JPS585519A - Foil journal bearing - Google Patents

Abstract

PURPOSE:To simplify the constructon of a journal bearing by forming a foil which is a main structure of the bearing with one sheet of elastic foil surrounding the substantially whole peripheral surface of a shaft. CONSTITUTION:An elastic foil 5 has a length enough to surround the whole peripheral surface of a shaft 2 over about 360 deg., one end of the foil being attached to a fixed rod 6, the other end thereof being a free end. Six short piece elastic foils 81-86 are adapted to elastically support the elastic foil 5 from the outside at intervals of 60 deg., so that the elastic foil 5 has wedge-shaped spaces at six places of the whole periphery surrounding the shaft 2. Thus, dynamic pressure is produced at plural wedge-places, and the shaft 2 is in suspension supported on the elastic foil 5. The size of short piece elastic foils 81-86 is adjusted so as to control preload.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foil journal bearing using foils.

Foil O-journal bearings consist of several thin elastic foils installed in the housing for the journal bearing, arranged correspondingly to the sides of the shaft, and forming an open wedge-shaped cavity between the foil surface and the circumference of the shaft as the shaft rotates. This is a dynamic pressure gas bearing that supports the shaft in suspension by increasing pressure (dynamic pressure). Since this bearing is non-contact, it can be used to support high-speed rotating bodies without causing seizure, and is used in air machines such as expansion turbines.

Normally, when this bearing is used in an expansion turbine, gas (process gas) from a compressor is introduced or actively supplied to this bearing part to increase the density of the gas in the wedge-shaped cavity and further increase the pressure. Efforts have been made to make it effective.

Various types of foil journal bearings are in practical use, but most of them have multiple elastic foils installed in the housing, and these foils are overlapped to correspond to the shaft. 7. The shaft is supported by the dynamic pressure generated between the oil and the shaft periphery, but since a plurality of elastic foils are installed, the structure tends to be complicated and large. In addition, when multiple 7 oils are superimposed, it becomes difficult to form a wedge-shaped space between the shaft circumference and the 7 oil, making it particularly difficult to adjust the contact pressure (preload) of the foil to the shaft, resulting in poor accuracy. There are also problems with functional fishing.

The present invention provides a bearing that eliminates the drawbacks of the conventional 7-oil journal bearing. The first feature of the foil journal bearing of the present invention is that the foil, which is the main body of the bearing, is located almost on the shaft. 1 that surrounds the entire circumference
The structure of the bearing is extremely simplified as it is made up of two pieces of elastic foil. Note that the length of this elastic foil, that is, the length in the circumferential direction surrounding the shaft, is the entire circumference of the shaft (36
0') is not strictly limited to a length that completely encloses the length.

A second feature of the present invention is that one end of the elastic foil is fixedly installed on the inner surface of the housing, and the peripheral portion surrounding the shaft is elastically supported at a fixed point with respect to the housing. .

A minimum of two elastic support points are required, and ideally there are four to six to avoid complicating the structure. Due to these elastic supports, a desired bleed occurs, and dynamic pressure is generated better from the periphery of the shaft due to rotation of the shaft, so that the function as a gas bearing is fully exhibited. The support for elastically supporting the foil can also consist of a relatively short elastic foil. This configuration also facilitates preload adjustment.

The illustrated embodiment will be described below. FIG. 1 is a perspective view schematically showing an air machine such as an expansion turbine;
is a support shaft (rotation shaft) of the lightweight rotating body 1, and is rotatably supported by a journal bearing 3. As this journal bearing 3, the 7 oil journal bearing of the present invention, which allows the rotating body 1 to rotate at high speed, is used. Figure 2, 4
7 is a cross-sectional view of the oil journal bearing 3 perpendicular to the axis when the shaft 2 is in a rotating state. 4 is a bearing housing, which is not shown, but is actually fixedly installed on the bearing support of the air machine. , rotatably supports the rotating shaft 2.

5 is an elastic foil, and as shown in FIG. 3A, one end is attached to a fixing rod 6 for fixed installation on the inner surface of the housing 4, and the other end (tip) 5/ is a free end. The length of this elastic foil 5 is approximately 360 degrees over the entire circumferential surface of the rotating shaft 2.
The width of the bearing 3 is selected in accordance with the axial length of the bearing 3. Although the foil 5 is shown as a plate with a constant thickness for convenience of illustration, it is usually formed of a thin foil with high wear resistance.

Elastic foils 8, - 86 are leaf-like elastic foils compared to the elastic foil 5, and as shown in FIG. 3B, fixed rods 7I - 76 similar to the elastic foil 5 are attached to one end of each. As shown in FIG. 2, the bearing housing 4 is installed to function as an elastic support that elastically supports an elastic foil 5 surrounding the shaft at a plurality of points (six locations) from the outside.

