JP2560658Y2 - Composite gas bearing - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to a high-speed rotating body (compressor,
The present invention relates to a composite gas bearing in which a static pressure type gas bearing and a dynamic pressure type gas bearing are used for a bearing portion of a turbine, a vacuum pump, a gas turbine, a helium expander, and the like.

[0002]

2. Description of the Related Art An example of a conventional composite gas bearing in which a static pressure gas bearing and a dynamic pressure gas bearing are combined will be described with reference to FIGS. In this composite bearing, a rotating body is freely rotatably supported by a composite thrust bearing and a composite radial bearing.

The rotating body 11 includes a rotating thrust disk 12
And a radial plate provided around the rotating body 11 and an upper plate 13 and a spacer 14 of the thrust gas bearing provided to surround the rotary thrust disk 12 and a lower plate 15 of the thrust gas bearing. It is supported by a gas bearing 16.
The upper plate 13, the lower plate 15, and the radial gas bearing 16 of the thrust gas bearing are provided with a plurality of nozzles 17, 20, 23 for a plurality of hydrostatic gas bearings, respectively. Further, the upper plate 13 and the lower plate 15 of the thrust gas bearing are provided with spiral grooves 43 for the dynamic pressure type gas bearing on the surface on the rotary thrust disk 12 side, respectively. Are provided with spiral grooves 33 and 35 for a dynamic pressure type gas bearing.

In this bearing, the static pressure supply ports 26, 27, 2
When the compressed gas is supplied to the nozzle 8, the gas is ejected from the plurality of static pressure nozzles 17, 20, and 23 to float the rotating body and support it in a non-contact manner. Further, when the rotating body 11 rotates at a high speed in the rotating direction N, in the thrust gas bearing, the gas is pulled in the direction of the arrow V by the rotation of the rotating body on a plane due to its own viscosity, as shown in FIG. Along the spiral groove 43, gas is compressed at the center of the bearing to generate pressure, and similarly supports the rotating body. On the other hand, in the radial gas bearing 16, when the rotating body 11 rotates at a high speed in the rotating direction N, as shown in FIG. The gas is compressed in the center of the bearing along the spiral grooves 33 and 35 to generate pressure, and similarly supports the rotating body.

FIG. 4 and FIG. 5 show the positional relationship between the spiral grooves and the multiple nozzles of each composite gas bearing in this bearing. First, as for the thrust bearing, as shown in FIG. 4, each spiral groove 43 communicates from the outer periphery of the bearing to the inner periphery of the bearing.
Of the width G of the land portion 44 having no groove formed between the spiral groove 43 and the width G of the land G is approximately 1 /.
1, the area of the groove where the gap with the rotary thrust disk 12 is large occupies half of the total area, and the plurality of static pressure nozzles 17 and 20 are also arranged in or near the spiral groove. In this structure, the gas flowing out of the nozzle easily leaks outside through the groove.

As for the radial bearing, as shown in FIG. 5, the spiral grooves 33, 35 communicate between the outer peripheral portions at both ends of the bearing and the inner peripheral portion of the bearing. Width G and this spiral groove 33 or 35
The ratio of the width R of the land portion 34 having no groove (G
/ R) is approximately 1/1, the area of the groove where the gap with the rotating body 11 is large occupies half of the total area, and the plurality of static pressure nozzles 23 are also spiral grooves 33, 3
5, the distance between the nozzle and the groove (land seal length) is short, and the gas flowing out of the nozzle easily leaks outside through the groove.

[0007]

The conventional composite-type gas bearing described above has a larger clearance by the depth of the spiral groove than the ordinary static-pressure type gas bearing, so that the dynamic pressure effect is reduced. When the rotation speed is small, the bearing load capacity and rigidity decrease. In particular, when the area occupied by the spiral groove is large and a plurality of nozzles for static pressure are located near the spiral groove or in the spiral groove, the characteristics are remarkably deteriorated, and rotation at low speed is performed. Stability is reduced and vibration abnormalities and the like are likely to occur.

