JPH0914262A - Dynamic pressure gas journal bearing - Google Patents

Abstract

PURPOSE: To stabilize bearing performance from no load to high load in a dynamic pressure gas journal bearing. CONSTITUTION: A bearing cylinder 2 made of an elastic thin plate is disposed at a rotary shaft 1 through a bearing clearance 6. Four axially extended ribs 3 are protrusively provided on the periphery of the bearing cylinder 2, and the radius of an imaginary circumscribed circle in the free state of the ribs 3 is set slightly larger than the inner diameter of a housing 4. At the time of assembly, the bearing cylinder 2 is thus compressed to generate an initial deformation to the inner surface, and the same lubricating film as a multi-plane bearing is effectively formed by this initial deformation so as to stabilize a bearing characteristic at the time of no load. Bearing performance at the time of high load can be also stabilized by adjusting the rigidity of the ribs 3. Such a bearing is also provided with vibration proof rubber 7a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure gas journal bearing used in high speed turbomachines such as expansion turbines and compressors.

[0002]

2. Description of the Related Art Conventionally, a dynamic pressure gas journal bearing as disclosed in Japanese Patent Laid-Open No. 3-24319 is known as a bearing device for equipment that requires high speed rotation.
This will be described with reference to FIG. 9. In FIG. 9, reference numeral 101 is a housing, 102 is a rotating shaft, and 103 is a cylindrical sleeve interposed between the housing 101 and the rotating shaft 102 so as to surround the rotating shaft 102. It is provided inside the housing 101 as shown in the drawing.

Reference numeral 104 denotes a bearing pad made of a porous material, which is provided at both ends of the housing 101. Each bearing pad 104 on the housing 101
An air supply passage 108 is formed corresponding to the above, and gas, for example, air is supplied to the bearing pad 104 from the gas supply source 120 via the air supply passage 108. The gas supplied to the bearing pad 104 is
It is jetted from the bearing pad 104 toward the sleeve 103, and then discharged to the outside of the housing 101 through the exhaust passage 109.

Reference numeral 105 denotes a herringbone groove for generating a dynamic pressure formed on the surface of the rotary shaft 102 along the rotational direction thereof, and as shown in the drawing, they are located near both ends of the housing 101. In addition, it is formed at two locations on the rotary shaft 102. An air layer (space) 106 is formed between the housing 101 and the sleeve 103, and an air layer (space) 107 is formed between the sleeve 103 and the rotating shaft 102. The air layer 106 and the air layer 107 are completely blocked by the sleeve 103.

In this structure, when the rotary shaft 102 is stopped or is rotating at a low speed, the rotary shaft 102 is rotated by the sleeve 1.
It is supported by the sleeve 103 while being in contact with 03. On the other hand, the sleeve 103 is rotatably supported in a non-contact manner as a body on the housing 101 (bearing pad 104) by a hydrostatic bearing composed of gas ejected from the bearing pad 104 to the air layer 106. There is. Therefore, at this time, the rotating shaft 102 rotates integrally with the sleeve 103 while being supported by the hydrostatic bearing.

After that, when the rotational speed of the rotary shaft 102 gradually increases, the viscous resistance of the air layer 106 between the housing 101 and the sleeve 103 increases, and this viscous resistance increases.
When the maximum static friction force between the rotary shaft 102 and the sleeve 103 becomes larger, a relative rotational difference occurs between the rotary shaft 102 and the sleeve 103, and in response to the relative rotational difference, the rotary shaft 10
Dynamic pressure is generated between the sleeve 2 and the sleeve 103 by the herringbone groove 105.

Further, when the rotational speed of the rotary shaft 102 increases and the rotational speed of the rotary shaft 102 reaches a steady rotational speed, the dynamic pressure (dynamic pressure bearing) generated by the herringbone groove 105 causes the rotary shaft to rotate. The sleeve 102 is supported in a non-contact state with the sleeve 103. That is, at this time, the sleeve 10 is provided by the hydrostatic bearing between the housing 101 and the sleeve 103.
3 is supported in a non-contact manner with the housing 101, and the rotating shaft 10
The rotary shaft 102 is supported by the dynamic pressure bearing between the sleeve 2 and the sleeve 103 in a non-contact manner with respect to the sleeve 103.

