JPH06137320A - Dynamic pressure fluid bearing device - Google Patents

Abstract

PURPOSE:To heighten lubricating fluid holding capacity by limiting a taper angle of a taper part as well as to improve durability significantly by improving a drawing-in effect of lubricating fluid supplied to a radial bearing surface. CONSTITUTION:A cylindrical radial bearing surface 3 is arranged in a shaft direction at an interval in two places on an inside diameter surface of a sleeve 2 in which a shaft 1 is fitted. On the other hand, a radial receiving surface 4 is arranged in a lengthwise direction at an interval in two places on the shaft 1, and the radial bearing surface 3 and the radial receiving surface 4 are opposed to each other through a radial bearing clearance 5, and a radial bearing R is constituted. A dynamic pressure generating groove 6 arranged on the radial bearing surface 3 is formed in an asymmetrical herringbone shape groove pattern where anti-shaft end side groove length I1 close to a bending part 6a is longer than shaft end side groove length I2 close to the bending part 6a. A lubricant reservoir 7 having clearance larger than the bearing clearance 5 is arranged in a place between the two radial bearing surfaces 3 on the inside diameter surface of the sleeve 2, and the place continuing to the bearing clearance 5 forms a taper part 8 toward the bearing clearance 5. This taper angle (3q) is larger than 10 deg. and is smaller than 60 deg.. An air vent hole 15 passing penetratingly in a radial direction through the intermediate sleeve 2 of the lubricant reservoir 7 puts inside and outside atmospheric pressures of the sleeve 2 in the same condition even if a temperature is changed, and prevents lubricating fluid in the radial bearing clearance 5 from leaking outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of durability of a hydrodynamic bearing device used in information equipment, office machines, measuring equipment and the like.

[0002]

2. Description of the Related Art A conventional hydrodynamic bearing device is shown in FIG.
As shown in (1), the cylindrical radial bearing surface 3 is provided at two locations on the inner diameter surface of the sleeve 2 with which the shaft 1 is fitted, with a space in the axial direction. On the other hand, the shaft 1 fitted into the sleeve 2 is provided with radial receiving surfaces 4 at two positions spaced apart in the longitudinal direction. The radial bearing surface 3 and the radial receiving surface 4 face each other through a bearing clearance 5 to form a radial bearing R. The radial bearing surface 3 is provided with a herringbone-shaped groove 6 for generating a dynamic pressure, which is composed of a large number of grooved grooves that are symmetrical in the axial direction. Then, when either the shaft 1 or the sleeve 2 rotates, a pressure is generated in an extremely small amount of lubricant retained in the radial bearing clearance 5 by the pumping action of the herringbone-shaped groove 6 for generating dynamic pressure, It is designed to perform hydrodynamic lubrication. A lubricant reservoir 7 having a clearance larger than that of the bearing clearance 5 is provided between the two bearing clearances 5 and 5.
A portion extending from the lubricant reservoir 7 to the bearing clearance 5 is a tapered portion 8 that narrows toward the bearing clearance 5.

In the conventional taper portion 8, the taper angle θ is 90 ° or 60 ° which is a standard chamfer for cutting.
Was processed into.

[0004]

However, in the above-described conventional hydrodynamic bearing device, since the taper angle θ of the taper portion 8 is as large as 60 ° or 90 °, the retaining force of the lubricating fluid due to the capillary phenomenon is weak and the high speed is achieved. When the centrifugal force is applied by the rotation or when the external impact is applied, there is a problem that the lubricating fluid in the taper portion 8 which serves to replenish the radial bearing clearance 5 is scattered and disappears.

When used in a high temperature environment, the lubricating fluid in the radial bearing clearance 5 is gradually lost due to evaporation,
Depending on the processing error of the radial bearing surface 3 and the processing error of the groove 6 for generating dynamic pressure, a force for pushing the lubricating fluid out of the bearing surface acts to replenish the lubricating fluid from the tapered portion 8 to the radial bearing clearance 5. There was a problem that I was not denied. Therefore, the present invention provides a hydrodynamic bearing device in which the ability to retain a lubricating fluid in the taper portion is enhanced, and the effect of drawing the lubricating fluid to be supplied to the radial bearing surface 3 is enhanced to significantly improve durability. It is intended to solve the above-mentioned conventional problems.

[0006]

According to the present invention, a cylindrical radial bearing surface provided on a sleeve faces a radial bearing surface provided on a shaft through a bearing clearance, and the radial bearing surface and the radial bearing surface are opposed to each other. A herringbone-shaped groove for dynamic pressure generation is provided on at least one side, and the sleeve is a hydrodynamic bearing device having a tapered portion adjacent to a bearing clearance,
The taper angle of the taper part is larger than 10 ° and 60
It is characterized by being smaller than °.

