JP2711584B2 - Fluid bearing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluid bearing which forms a fluid film in a small clearance between a bearing surface and a rotating body and supports the rotating body in a non-contact manner.
In particular, the present invention relates to a fluid bearing used for a machine tool, a measuring machine, and the like that require high-speed rotation and high-precision rotation.

[Prior Art] As a conventional hydrostatic bearing, one having a configuration shown in FIG. 4 is known. In the figure, 1 is a thrust plate as a rotating body, 2 is a rotor as a rotating body, 3 is a housing, 4 is a ring-shaped porous body fixed to the housing 3, and 5 is a cylinder fitted to the housing 3. A porous body, 6 is an air supply hole, 7 is a hollow air supply chamber formed between the porous bodies 4, 5 and the housing 3, and 8 is an exhaust groove provided on the circumference of the porous body 5. , 9 are exhaust holes, 10 is a minute clearance between the bearing surface 4a of the porous body 4 and the thrust plate 1, and 11 is a minute clearance between the bearing surface 5a of the porous body 5 and the rotor 2.

In the above configuration, when a pressurized gas is supplied from the air supply hole 6, the pressurized gas passes through the porous bodies 4 and 5 from the air supply chamber 7 and gushes out of the open air holes of the bearing surfaces 4 a and 5 a, and the fine clearance 10 is formed. , 1
A gas film is formed on 1 to support the thrust plate 1 and the rotor 2. The gas ejected to the bearing surface 4a is discharged to the outside. The gas ejected to the bearing surface 5a passes through the exhaust groove 8 and is exhausted from the exhaust hole 9 to the outside.

[Problems to be Solved by the Invention] However, such a conventional example has a disadvantage that the surface 1a of the thrust plate 1 and the bearing surface 4a come into contact with each other due to deformation when the rotating body rotates at high speed.

An object of the present invention is to provide a fluid bearing in which a bearing surface and a rotating body are prevented from coming into contact with each other at a thrust bearing portion due to deformation of the rotating body during rotation.

[Means for Solving the Problems] In order to achieve this object, in the present invention, a rotating body having a thrust plate and a rotor coupled to only one surface of the thrust plate, and a rotor of the thrust plate are coupled. And a fluid bearing having a thrust bearing surface opposed to the side surface of the rotating body and supported in a non-contact manner by a fluid film, wherein the thrust plate falls down by centrifugal force when the rotating body rotates and faces the thrust bearing surface. In consideration of the fact that the side surface of the thrust plate is inclined in advance, the bearing interval is set such that the interval between the thrust bearing surface and the thrust plate side surface becomes larger toward the outer periphery when the rotating body is stopped.

[Operation] In the conventional fluid bearing, the reason why the bearing surface and the rotating body come into contact with each other in the thrust bearing portion due to deformation when the rotating body rotates at high speed is as follows.

That is, a rotating body as shown in FIG. 4 comprising the thrust plate 1 and the rotor 2 is driven by driving means (not shown).
It is known that when the rotor 2 is rotated at a high speed, the rotor 2 is deformed by centrifugal force, the minute clearance 11 is reduced, and the rotating body comes into contact with the bearing surface 5a. Therefore, generally, the rotor 2 and the porous body 5 are expected to be deformed by centrifugal force in advance.
Are set to be larger by an equal amount. In general, it is known that the deformed shape of the rotating disk due to the centrifugal force is as shown by the broken line in FIG. 5, but conventionally, the surface perpendicular to the rotation axis, that is, the thrust plate 1 in FIG. It was thought that the deformation of the surface 1a was a deformation having the same tendency, that is, the small gap 10 tended to widen at the time of high-speed rotation. For this reason, the fact is that little consideration has been given to the change in the small clearance 10 between the thrust plate 1 and the porous body 4 during high-speed rotation.

On the other hand, according to the knowledge of the present inventor, when the rotating body as shown in FIG. 4 rotates at a high speed, the rotor 2 is provided on one side of the thrust plate 1 and is thus connected to the rotor 2. The elongation due to the centrifugal force of the surface 1a on the side
As a result, the surface 1a of the thrust plate 1 on the rotor side is deformed so as to fall down to the rotor side as shown by a broken line in FIG. That is, when the rotating body rotates at a high speed, the minute clearance 10 becomes small. Therefore, even if the minute clearance 11 is set to be large as in the conventional example, the surface 1a of the thrust plate 1 and the bearing surface 4a come into contact with each other. Would be.