The angular velocity ω of the sleeve 103 at this time is such that the radial thickness of the air layer 106 is h ₁ (about 5 to ₁₀ μm) and the radial thickness of the air layer 107 is h ₂ (about 5 to 10 μm). , Where the angular velocity of the rotating shaft 102 is ω ₀ , it is expressed by the formula [1].

(Equation 1) However, the radial thickness t of the sleeve 103 is determined by
It should be sufficiently smaller than the shaft diameter d.

Therefore, when the rotation speed of the rotary shaft 102 reaches a steady speed, the sleeve 103 also rotates at a desired speed lower than the rotation speed of the rotary shaft 102. Therefore, even when the rotating shaft 102 swells in the radial direction due to centrifugal force during high-speed rotation, the inner and outer diameters of the sleeve 103 also swell, so that they do not come into contact with each other. Also the sleeve
Since the angular velocity ω of 103 is smaller than the angular velocity ω ₀ of the rotating shaft 102, the bulge due to the centrifugal force is small, and the sleeve 103 can be formed without increasing the radial thickness h ₁ of the air layer 106.
Can be prevented from contacting the bearing pad 104. That is, contact at high speed rotation can be prevented without reducing the rigidity of the hydrostatic bearing.

In the above-mentioned dynamic pressure gas journal bearing (shown in FIG. 9), the sleeve 103 is supported by the gas supplied from the gas supply source 120 in the floating state in the casing 101.
Instead of this, a sleeve support structure as shown in FIGS. 7 and 8 has been conventionally proposed. FIG. 7 shows a bump foil type journal bearing, which has a bearing gap 6 around the rotary shaft 1 (the bearing gap 6 is the air layer 107 of FIG. 9).
The bearing cylinders 2 (top foil, corresponding to the sleeve in FIG. 9), which are arranged with a space (corresponding to the gap of 1), are elastically supported to the housing 4 via bump foils 17. There is.

When a load is applied to the rotary shaft 1, the bearing cylinder 2 is deformed so as to fit the rotary shaft 1, which gives strain to the bump foil 17 and also to the bump foil.
A contact surface between 17 and the housing 4 is slipped to provide bearing damping. FIG. 8 shows a leaf foil type journal bearing in which a plurality of leaf foils 18 are arranged around the rotary shaft 1 with a bearing gap 6 therebetween so as to partially overlap each other. The leaf foil 18 is deformed so as to fit the rotating shaft 1 due to the action of the axial load, but at that time, the friction between the leaf foils 18 is generated in the foil contact portion 19 to assist the damping in the bearing. There is.

[0012]

By the way, in the conventional dynamic pressure gas journal bearing having a bearing surface made of an elastic body as shown in FIGS. 7 and 8, when the load changes during operation, (1) Under load or extremely light load, in the case of the bump foil type, the amount of deformation of the bearing cylinder is small and the operating state is similar to that of a rigid true circular bearing, so that stability is lacking. In this respect, the leaf foil bearing has a multi-faceted bearing surface, and a lubricating film pressure is generated in the entire interior of the bearing, so that the vibration damping effect is high even under no load. (2) On the other hand, when a heavy load is applied, the bump foil type can withstand the heavy load by adjusting the rigidity of the bearing cylinder and the bump foil, but the leaf foil type can increase the rigidity of the foil. Since the foil has a simple support structure, it is difficult to increase the structural rigidity, and the load bearing limit becomes low. For these reasons, a bearing whose bearing surface is made of an elastic material is
There is a problem that the applicable range is limited to a self-supporting rotary machine or a vertical rotary machine in which the load does not change during operation. An object of the present invention is to provide a dynamic pressure gas journal bearing which solves the above problems.

