves for generating dynamic pressure on the shaft surface, the magnetic fluid can be prevented from scattering, and the bearing can be Rigidity can be increased. Furthermore, the configuration of the thrust bearing with two pairs of permanent magnets arranged opposite to each other increases the support rigidity of the rotating body in the axial direction, and enables highly accurate positioning. Furthermore, even if the temperature inside the device increases, the pressure inside the device is balanced at atmospheric pressure, so the magnetic fluid in the radial bearing does not flow out, making it possible to provide a highly reliable bearing structure. Therefore, by using the bearing structure according to the present invention, there is no fear of contamination due to scattering of magnetic fluid, which was a problem with the prior art, and high-precision rotation can be maintained, so that high-density recording in magnetic disk devices can be achieved. . In addition, when the radial bearing and thrust bearing structure of the present invention is used in a polygon mirror driving motor of a laser beam printer or a cylinder motor of a VTR, etc., which require high rotational accuracy and cleanliness, similar to magnetic disk drives, the same effect can be obtained. This is effective and improves the performance of the main engine.

[Brief explanation of the drawing]

1, 5, 6, and 7 are longitudinal cross-sectional views of a magnetic disk drive according to the present invention, FIG. 8 is a longitudinal cross-sectional view of a motor according to the present invention, and FIG. 9 is a longitudinal cross-sectional view of a conventional magnetic disk drive. The explanatory drawings, FIG. 2, FIG. 3, and FIG. 4 are explanatory drawings of the bearing structure according to the present invention. 1... Shaft, 2a, 2b... Radial bearing, 3a, 3
b...Magnetic fluid, 4a, 4b, 5a, 5b, 15a. 15b... Permanent magnet, 6... Hub, 7... Magnetic disk, 11... Motor rotor, 12... Motor stator, 13°25... Hole.

Claims (1)

[Claims] 1. A rotating body including a magnetic disk is rotatably supported by two sets of radial bearings using magnetic fluid as a lubricant and two sets of magnetic thrust bearings using permanent magnets. ,
A shaft supporting the rotating body is provided at the axial center of the rotating body, the radial bearing and the thrust bearing are arranged at both ends of the rotating body, and the shaft at a position facing the inner circumferential surface of the radial bearing is hollow. A permanent magnet is fixed in this hollow part, and a radial bearing structure is formed by sealing a magnetic fluid in the gap between the radial bearing and the shaft, a ring-shaped permanent magnet, the rotating body, and the rotating body. The magnetic disk can be freely rotated by a magnetic thrust bearing structure that is disposed opposite to a stationary body supported via the bearing structure and positions the rotating body including the magnetic disk in the axial direction by magnetic attraction or repulsion. A magnetic disk device characterized by supporting. 2. A permanent magnet is placed in the hollow part of the shaft that passes through the radial bearing, and the outer circumferential surface of this permanent magnet and the inner circumferential surface of the radial bearing face each other, and the radial bearing inner circumferential surface and the shaft outer circumferential surface are composed of A radial bearing structure with magnetic fluid sealed in the gap. 3. The radial bearing structure according to claim 2, wherein grooves are provided at both ends of the inner peripheral surface of the bearing. 4. The radial bearing structure according to any one of claims 1, 2, and 3, characterized in that the bearing sliding portion is provided with a polymorphous member. 5. A rotating magnetic disk device according to claim 1, comprising a magnetic thrust bearing and a magnetic disk, in which a permanent magnet is placed in a hollow part of the shaft and a permanent magnet is placed on a stationary body to face the permanent magnet in the axial direction. A magnetic disk device characterized in that a magnetic disk is positioned in the axial direction by a magnetic thrust consisting of a body and a stationary body with ring-shaped permanent magnets arranged facing each other. 6. In the magnetic disk drive according to claim 1 or 5, the magnetic thrust bearing structure is configured by magnetic attraction force and magnetic repulsion force to position the magnetic disk in the axial direction, and the magnetic disk drive has magnetic repulsion force. A magnetic disk device characterized in that the magnetic force is greater than the magnetic attraction force. 7. A magnetic disk device according to claim 1 or 5, characterized in that the shaft is provided with a hole that communicates the space between the radial bearings with the outside of the device. 8. The radial bearing structure according to claim 2, wherein the shaft sliding surface is provided with a groove for generating dynamic pressure. 9. The rotor is rotatably supported by two sets of radial bearings using magnetic fluid as a lubricant and two sets of magnetic thrust bearings using permanent magnets, and a rotating body is centered around the axis of the rotor. The radial bearing and the thrust bearing are arranged at both ends of the rotor, and the shaft at a position facing the inner peripheral surface of the radial bearing is hollow, and a permanent A radial bearing structure in which a magnet is fixed and a magnetic fluid is sealed in a gap formed between a radial bearing and a shaft, and a ring-shaped permanent magnet are supported by the rotating body and the rotating body via the bearing structure. A motor in which a rotor is rotatably supported by a magnetic thrust bearing structure that is disposed facing the body and positions the rotor in the axial direction by magnetic attraction or repulsion.