JPS63176817A - Fluid bearing - Google Patents

Abstract

PURPOSE:To avoid any defection of bearing end surfaces so as to prevent biting thereof by forming taper surfaces which enlarge outward on the end portions of the bearing surface of a porous body and connecting said taper surfaces to the bearing surface in arc forms. CONSTITUTION:A porous body 3 formed with cylindrical porous ceramics is fixedly fitted to a housing 2, and a shaft 1 rotates in it. When pressurized gas is supplied from an air supply hole 4 by an air supply pump 4a in this structure, the gas passes the porous body 3 from an air supply chamber 5 and blows out from the opening pore of a bearing surface 3a and then forms a gaseous film in a microclearance 6 so as to maintain the shaft 1. Taper surfaces 7 are formed on the inner surface end portions of the porous body 3, and the boundary portions 8 between respective taper surfaces 7 and the bearing surface 3a are connected together in form of circular arcs with the radius of r, and thereby even though the shaft 1 in its rotating state inclines a little bit, it can not be brought into contact with the end portions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a fluid bearing, and particularly to an improvement in a porous fluid gas bearing using a porous material as a bearing member.

[Prior art]

Porous hydrostatic gas bearings eject pressurized gas through a porous material into a minute gap between the bearing surface and the shaft to form a gas film that supports the shaft without contact. Used with a mechanism that detects the drop in pressure of pressurized gas and stops rotation of the shaft when the supporting force of the shaft due to the gas film is lost due to stoppage or a drop in the supply pressure of pressurized gas. be done.

However, since the shaft and the rotating body connected to the shaft have inertia, the rotation of the shaft cannot be stopped instantaneously even if a drop in the pressure of the pressurized gas is detected. In particular, when the pressure of the pressurized gas supplied to the bearing drops rapidly, the shaft rotates in contact with the bearing surface until the shaft stops rotating after the bearing loses its supporting force.

In bearings that use porous ceramics for the porous body, the hardness of the bearing surface is high, so even if the shaft and bearing surface come into contact, galling is less likely to occur if the hardness of the shaft is high. Furthermore, when porous graphite is used as the porous body, galling is even less likely to occur due to the high hardness of the bearing surface and its self-lubricating effect. In this way, porous ceramics or porous graphite It has excellent properties as a bearing member for this type of hydrostatic gas bearing.

However, although such porous materials have high hardness, they are fragile (vulnerable to local stress concentration). Since stress concentration occurs, it is easy for defects to occur at the end of the bearing surface (and the defect is that these defective pieces enter the bearing gap and cause galling).

[Problems to be Solved by the Invention] The purpose of the present invention is to eliminate such drawbacks of porous bodies, avoid damage to the bearing end surface even when the shaft and bearing surface come into contact, and eliminate the possibility of galling. An object of the present invention is to provide a porous hydrostatic gas bearing that eliminates the above problems.

[Means for Solving the Problems] This purpose is to form a tapered surface expanding outward at the end of the bearing surface of a porous body according to an embodiment of the present invention to be described later, and further to form a tapered surface so as to expand outward. This is achieved by forming the tapered surface in an arcuate and continuous manner so that local stress concentration does not occur on the bearing surface when the shaft contacts the bearing surface.

That is, the porous hydrostatic gas bearing according to one embodiment of the present invention has the following characteristics:
A housing having a hollow air supply chamber on its inner surface that communicates with the air supply means through an air supply hole, and a porous member provided on the inner surface of the housing so as to close the air supply and form a bearing surface. The bearing surface of this porous body has an end portion formed with a tapered surface so as to continuously expand outward in an R-shape with the bearing surface.

FIG. 1 is a sectional view showing the basic structure of a porous hydrostatic gas bearing according to an embodiment of the present invention, where l is a rotating shaft, 2 is a housing,
3 is a cylindrical porous body made of porous ceramics, which is fitted into the inner surface of the housing 2 . 4 is an air supply hole, 4a is an air supply pump, 5 is a hollow air supply chamber formed between the housing 2 and the porous body 3, and 6 is a small hole between the bearing surface 3a of the porous body 3 and the shaft 1. It is a gap. The bearing surface 3a is formed so as to be parallel to the surface of the shaft l in a supported state.

