JPH03213715A - Thrust bearing - Google Patents

Abstract

PURPOSE:To increase rigidity against thrust load by providing at least one of a thrust receiving face and a thrust bearing face with a groove for inducing a fluid in a thrust bearing space to act as negative pressure at the time of rotation. CONSTITUTION:An axially magnetized magnet 11 is buried into the thrust bearing face 8 of a thrust bearing S, as well as an axially magnetized magnet 12 is buried into a thrust receiving face 9. Both magnets 11, 12 are disposed in such a way that their like poles are mutually opposed in the axial direction. At the time of rated rotation, a fluid in a thrust bearing space (s) flows out of the thrust bearing space (s) by the pumping action of a groove 13 so as to become negative pressure, and the thrust receiving face 9 and the thrust bearing face 8 approach mutually against the magnetic resiliency of the magnets 11, 12. Rigidity against thrust load can be thus increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thrust bearing used in office equipment, information equipment, etc.

[Conventional technology]

As a conventional thrust bearing, for example, Japanese Patent Application Laid-Open No. 63-19
There is one presented in Publication No. 5414.

This conventional thrust bearing is a magnetic repulsion type thrust bearing in which the same magnetic pole faces of magnets magnetized in the axial direction are opposed to each other with a predetermined gap between them, and one of the magnetic pole faces of the opposing magnetic pole faces is By forming the surface to be larger than the other magnetic pole surface, the outer circumferential end of one of the magnetic pole surfaces is axially opposed to the other, and the outer circumferential edge of the other magnetic pole surface is configured not to oppose the other in the axial direction. It is what was done.

By arranging both magnetic pole faces to face each other in this way, even if the magnetic centers shift, there is almost no force to move the magnets in the lateral direction, and the load and starting torque applied to the radial bearing can be reduced. There are advantages.

[Problem to be solved by the invention]

However, in the conventional magnetic repulsion type thrust bearings mentioned above, the thrust load was supported only by the repulsive force of the magnets, so there was a problem that the rigidity against the thrust load was low and it was easy to vibrate due to the excitation force in the axial direction. Ta.

SUMMARY OF THE INVENTION The present invention has been made by focusing on the above-mentioned conventional problems, and its purpose is to provide a thrust bearing that has high rigidity against thrust loads even if it is a magnetic repulsion type, thereby overcoming the above-mentioned conventional problems. It is about solving problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a thrust bearing in which a thrust bearing surface provided on a shaft member faces a thrust bearing surface provided on a bearing member via a thrust bearing clearance,
One magnet provided on the thrust bearing surface and the other magnet provided on the thrust bearing surface have the same polarity facing each other in the axial direction,
At least one of the thrust receiving surface and the thrust bearing surface is provided with a groove that causes the fluid in the thrust bearing clearance to exert negative pressure when either the shaft member or the bearing member rotates. do.

The groove may be a herringbone groove or a spiral groove.

[Function] The thrust bearing of the present invention is non-contact during stopping, starting, and stopping due to the magnetic repulsion of the magnets whose like poles face each other in the axial direction.

On the other hand, at rated rotation, the fluid in the thrust bearing clearance flows out from the thrust bearing clearance due to the pumping action of the groove, creating negative pressure, and the thrust bearing surface and the thrust bearing surface approach against the magnetic repulsion of the magnet. . This increases thrust bearing rigidity.

〔Example〕

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

FIG. 1 shows a thrust bearing S of the present invention incorporated into a scanner unit for a laser beam printer.

A fixed shaft 1 as a shaft member has one end fixed to a base 2 also as a shaft member by press fitting or the like, and the fixed shaft 1
A cylindrical radial receiving surface 3 is provided on the outer circumferential surface of.

The other end of the fixed shaft 1 is a free end. A sleeve 5, which is a bearing member, is rotatably fitted onto the fixed shaft 1. The inner peripheral surface of the sleeve 5 is a cylindrical radial bearing surface 7 in which a herringbone-shaped groove 6 for generating dynamic pressure is formed. The opposing components constitute a dynamic pressure type radial bearing.

The lower end surface of the sleeve 5 is a flat thrust bearing surface 8.
The thrust bearing surface 8 and the thrust bearing clearance S
A planar thrust bearing surface 9 is provided on the surface of the base 2 that faces the base 2 with the diaphragm interposed therebetween, thereby configuring a dynamic pressure type thrust bearing S. A donut plate-shaped magnet 11 magnetized in the axial direction is embedded in the thrust bearing surface 8 of the thrust bearing S so as to be flush with the magnet 11 . On the other hand, a donut plate-shaped magnet 12, which is similarly magnetized in the axial direction, is mounted flush with the thrust receiving surface 9 around the fixed axis l. Both of these magnets 11 and 12 are arranged so that the same poles face each other in the axial direction.

