JP2614630B2 - Fluid dynamic pressure bearing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluid dynamic pressure bearing that generates a dynamic pressure in a dynamic pressure groove with rotation of a shaft and supports a radial load.

<Prior Art> Conventionally, as this kind of fluid dynamic pressure bearing, there is known a fluid dynamic pressure bearing as shown in FIG.
-131736 publication). The motor spindle comprises a fixed shaft 11 having a herringbone-shaped dynamic pressure groove 12 on the outer periphery.
On the fixed shaft 11, a rotor 14 having a driving magnet 15 on the outer periphery and a polygon mirror 16 on the lower outer periphery is rotatably fitted on the fixed shaft 11, while an inner surface of a housing 17 covering the rotor 14 is The stator 18 is fixed to the driving magnet 15 by being shifted axially upward by Δh. And
The polygonal mirror 16 of the rotating rotor 14 is rotated while the driving magnet 15 is lifted upward by the rotating magnetic field generated by the stator 18.
The mirror 14 reflects the laser light incident from the opening window 17a of the housing 17 and scans the laser light, and the rotor 14 which tends to float upward with an increase in the rotation speed is provided with a permanent magnet 19 provided on the upper end surface of the rotor 14. In opposition to this, the permanent magnet 20 of the same polarity provided on the lower surface of the flange 11a at the upper end of the fixed shaft 11 is urged downward by the repulsive force. That is, in the above-mentioned motor spindle, the fluid dynamic pressure bearing is composed of a fixed shaft 11 having a dynamic pressure groove 12 and a rotor 14 externally fitted thereto.
The radial load acting on the rotor 14 is supported by the dynamic pressure generated by the rotation in the dynamic pressure groove 12, while the thrust load is attracted by the stator 18 and the magnet 15 for driving and the permanent magnet.
The rotor 14 is supported by the repulsion force of 19 and 20, thereby increasing the axial rigidity of the rotor 14 and rotating the rotor 14 stably.

<Problems to be Solved by the Invention> However, the above-mentioned conventional fluid dynamic bearings require a thrust load acting on the rotor 14 upward as the rotation speed increases.
Since the permanent magnets 19 and 20 provided on the upper end face of the rotor and the lower face of the fixed shaft flange are received by the repulsive force between the two magnets, it is often experienced when the end faces of the same polarity of the two magnets are brought close to each other. In addition, if the end faces are slightly displaced from each other, a large repulsive force acts on the two magnets in the transverse direction due to the interaction of the magnetic fields, that is, the rotor 14 which is loosely fitted on the fixed shaft 11.
If the permanent magnet 19 is slightly displaced in the radial direction due to a load variation or the like with respect to the permanent magnet 20 on the fixed shaft side, a large lateral force as indicated by arrows A and A ′ is applied between the two magnets 19 and 20. In addition, the rotating rotor 14 is strongly pressed against the fixed shaft 11 in the radial direction, and the dynamic pressure generated by the dynamic pressure groove 12 does not work, so that it does not serve as a fluid dynamic bearing. There is a disadvantage that the rotor 14 and the fixed shaft 11 are deformed and damaged by the force, and the bearings and, consequently, the motor spindle are broken.

Accordingly, an object of the present invention is to support a thrust load and a radial load in addition to the thrust load without generating a large radial force between the shaft and the sleeve by a novel means regardless of the repulsive force of the two permanent magnets. An object of the present invention is to provide a fluid dynamic pressure bearing which can be used stably without failure for a long period of time.

<Means for Solving the Problems> In order to achieve the above object, a fluid dynamic pressure bearing of the present invention comprises:
A shaft and a sleeve that are fitted to each other are fixed, the other is rotated, and a dynamic pressure is generated by a dynamic pressure groove provided on at least one side of both the fitting surfaces to support a radial load. , One of a permanent magnet and a superconductor having diamagnetism is fixed to the end face, and the other of the permanent magnet and the superconductor is fixed to an end face of a member facing the end face.

<Operation> The fluid dynamic bearing is, for example, as shown in FIG.
A permanent magnet 3 is fixed to an end surface of a rotating shaft 1 having a dynamic pressure groove 2 on its outer periphery, and a diamagnetic superconducting member is provided on an end of the fixed side sleeve 4 externally fitted to the shaft 1 opposite to the end surface. The body 5 is fixed. The superconductor 5 at the end of the sleeve enters a superconducting state at a predetermined temperature and magnetic field, and a superconducting current, such as a Meissner current, flows on its surface to cancel the external magnetic field generated by the permanent magnet 3 at the shaft end. Since the magnetic field due to the superconducting current and the magnetic field of the permanent magnet 3 repel each other, the shaft 1 is urged in a direction away from the superconductor 5 of the sleeve 4 by this repulsive force. The thrust load acting on the bearing is supported.
At this time, no matter how the shaft 1 loosely fitted in the sleeve 4 is displaced in the radial direction due to a load change or the like, the magnetic field of the displaced permanent magnet 3 is generated in the superconductor 5 on the sleeve side due to its diamagnetism. , A large repulsive force does not act in the radial direction as in the case of the conventional bearing by the repulsive force of the two permanent magnets.
The shaft 1 receives the above-mentioned axial biasing force, and smoothly rotates while carrying a thrust load. Further, even if the magnetic force of the permanent magnet 3 changes with time, the axial biasing force does not fluctuate greatly unlike the conventional example for the same reason,
The shaft rotation is stabilized for a long time.

<Example> Hereinafter, the present invention will be described in detail with reference to an illustrated example.

