JPH0211615Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of application of the invention] The invention uses a high-temperature rotating shaft that rotates at high speed to
This invention relates to a hydrodynamic gas bearing that is rotatably supported in a suspended state by a film of gas such as nitrogen or helium.

[Background of the idea]

First, a conventional example of a hydrodynamic journal gas bearing will be explained based on FIG.
(Refer to Publication No. 35816 and Japanese Patent Publication No. 17851/1983). In the figure, reference numeral 1 is a holder, and the holder 1
is formed into a cylindrical shape, and a corrugated elastic bump oil 3 is disposed in the cavity 2 so as to circumferentially surround the inner surface of the holder 1 . The bump oil 4 is fixed to the bump oil 3. The top oil 4 surrounds the entire circumference of the rotating shaft 5 while being spaced apart from the rotating shaft 5. Further, one ends of the top oil 4 and the bump oil 3 are clamped and fixed by a key 6 fixed to the inner surface of the holder 1. Holder 1
The outer surface of is held in surface contact with the outer casing 7.

Next, the operation will be explained. When the rotating shaft 5 rotates,
The surrounding gas is drawn into the minute gap between the outer surface of the rotating shaft 5 and the top oil 4 due to its viscosity.
Pressure is generated by a so-called wedge film action, and the rotating shaft 5 is rotatably supported by the gas film based on the pressure. The pressure of this gas film is determined by the gap between the rotating shaft 5 and the top oil 4, that is, the thickness of the gas film. In the case of a gas bearing with a bump oil 3, the rotating shaft 5 deviates from the axial center position due to dynamic loads, impact loads, etc. caused by the rotation of the rotating shaft 5, but the deviation of the rotating shaft 5 can be accommodated. As a result, the bump oil 3 is deformed to a certain extent, so that the area where the gas film has a uniform thickness becomes wider with respect to the deviation of the rotating shaft 5. Therefore, the effects of the impact etc. are absorbed and alleviated, and the load capacity is reduced. It has a large gas bearing.
During normal operation, the bearing can operate with a large gas film thickness, making it a highly reliable bearing.

On the other hand, to explain conventional examples of dynamic pressure type thrust gas bearings, among the thrust gas bearings, as a prior art of the foil type in which the bearing surface is formed of a flexible foil, Japanese Patent Application Laid-Open No. 55-166524, US patent
Examples include those disclosed in Publication No. 4227752 and the like. That is, FIGS. 8a and 8b show an example structure similar to the dynamic pressure type thrust gas bearing disclosed in U.S. Pat. It consists of Further, as shown in FIG. 8b, the bearing segment 9 is disposed on the base plate 8 and includes a wave-shaped bump oil 10 having elastic properties;
It is composed of a top oil 11 supported by the bump oil 10 and a spacer 12 fixed to the base plate 8, and the top oil 11 is further fixed to the spacer 12. Note that the height of the spacer 12 is the same as that of the bump oil 10.
It is slightly smaller than the height of

When the thrust runner 13 fixed to a rotating shaft (not shown) rotates in the direction of arrow A in FIG. The gas drawn into the gap is compressed by the wedge film action and generates pressure, thereby supporting the rotating shaft in an axial direction without contact. To explain this in more detail, when the thrust runner 13 rotates, the surrounding gas is drawn in by the slant runner 13, and the thrust runner 13 and the top oil 1
A wedge film of gas film is formed between the thrust runners 1 and 1, which causes the thrust runner 13 to float above the top oil 11, making it possible to rotate at high speed. Note that when the rotating shaft is stopped, the thrust runner 13 is in solid contact with the top oil 11.

However, in general, in the hydrodynamic journal and thrust gas bearings described above, when a large fluctuating load or impact load is applied to the rotating shaft, the bump oils 3 and 10 may deform beyond their elastic limit. Repeated deformation exceeding this value causes the bump oils 3 and 10 to become distorted in shape and the spring rigidity to deteriorate, resulting in so-called "settling", which deteriorates bearing performance and also causes the bump oil to become deformed. There was a risk that parts 3 and 10 would be damaged.