In the present invention, it is anticipated that the thrust plate will fall down due to the centrifugal force when the rotating body rotates, and the side surface of the thrust plate facing the thrust bearing surface will tilt in advance, and the thrust bearing surface and the thrust plate side surface when the rotating body stops. The distance between the thrust plate and the side of the thrust plate can be prevented from contacting even if the side of the thrust plate falls down due to centrifugal force during rotation. it can.

In a more specific aspect of the present invention, the bearing interval at the time of stop is set such that the bearing surface and the opposing surface of the thrust plate are parallel when the rotating body reaches the target rotational speed. Further, the shape of the bearing surface or the shape of the side surface of the thrust plate is set according to the deformation amount and the deformation shape of the rotating body determined by the shape and material of the rotating body and the target number of rotations.

Embodiment FIG. 1 is an enlarged view of a small clearance 10 of a gas bearing according to one embodiment of the present invention. The overall configuration of the bearing shown in FIG. 1 is the same as that of the conventional example shown in FIG. 4, but the structure of the minute clearance 10 is different. In FIG. 1, the deformed shapes (broken lines in the figure) of the minute gaps 10 and 11 and the surface 1a are exaggerated for explanation.

Pre-rotation of the minute gap 10 (width C) is the amount of deformation of the thrust plate 1 by the rotation and [Delta] x, the gap design for obtaining the bearing performance of the target (mainly rigidity and load capacity) as C _o, The relationship is C = _Co + Δx.

In the above configuration, the thrust plate 1 as a rotating body
When the rotor 2 is rotated at a high speed, the surface 1a of the thrust plate 1 is affected by the rotor 2 so that the bearing surface 4a as shown by the broken line in FIG.
It falls down to the side. However, in the fluid bearing shown in FIG. 1, the width C of the minute clearance 10 is set in consideration of the amount of fall (Δx), so that contact between the surface 1a and the bearing surface 4a is prevented. .

The amount C of the minute clearance 10 will be described with a specific example. Outer diameter of thrust plate 1 is 105mm, inner diameter is 30mm, thickness is 25m
m, the outer diameter of the rotor 2 is 50 mm, the inner diameter is 30 mm, and the length is 5
When a rotating body with 6 mm, Young's modulus of 21000 kgf / mm ² , Poisson's ratio of 0.33 and specific gravity of 7.8 g / cm ³ was rotated at 30,000 rpm, it was analyzed using the finite element method. The maximum deformation (Δx) of the surface 1a is about 8.6 μm.

For example, when the rotating body rotates at 30000 rpm, a small clearance 10
In order to make C _o = 10 μm, the deformation amount Δ of the surface 1a
C at the time of manufacture in anticipation of _{x = 8.6μm = C o + Δx} = 18.6μ
If the size C of the small clearance 10 is set so as to be m, the surface 1a and the bearing surface 4a do not come into contact with each other, and rigidity and load capacity can be secured.

FIG. 2 shows a minute gap 10 according to a second embodiment of the present invention.
It is an enlarged view of the part. The overall configuration is the same as that of the conventional example shown in FIG. Here, the deformed shapes (dashed lines in the figure) of the minute gaps 10 and 11 and the surface 1a are exaggerated for explanation.

The small clearance 10 (= C, C ') before rotation is determined by the amount of deformation .DELTA.x on the outer circumferential side of the thrust plate 1 and the amount of deformation .DELTA.x'
If consists of a clearance C _o the design for obtaining the bearing performance of the target (mainly rigidity and load capacity), each C = [Delta] x
_{+ C o, C '= Δx} ' + C o as a relationship, the bearing surface 4a
Are tapered.

In the above configuration, the thrust plate 1 as a rotating body
When the rotor 2 is rotated at high speed, the surface 1a of the thrust plate 1 is brought into contact with the bearing surface as shown by the broken line in FIG.
It falls to 4a. The minute clearance 10 (= C, C ') is set in consideration of the outer-side deformation amount Δx and the inner-side deformation amount Δx ′ of the thrust plate at this time. For this reason,
The contact between the surface 1a and the bearing surface 4a is eliminated.

The amounts C and C 'of the minute clearances 10 and the amount of taper of the bearing surface 4a will be described using specific examples. Outer diameter of thrust plate 1 is 10
5mm, inner diameter 30mm, thickness 25mm, rotor 2 outer diameter 50mm, inner diameter 30mm, length 56mm, Young's modulus 21000kgf
/ mm ² , a body with a Poisson's ratio of 0.33, and a specific gravity of 7.8 g / cm ³ , when rotated at 30000 rpm using a finite element method, the amount of deformation on the outer peripheral side of the thrust plate ( Δx) and the amount of deformation on the inner circumference side (Δx ′) are 8.6
μm and 5.4 μm.