FIG. 1 is an axial sectional view showing a first embodiment of a fluid dynamic pressure bearing according to the present invention, wherein 1 is a shaft which rotates with a herringbone-shaped dynamic pressure groove 2 on its outer periphery, and 3 is this shaft 1. The permanent magnet 4 fixed to the end surface of the fixed magnet 4 is a fixed sleeve which is fitted around the shaft 1 by loose fit. The permanent magnet 5 is fixed to the end of the sleeve 4 so as to face the permanent magnet 3 with a gap. It is a superconducting material having magnetism, and the clearance between the shaft 1 and the sleeve 4 is filled with lubricating oil.

The operation of the fluid dynamic bearing having the above configuration is as follows.

The superconducting material 5 fixed to the end of the sleeve 4 enters a superconducting state at a predetermined temperature and magnetic field, and the shaft 5
A superconducting current such as a Meissner current flows to cancel the external magnetic field by the permanent magnet 3 fixed to the end face of the
5b shows a completely diamagnetic state in which the magnetic flux density becomes zero. Therefore, the magnetic field of the superconducting current and the magnetic field of the permanent magnet 3 repel each other, and the repulsive force urges the shaft 1 in a direction away from the superconducting material 5 of the sleeve 4, that is, in an axially downward direction, thereby acting on the shaft 1. Thrust load is supported. At this time, no matter how the shaft 1 loosely fitted in the sleeve 4 is shifted in the radial direction due to a load change or the like, the sleeve 4
On the other hand, the superconducting material 5 on the side has an opposite magnetic field which counteracts the magnetic field of the displaced permanent magnet 3 based on its complete diamagnetism, so that the conventional superconducting material 5 supports the thrust load due to the repulsive force of the two conventional permanent magnets. As in the case (see FIGS. 19 and 20), a large repulsive force does not act in the radial direction, and therefore the dynamic pressure of the lubricating oil by the rotating dynamic pressure groove 2 always works effectively. It rotates smoothly while carrying the thrust load under the urging force. In other words, since the shaft 1 and the sleeve 4 are not deformed or damaged by a large radial force, they can be stably used for a long period without failure. Further, even if the magnetic force of the permanent magnet 5 changes over time, the axial biasing force does not fluctuate greatly as in the above-described conventional example for the same reason, and the rotation of the shaft 1 is stabilized for a long period of time.

FIG. 2 is an axial sectional view showing a second embodiment of the present invention. In the second embodiment, a high-height permanent magnet 8 is fixed to the upper end of a shaft 1, and a cylindrical superconducting material 9 that covers not only the upper part but also the side part of the permanent magnet 8 is fitted with its fitting projection. This is the same as the first embodiment described with reference to FIG. 1 except that 9c is fitted into the fitting groove 4a and fixed to the upper end of the sleeve 4. Therefore,
The second embodiment operates in the same manner as the first embodiment, and
In addition to the same effect, a repulsive force acts in the radial direction even between the outer periphery of the permanent magnet 8 and the inner periphery of the superconducting material 9, and the shaft 1 is pressed from the outer periphery toward the center by a uniform force, ie, hydrostatic pressure. Therefore, there is an advantage that the radial load can be supported so much and the radial load capacity increases.

In the above embodiment, the shaft 1 is on the rotating side and the sleeve 4 is on the fixed side, and the permanent magnet 3 is fixed on the end face of the shaft 1 and the superconducting material 5 is fixed on the end face of the sleeve 4, respectively. Alternatively, the permanent magnet and the superconducting material may be fixed in reverse.
A cooling device may be appropriately provided around the superconducting material 5. Further, the dynamic pressure groove may be provided not on the shaft 1 side of the embodiment but on the inner peripheral surface of the sleeve, and the dynamic pressure may be generated not by lubricating oil but by air. It goes without saying that the present invention is not limited to the above embodiment.

<Effects of the Invention> As is clear from the above description, the fluid dynamic bearing of the present invention is configured such that one of the shaft and the sleeve that are fitted to each other is fixed, the other is rotated, and the dynamic pressure groove provided on the fitting surface is used. In a device that generates a dynamic pressure to support a radial load, one or the other of a permanent magnet and a superconductor is fixed to the end surface of the shaft and the end surface of a portion facing the end surface, respectively. Even if the shaft and sleeve are displaced from each other in the radial direction due to complete diamagnetism, unlike the conventional two permanent magnets, a repulsive force that supports the thrust load only in the axial direction without exerting a large repulsive force in the radial direction is applied. Can be used for a long period of time with little change over time, with the dynamic pressure generated by the dynamic pressure groove always acting effectively to achieve smooth and stable rotation, without the risk of shaft or sleeve deformation or damage. You.

[Brief description of the drawings]

1 and 2 show the first and second fluid dynamic pressure bearings of the present invention, respectively.
FIG. 3 is an axial sectional view showing an embodiment, and FIG. 3 is a sectional view of a motor spindle having a conventional fluid dynamic bearing. 1 ... Shaft, 2 ... Dynamic pressure groove, 3,8 ... Permanent magnet, 4 ... Sleeve, 5,9 ... Superconducting material.

Claims (1)

(57) [Claims] An axial shaft and a sleeve which are fitted to each other are fixed, and the other is rotated, and a dynamic pressure is generated by a dynamic pressure groove provided on at least one side of both fitting surfaces to support a radial load. In the fluid dynamic pressure bearing, either one of a permanent magnet or a superconductor having diamagnetism is fixed to an end face of the shaft, and either the permanent magnet or the superconductor is fixed to an end face of a member facing the end face. A fluid dynamic pressure bearing characterized in that: