JPS5829405B2 - bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bearing device with good high-speed stability.

What is shown in FIGS. 1 and 2 is a static pressure gas bearing device of the self-diaphragm type that has been widely used in the past.
This is a cross section taken along the line AA in FIG.

In the figure, 1' is the bearing body, 2' is the sliding surface, and 3 is the bearing body.
' is an air supply hole, and 4' is an 01J groove.

This bearing device supplies pressurized gas to the air supply hole 3', and although not shown, hydrostatic film pressure is generated in the bearing gap created between the shaft and the shaft. This prevents contact.

A feature of hydrostatic bearing devices is that when pressurized gas is supplied from the outside, a film is formed regardless of the rotation of the shaft.
It prevents contact with the shaft, has a semi-permanent life, and has extremely low friction torque during rotation.

However, the hydrostatic bearing devices shown in Figures 1 and 2 are so-called full-circle bearings in which the entire inner circumference slides on the shaft, so the rotation of the shaft is high and fluid dynamics occur within the bearing clearance. When pressure is applied and this increases to a certain extent, whirling occurs.

This poses a major problem when using this type of bearing.

In order to prevent this, an elastic member such as an O-ring is inserted into portion 4' in FIG. 1 to support the entire bearing body 1' with a degree of freedom in the radial direction.

So-called elastic support methods have been adopted, and although they are not sufficient, they have achieved considerable results.

On the other hand, the examples shown in FIGS. 3 and 4 are tilting pad type bearings that are said to be very stable against the above-mentioned whirling.

FIG. 4 shows a BB cross section in FIG. 3.

In the figure, 1" is a pad, 2" is a pivot, and 3" is a pad.
is a bearing body, 4" is an adjustable upper pivot for pad 1", 5" is a set screw for upper pivot 4", 6" is a ring, and 7" is a snap ring.

This bearing device is a hydrodynamic bearing that, by rotation of the shaft, creates a film pressure and thereby prevents contact between the band 1" and the shaft, and when the rotation is not high enough, the pad 1" and the shaft comes into contact.

In order to prevent this, a method is sometimes used in which a preliminary air supply hole is provided through the pivot 2'' and pressurized gas is sent from the outside to lift it up.

The purpose of the tilting pad bearing is to use pivot r as a fulcrum,
Since pad 1" can rotate to a limited extent,
The point of application of the force obtained by integrating the fluid dynamic pressure generated on the sliding surface of the pad 1" is on the pivot 2", and at the same time, its direction is toward the center of the axis. The point is that it does not generate whirling force on the shaft.

However, since the tilting pad bearing is a hydrodynamic bearing, even if the shaft rotation is considerably high, the film pressure is small and the film rigidity is small. , the frictional force of the pivots 2", 4" cannot be ignored, and whirling cannot be completely prevented.

Improving the whirling stability of gas bearings is very important for practical use.

Focusing on this, the present invention has developed a gas bearing with good high-speed stability by incorporating the advantages of the bearings shown in FIGS. 1 and 2 and the advantages of the tilting pads shown in FIGS. 3 and 4. It provides equipment.

The tilting pad bearing is a hydrodynamic bearing, and the rigidity of the film is low, but in the present invention, this is replaced by a hydrostatic bearing (
A hydrostatic bearing) is used to increase the rigidity of the film, and support is provided by a bellows with no friction between the pivot and at the same time, elastic support is provided using the elasticity of the bellows.

Furthermore, in order to prevent instability due to film pressure that occurs during ultra-high-speed rotation, the area of the bellows' pressure-receiving part and bearing sliding surface is selected so that the rigidity of the bellows is more supportive than the film pressure. I made it.

By doing so, an extremely stable gas bearing device can be obtained.

The bearing device of the present invention can be applied to a hem worm circulator, a gas expansion turbine, a high-speed rotation gas compressor, a high-speed rotation compressor (
It can be applied to small Freon turbine compressors.

Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

5 and 6 show a static pressure gas bearing device of the present invention.

FIG. 6 is a side view taken along the line CC in FIG. 5.

FIG. 7 is a diagram for explaining the operation, and shows one bat taken out.

In FIGS. 5 and 6, reference numeral 1 is a pad, 2 is a bellows, and 3 is a base of the bellows, which are fixed to the bearing body 8.

4 is also a bellows cap, which is screwed into pad 1.

A spring 5 adjusts the relative positions of the three pads 1.

6 is an adjustment screw, and 7 is a set screw for fixing the adjustment screw 6.

8 is a bearing body, and 9 is an air supply hole of the pad 1.

As shown in Fig. 6, in a tilting pad bearing composed of a plurality of pads 1 (usually three, but some have four, five, or six pads), the pad 1 has an air supply hole. 9
will be established.

