JPS61211517A - Dynamic pressure hydraulic bearing device - Google Patents

Abstract

PURPOSE:To prevent excessive reduction in pressure by using porous member in the bottom face of the thrust bearing of a housing and having fluid flow outside through the porous member. CONSTITUTION:A housing 1 has a cylindrical porous member 33 settled in the center part of the bottom face 3 of a thrust bearing by use of the press-fit method. When a rotary shaft 4 is turned to float upward, fluid is throttled by the porous member 33 and then flows outside from the housing 1, whereby enabling moderation of reduction in pressure which is to be applied on the bottom face 3 of the thrust bearing. The permeability of the porous member 33 can be selected to the specified value so that excessive reduction in pressure inside the housing 1 may be prevented.

Description

[Detailed description of the invention] (Scope of industrial use) The present invention relates to a hydrodynamic bearing device, in particular, for example.

The present invention relates to a hydrodynamic bearing device used as a bearing device for a rotating unit used in a rotating polygon mirror light polarizer used in a laser beam printer or the like.

(Prior Art) As shown in FIG. 4, a conventional hydrodynamic bearing device has a radial bearing inner surface 2 and a planar thrust bearing bottom surface 3 in a housing 1, and has a radial bearing inner surface 2 and a flat thrust bearing bottom surface 3 facing the bearing inner surface 2. The disposed shaft 4 has a radial bearing outer surface 6 having a shallow groove 5 for generating dynamic pressure and a convex thrust end surface 7. In addition, a communication hole 11 (diameter of about 0.5 cm) is provided in the central part of the thrust bearing bottom surface 3 of the housing 1 in the axial direction, and this communication hole 11 opens to the outside of the housing 1.

The housing 1 is made of, for example, a self-lubricating resin containing carbon in a weight ratio of 25% or more.

Therefore, when the shaft 4 rotates and floats up, the fluid flows through the circulation hole 11.
The air flows out from the housing 1, and the flying height of the shaft 4 is kept almost constant.

However, in the conventional configuration, since the fluid flows out through the circulation hole 11, the pressure on the thrust end face 7 decreases, the thrust flying height decreases, and the thrust rigidity and thrust load capacity decrease. Moreover, since the number of revolutions required until the thrust end face 7 and the thrust bearing bottom face 3 reach a non-contact state is high, the thrust end face and the thrust bearing bottom face are easily damaged. Also.

Making the communication holes smaller in order to prevent the above-mentioned drawbacks is not preferable because it has limitations in terms of processing and increases processing costs.

For reference, the overall configuration of the polygon scanner motor is shown in Figure 5. In Figure 0, 20 is a polygon mirror;
21 is a coil, 22 is a magnet, and 23 is a case.

(Object of the invention) The present invention has been made in view of the drawbacks of the above-mentioned conventional examples, and
It is an object of the present invention to provide a hydrodynamic bearing device that can maintain a stable bearing clearance and prevent damage during startup and deactivation.

(Means for Solving the Problems) In order to achieve the above object, the hydrodynamic bearing device of the present invention is characterized in that a porous member is used on the bottom surface of the thrust bearing of the housing.

(Function) According to the above structure, the fluid flows out through the porous member, and the pressure between the thrust end face and the bottom face of the thrust bearing is kept constant. Since it is constricted and restricted by the member, the pressure will not decrease too much.

(Example) Hereinafter, specific embodiments of the present invention will be described in detail.

FIG. 1 shows an embodiment of a hydrodynamic bearing device according to the present invention, and the same members as those in FIG. 4 are given the same numbers and their explanation will not be repeated.

In the figure, the housing l has a cylindrical porous member 33 (with a diameter of 0.5 to
31) are fixed by a method such as press-fitting. Porous members include sintered alloys such as cemented carbide, ceramics, and the like.

In the hydrodynamic bearing device configured as described above, the rotating shaft 4
When it rotates and floats up, the fluid is squeezed by the porous member 33 and flows out of the housing 1, making it possible to reduce the decrease in pressure on the bottom surface 3 of the thrust bearing. In addition, by selecting the air permeability of the porous member 33 to a predetermined value (approximately 6 to 10% (5 to 20% if taken broadly) with a diameter of 2 C), it is possible to maintain an appropriate floating height. ,
Thrust rigidity and thrust load capacity increase.

Furthermore, it is possible to lower the number of revolutions until the bottom surface of the thrust bearing and the end surface of the thrust bearing come into a non-contact state, thereby preventing damage to the bottom surface of the thrust bearing and the end surface of the thrust bearing.

In addition, by using a fixed lubricant (for example, graphite) in the porous member 33, it is possible to reduce the torque during startup and shutdown, and it is also possible to further prevent damage to the bottom surface of the thrust bearing and the end surface of the thrust bearing. becomes. If chips or the like are generated due to damage to the bottom surface or end surface of the thrust bearing, it may cause seizure, etc., and the bearing may become unable to rotate.

FIGS. 2(a) and 2(b) show another embodiment of the present invention, in which the housing l has a cylindrical shape approximately coaxial with the central axis of the bottom surface 3 of the thrust bearing and has a diameter of approximately 4I1m (the housing l is located at the center). A porous member 43 (into which a pin (approximately 2 mm in diameter) made of the same material as 1 is press-fitted) is fixed by a method such as press-fitting.

In this case, the area where the pressure is reduced by the porous member 43 will increase, but the air permeability of the porous member 43 will be reduced by 2 to 5%.
By reducing it to about 1-10% (widely speaking),
Effects similar to those described above can be obtained. According to this configuration, a material with high frictional resistance is placed in the center, resulting in a long life.

FIG. 4 shows still another embodiment of the present invention, in which the housing l is constructed by fixing a porous member 53 having a diameter of about 10 mm to the entire bottom surface 3 of the thrust bearing by a method such as press fitting. In this case as well, similar effects can be obtained by lowering the air permeability. Note that the air permeability is 2 to 3% or less.

In the above description, the case where the shaft rotates is taken as an example, but the same effect can be obtained even when the shaft is fixed and the housing rotates.

Of course, the diameter and air permeability of the porous member are merely examples and are not limited.

(Effects of the Invention) As explained above, according to the configuration of the present invention, a stable bearing clearance can be maintained and damage can be prevented from occurring during starting and stopping.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a hydrodynamic bearing device according to the present invention, FIG. 2(a) is a sectional view of another embodiment, FIG. 2(b) is a bottom view, and FIG. 4 is a sectional view of another embodiment, FIG. 4 is a sectional view of a conventional example, and FIG. 5 is a sectional view showing the overall structure of a polygon scanner motor. 1--Housing, 2-m-Sial bearing inner surface, 3-
m-Thrust bearing bottom surface, 4-11 shaft, 5-11 groove, 7-
--Thrust end face, 33.43.53-m-Porous member.

Claims (5)

[Claims] (1) A hydrodynamic bearing that has a housing that has an inner surface of a radial bearing and a bottom surface of a thrust bearing, and a shaft that faces the bearing surface, and that rotates relative to each other in a non-contact state with a fluid interposed between the two. A dynamic pressure fluid bearing device characterized in that the bottom surface of the thrust bearing of the housing is made of a porous material. (2) The hydrodynamic bearing device according to claim (1), wherein the entire bottom surface of the thrust bearing is made of a porous member. (3) The hydrodynamic bearing device according to claim 1, wherein the vicinity of the central portion of the bottom surface of the thrust bearing is made of a porous member. (4) The hydrodynamic bearing device according to any one of claims (1) to (3), wherein the porous member is a solid lubricant. (5) The hydrodynamic bearing device according to claim (4), wherein the solid lubricant is graphite.