JPS60136615A - Fluid bearing construction - Google Patents

Abstract

PURPOSE:To improve stability at a high speed by providing a bearing foil on which a pressure releasing passage is formed, a damp foil for damping vibration, between said bearing foil and a supporting surface, and a spring foil for resiliently supporting said damp foil on said supporting surface. CONSTITUTION:A bearing foil 3 is provided close to a rotary shaft 1, to form a gas film on a bearing surface 3a on the inner periphery of the foil 3. More than one small hole 8, as a pressure releasing passage, is formed through the bearing foil 3 in the board thickness direction, nearly at the center in the axial direction of the rotary shaft. A damp foil 4 is provided on the bearing-foil 3 supporting surface 2a side, and a vacant space H is formed between this damp foil 4 and the outside of the bearing foil 3, to admit the surplus pressure of the gas film on the bearing surface 3a through the small holes 8, fulfilling a vibration damping function. Furthermore, a spring foil 5, which resiliently supports the damp foil 4, is provided on the damp-foil 4 supporting surface 2a side.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a hydrodynamic bearing structure for gas, oil, water, steam, etc.
In particular, the present invention relates to a hydrodynamic bearing structure that can exhibit excellent high-speed stability in foil bearings that utilize elastic foils.

[Technical background of the invention and its problems] A fluid bearing is a type of bearing that forms a high-pressure fluid film between a rotating shaft and a bearing surface and supports the rotating shaft using this fluid film pressure. It has the characteristics of low friction loss and high load capacity, and is extremely effective as a bearing for high-speed rotating shafts of turbo compressors, turbo expanders, turbo chargers, turbo refrigerators, etc.

Rigid bearings and foil bearings are known as gas bearings. In rigid bearings, the gas film breaks due to shaft deformation, etc., so foil bearings are currently being researched and developed.

The applicant of this application also previously proposed the basic structure of a foil bearing and found that it exhibits excellent performance.

By the way, in general, when the bearing surface type of a gas bearing is a high load capacity type such as a brane, spiral group, or pocket 1 type, self-excited vibration is induced in the high speed rotation range and the bearing surface becomes unstable. This phenomenon is caused by the compressibility of the gas film and the shape of the bearing, and is an unavoidable problem in high-load-capacity bearings, but improvements are desired in view of the need for faster rotating shafts.

[Object of the Invention] The present invention was devised in view of the above-mentioned problems, and its purpose is to provide a hydrodynamic bearing structure that can exhibit excellent high-speed stability in a foil bearing.

[Summary of the Invention] According to the present invention, the above object is achieved by the following configuration.

That is, in a fluid bearing that is formed by laminating elastic foils on a bearing surface and supports a rotating shaft by fluid film pressure, the bearing foil forms a fluid film on the bearing surface and the fluid on the bearing surface. a pressure release path that releases pressure in order to regulate membrane pressure; and a dump foil that is provided between the bearing surface and the bearing foil and that introduces the pressure released from the pressure release path to damp vibration. , a springf for elastically supporting the dump foil on the support surface [Embodiment of the Invention] A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, a journal gas bearing is exemplified as the fluid bearing.

As shown in FIG. 1, 1 is a rotating shaft of a turbo compressor or the like, and an annular bearing case 2 is provided around the outer periphery of this rotating shaft 1. As shown in FIG. Between the rotating shaft 1 and the bearing surface 2a on the inner circumference of the bearing case 2, elastic foils 3.4.5 for supporting the rotating shaft 1 by gas film pressure are laminated.

These elastic foils 3.4.5 are shown in FIG.
One end thereof is joined to a fixed piece 6 to be integrated, and this fixed piece 6 is engaged and attached to an engagement groove 7 formed in the support surface 2 along the direction of the rotation axis.

A bearing foil 3 is provided closest to the rotating shaft 1 and is used to form a gas film on the inner circumferential bearing surface 3a. In the illustrated example, a plain bearing surface 3a with a smooth bearing surface is shown, but it may also be formed with spiral groups, tapered lands, pockets, etc.

In particular, a plurality of small holes 8 serving as pressure release passages are formed in the bearing foil 3 at approximately the center of its width in the direction of the rotation axis and extending through the plate thickness direction. The pores 8 are configured to release the excess pressure of the gas film formed on the bearing surface 3a, thereby controlling the pressure of the gas film on the bearing surface 3a, thereby suppressing excessive pressure rise.

