JPH09119429A - Dynamic pressure gas bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the temperature increase of a pad and assure the bearing performance of a dynamic pressure gas bearing. SOLUTION: This is a dynamic pressure gas bearing in which three or more pads 13 are installed in a circumference direction so as to surround a rotary shaft 4 through a pivot 12 in a bearing housing 11, the rotary shaft 4 is supported by forming a gas film 5 between the rotating rotary shaft 4 and the pad 13 and a minute pressure difference is installed between the end surfaces of a bearing in an axial direction and gas for cooling is circulated. Plural recessed grooves are formed in the longitudinal direction of the back surface of the pad 13.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a compressor, a supercharger,
The present invention relates to a dynamic pressure gas bearing applied to a circulator, an expander, a turbomachine, etc.

[0002]

2. Description of the Related Art FIG. 2 shows a vertical sectional view of a conventional general dynamic pressure gas bearing. The pivot 2 is directly fixedly mounted to the bearing housing 1 by a fastening member such as a bolt, and three pads 3 which can be tilted in any direction are attached to the inner tip of the pivot 2 in the direction of the arrow with the pad 3. A gas film 5 is formed between the rotating shaft 4 and the rotating shaft 4 so as to support the rotating shaft 4. Then, in the axial direction, a slight differential pressure is provided between the end faces of the bearings, cooling gas flows around the pad 3 and between the pad 3 and the rotating shaft 4 to perform gas replacement, and the pad 3 is replaced. Is to be cooled.

The bearing housing 1 radiates heat by transferring heat to the outside air, while the pad 3 inside the bearing housing 1 is cooled by the cooling gas flowing through this portion. Generally, the gap of the gas bearing is at a level of several μm, so the thermal expansion of the pad 3 has a great influence on the change of the bearing gap. Further, most of the shear heat generated in the gas film is radiated through the pad 3 on the fixed side, so that the rotor temperature of the bearing is indirectly cooled by cooling the pad 3. Therefore, if the pad 3 is insufficiently cooled, the thermal expansion of the rotor also increases, and the reduction of the gap becomes remarkable,
Problems such as closing gaps at high speeds are likely to occur.

[Problems to be solved by the invention]

In the conventional dynamic pressure gas bearing, a slight differential pressure is provided in the axial direction, and a cooling gas flows between the periphery of the pad and between the pad and the rotary shaft to perform gas replacement, thereby cooling the pad. It is supposed to be done. However, when the rotational speed of the rotating shaft increases, the main flow velocity in the rotating direction increases between the pad and the rotating shaft, so that gas displacement cannot be effectively performed only by the slight differential pressure in the axial direction. Therefore, the temperature of the pad rises, the pad is deformed, the expansion of the rotary shaft is also promoted, the clearance is not fixed as designed, and the predetermined bearing performance cannot be maintained. The present invention
It is an object of the present invention to solve these problems and provide a dynamic pressure gas bearing in which a concave groove is provided on the back surface of the pad to improve the cooling performance of the pad of the dynamic pressure gas bearing.

[0005]

According to the present invention, three or more pads are circumferentially attached to a bearing housing so as to surround a rotary shaft via a pivot, and a gas film is formed between the rotary shaft and the pad. Is a dynamic pressure gas bearing that supports a rotating shaft and has a slight differential pressure between the end faces of the bearing in the axial direction to allow cooling gas to flow. It is a dynamic pressure gas bearing characterized in that a groove is formed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION According to the dynamic pressure gas bearing of the present invention,
A gas film generated by the dynamic pressure is formed between the pad mounted on the bearing housing via a pivot and the rotating rotary shaft, and the rotary shaft is supported by the rotary shaft. The pressure causes cooling gas to flow around the pad and between the pad and the rotating shaft to perform gas replacement and cool the pad. A plurality of concave grooves are formed in the longitudinal direction on the back surface of the pad, and the cooling gas induces an axial flow along the concave groove, causing turbulence in the gas flow on the rear surface of the pad to cool the rear surface of the pad. The effect of doing is great.

[0007]

The present invention will be described below with reference to the embodiment shown in FIG. 1A and 1B are structural views of a dynamic pressure gas bearing. FIG. 1A is a longitudinal sectional view, FIG. 1B is a view taken along the line AA of FIG. 1A, and FIG. 1C is a perspective view of a pad. d) The figure is a view showing the groove shape formed in the pad. The same members as those in the conventional example of FIG. 2 are designated by the same reference numerals. Bearing housings 11 are provided at both ends of a rotor (not shown) of a turbomachine or the like so as to surround the rotating shaft 4 rotating in the arrow direction.
Is tiltably held by a pivot 12 mounted on a bearing housing 11 and supported by three pads 13 arranged in the circumferential direction.