In order to supply pressurized gas from the outside to this air supply hole 9 without impairing the degree of freedom of the pad 1, the bearing body 8 and the pad 1 are connected via the bellows 2 and the bases 3 and 4. .

Since it is difficult to make the length of the bellows 2 equal just by the precision in manufacturing, the shaft is inserted inside the bellows 2 using a spring 5 and an adjusting screw 6 (not shown). Adjust so that it is concentric with the bearing body 8.

The adjustment screw 6 is fixed by a set screw 7 after adjustment.

In the embodiment, the adjusting screw 6 and the set screw 7 have hexagonal holes, which serve both as a flow path for the supply gas and for tightening.

The pressure of the supplied gas acts within a circle whose diameter is the effective diameter of the bellows 2 (de in Figure 7), and this area is
The projected area of the sliding surface should be larger than 1i0.

In principle, the bellows 2 is provided in the center of the pad 1.

Next, the functions and effects of the present invention will be explained.

In the action explanatory diagram of Fig. 7, the reference numbers of parts are shown in Fig. 5 and 6.
It is similar to the figure.

When pressurized gas is supplied to this bearing device from the outside, it flows through the inside of the bellows 2 and onto the sliding surface of the pad 1, and although not shown, the gas flows through a small gap created between the shaft and the pad 1. At this time, as shown in FIG. 7, the pressure between the air supply hole 9 is approximately constant, and the pressure between the air supply hole 9 and the end of the pad 1 is as follows.
This results in a smooth depressurization distribution.

It is well known that the air supply hole 9 is a self-limiting restriction, and as the bearing clearance becomes smaller, the overall pressure increases, and as the bearing clearance becomes larger, the pressure decreases, which is called bearing rigidity. It is.

Since the pad 1 is fastened to the bearing body 8 via the bellows 2, gas supply pressure acts within a circle whose diameter is the effective diameter de of the bellows 2.

Therefore, the film pressure acts on the pad 1 from the sliding surface, the supply gas pressure acts from the back side, and the elastic force of the bellows 2 acts on the pad 1, and these forces are balanced during steady operation.

In such a static pressure bearing, the pressure on the sliding surface is determined by the film thickness and the size of the air supply hole 9, but roughly speaking,
The pressure of the gas exiting the air supply hole 9 is approximately 1/ of the supply pressure PS.
2, assuming that the pressure distribution on the sliding surface of the film is square pyramidal, the force on the sliding surface is equal to the projected length 3 of pad 1.
1 width is b, the force on the back surface to be soothed is calculated by dividing the area of the circle made by the effective diameter de of bellows 2 into the projected area of pad 1 (aXb
)of! /10 ~ It would be good to do it.

In order to improve the stability of the bearing, the elastic modulus of the bellows 2 is made smaller than the rigidity of the bearing film, so that the force due to the film pressure on the sliding surface is equal to the force due to the supply gas pressure on the back side. In balance, the thickness of the film remains approximately constant regardless of the eccentricity of the shaft, and the stiffness of the bearing is approximately equal to the elastic modulus of the bellows 2.

In such a state, there is no influence of elements having a hydrodynamic delay due to the rotation of the film pressure axis, and only the mechanical elastic modulus of the bellows 2 acts.

Since this elastic modulus can also be selected to be relatively small, whirling does not occur at all, and high-speed rotation close to the critical rotation speed of free support is possible.

Although the bearing device according to the present invention has been explained above, other application examples of the present invention will be described below.
If a cylindrical elastic body with large internal damping, such as rubber, is used instead, a vibration absorption effect at the natural frequency can be obtained, suppressing not only the vibrations that occur when the vibration exceeds the natural frequency. I can do it.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional bearing device, Fig. 2 is a sectional view taken along the line A-A in Fig. 1, Fig. 3 is a sectional view of a conventional tilting pad type bearing, and Fig. 4 is a sectional view of a conventional tilting pad type bearing. B-B in Figure 3
5 is a cross-sectional view of the bearing device according to the present invention, FIG. 6 is a cross-sectional view taken along the line CC in FIG. 5, and FIG. 7 is an explanatory diagram of the operation of the present invention. . 1... Pad, 2... Bellow 3,4
...Base, 5...Spring, 6...
・Adjusting screw, 7... Set screw, 8...
Bearing body, 9... Air supply hole.

Claims (1)

[Claims] 1. A plurality of tilting pads with air supply holes that open on the bearing sliding surface are arranged inside the bearing body, and tilting pads that occur on the sliding surface when the rigidity is lower than the rigidity of the bearing film and the required film thickness are provided. One side is used as a tilting pad, and the other is used as a tilting pad so as to form a passage for supplying pressurized fluid to the air supply hole, which has an effective diameter that balances when air supply pressure acts on the inside of the film pressure force. A bearing device characterized in that a tilting pad is elastically supported only via a bellows fastened to a bearing body.