JPH0520606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a foil thrust bearing in which elastic foils are laminated, and more particularly to a foil thrust bearing with an improved support structure for elastic foils.

[Technical background of the invention and its problems] Hydrodynamic bearings are a system that forms a high-pressure fluid film between the rotating shaft and the bearing surface and supports the rotating shaft using the film pressure, so there is little friction loss and turbo compression. It is extremely suitable for high-speed rotating shafts of machines, turbo expanders, turbo chargers, turbo refrigerators, etc.

As hydrodynamic bearings, there are known rigid bearings in which the bearing member is rigid and foil bearings in which the bearing member is elastically deformable. However, rigid bearings have a drawback in that the fluid film is prone to breakage due to shaft deformation or the like. For this reason, research and development on foil bearings is currently underway, but there has been a problem with foil bearings in that they lack high-speed stability.

Therefore, the present inventor proposed a new foil bearing (Japanese Patent Application No. 58-242082) which has excellent high-speed stability. This bearing is made by stacking elastic foils a, b, c, d, and e in the order shown in Figure 1, and the elastic foils a to e have their mounting holes f provided on their outer peripheries aligned. It is fixed and assembled onto the bearing surface using bolts, etc.

However, due to the supporting structure of this foil bearing, there is a problem with thermal deformation of the elastic foils a to e, particularly thermal expansion and contraction in the radial direction of the foils. That is, when the elastic foils a to e undergo thermal expansion (or thermal contraction), the mounting hole f can be regarded as a fixed point, so excessive stress is generated in the mounting hole f, and the elastic foil, which is the bearing surface, is wrinkled. This will lead to a decline in bearing performance.

As a countermeasure against such thermal expansion, a "thrust bearing" (Japanese Unexamined Patent Publication No. 1983-6131) has been proposed. This proposal provides a flexible bearing insert assembly with a flexible foil-like membrane, a concentric contour ring supporting the foil-like membrane, and a spring element mounting this ring on a base member,
The recovery effect of the radial spring elements prevents crown-shaped thermal deformation.

However, this proposal requires a supporting spring and a base member with a complicated structure in addition to the foil-like thin film, which may lead to an increase in the number of parts, an increase in the number of processing steps, and an increase in cost.

In view of the above circumstances, the present invention was devised to provide a foil thrust bearing that can prevent thermal deformation of an elastic foil, and that can be easily and inexpensively manufactured with a simple structure.

[Means for Solving the Problems] The present invention supports the thrust load of the rotating shaft by the fluid film pressure formed between the rotating shaft and the rotating shaft by layering an elastic foil on the bearing surface while surrounding the rotating shaft. In such a foil thrust bearing, there is a support plate provided radially outward of the elastic foil and having a mounting hole for fixing to the bearing surface, and a position of the mounting hole to connect the support plate and the elastic foil. and a connecting member provided circumferentially apart from the connecting member.

[Operation] With the above configuration, the elastic form forms a fluid film between itself and the rotating shaft, and supports the thrust load of the rotating shaft by the pressure of the fluid film. The support plate fixes the elastic form via the connecting member by inserting bolts or the like into the mounting holes. The connecting member allows thermal displacement of the elastic form in the radial direction at a position offset from the mounting hole, and prevents deformation such as wrinkles from occurring.

[Embodiment of the Invention] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 2 and FIG. 3, which are circumferential cross-sectional views, 12 is a rotating shaft of a turbo compressor, etc.;
Further, 1 is a thrust collar of the rotating shaft. A bearing case 2 is provided opposite the thrust collar 1 to support the thrust load W of the thrust collar 1 by forming a high-pressure fluid film of gas, oil, water, steam, or the like. On the bearing surface 2a of the bearing case 2 facing the thrust collar 1, the bearing case 2 is attached from the thrust collar 1 side.
A bearing foil 3, a damping foil 4, a comb-shaped foil 5, a spring foil 6, and a comb-shaped foil 7, which are elastic foils, are stacked one on top of the other in order. These oils 3, 4,
As shown in FIG. 4, 5, 6, and 7 are all annular so as to surround the rotating shaft.