[0013]

In order to achieve the above-mentioned object, the dynamic pressure gas journal bearing of the present invention is disposed in the dynamic pressure gas journal bearing outside the rotary shaft with a gap between the rotary shaft and the bearing gap. A bearing cylinder made of a thin plate of metal or other elastic body, and a housing made of a cylindrical body that is arranged outside the bearing cylinder with a gap and is stiffer than the bearing cylinder. A plurality of ribs that extend in the axial direction on the outer peripheral surface and whose outer end surface is inscribed in the inner peripheral surface of the housing are provided, and the diameter of the virtual circumscribed circle of the plurality of ribs in the free state is It is characterized in that it is set to be the same as the diameter of the peripheral surface or slightly larger than the diameter of the inner peripheral surface of the housing.
Further, in the dynamic pressure gas journal bearing of the present invention, the first space formed by the outer peripheral surface of the bearing cylinder, the rib and the inner peripheral surface of the housing is made of a vibration-proof rubber, a polymer gel or powder. It is characterized by enclosing a vibration damping material.

Further, in the dynamic pressure gas journal bearing of the present invention, the intermediate cylinder is provided between the bearing cylinder and the housing, and the outer peripheral surfaces of the plurality of ribs are in contact with the inner peripheral surface of the intermediate cylinder. And a plurality of second ribs that extend in the axial direction on the outer peripheral surface of the intermediate cylinder and can be inscribed on the inner peripheral surface of the housing. The diameter of the virtual circumscribed circle is set to be the same as the diameter of the inner peripheral surface of the housing or slightly larger than the diameter of the inner peripheral surface of the housing.

Furthermore, in the dynamic pressure gas journal bearing of the present invention, the cooling fluid formed in the housing in the second space formed by the outer peripheral surface of the bearing cylinder, the rib and the inner peripheral surface of the intermediate cylinder. It is characterized in that the cooling fluid can be supplied through the supply hole.

Further, in the dynamic pressure gas journal bearing of the present invention, the vibration damping rubber, polymer gel or powder is provided in the third space formed by the outer peripheral surface of the intermediate cylinder, the second rib and the inner peripheral surface of the housing. It is characterized by containing a vibration damping material such as the body.

[0017]

In the above dynamic pressure gas journal bearing of the present invention,
Since the bearing cylinder is made of an elastic body, the thickness can be adjusted so as to have appropriate rigidity with respect to the maximum load to be supported, and there is no problem in structural load capacity. Further, by applying compression to the inner diameter side of the bearing cylinder through the rib as a supporting member provided on the outer periphery of the bearing cylinder, the inner surface of the bearing cylinder will have some deformation in the initial state, and thus the multifaceted bearing Similarly, the lubricating film is effectively formed, and effective bearing characteristics can be exhibited even under no load. Further, the vibration damping material enclosed in the first space or the third space acts to damp the vibration of the rotating shaft. Further, the cooling fluid also serves to cool the bearing portion.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A dynamic gas journal bearing as an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a bearing surface of the first embodiment, and FIG. 2 is a bearing surface of the second embodiment. 3 (a) to 3 (c) are sectional views of a modified example of the rib and are enlarged views of a portion III in FIG. 1, FIG. 4 is a sectional view of a bearing surface of the third embodiment, and FIG. 6A is a sectional view of the bearing surface of the fourth embodiment, FIG. 5B is a sectional view taken along the line AA of FIG. 5A, and FIG.
6A is a sectional view of the bearing surface of the fifth embodiment, and FIG.
It is a BB arrow sectional drawing of (a).