4 to 4 to 6 are elastic foils 81 to 86 fixing rods 7
This is a co-running groove formed on the inner circumferential surface of the bearing housing No. 1 to 76 in a fixed manner. Note that the fixing groove 4 is formed to have a groove width larger than that of the other grooves so that the fixing rods 6 of the elastic foil 5 can be fixedly installed all together. However, it is not necessary to fix the large elastic foil 5 to the same groove 4Kl as the support elastic foil 8I, and it is of course possible to fix the large elastic foil 5 to separate grooves. This elastic foil 81
.about.86 may be spring bodies of other shapes.

The six short elastic foils 81 to 86 are the elastic foil 5.
is elastically supported from the outside at intervals of 6C3, and wedge-shaped cavities are formed at six locations around the entire circumference of the elastic foil 5 surrounding the shaft 2.

As shown in FIG. 2, when the shaft 2 is rotated at high speed in the direction of the arrow, dynamic pressure is generated in a plurality of wedge-shaped cavities formed between the curved surface of the shaft 2 and the elastic foil 5, and the shaft 2 is floatingly supported on an elastic foil 5.

The elastic foil 5 surrounding the shaft 2 is called an upper foil because it supports the shaft 2 upwardly with respect to the bearing housing 4, and the six strip-shaped elastic foils 81 to 86 can be called under foils.

While the upper foil 5 contributes to dynamic pressure generation, the under foils 81 to 86 are useful for setting preload and load capacity. That is, the elastic force and magnitude are set in consideration of the capacity of the rotating shaft 2 including the rotating body 1 and the magnitude of the load. under foil 8
The number may be adjusted depending on the capacity of the 1st to 86th axes.

If an abnormality occurs and the shaft 2 is displaced while the shaft 2 is rotating at high speed and the elastic foil 5 is exerting its bearing function, the gap between the shaft 2 and the elastic foil (upper 7 oil) 5 is maintained at one stroke. The upper foil 5 and the under foils 81 to 86 are deformed in this manner.

Although one embodiment of the present invention has been described above, the present invention is not limited to this and includes various modified embodiments.

In the illustrated example, the long-side elastic foil, ie, the upper foil, and the short-side elastic foil, ie, the underfoil, are constructed as separate members or separate members, but they can also be constructed as a single body. Of course, it is also possible to use foils that are made of the same material and processed as an integrally molded product, or it is also possible to use a foil that is made of the same material and processed as an integral product.

The fixing rod (guide) is also shown as one straight body, but it can also be two. The foil (leaf) can be held between both fixing rods, and depending on the shape of the groove, the position of the fixing rod can be adjusted as necessary.

In the present invention, the term "foil journal bearing" is intentionally used, but the term "journal" should be interpreted as synonymous with radial bearing.

Of course, the present invention can also be implemented in a journal-type radial bearing equipped with a journal.

Since the 7 oil journal bearing of the present invention has the above configuration, it has the following advantages.

First, the structure of the bearing becomes extremely simple, and therefore the entire bearing can be made more compact. This is because the elastic foil that directly supports the shaft is composed of one foil, and the number of parts of the device can be reduced.

In connection with the above-mentioned advantages, the thickness of the foil can be freely selected within a certain range 1 and does not require particularly high precision. Conventionally, abnormal pressure fluctuations could occur due to shaft displacement due to the thickness of several superimposed foils, but in the present invention there is only one foil, and furthermore, displacement is possible due to the intervention of an elastic support. There is no need for precision in dovetail thickness, which makes the bearing easier to process.

Furthermore, in relation to the first and second advantages mentioned above, the possibility of weakening the generation of dynamic pressure due to foreign matter contamination is eliminated, and the bearing has high durability and is resistant to foreign matter contamination (intrusion). is obtained.

It is also a great advantage that the preload can be adjusted by adjusting the size of the elastic support (underfoil). Furthermore, by setting this elastic support, it is possible to select a bearing mechanism according to the application and load capacity, and since foil accuracy is not required, it is suitable for mass production of foil journal bearings. In addition, it is less affected by thermal distortion and can withstand long-term bearing use, and in addition to the above advantages, it is effective for bearings of high-speed rotating bodies, and can improve the reliability of turbine machines and air machines.

[Brief explanation of the drawing]

Fig. 1 is a perspective view schematically showing the external appearance of an air machine in which a foil journal bearing is used; Fig. 2 is a sectional view perpendicular to the axis of a foil journal bearing according to an embodiment of the present invention; Figure A is a perspective view of the elastic foil, and Figure 3B is a perspective view of the elastic support. DESCRIPTION OF SYMBOLS 1...Rotating body, 2...Rotating shaft, 3...Foil 0 journal bearing, 4...Bearing housing, 4 to 4...Fixing groove, 5...Elastic foil, 6171-76... Fixed rod, 81-86... Elastic support.

Claims (1)

[Claims] A journal which supports the shaft by means of an elastic foil installed in the housing for the bearing, and which provides floating support for the shaft by increasing pressure in the wedge-shaped cavity between the peripheral surface of the shaft and the surface of the oil as the shaft rotates. In the bearing, an elastic foil surrounds the shaft surface approximately 360°, and the foil is elastically supported at multiple points inside the housing and outside the oil.
A foil journal bearing characterized in that it is provided with several elastic supports.