Further, at least one of the thrust bearing surface 8 and the thrust bearing surface 9, in this embodiment, the thrust bearing surface 8 is provided with a spiral-shaped groove 13 for generating dynamic pressure over the entire surface including the surface of the magnet 11. It is provided. This groove 13 for generating dynamic pressure is formed in the thrust bearing clearance S when the sleeve 5 rotates.
The function is to pump the fluid inside radially outward to create negative pressure.

A stepped portion 15 is provided on the outer diameter surface of the sleeve 5, and a polygon mirror 16 fitted into the sleeve 5 is supported by this stepped portion 15 and fixed by a member 17.

Further, a rotor magnet 20 surrounding the sleeve 5 is attached to another step 18 formed on the lower side of the step 15 of the sleeve 5 via a support member 19, and a stator 20 that surrounds the sleeve 5 is attached to the stator which is circumferentially opposed to the rotor magnet 20 in the radial direction. A coil 21 is disposed on the upper surface of the base 2, and the rotor magnet 20 and the stator coil 21 constitute a drive motor M having opposed peripheral surfaces.

Next, the action will be explained.

When the scanner unit is stopped, the magnetic repulsion of both magnets 11 and 12, whose poles are axially opposed to each other, acts, and the thrust bearing surface 8 and the thrust bearing surface 9 are out of contact, and the thrust A thrust bearing clearance S corresponding to the load is maintained.

When activated by the operation of the drive motor M, the polygon mirror 16 begins to rotate together with the sleeve 5 in a predetermined rotational direction. In this case, since the thrust bearing surface 8 and the thrust bearing surface 9 are not in contact with each other, there is no starting resistance and no wear occurs.

When the sleeve 5 rotates, the fluid in the thrust bearing S flows outward in the radial direction due to the pumping action of the groove 13 for generating dynamic pressure in the thrust bearing S. Therefore, the pressure inside the bearing clearance S of the thrust bearing S becomes negative. The magnitude of this negative pressure is greatest at the center side in the radial direction, and decreases linearly toward the outside in the radial direction. Due to the suction effect of this negative pressure, the thrust bearing surface 8 is drawn toward the thrust bearing surface 9 and approaches it. Since the magnetic repulsion of both magnets 11 and 12 is inversely proportional to the square of the distance according to Coulomb's law, the thrust bearing stiffness increases as they approach each other. Thus, the thrust bearing S maintains a balance in a non-contact state where the negative pressure corresponding to the rotational speed of the sleeve 5 and the magnetic repulsion force corresponding to the dimension of the thrust bearing clearance S are balanced.

Furthermore, when the sleeve 5 rotates, the pressure of the fluid in the radial bearing clearance r increases due to the pumping action of the groove 6 for generating dynamic pressure in the radial bearing, and the radial bearing surface 7 rotates without contacting the radial bearing surface 3. .

In this way, the sleeve 5 has high rigidity in the thrust direction and rotates around the fixed axis I in a non-contact manner while maintaining a constant flying height without vibrating due to the excitation force in the axial direction.

When stopped, when the power to the drive motor M is cut off, the rotational speed of the sleeve 50, which was rotating steadily, gradually decreases, the pumping action of the groove 13 for generating dynamic pressure of the thrust bearing S weakens, and the thrust bearing clearance S decreases. The fluid gradually returns to positive pressure, and the sleeve 5 is supported by the magnetic repulsion of the magnets 11 and 12, and the thrust bearing surface 8 and the thrust bearing surface 9 are stopped without contacting each other. Therefore, bearing wear does not occur even when the machine is stopped, and a semi-permanent bearing life is guaranteed.

In the above embodiment, the groove 13 for generating dynamic pressure of the thrust bearing S is provided on the entire surface of the thrust bearing surface 8, but the groove 13 for generating dynamic pressure in the thrust bearing S is provided only in a portion of the thrust bearing surface 8 excluding the magnet 11. A groove may be provided, or a groove may be provided only in the portion of the thrust bearing surface 8 where the magnet 11 is located.