First, the first embodiment will be described with reference to FIG. Also in this first embodiment, a bearing cylinder 2 made of a thin plate of metal or other elastic body is arranged around the rotary shaft 1 with a proper bearing gap (space for dynamic pressure gas) 6 therebetween. The bearing cylinder 2 has a structural rigidity suitable for bearing performance due to its thickness and the arrangement interval of the plurality of ribs 3 provided on the outer periphery thereof. In this embodiment, four ribs 3 are provided at 90 ° intervals. Reference numeral 4 indicates a housing, and reference numeral 5 indicates a bearing back space formed by the bearing cylinder 2, the housing 4 and the rib 3. Further, the inner diameter of the housing 4 is set to be smaller than the virtual circumscribing circle of the rib in the free state, and when the bearing cylinder 2 and the rib 3 are inserted into the housing 4, the bearing cylinder 2 is distorted into a non-circular state in advance. Is able to.

With this configuration, even when the center of the rotary shaft 1 operates near the center of the housing 4 under a very light load, the bearing clearance 6 formed by the rotary shaft 1 and the bearing cylinder 2 is formed. The shape can be maintained in a wedge shape, the pressure of the lubricating film can be easily generated, and the stability of the shaft system can be increased. Further, by increasing the rigidity of the ribs 3, the load capacity can be increased and stable bearing performance can be exhibited even under high load.

Next, a second embodiment will be described with reference to FIG.
Although the first embodiment described above improves the performance of the lubricating film itself in the conventional example, it does not support the deceleration of the bearing due to the friction effect of the foil. In the second embodiment, in the bearing back space (first space) 5 formed by the bearing cylinder 2, the housing 4 and the ribs 3 in the first embodiment, a bearing made of vibration-proof rubber, polymer gel or powder is used. Damping material (vibration damping material)
7a is enclosed. In the second embodiment, with this configuration, it is possible to delay the deformation of the bearing cylinder 2 with respect to the vibration of the rotary shaft 1, thereby improving the vibration damping effect in addition to the above effects of the first embodiment. The effect of being able to do is obtained.

FIG. 3 shows a modification of the rib 3 in the first and second embodiments. The rib indicated by reference numeral 3a in FIG. 3 (a) is composed of a flexible circular pipe, It is configured to allow the deformation of the rib 3a. As a result, stable operation can be guaranteed even when the load direction of the bearing load changes. Further, the rib indicated by reference numeral 3b in FIG. 3 (b) is composed of a mountain-shaped spring, and if both ridges 31b and 31b of the housing 4 and the rib 3b are allowed to slip,
A friction damping effect similar to that of the conventional bump foil bearing can be added to the bearing characteristics. Further, as shown by reference numeral 3c in FIG. 3 (c), the rib is composed of an elastic body having a triangular cross section, and the rib 3c and the surface of the housing 4 are rotatably supported. When set to be relatively rigid,
An optimal gap shape can be autonomously formed by the inclination of the ribs, and the load capacity can be improved.

Next, a third embodiment will be described with reference to FIG.
In the third embodiment, the intermediate cylinder 8 is interposed between the bearing cylinder 2 and the casing 4 in the above-described first embodiment, so to speak, the bearing cylinder has a double structure. The four second ribs 8 are also provided in the intermediate cylinder 8 at 90 ° intervals, and when the bearing cylinder 2 and the intermediate cylinder 8 are assembled to the casing 4, the second rib 8 and the rib 3 (hereinafter referred to as “the first 1 rib 3 ") are arranged at 45 ° intervals. In the first embodiment, the bearing characteristics become non-uniform in the circumferential direction depending on the position where the first rib 3 exists, and the design becomes complicated when the load direction changes, but this can be avoided in the third embodiment. .

That is, as shown in FIG. 4, when the first ribs 3 are arranged vertically and horizontally and there is no intermediate cylinder 8, when the load applied to the rotary shaft 1 is vertically downward, The bearing cylinder 2 and the first rib 3 directly contact the housing 4, and the rigidity of the first rib 3 causes the bearing cylinder 2 to move.
Is less likely to deform. On the other hand, by providing the intermediate cylinder 8, when the rotating shaft 1 receives a vertically downward load, the first rib 3 and the bearing cylinder 2 existing in that direction are displaced downward. This is transmitted to the intermediate cylinder 8
Is vertically distorted, so that
The first ribs 3 distort the bearing cylinder 2 vertically, and as a deformation effect, the same deformation effect as that of the first embodiment when the first rib 3 does not exist in the load direction can be produced.