[Purpose of the invention] The purpose of the invention was made in view of the above-mentioned drawbacks, and is to prevent the bump oil from deforming or becoming flat even when a large fluctuating load is applied to the rotating shaft, and furthermore to prevent the bump oil from being damaged. The object of the present invention is to provide a gas bearing that always ensures proper bearing performance.

[Summary of the idea]

In order to achieve this purpose, the present invention
In a gas bearing in which the inner surface of a cylindrical holder is provided with a bump oil that elastically supports a surface member constituting the bearing surface, the inner surface of the holder is formed of two inner surfaces with different curvatures, and the inner surface with a larger curvature is provided with a compensating elastic layer. A movable body having a substantially crescent-shaped cross section is disposed through the member, and the bump oil is held by the inner arcuate surface of the movable body and the inner surface of the small curvature, and the elasticity of the compensating elastic member is determined from the elastic constant of the bump oil. The constant is set small, and a restriction oil is provided on the lower surface of the surface member, the restriction oil having a protrusion that protrudes toward the bump oil at a position corresponding to the flat surface of the bump oil.

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

[Example of idea]

First, FIG. 2 shows the structure of a hydrodynamic journal gas bearing as a comparative example of the present invention. In this figure, the same parts as in FIG. 7 are given the same reference numerals.
In this comparative example, a surface member that is arranged with a slight clearance a on the outer circumferential side of the rotating shaft 5 and that constitutes the bearing surface 4a, that is, a top oil 4,
In addition to the bump oil 3 which is disposed circumferentially on the inner surface of the holder 1 to elastically support the top oil 4 and has spring characteristics, the top oil 4 is
A restriction oil 15 is provided between the bump oil 3 and the bump oil 3. Further, one end of this restriction oil 15 is fixed to a key 6, and the key 6 is further fixed to the holder 1. Further, as shown in FIG. 3a, the restriction oil 15 has a protruding portion 15a formed to protrude toward the bump oil 3 side, and is provided at a distance H ₁ from the flat surface portion 3a of the bump oil 3. It is being Furthermore,
The restriction oil 15 has a flat surface portion 1.
5b is in contact with the top oil 4 and the bump oil 3.

Therefore, in the configuration of this comparative example, when a large fluctuating load or impact load is applied to the rotating shaft 5, the bump oil 3 is protected by the action of the restriction oil 15.
It is possible to prevent the occurrence of so-called "settling", which is the deterioration of the shape of the spring and the spring stiffness, thereby ensuring proper bearing performance at all times. Now, to explain the action of this restriction oil 15, the bump oil 3 normally has the shape shown in FIG. When the bump oil 3 approaches the bump oil 3 and the gas film pressure becomes very large, causing a large deflection, the protruding portion 15a of the restriction oil 15 will move against the flat surface portion 3a of the bump oil 3, as shown in FIG. 3b. By contacting the bump oil 3, no further large force is applied to the bump oil 3. Therefore, this action reliably prevents the bump oil 3 from exceeding its elastic limit and causing large deformation.

In addition, by appropriately setting the distance H ₁ and the rigidity of the restriction oil 15 in FIG. In addition, even when a large fluctuating load or impact load is applied, bearing performance can be appropriately ensured, and a highly reliable and durable bearing can be provided.

Further, by providing the restriction oil 15, a contact surface is created between the bump oil 3 and the top oil 4, thereby increasing the metal contact surface compared to the conventional example. Therefore, the damping capacity due to Coulomb friction is increased, and a bearing with excellent high-speed stability can be obtained.

In addition, since the flat surface portion 15b of the restriction oil 15 is in contact with the top oil 4, the load capacity of the bearing can be increased. That is, this is because the deflection of the topfoil 4 can be reduced over the span supported by the bumpfoil 3 due to the gas film pressure generated in the bearing gap between the rotating shaft 5 and the topfoil 4. This is because it is possible to prevent a decrease in gas membrane pressure due to an increase in .