Furthermore, grooves may be provided on the entire surface of the thrust bearing surface 9 instead of the thrust bearing surface 8, or grooves may be provided only on the portions of the thrust bearing surface 9 excluding the magnets 12. The groove may be provided only in the magnet 12 portion.

Further, grooves may be provided in both the thrust bearing surface 8 and the thrust bearing surface 9.

Further, the pattern of the grooves 13 for generating dynamic pressure is not limited to a spiral groove, and may be a herringbone groove. That is, for example, by providing a herringbone-shaped groove in the thrust bearing surface 8 of the thrust bearing S, when the sleeve 5 rotates, the fluid in the thrust bearing clearance S flows out radially outward and radially inward. It's okay.

FIG. 2 shows another embodiment of the present invention, in which a cylindrical hole 30 provided in a bearing member 2 is provided with a cylindrical radial bearing surface 7 and a planar thrust bearing surface 8. The shaft body 1 that fits into the cylindrical hole 30 has a radial bearing surface 3 that faces the radial bearing surface 7 with a radial bearing clearance r in between, and a thrust bearing surface that faces the thrust bearing surface 8 with a thrust bearing clearance S therebetween. 9 is provided. Radial bearing surface 3
Herringbone-shaped grooves 6 are provided at two locations separated in the axial direction, and one magnet 12 provided on the thrust bearing surface 9 and the other magnet 11 provided on the thrust bearing surface 8 have the same polarity. are axially opposed. Thrust receiving surface 9
is provided with a spiral dynamic pressure generation groove 13 that causes the fluid in the thrust bearing clearance S to flow outward in the radial direction when the shaft member 1 rotates, and causes the thrust bearing clearance S to act as a negative pressure. . Further, a polygon mirror 16 and a rotor magnet 20 are attached to the upper part of the shaft member 1, and a stator coil 21 facing the rotor magnet 20 is attached to the bearing member 2. The shaft member 1 is covered with a bearing member 2 and hermetically sealed.

In this embodiment, when the shaft member 1 rotates, the fluid in the thrust bearing clearance S flows out into the radial bearing clearance r, but the fluid flowing upward from the radial bearing clearance r is suppressed. Therefore, from the thrust bearing clearance S to the radial bearing clearance r
The thrust bearing has high rigidity because the outflow of fluid to the bearing is suppressed.

Note that one magnet 12 and the other magnet 11 may be electromagnets instead of permanent magnets.

Further, the thrust bearing clearance S is preferably 0 to 10 μm. When the thrust bearing surface 8 and the thrust bearing surface 9 are in contact, the starting torque is large, and the thrust bearing clearance S is 10 μm.
If it is larger, the pumping effect of the groove 13 for generating dynamic pressure will be weakened. However, the thrust bearing clearance S may exceed 10 μm.

〔Effect of the invention〕

As explained above, according to the present invention, one magnet provided on the thrust bearing surface of the thrust bearing and the other magnet provided on the thrust bearing surface that face each other through the thrust bearing clearance have the same polarity. The magnetic repulsion type thrust bearing facing in the direction has a structure in which at least one of the thrust receiving surface and the thrust bearing surface is provided with a groove that causes the fluid in the thrust bearing clearance to act on negative pressure during rotation. Therefore, when the bearing is operated, the thrust bearing surface and the thrust bearing surface are attracted to each other by negative pressure and approach each other, so that the magnetic repulsion increases, and as a result, the effect of increasing the rigidity against the thrust load is obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, and a longitudinal cross-sectional view of another embodiment of the present invention. In the figure, 1.2 is the shaft member, 5 is the bearing member, 8 is the thrust bearing surface, 9 is the thrust bearing surface, S is the thrust bearing, S is the thrust bearing clearance, 11.12 is the magnet, and 13 is the inside of the thrust bearing clearance. A groove that creates a negative pressure on the fluid. Figure 2 is

Claims (3)

[Claims] (1) In a thrust bearing in which a thrust bearing surface provided on the shaft member faces a thrust bearing surface provided on the bearing member with a thrust bearing clearance, one magnet provided on the thrust bearing surface and one magnet provided on the thrust bearing surface. The other magnet has the same polarity facing each other in the axial direction,
At least one of the thrust receiving surface and the thrust bearing surface is provided with a groove that causes the fluid in the thrust bearing clearance to exert negative pressure when either the shaft member or the bearing member rotates. thrust bearing. (2) The thrust bearing according to claim (1), wherein the groove is a herringbone-shaped groove. (3) The thrust bearing according to claim (1), wherein the groove is a spiral groove.