Further, when the vibration damping material 7a such as the vibration-proof rubber, polymer gel, powder, etc. shown in the second embodiment is enclosed in the space on the back side of the bearing to provide damping, of the two spaces It is suitable to fill the outer space (third space) 7 formed by the intermediate cylinder 8, the second rib 9 and the bearing housing 4. This is because the space 7 formed by the bearing cylinder 2, the intermediate cylinder 8 and the second rib 9 moves due to the deformation, so that an inertial force is generated and the expected bearing performance may not be exhibited.

Further, a fourth embodiment will be described with reference to FIGS. 5 (a) and 5 (b). In the fourth embodiment, the cooling fluid 12 is supplied from the outside of the bearing to the bearing back space (second space) 5A from the outside of the bearing through the space 7 in which the housing 4 and the anti-vibration rubber are sealed. The hole 10 is provided. Sign
Reference numeral 11 denotes a supply groove for the cooling fluid 12 formed on the outer peripheral surface of the housing 4, and the supply groove 11 communicates with the supply hole 12. This is a cooling fluid from the outside for the purpose of removing frictional heat generated when the shaft rotation speed is extremely high.
The cooling effect is measured by supplying 12 to the bearing back space 5A and discharging it from the bearing side.

In the conventional type, since the structural elasticity of the foil is generally small, the influence of thermal elongation of the shaft is not important,
Since the dynamic pressure gas journal bearing of the present invention is a bearing for heavy loads, the structure rigidity of the bearing is high, and when used at high speed, cooling is important because the structure tends to clog gaps. To deal with. The fifth embodiment shown in FIGS. 6 (a) and 6 (b) corresponds to the fourth embodiment shown in FIGS. 5 (a) and 5 (b).
According to the improvement of the embodiment, the supply hole 10 is formed parallel to the rotary shaft 1,
In order to prevent the fluid 12 supplied from the supply hole 10 from leaking from the side end of the casing 4, an outer peripheral wall 13 and an inner peripheral wall 15 are provided at one end of the casing 4 so as to project from the outer peripheral wall 13 and the inner peripheral wall 13. A bellows 14 is stretched between the peripheral wall 15 and the peripheral wall 15.

With this configuration, the cooling fluid 12 is guided to the radial passage 16 surrounded by the bellows 14 at one end of the casing 4,
From here, the fluid can be cooled through the bearing back space 5 to cool the bearing. This embodiment is shown in FIG.
This structure is most suitable for applications where it is desired not to leak the cooling fluid 12 to the right side of the radial passage 16. The fluid 12 is shown in FIG.
Supplied from the left side in (b). Although FIG. 6 (b) shows an example in which the radial passage 16 is provided at one side end portion of the casing 4, this is used in combination with the fourth embodiment to provide the radial passages at both side end portions of the casing 4. The gas flowing through the bearing gap 6 and the cooling fluid 12 can be separated from each other.

[0029]

As described in detail above, according to the dynamic pressure gas journal bearing of the present invention, the following effects and advantages can be obtained. (1) Stable bearing performance can be exhibited from no load to high load. As a result, not only conventional self-weight bearing type rotary machines and vertical machines, but also both bearing stability under no load and load bearing capacity under rated load such as compressors with built-in gearbox The present invention can be applied to rotary machines that require the above-mentioned requirements, and by applying the present invention to these machines, the seal system can be simplified and the structure can be made compact. (2) Since the bearing structure can be simplified, the manufacturing cost is lower than that of the conventional gas bearing configured with a rigid body, and the bearing clearance can be easily set, so that the assembly cost can be reduced. (3) Since it can perform effective cooling, it can be applied to heavy-duty bearings with high structural rigidity.