The other 5 is a spring foil which is arranged on the bearing surface 2a and elastically supports a dump foil 4, which will be described later, in order to resiliently support the gas film pressure acting on the bearing foil 3 from the bearing surface 2a. The spring foil 5 is formed into an elongated rectangular shape as shown in Fig. M3, and bent grooves 58 are formed at predetermined pitches in the longitudinal direction. And this spring foil 5
is bent along the bearing surface 2a as shown in FIG.

A dump foil 4 is provided between the spring foil 5 disposed on the support surface 2a and the bearing foil 3 disposed on the rotating shaft 1 side. The spring foil 5 is brought into frictional contact with the outer periphery of the dump foil 4, and the inner periphery faces the outer periphery of the bearing foil 3 in which pores 8 are formed. And the air gap H between these foils 3.5
The structure is such that pressure is introduced from the pores 8... into the pores 8. That is, the dump foil 4 forms a void 1-1 on the outside of the bearing foil 3, and the excess pressure of the gas film on the bearing surface 3a is introduced into the void ml-1 from the pores 8 serving as pressure release paths. It is configured to exhibit a vibration damping function. In this embodiment, the inner circumferential surface on the gap side is formed into a plain shape.

Next, the operation of the present invention will be described.

As shown in FIGS. 1 and 5, when the rotating shaft 1 rotates at a speed V in the direction of the arrow, a load is applied between the bearing foil 3 and the rotating shaft 1 due to the entrainment action based on the viscosity of the gas around the rotating shaft 1. A gas film for supporting W is formed with a considerable thickness.

In the plain journal bearing shown in this embodiment, if the external damping is not very large, self-excited vibration called whirl will occur at twice or more the primary critical speed, making it unstable. This phenomenon is based on the reduction in shaft eccentricity due to excessive gas film pressure that occurs due to the thickness of the gas film.

The present invention has a pressure release path (in this embodiment, the pore 8...
) The damping foil 4 controls the generation of excessive gas film pressure, and the released pressure is effectively used as external damping to exert a damping effect.

In other words, part of the gas film pressure generated on the bearing surface 3a is absorbed by the pores 8.
... flows into the gap 1-1 between the dump foil 4 and the bearing foil a. Therefore, an excessive increase in gas membrane pressure can be controlled as much as possible.

In addition, the void H into which the released pressure is introduced functions as a squeeze film damper in the film thickness direction and exhibits a vibration damping effect. This effect is exerted by the elastic foil component of 3°4.5, and has a remarkable effect in the high speed range. In addition, in the case of a journal bearing in which the rotating shaft 1 is placed horizontally, an inverted wedge-shaped gas film (spreading toward the end in the rotational direction) is formed on the bearing surface on the anti-load side (the upper bearing surface in Fig. 1). Negative pressure tends to occur.

In this case, the negative pressure acts to lift the rotating shaft 1, leading to instability. On the other hand, in the present invention, the generation of negative pressure can also be prevented by the pressure release path (pores 8...).

These synergistic effects make it possible to stabilize rotations up to high speeds without sacrificing the advantages of high load capacity dynamic pressure type gas bearings. Therefore, it is possible to improve the efficiency of high-speed rotating equipment such as turbo machinery.

Furthermore, by forming the pores 8, which serve as pressure release channels, dust, etc. that tend to accumulate on the bearing surface 3a can be removed to the outside of the bearing surface 3a as the pressure is released, improving reliability. You can improve.

The bearing structure of the present invention also includes a deformable elastic foil 3,
4.5, it can also cope with thermal deformation and centrifugal expansion of the rotating shaft 1.

In the above explanation, the gap 1-1 formed by the bearing foil 3 and the dump foil 4 is a local self-restriction type static pressure gas bearing that supplies air using the pores 8 as fluid restrictors. By distributing and arranging them, it contributes to high-speed stabilization. The self-throttling type static pressure gas bearing is a type of static pressure gas bearing with a small gas flow rate, and it limits the drop in the load capacity of the gas group formed on the upper surface of the bearing foil 3 while also reducing excess pressure. ] can be released. This function is achieved by the fact that the bearing foil 3 and the dump foil 4 are made of highly elastic foils, and is a feature not found in rigid bearings.