The pad 13 has a rotary shaft 4 so that an optimum gas film 5 is formed between the pad 13 and the rotary shaft 4 which rotates at high speed during operation.
There is a proper clearance between and. The pivot 12 holds a pad 13 so that it can be freely tilted, and the back surface (outer surface) of the pad 13 is in the axial direction of the pad (same as the longitudinal direction of the rotation axis) as shown in FIG. A plurality of concave grooves 13a are formed. The diagram (d) shows an example of the groove shape of the groove 13a, and the groove is not limited to this as long as it is a groove that easily induces an axial flow, and another shape may be used.

Further, in the axial direction, a slight differential pressure is provided between the end faces of the bearing, and cooling gas flows around the pad 13 and between the pad 13 and the rotary shaft 4 to perform gas replacement. ，
The pad 13 is designed to be cooled.

In this embodiment constructed as described above, there is no movement between the three stationary pads 13 arranged in the circumferential direction so as to surround the rotary shaft 4 and the rotary shaft 4 rotating at high speed. A gas film 5 generated by pressure is formed and the rotating shaft 4 is supported. Then, the cooling gas flows around the pad 13 and between the pad 13 and the rotary shaft 4 by a slight differential pressure provided in the axial direction to perform gas replacement, and the pad 13 is cooled. Further, a plurality of concave grooves 13a are formed on the back surface of the pad 13 in the longitudinal direction, and the cooling gas is supplied to the grooves 13a.
The back surface of the pad 13 is cooled by flowing to the low-pressure side while inducing an axial flow along.

FIG. 3 is a graph showing the relationship between the number of grooves, the flow rate, and the temperature rise. When the number of the concave grooves 13a increases, the flow rate of the pad cooling gas increases and the temperature rise of the pad 13 decreases. Is represented. According to the present invention, since a plurality of concave grooves are formed on the back surface of the pad 13 in the longitudinal direction as described above, it is easy to induce an axial flow along the concave groove 13a, and the gas flow on the back surface of the pad is disturbed to provide a cooling effect. In addition, the groove 13a on the back surface of the pad 13 increases the surface area of the gas flow, thereby enhancing the cooling effect.

Therefore, since the cooling effect is increased, the thermal deformation of the pad 13 and the shaft is reduced, the clearance between the pad 13 and the rotary shaft 4 becomes constant, the performance of the dynamic pressure gas bearing is prevented from being deteriorated, and the compressor etc. The rotating shaft of can be stably floated and held.

[0013]

In summary, according to the present invention, the bearing housing is circumferentially arranged so as to surround the rotary shaft through the pivot.
Attaching more than one pad, forming a gas film between the rotating rotary shaft and the pad to support the rotary shaft. A slight differential pressure is provided between the end faces of the bearing in the axial direction to allow the cooling gas to flow. Since the dynamic pressure gas bearing is formed by forming a plurality of concave grooves in the longitudinal direction on the back surface (outer surface of the pad) of the pad, the cooling surface area increases and the axial flow along the groove is increased. Is easily induced, the flow on the back of the pad is disturbed, and the cooling effect is increased. Further, since the temperature rise of the pad is prevented by the cooling effect, the thermal deformation of the pad and the shaft is reduced, and the clearance between the pad and the rotating shaft is constant. As a result, the bearing performance of the dynamic pressure gas bearing is guaranteed, and it becomes possible to provide a dynamic pressure gas bearing in which the rotating shaft can be stably floated and held, which is extremely useful in industry.

[Brief description of the drawings]

1A and 1B are configuration diagrams of a dynamic pressure gas bearing according to an embodiment of the present invention, in which FIG. 1A is a longitudinal sectional view and FIG. 1B is AA in FIG. 1A.
An arrow view, (c) drawing is a perspective view of the pad, and (d) is a sectional view showing the groove-shaped end surface of the pad.

FIG. 2 is a sectional view showing a structure of a conventional dynamic pressure gas bearing.

FIG. 3 is a graph showing the number of grooves, the flow rate, and the temperature rise according to the embodiment of the present invention.

[Explanation of symbols]

 4 rotating shaft 5 gas film 11 bearing housing 12 pivot 13 pad 13a groove

Claims (1)

[Claims] 1. A bearing housing is provided with three or more pads in the circumferential direction so as to surround the rotary shaft via a pivot, and a gas film is formed between the rotating rotary shaft and the pads to support the rotary shaft. However, in the dynamic pressure gas bearing in which a slight differential pressure is provided between the end faces of the bearing in the axial direction and the cooling gas flows, a plurality of concave grooves are formed in the longitudinal direction of the back surface of the pad. Dynamic pressure gas bearing.