For example, when the rotating body rotates at 30000 rpm, a small clearance 10
To make 10 μm (= C _o )
In consideration of the deformation amounts Δt = 8.6 μm and Δt ′ = 5.4 μm of the surface 1 a, if the bearing surface 4 a is tapered so that C = 18.6 and C ′ = 15.4 μm, the surface 1 a and the bearing surface 4 a Are not in contact with each other, and a uniform clearance is provided over the entire bearing surface 4a, so that rigidity and load capacity can be reliably ensured.

FIG. 3 shows a third embodiment of the present invention. The bearing shown in the figure has a taper in a range where the surface 1a of the thrust plate 1 faces the bearing surface 4a. This taper amount h
Is the thrust plate outer peripheral side deformation amount Δx in FIG.
And the inner peripheral side deformation amount Δx ′, h = Δx−Δx ′
And C = C _o + Δx ′ + h. Explaining using the above specific example, when the rotating body rotates at 30000 rpm, Δx = 8.6 μm and Δx ′ = 5.4 μm, so that the taper amount becomes h = 3.2 μm. μm taper, C = 18.6μm
If the small clearance 10 is set so that the surface 1a and the bearing surface 4a do not come into contact with each other and the clearance is uniform over the entire surface of the bearing surface 4a, rigidity and load capacity can be surely secured.

Although the above description has been made with respect to the gas bearing of the porous drawing method using the porous body, the present invention can also be applied to gas bearings of other drawing methods, for example, self-contained drawing, surface drawing, orifice drawing, and the like. Further, the present invention can be applied to a dynamic pressure gas bearing, and not only to a gas but also to a bearing using a liquid such as oil.

[Effects of the Invention] As described above, according to the present invention, it is anticipated that the thrust plate falls down due to the centrifugal force when the rotating body rotates and the side surface of the thrust plate facing the thrust bearing surface is inclined in advance. Since the distance between the thrust bearing surface and the thrust plate side surface is set to be larger toward the outer circumference when the rotating body stops, the thrust plate side surface is affected by the rotor when the rotating body rotates at high speed. Even if the bearing is deformed so as to fall to the side, contact between the bearing surface and the thrust plate can be avoided, seizure during rotation of the bearing, reduction in rotation accuracy, and the like can be prevented.

In addition, by adjusting the shape of the bearing surface or the side surface of the thrust plate in accordance with the deformation amount and deformation shape of the rotating body, a uniform bearing clearance can be secured over the entire bearing surface in accordance with the above-described effects. As a result, a value as designed is obtained as the load capacity.

[Brief description of the drawings]

FIG. 1 is a partially enlarged view of a gas bearing according to one embodiment of the present invention, FIG. 2 is a partially enlarged view of a gas bearing according to a second embodiment of the present invention, and FIG. FIG. 4 is a cross-sectional view of a conventional gas bearing, FIG. 5 is a view schematically showing a deformed state of a rotating disk during rotation, and FIG. The figure is a view schematically showing a deformed state during rotation of the rotating body. 1: Thrust plate 1a: Surface 2: Rotor 4a: Bearing surface 10: Micro clearance 11: Micro clearance

Claims (4)

(57) [Claims] 1. A rotating body having a thrust plate and a rotor coupled to only one surface of the thrust plate, and a non-contact support by a fluid film facing a side surface of the thrust plate to which the rotor is coupled. A fluid bearing having a thrust bearing surface, in advance, considering that the thrust plate falls down by centrifugal force when the rotating body rotates and the side surface of the thrust plate facing the thrust bearing surface is inclined. A fluid bearing device, wherein a bearing interval is set such that an interval between the thrust bearing surface and the side surface of the thrust plate becomes larger toward the outer periphery when the rotating body stops. 2. The bearing interval at the time of stoppage is set such that the bearing surface and the opposing surface of the thrust plate become parallel when the rotating body reaches a target rotation speed.
The hydrodynamic bearing device as described in the above. 3. The fluid according to claim 2, wherein the shape of the bearing surface is set in accordance with the deformation amount and deformation shape of the rotating body determined by the shape, material, and target rotation speed of the rotating body. Bearing device. 4. The thrust plate according to claim 2, wherein the shape of the thrust plate is set in accordance with the deformation amount and the deformation shape of the rotating body determined by the shape and material of the rotating body and a target rotation speed. Fluid bearing device.