[Brief description of the drawings]

FIG. 1 is a sectional view of a bearing surface of a dynamic pressure gas journal bearing according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a bearing surface of a dynamic pressure gas journal bearing according to the second embodiment.

FIG. 3A is a cross-sectional view of a modified example of the rib. (b) A sectional view of a modified example of the rib. (c) A sectional view of a modified example of the rib.

FIG. 4 is a sectional view of a bearing surface of a dynamic pressure gas journal bearing as the third embodiment.

FIG. 5 (a) is a sectional view of a bearing surface of a dynamic pressure gas journal bearing as the fourth embodiment. (b) A sectional view taken along the line AA of FIG.

FIG. 6 (a) is a sectional view of a bearing surface of a dynamic pressure gas journal bearing as the fifth embodiment. (b) BB arrow sectional drawing of FIG. 6 (a).

FIG. 7 is a sectional view of a bearing surface of a bump foil type bearing in a conventional dynamic pressure gas journal bearing.

FIG. 8 is a sectional view of a bearing surface of a leaf foil type bearing in a conventional dynamic pressure gas journal bearing.

FIG. 9 is a sectional view of a bearing surface of a conventional dynamic pressure gas journal bearing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 rotating shaft 2 bearing cylinder 3 (first) rib 4 housing 5 bearing back space (first space) 5A second space 6 bearing clearance 7 third space 7a vibration damping rubber / vibration damping material such as polymer gel or powder 8 Intermediate Cylinder 9 Second Rib 10 Cooling Fluid Supply Hole 11 Supply Groove 12 Cooling Fluid 13 Outer Wall 14 Bellows 15 Inner Wall 16 Radial Passage 17 Bump Foil 18 Leaf Foil 19 Foil Contact Area

Claims (5)

[Claims] 1. A dynamic pressure gas journal bearing, wherein a bearing cylinder made of a thin plate of metal or other elastic body is disposed outside the rotary shaft with a gap between the rotary shaft and the bearing, and outside the rotary cylinder. The housing is provided with a gap and is made of a cylindrical body that is stiffer than the bearing cylinder, and extends axially to the outer peripheral surface of the bearing cylinder, and the outer end surface can be inscribed in the inner peripheral surface of the housing. A plurality of ribs are provided, and the diameter of the virtual circumscribing circle in the free state of the plurality of ribs is set to be the same as the diameter of the inner peripheral surface of the housing or slightly larger than the diameter of the inner peripheral surface of the housing. A dynamic pressure gas journal bearing, which is characterized in that 2. A vibration damping material such as a vibration-proof rubber, a polymer gel or a powder is enclosed in a first space defined by the outer peripheral surface of the bearing cylinder, the rib and the inner peripheral surface of the housing. The dynamic pressure gas journal bearing according to claim 1, wherein 3. Between the bearing cylinder and the housing,
The intermediate cylinder is interposed so that the outer end surfaces of the plurality of ribs come into contact with the inner peripheral surface of the intermediate cylinder, and the intermediate cylinder extends axially to the outer peripheral surface of the intermediate cylinder and the inner peripheral surface of the housing. A plurality of second ribs that can contact each other are provided, and the diameter of the virtual circumscribing circle in the free state of the plurality of second ribs is the same as the diameter of the inner peripheral surface of the housing or the inner peripheral surface of the housing. The dynamic pressure gas journal bearing according to claim 1, wherein the diameter is set to be slightly larger than the diameter. 4. The cooling fluid can be supplied to a second space formed by the outer peripheral surface of the bearing cylinder, the rib and the inner peripheral surface of the intermediate cylinder through a cooling fluid supply hole formed in the housing. The dynamic pressure gas journal bearing according to claim 3, wherein the dynamic pressure gas journal bearing is configured as follows. 5. A vibration damping material such as a vibration-proof rubber, polymer gel or powder is enclosed in a third space formed by the outer peripheral surface of the intermediate cylinder, the second rib and the inner peripheral surface of the housing. The dynamic pressure gas journal bearing according to claim 3 or 4, characterized in that