The bearing oil 3 is the thrust collar 1.
The side surface serves as a bearing surface 3a, and a spiral groove 3b is formed on the bearing surface 3a as a mechanism for generating high fluid film pressure. The thickness of the spiral groove 3b portion is approximately half the thickness of the bearing foil 3 surrounding the spiral groove 3b. spiral groove 3b
A small hole 8 is formed at the tip of the bearing oil 3 so as to pass through the bearing oil 3. The small holes 8 release excess fluid film pressure to the damp oil 4 side, causing the oil system to function as a squeeze damper. This can suppress self-excited vibrations during high-speed rotation and improve the high-speed stability of the bearing.

Further, a mounting foil ring 9 serving as a support plate is provided on the outer peripheral side of the bearing foil 3, and the bearing foil 3 and the mounting foil ring 9 are connected by a thin plate-shaped rib 10 as a connecting member. . Bearing oil 3 and rib 1
0 and the mounting foil ring 9 are manufactured integrally. Mounting holes 1 are provided at equal intervals on the mounting foil ring 9.
1 are formed (in the illustrated example, there are three locations). Also,
In a similar configuration, mounting fail rings 9 are connected to the dump oil 4, the comb oil 5, the spring oil 6, and the comb oil 7 via ribs 10, respectively. The mounting holes 11 of the mounting foil ring 9 of each foil are provided on the same circumference at the same intervals. The foils 3 to 7 are stacked in the order shown in FIG. 2, the mounting holes 11 of each foil are aligned, and the stacked foils 3 to 7 are mounted on the support surface 2a using mounting bolts 13 or the like.

The processing position of the mounting hole 11 is provided so as to be offset from the connecting portion between the rib 10 and the mounting foil ring 9 by a central angle φ on the circumference as shown in FIG. Further, the rib 10 of the bearing oil 3 has a shape that is an extension of the curve of the spiral groove 3a, and is a thin plate whose thickness is equal to that of the spiral groove 3b. The ribs 10 of the other foils 4 to 7 are provided in the radial direction.

The dump oil 4 and the spring oil 6 have a flat plate shape. The comb-shaped oils 5, 7 have comb teeth 5a, which extend radially inward from the outer periphery thereof.
It has 7a. The comb teeth 5a, 7a have an outer peripheral portion 5b,
They are arranged radially at equal pitches along 7b. There is a misalignment in the machining positions of the mounting holes 11 of the comb-shaped oil 5 and the mounting holes 11 of the comb-shaped oil 7,
1/2 of each other for equally spaced comb teeth
They are staggered. For this reason, as shown in FIG. 3, the comb teeth 5a, 7b are arranged alternately at 1/2 pitch on both sides of the spring foil 6 along the foil circumferential direction.

Next, the operation of this embodiment will be described.

When the thrust collar 1 of the rotating shaft rotates at an angular velocity ω in the direction of the arrow in FIGS. 2 and 3, a fluid film is formed between the thrust collar 1 and the bearing foil 3, and the pressure of this fluid film reduces the thrust load W.
is supported. During high-speed rotation, torque is generated due to shearing of the fluid film. In addition, in a dynamic pressure type thrust bearing such as this embodiment in which high-pressure fluid is not supplied from the outside, the thrust collar 1 and the bearing oil 4 come into sliding contact at the time of starting and stopping. As a result, a force in the ω direction acts on the foils 3 to 7, and this force is transmitted to the mounting foil ring 9 via the tension of the rib 10, and is fixedly supported at the mounting hole 11 thereof. The foils 3 to 7 undergo thermal deformation due to heat generated by shearing of the fluid film during high-speed rotation and heat generated by sliding during startup and shutdown. This thermal deformation is the largest in the bearing foil 3, and is mainly caused by thermal expansion in the radial direction of the foil. If the thermal expansion of the foils 3 to 7 is suppressed by the foil support method shown in FIG. Partial contact with the foil 3 occurs, leading to damage to the foil.