[0007]

In the present invention, since the taper angle of the taper portion is formed to be larger than 10 ° and smaller than 60 °, the taper portion based on the capillary phenomenon has a high ability to retain the lubricating fluid, and further, the taper capable of retaining the lubricating fluid. The space volume of the part can be large. Further, the herringbone-shaped groove is an asymmetric herringbone-shaped groove in which the axial length of one of the grooves connected to the tapered portion is longer than the axial length of the other groove,
The action of drawing the lubricating fluid to the radial bearing surface is enhanced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. The same or corresponding parts as in the conventional case are designated by the same reference numerals. FIG. 1 is a vertical cross-sectional view of an embodiment of the present invention, in which a cylindrical radial bearing surface 3 is axially spaced at two positions on an inner diameter surface of a sleeve 2 with which a shaft 1 is fitted. It is provided. On the other hand, the shaft 1 is provided with radial receiving surfaces 4 at two locations spaced apart in the longitudinal direction. The radial bearing surface 3 and the radial receiving surface 4 face each other with a radial bearing clearance 5 therebetween. It constitutes R. The radial bearing surface 3 has a herringbone-shaped groove 6 for generating dynamic pressure.
Is provided. The groove 6 for generating the dynamic pressure has a bent portion 6
The groove length l ₁ on the opposite shaft end side from a is longer than the groove length l ₂ on the shaft end side from the bent portion 6a, which is an asymmetric herringbone groove pattern.

On the inner diameter surface of the sleeve 2, a lubricant reservoir 7 having a clearance larger than the bearing clearance 5 is provided at a location between the two radial bearing surfaces 3. A portion extending from the lubricant reservoir 7 to the bearing clearance 5 is a tapered portion 8 that narrows toward the bearing clearance 5. The taper angle θ of the taper portion 8 is formed to be larger than 10 ° and smaller than 60 °.

An air vent hole 15 is provided in the middle portion of the lubricant reservoir 7 so as to penetrate the sleeve 2 in the radial direction. The air vent hole 15 keeps the air pressure inside and outside the sleeve 2 the same even if the temperature changes, and prevents the lubricating fluid in the radial bearing clearance 5 from leaking to the outside. The lower surface of the shaft 1 is a thrust receiving surface 9, and the thrust plate 10 attached to the lower surface of the sleeve 2 is provided with a thrust bearing surface 11 facing the thrust receiving surface 9 having a groove 12 for generating a dynamic pressure. The thrust bearing S of FIG.

Further, the groove 1 for generating the dynamic pressure of the thrust bearing S
2 may be provided on the thrust receiving surface 9 or on the thrust bearing surface 11 facing the thrust receiving surface 9, or may be provided on both the thrust receiving surface 9 and the thrust bearing surface 11. The thrust bearing S may be a point-contact type pivot bearing without a groove for generating dynamic pressure. Its sleeve 2
A lubricant reservoir 16 having a diameter larger than that of the lower radial bearing surface 3 is provided on the inner diameter surface 3 at the lower end of the, and an air vent hole 17 penetrating the sleeve 2 from the lubricant reservoir 16 in the radial direction is provided.

This hydrodynamic bearing device is lubricated with an extremely small amount of lubricant which is retained in the radial bearing clearance 5 and the thrust bearing clearance between the thrust bearing surface 9 and the thrust bearing surface 11 by a capillary phenomenon. Next, the operation will be described.
The lubricating pool 7 is filled with a lubricating fluid in advance. According to the present invention, since both ends of the lubricant reservoir 7 are tapered, the lubricating fluid in the lubricant reservoir 7 is pulled by the capillary phenomenon toward the narrower clearance between the shaft 1 and the sleeve 2. It is easy to be beaten. However, when the taper angle θ of the taper portion 8 is less than 10 °, the volume for holding the lubricating fluid becomes too small. On the other hand, when the taper angle θ is 60 ° or more, the lubricating fluid retaining ability due to the capillary phenomenon becomes weak.