FIG. 1 is a sectional view showing an embodiment of a hydrodynamic journal gas bearing according to the present invention. In the figure, the reference numeral 16 indicates a movable body, and the movable body 16 is
It has a substantially crescent-shaped cross section and is disposed in a part of the cavity 2 between the inner surface of the holder 1 and the bump oil 3. Inner circular arc surface 1 of this movable body 16
One end 3b of the bump oil 3 is welded and fixed to 6a. Further, in the cavity 2 between the outer arcuate surface 16b of the movable body 16 and the inner surface of the holder 1, there is a corrugated plate-shaped compensating elastic member 17, a part of which is welded and fixed to the inner surface of the holder 1. It is arranged. The compensating elastic member 17 has an elastic constant set smaller than that of the bump oil 3. Further, the inner surface of the holder 1 is formed by two inner surfaces 1a and 1b having different curvatures. That is, the curvature of the inner surface 1a is larger than that of the inner surface 1b. The inner surface 1b is formed within an arc angle range of 120 degrees,
A flat surface 3 of a bump oil 3 is provided on the inner surface 1b.
a, 3a, ... are in contact. Also, the movable body 16
The curvature of the inner circular arc surface 16a is formed to be slightly larger than the curvature of the inner surface 1b, so that even when the movable body 16 moves outward, there is an appropriate bearing gap around the entire circumference of the bearing.

In this embodiment, as described above, the movable body 1
6. In the configuration including the compensating elastic member 17,
A restriction oil 15 is provided between the top oil 4 and the bump oil 3. The one end 15c of this restriction oil 15 is connected to the inner arcuate surface 16 of the movable body 16 via the one end 3b of the bump oil 3.
It is fixed at a.

Therefore, in the above embodiments,
In addition to the same functions and effects as those of the comparative example described above, the following functions and effects are also provided. That is, the rotating shaft 5 thermally expands due to heat transfer from a turbine (not shown), and as the gap between it and the top oil 4, that is, the thickness of the gas film becomes smaller, the pressure increases. Then, the top oil 4 receives a force in a direction in which it expands, and this force presses the movable body 16 in a direction away from the rotating shaft 5. At this time, the compensating elastic member 17
Since the elastic constant of the bump oil 3 is set smaller than that of the bump oil 3, the compensating elastic member 17 is deformed.
Thereby, the thermal expansion of the rotating shaft 5 is compensated for by the movement of the movable body 16, and the gas film thickness is kept constant. Therefore, even if the gas bearing is used in a high temperature field, there is less risk of damage due to seizure or the like as in the conventional case, and a highly reliable gas bearing can be provided.

4 and 5 are hydrodynamic thrust gas bearings among gas bearings according to comparative examples, and the base plate 18 has bearing segments 19 arranged at equal intervals in the circumferential direction, as shown in FIG. A plurality of bearing segments 19 are fixed, and the bearing segments 19 are constructed as shown in FIG. That is, the bearing segment 16 is fixed to the base plate 18 and has an elastic wave-shaped bump oil 20.
and a top oil 22 having one end fixed to a spacer 21 fixed to the base plate 18, a lower surface supported by a bump oil 20, and an upper surface forming a bearing surface 22a, and a top oil 22 and a bump oil 20. A restriction oil 23 is arranged between the spacers 21 and 23 and has one end fixed to the spacer 21. Further, the flat surface portion 23a of the restriction oil 23 is in contact with the top oil 22, and the protruding portion 23b is formed to protrude toward the bump oil 20 at a position corresponding to the flat surface portion 20a of the bump oil 20. . A thrust runner 24 fixed to a rotating shaft (not shown) is disposed so as to face the bearing surface 22a of the top oil 22.