However, in the present invention, the thermal expansion (thermal deformation) of the foils 3 to 7 is absorbed by the deformation of the ribs 10. In particular, since the connecting portion between the rib 10 and the mounting foil ring 9 is offset from the mounting hole 11 by the center angle φ, the deformation or displacement of the foils 3 to 7 with respect to the mounting hole 11, which can be regarded as a fixed point, is less restricted.
Thermal expansion displacement in the radial direction of the foils 3 to 7 is allowed. This displacement is absorbed by the deformation of the mounting foil ring 9 and the rib 10, and does not have any adverse effect on the mounting hole 11. Therefore, wrinkles can be prevented from forming on the bearing surface 3a, and the parallel gap between the side surface of the thrust collar 1 and the bearing surface 3a can be maintained constant. Therefore, the load capacity of the bearing can be maintained up to the high-speed rotation range, resulting in excellent high-speed stability. Furthermore, oil 3
-7 stress concentration can be avoided, and partial contact due to wrinkles on the bearing surface 3a can be prevented, so the durability and reliability of the elastic foil can be improved. In particular, the bearing oil 3 receives the most thermal and mechanical loads, but as shown in Fig. 4, the ribs 10 have a shape that is an extension of the curve of the spiral groove 3b, so that the steam load can be effectively reduced. can be reduced to Further, since thermal deformation of the foils 3 to 7 is difficult to occur, the bearing can be used from high temperatures to low temperatures, and the applicable temperature range of the bearing can be expanded. Furthermore, the present invention has a simple configuration that only requires changing the shape of the outer peripheral portion of the foils 3 to 7, and can be easily processed and manufactured by photo etching, etc., without increasing the number of parts or excessively increasing the number of processing steps. Therefore, there is no increase in costs.

In the above embodiment, the bearing surface 3a of the bearing oil 3 is of a spiral groove type in which a spiral groove 3b is provided as a dynamic pressure generating mechanism, but other types such as a step type, a tailing pad, etc. are also possible. type, taper land type,
It can also be applied to a herringbone type and produces the same effect.

[Effects of the Invention] In summary, according to the present invention, the following excellent effects can be achieved.

a support plate provided radially outward of the elastic foil and having a mounting hole for fixing to the bearing surface;
Since the support plate and the elastic foil are connected to each other by a connecting member spaced apart from the mounting hole in the circumferential direction, harmful thermal deformation is prevented by allowing thermal displacement of the elastic foil in the radial direction. Moreover, since it has a simple structure, it can be manufactured easily and at low cost.

[Brief explanation of drawings]

Figure 1 is an exploded front view of a conventional foil thrust bearing in which elastic foils are laminated, Figure 2 is an assembled sectional view of the foil thrust bearing according to the present invention, Figure 3 is a sectional view in the same circumferential direction, and Figure 4. is an exploded front view of the same bearing. In the figure, 1 is the thrust collar of the rotating shaft, 2 is the bearing case, 2a is the bearing surface, 3 is the bearing oil,
3a is a bearing surface, 4 is a dump oil, 5 is a comb oil, 6 is a spring oil, 7 is a comb oil, 9 is a mounting oil ring (support plate), 10 is a rib (connecting member), 11 is a mounting hole, 1
2 is a rotating shaft, and 13 is a mounting bolt.

Claims (1)

[Claims] 1. In a foil thrust bearing in which an elastic foil is layered on the bearing surface while surrounding the rotating shaft, and the thrust load of the rotating shaft is supported by the fluid film pressure formed between the rotating shaft and the rotating shaft, the above-mentioned elastic a support plate provided radially outward of the foil and having a mounting hole for fixing to the bearing surface; and a support plate spaced circumferentially from the position of the mounting hole to connect the support plate and the elastic foil. A foil thrust bearing comprising a connecting member provided.