Furthermore, the following configuration of a foil gas bearing for supporting small, high-speed, low-load vehicles, etc. is also effective. In the case of low loads, the self-restriction type static pressure gas bearing can be replaced with a locally pocketed orifice restriction type or surface restriction type static pressure gas bearing to increase the gas flow rate and fill the air gap H more actively and locally. It can function as a distributed hydrostatic bearing, increasing damping capacity and improving stability.

The pocket or surface aperture may be formed on either the dump foil 4 or the dump foil side surface of the bearing foil 3.

[Modifications] Figures 6 to 19 show modifications of the above embodiment.

What is shown in FIGS. 6 to 9 employs an elastic body 9 constructed as follows in place of the bent spring foil in the above embodiment.

As shown in FIG. 8, the projectile body 9 consists of a spring foil 5 and a lattice foil 1O, and the lattice foil 10 has m11... arranged in a vertical lattice at regular intervals along its longitudinal direction. The spring foil 5 is a lattice foil 1O.
The teeth 11 are assembled so that they are alternately placed on the front and back sides. The other configurations are the same as those of the above embodiment.

10 and 11, instead of the bearing foil formed of a plain bearing surface in the above embodiment, the bearing surface 3a is oriented from the side to the center along the rotational direction V of the rotating shaft. A herringbone-shaped group 12 is machined deeper than the bearing surface 3a. In this embodiment, the pressure release path includes a plurality of pores 8 formed in the central part of the bearing surface 3a along the circumferential direction and through the plate thickness direction, and these pores 8 . It is composed of a central end of the group (group end) 12a, and a throttle passage 13 formed between. Also, although not shown, the throttle passage is omitted and the group end 1 is directly connected.
Pores may be formed in 2a...

In gas bearings in which groups are formed on the bearing surface 3a in this way (the same applies to the spiral group type and pocket type described later), the above-mentioned brane type bearing is formed between the bearing surface and the rotating shaft. On the other hand, it has a pressure generating mechanism similar to a viscous pump that increases the pressure by entraining action of gas along the groups 12... Therefore, bearing surface 3a
Even if the rotary shaft 1 and the rotary shaft 1 are configured coaxially, the boosting function can be achieved.

That is, when the rotating shaft 1 rotates, gas is drawn into the group 12 from one end 12b of the group 12 released outward from the bearing surface 3a. The pressure is gradually increased within the groups 12..., and the maximum pressure is generated at the group ends 12a, forming a gas film.

This group type bearing also has a high load capacity, but like the brane type bearing described above, it becomes unstable at high speeds. On the other hand, in the present invention, the excess pressure is removed from the group ends 12a... and the passages 13... and the pores 8...
Since the pressure can be released through the air gap 1, the generation of self-excited vibration can be suppressed, and the released pressure can be used for the squeeze damper function as external damping in the air gap 1, thereby greatly improving stability.

12 to 18 show the case where the present invention is applied to a thrust gas bearing. In FIG. 12, 14 is a thrust collar of a rotating shaft, and the thrust collar 14 is rotating in the V direction. In addition, in order to support the thrust load W of the thrust collar 14 by forming a gas film,
A bearing case 2 is provided facing and facing the thrust collar 14, and the bearing surface 2a of the bearing case 2 is provided with annular elastic foils 3, 4.15.
16.5 is installed. These elastic foils3
．． 4,15.16. ．． 5 is a bearing foil 3.5 facing the bearing case 2 from the thrust collar 14 side. Five dump foils 4, comb foils 15, spring foils 5, and comb foils 16 are sequentially laminated. These foils 3゜4.15.16.5 are all annular,
Their plan views are shown in FIGS. 13 to 17, respectively.

The surface of the bearing foil 3 forms a bearing surface 3a, and a spiral groove, ie, a spiral group 12, for generating gas film pressure is formed on this bearing surface 3a. In addition, the bearing foil 3 includes a comb-shaped foil 15, etc.
A plurality of attachment holes 3b for fixing the foil in a stacked state with another foil are provided on the outer circumference thereof at appropriate intervals (six holes in the illustrated example). Also dump foil 4. Similarly, the spring foil 5 is provided with mounting holes 4a and 5a on its outer circumference.

The comb-shaped foil 15 consists of a ring-shaped outer peripheral part 15b and a ring-shaped outer peripheral part 15b extending radially from the inner peripheral surface toward the center of the comb-shaped foil 15 (the comb teeth 15C extend along the outer peripheral part 15b). A plurality of mounting holes 15a are provided radially at equal pitches.Furthermore, mounting holes 15a are provided in the outer peripheral portion 151) of the comb-shaped foil 15. The comb-shaped foil 16 also has the same shape and dimensions as the comb-shaped foil 15, and has comb teeth 160 provided at an equal pitch on the outer peripheral portion 16tl, as well as attachment holes 16a.