Furthermore, FIG. 6 shows another comparative example of a dynamic pressure type thrust gas bearing, and the bearing segment of this comparative example includes a wave-shaped bump oil 26 fixed to a base plate 25 and having elasticity, and an upper surface of the bump oil 26. It is composed of a surface member made of a rigid body fixed to the surface plate 27, and a restriction oil 28 disposed between the surface plate 27 and the bump oil 26. Further, a thrust runner 29 fixed to a rotating shaft (not shown) is arranged to face the restriction oil 28, and the surface of the surface plate 27 facing the thrust runner 29 is a bearing surface. 27a. Furthermore, the restriction oil 28 has a flat surface portion 28 thereof.
a is in contact with the surface plate 27, and the protruding portion 28b is in contact with the flat surface portion 26a of the bump oil 26.
The bump oil 26 is formed protrudingly at a position corresponding to the bump oil 26 side.

Even if the configuration is as shown in the comparative example in FIGS. 4 and 5 and the comparative example in FIG. 6, the
It has exactly the same action and effect as explained using .

[Effect of idea]

According to the present invention, the inner surface of the holder is formed of two inner surfaces with different curvatures, and a movable body having a substantially crescent-shaped cross section is disposed on the inner surface with a larger curvature via a compensating elastic member, and the inner arcuate surface of the movable body is and the inner surface with a small curvature hold the bump oil, the elastic constant of the compensating elastic member is set smaller than the elastic constant of the bump oil, and the lower surface of the surface member is provided with:
Since a restriction oil having a protrusion protruding toward the bump oil is provided at a position corresponding to the flat surface of the bump oil, even if the rotating shaft thermally expands, the gas film thickness decreases, and the pressure increases. The movable body moves to compensate for the thermal expansion of the rotating shaft, thereby keeping the gas film thickness constant. Therefore, even if the gas bearing is used in a high-temperature environment, there is less risk of damage due to seizure or the like as in conventional gas bearings, resulting in a highly reliable gas bearing.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of a hydrodynamic journal gas bearing according to the present invention, Fig. 2 is a sectional view showing an embodiment of a hydrodynamic journal gas bearing according to a comparative example, and Figs. 3 a and b. 1 is an explanatory diagram of the operation of the gas bearing shown in FIG. 1, FIG. 4 is a partial plan view showing an example of a hydrodynamic thrust gas bearing according to a comparative example, and FIG. 5 is a cross-section of a main part of the hydrodynamic thrust gas bearing 6 is a sectional view of a main part showing another example of a hydrodynamic thrust gas bearing according to a comparative example, FIG. 7 is a sectional view showing an example of a conventional hydrodynamic journal gas bearing, and FIG. 8a, b
1 is a partial plan view and a sectional view of a main part of a conventional dynamic pressure type thrust gas bearing. 3... Bump oil, 3a... Flat surface part, 4
...Topf oil, 4a...Bearing surface, 15...
Restriction oil, 15a...protrusion,
20...bump oil, 20a...flat surface part,
22...Topf oil, 22a...Bearing surface, 2
3...Restriction oil, 23b...Protrusion part, 26...Bump oil, 26a...Flat surface part, 27...Surface plate, 27a...Bearing surface, 28...Restriction oil, 28b
...protrusion.

Claims (1)

[Claims for Utility Model Registration] A gas bearing in which the inner surface of a cylindrical holder is provided with a bump oil that elastically supports a surface member constituting the bearing surface, the inner surface of the holder being formed of two inner surfaces with different curvatures, A movable body having a substantially crescent-shaped cross section is disposed on the inner surface of the large curvature via a compensating elastic member, and the bump oil is held between the inner arcuate surface of the movable body and the inner surface of the small curvature, and the elastic constant of the bump oil is The elastic constant of the compensating elastic member is set to a small value, and a restriction oil is provided on the lower surface of the surface member at a position corresponding to the flat surface of the bump oil, the restriction oil having a protrusion protruding toward the bump oil. Characteristic gas bearing.