In particular, when the sleeve 2 is rotated, the taper angle θ is reduced to reduce the influence of the centrifugal force acting on the lubricating fluid held in the taper portion 8 and reduce the scattering of the lubricating fluid. Now, when the shaft 1 rotates, the lubricating fluid in the radial bearing clearance 5 flows into the bent portion 6a of the herringbone groove by the pumping action of the groove 6 for generating the dynamic pressure of the radial bearing R. And the bent portion 6a of the groove
The lubricating fluid that has filled the space passes through the radial bearing clearance 5 and moves to both axial ends of the radial bearing clearance 5 to circulate. In the case of this embodiment, since the pattern of the herringbone-shaped groove 6 for generating a dynamic pressure connected to the tapered portion 8 is asymmetrical, the pressure generated in the groove of the long inner pattern having the groove length l ₁ is It becomes larger than that of the groove of the outer pattern having a short groove length l ₂ , and the lubricating fluid in the radial bearing clearance 5 flows more to the shaft end side of the radial bearing R. As a result, the action of drawing the lubricating fluid held in the tapered portion 8 into the radial bearing clearance 5 is enhanced.

Therefore, even if the lubricating fluid in the radial bearing clearance 5 gradually decreases due to evaporation, the lubricating fluid can be smoothly replenished from the tapered portion 8 to the radial bearing clearance 5. Also,
As in this embodiment, when the inner groove is a herringbone-shaped groove for generating dynamic pressure, which is an asymmetric groove longer than the outer groove, the bearing span (the maximum pressure generation point of the upper bearing clearance 5 and
Since the distance between the lower bearing clearance 5 and the position where the maximum pressure is generated is large, there is an advantage that the bearing device can be strong against an external moment.

Thus, in the radial bearing R, the dynamic pressure is generated by the pumping action of the groove 6 for generating the dynamic pressure, the pressure of the lubricating fluid in the radial bearing clearance 5 becomes high, and the shaft 1 becomes the radial bearing surface of the sleeve 2. It is supported in a radial direction without contacting with 3. On the other hand, in the thrust bearing S, dynamic pressure is generated by the pumping action of the groove 12 for generating dynamic pressure on the thrust bearing surface 11, and the shaft 1 is supported in non-contact with the thrust bearing surface 11 of the thrust plate 10.

Even when the amount of the lubricating fluid in the radial bearing clearance 5 decreases due to the outflow of the lubricating fluid to the outside of the bearing due to the scattering of the lubricating fluid during the start / stop of the hydrodynamic bearing device and during rotation, and the evaporation of the lubricating fluid, Lubricating fluid is gradually and automatically gradually replenished by the capillary phenomenon from the lubricant reservoir 7 through the taper portion 8 toward the narrow side of the taper clearance. Therefore, the bearing performance does not deteriorate for a long period of time, and excellent durability can be obtained.

The groove 6 for generating the dynamic pressure in the radial bearing R of the above embodiment may be provided on the radial bearing surface 4 of the shaft 1 or the radial bearing surface 3 of the sleeve 2, or the radial bearing surface. 3 and the radial receiving surface 4 may be provided. Further, either the shaft 1 or the sleeve 2 may rotate, but since the lubricating fluid is drawn in by the groove 6 for generating the dynamic pressure, the groove 6 for generating the dynamic pressure is formed in order to make the drawing effect of the lubricating fluid effective. It is preferable to provide the taper portion 8 side.

[0018]

As described above, in the hydrodynamic bearing device of the present invention, at least one of the cylindrical radial bearing surface and the radial receiving surface facing the radial bearing surface via the bearing clearance is herring. Bone-shaped grooves for generating dynamic pressure are provided, the sleeve has a tapered portion adjacent to the bearing clearance, and the taper angle of the tapered portion is larger than 10 ° and smaller than 60 °. Therefore, the ability of the tapered portion to retain the lubricating fluid is enhanced, and durability is extended even under high-speed rotation and use conditions in which an external impact is applied.

If the herringbone-shaped groove for generating the dynamic pressure is an asymmetric groove so that the lubricating fluid from the tapered portion can be smoothly supplied to the radial bearing surface, it is used at high temperature and the evaporation of the lubricating fluid is neglected. Even under usage conditions that cannot be achieved, it has the effect of extending durability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a hydrodynamic bearing device of the present invention.

FIG. 2 is a vertical cross-sectional view of a conventional hydrodynamic bearing device.

[Explanation of symbols] 1 shaft 2 sleeve 3 radial bearing surface 4 radial receiving surface 5 bearing clearance 6 groove for generating dynamic pressure 7 lubricant reservoir 8 taper part

Claims (1)

[Claims] 1. A cylindrical radial bearing surface provided on a sleeve faces a radial receiving surface provided on a shaft through a bearing clearance, and at least one of the radial bearing surface and the radial receiving surface has a herringbone movement. A groove for pressure generation is provided,
In the hydrodynamic bearing device, wherein the sleeve has a taper portion adjacent to the bearing clearance, the taper portion has a taper angle of more than 10 ° and 60 degrees or less.
A hydrodynamic bearing device characterized by being smaller than °.