The structural difference between the comb-shaped foil 15 and the comb-shaped foil 16 is that the mounting holes 15a for the comb teeth 15C and 16C,
There is a shift in the processing position of 16a. That is, the mounting hole 15a,
16a are comb teeth 15C and 16 provided at equal pitches.
They are provided so as to be shifted by 1/2 pitch from each other with respect to G. Therefore, bearing foil 3, dumping foil 4. Comb-shaped foil 15, spring foil 5, comb-shaped foil 1G
These mounting holes 3a, 4a, 15a, 5a
, 16a are aligned and attached to the bearing case 2 in a stacked manner, as shown in FIG. 12, the comb teeth 15
C and 16c are alternately arranged at 1/2 bits on both sides of the spring foil 5 along the circumferential direction.

In such a thrust gas bearing, as shown in FIG. 18, the group end 1 of the spiral group 12...
A pore 8 is formed in 2a..., and this pore 8... communicates with the FJf I-1 to produce the same effect as in the above embodiment.

In addition, FIG. 19 shows a pocket type group 17 in place of the spiral croup.

Although not shown, the present invention can also be applied to a conical bearing.

Incidentally, in the above-mentioned embodiments and modified embodiments, the bearing surface of the bearing foil 3 and the surface processing of the dump foil 4 can be easily performed by photo-etching or the like, and are excellent in mass production and cost advantages.

In the above embodiments and modified embodiments, a fluid bearing that uses gas has been exemplified and explained, but a fluid bearing that uses oil, water, steam, or the like can have similar effects.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

(1) In order to control an excessive rise in fluid film pressure on the bearing surface, a squeeze damper is installed between a pressure release path that releases excess pressure and the bearing foil by introducing the pressure released from this pressure release path. By using the dump foil etc. that make up the structure, it is possible to suppress the occurrence of self-excited vibration and achieve excellent high-speed stability.

(?) Also, the pressure release path can remove foreign matter such as dust contained in the fluid from the bearing surface, improving the reliability of the bearing function.

(3) The pressure release path can be easily and inexpensively formed by photoetching.

(4) There is little decrease in load capacity.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing a preferred embodiment of the present invention, and FIG.
3 is a perspective view of a spring foil, FIG. 4 is a perspective view of a bent state of the spring foil, FIG. 5 is a developed cross-sectional view in the circumferential direction of FIG. 7 is a perspective view of the bearing component, FIG. 8 is a plan view showing the assembled state of the projectile body, FIG. 9 is a developed sectional view in the circumferential direction of FIG. 6, Fig. 10 is a perspective view showing a herringbone-shaped bearing foil, Fig. 11 is an enlarged plan view of section A in Fig. 10, Fig. 12 is a partial side sectional view when applied to a thrust bearing, Fig. 13 14 is a plan view showing a dump foil, FIG. 15 is a plan view showing a comb-shaped foil, FIG. 16 is a plan view showing a spring foil, and FIG. 17 is a plan view showing a spiral group thrust bearing foil. Plan view showing another comb foil, 1st
FIG. 8 is an enlarged plan view of section B in FIG. 13, and FIG. 19 is a partial perspective view showing a bearing foil having pocket-type groups. In the figure, 1 is the rotating shaft, 2a is the bearing surface, 3 is the bearing foil,
3a is a bearing surface, 4 is a dump foil, 5 is a spring foil, and 8 and 13 are pores and throttle passages illustrated as pressure release passages. Patent applicant: Patent attorney representing Ishikawajima-Harima Heavy Industries Co., Ltd.
Nobuo Kinuya 16th Ward

Claims (1)

[Claims] In a fluid bearing that is formed by laminating an elastic foil on a bearing surface and supports a rotating shaft by fluid film pressure,
a bearing foil for forming a fluid film on the bearing surface; a pressure release path for regulating the pressure of the fluid film on the bearing surface; and a pressure release path provided between the bearing surface and the bearing foil. 1. A fluid bearing structure comprising: a dump foil for damping vibration by introducing release pressure from the pressure release path; and a spring foil for elastically supporting the dump foil on the support surface.