With this structure, when pressurized gas is supplied from the air supply hole 4 by the air supply pump 4a, it passes from the air supply chamber 5 through the porous body 3 to the bearing surface 3.
It is ejected from the open pores of a, forming a gas film in the micro gap 6,
The pressurized gas is discharged while supporting the shaft 1.

FIG. 2 is a partially enlarged view showing the state in which the present invention is implemented at the end of the porous hydrostatic gas bearing shown in FIG. 7 is a tapered surface,
Reference numeral 8 denotes a boundary between the tapered surface 7 and the bearing surface 3a, which is formed into an arc shape with a radius r and whose center is inside the porous body, and smoothly connects the bearing surface 3a and the tapered surface 7. porous body 3
The end face 3b of is provided with measures to prevent gas leakage. Since the bearing clearance at the end is larger than that at the back, even if the shaft and the bearing surface contact each other at a slight inclination, they will not contact at the end but at the boundary 8.

Therefore, a large stress is likely to be applied to the boundary 8, but unlike the end portion, the bearing is also porous toward the outside, and the boundary 8 is also supported from the outside of the bearing, making it difficult for breakage to occur. That is, when the shaft 1 and the bearing surface 3a come into contact,
The arc-shaped boundary portion 8 and the tapered surface 7 at the end of the bearing surface 3a effectively avoid stress concentration, thereby preventing damage to the porous body 3 due to stress concentration. Even if a part of the boundary 8 is chipped, the chipped part communicates with the outside through the tapered surface 7, so that it becomes an air pocket and the shaft 1 does not vibrate due to the elasticity of the collected air. Further, by making the boundary between the tapered surface 7 and the bearing surface 3a into an arc shape, the contact area between the boundary and the shaft surface is expanded, and wear of the boundary and damage to the shaft are less likely to occur.

Since only the boundary portion has an arc shape and the tapered surface 7 has a constant taper angle, processing is easy during manufacturing.

Although the present invention has been described in detail regarding radial bearings above,
Even if the present invention is applied to the end portion of the bearing surface of a thrust bearing, similar effects can be obtained. Alternatively, a tapered surface may be formed on the shaft surface facing the end of the bearing instead of the porous side so as to widen the gap, and the boundary portion may be formed into an arc shape.

〔effect〕

As is clear from the above, the present invention can avoid the occurrence of damage to the bearing end face due to unexpected contact between the shaft of the porous hydrostatic gas bearing and the bearing surface, and eliminate the possibility of galling. The effects of the present invention include the following.

(1) Even if the bearing gap is small, the large end of the bearing is tapered, making it easy to assemble the shaft into the bearing hole.

(2) Even if the shaft and the bearing come into contact due to sudden changes in load during rotation of the shaft, scratches on the shaft surface and stress concentration on the bearing end face are avoided. When porous graphite is used as the porous body, the porous graphite has a self-lubricating effect, and this effect, together with the effect of eliminating local stress concentration in the present invention, increases the galling prevention effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the overall structure of a porous hydrostatic gas bearing according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the essential parts thereof. 1 is a shaft, 2 is a housing, 3 is a porous body, 7 is a tapered surface, and 8 is a boundary portion.

Claims (4)

[Claims] (1) A hydrodynamic bearing characterized in that a gap formed between an ejection surface of a porous body and a surface opposing the surface is formed in the order of a parallel portion, an arcuate portion, and a tapered portion toward the end. (2) The hydrodynamic bearing according to claim 1, wherein the ejection surface includes a parallel portion, an arcuate portion, and a tapered surface in this order toward the end. (3) The fluid bearing according to claim 1, wherein the porous body is porous ceramics. (4) The fluid bearing according to claim 1, wherein the porous body is porous graphite.