The present invention is to solve the above problems of the conventional composite gas bearing.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a composite gas bearing in which a static pressure type gas bearing having a plurality of air supply nozzles and a dynamic pressure type bearing having a land portion and a spiral groove are combined. A central land portion that is continuous in the circumferential direction is provided, a plurality of spiral grooves that do not communicate with each other are provided from the inner and outer ends of the bearing to the central land portion, and the spiral that is substantially adjacent to the center of the central land portion is provided. place each air supply nozzles of the plurality of hydrostatic gas bearing in an intermediate position of the shaped groove, the width G of the circumferential direction of the spiral grooves
The ratio G / R of the circumferential width R of the land portion having no groove between the spiral groove and the land portion is set to 1/3 to 1/4.

[0010]

In the case of a static pressure type gas, pressure rises due to viscous resistance while gas flowing in from a plurality of air supply nozzles flows out through a minute gap of, for example, several tens of μm, and a pressure rise occurs, thereby generating a load capacity. . Since the viscous resistance is determined by the product of the viscosity coefficient of gas, the square of the gap size, and the streamline length, the generated pressure becomes extremely large by reducing the gap, and a minute gap is formed. The load capacity is also improved by increasing the effective area of the portion where the load is applied.

[0011] The in this devise, a groove in which the central land portion and the inner and outer ends of the bearing circumferentially continuous provided in the bearing central portion not in communication with each other in a spiral leading to the central land portion, the central Each of the plurality of air supply nozzles is arranged at an intermediate position of the adjacent spiral groove substantially at the center of the land portion, and since each air supply nozzle is arranged apart from the spiral groove, Since the seal length of the land portion, that is, the streamline length becomes longer and the equivalent gap becomes smaller, the load capacity as a hydrostatic bearing is improved.

Further, in this devise, the groove width ratio G / R of the circumferential width R of the land portion without groove between the circumferential width G and a spiral groove of the spiral-shaped groove 1 / 3 to 1/4
By increasing the area ratio of the groove portion to the entire area, that is, the area ratio of the portion having a small gap, the load capacity as the hydrostatic bearing is improved. In addition, by setting G / R to 1/3 to 1/4 as described above, a decrease in characteristics as a dynamic pressure bearing can be suppressed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. This embodiment comprises a composite type thrust gas bearing and a composite type radial gas bearing, each of which is a combination of a static pressure type gas bearing and a dynamic pressure type gas bearing as shown in FIGS. 5 will be mainly described, and the same portions will be denoted by the same reference numerals and description thereof will be omitted. 1 and 2 are explanatory views showing cross sections taken along lines X ₁ -X ₁ and YY in FIG. 3, respectively.

As shown in FIG. 1, the upper plate 13 of the composite thrust gas bearing includes a plurality of nozzles 17, a plurality of spiral grooves 43, 46, a plurality of lands 44, 45, 47, and the like. The annular land portion 47 is provided continuously in the circumferential direction of the upper plate 3 at the radial center between the inner and outer ends of the bearing of the upper plate 13. Each of the plurality of spiral grooves 43, 46 extends from the outer end and the inner end of the bearing to the central land portion 47 at equal intervals from each other. 46 are formed so as not to communicate with each other, and adjacent spiral grooves 4
Land portions 44 and 45 are formed between the spiral grooves 46 adjacent to each other. The ratio of the circumferential width G of the spiral grooves 43 and 46 to the circumferential width R of the lands 44 and 45, that is, the groove width ratio G / R is 1/3 to 1 /.
4 is set. The spiral groove 43, which is substantially adjacent to the center of the center land portion 47 in the radial direction and adjacent thereto,
A plurality of air supply nozzles 1
7 are provided.

Although not shown, the lower plate 15 of the thrust bearing shown in FIG. 3 has the same configuration as described above.

As shown in FIG. 2, the composite radial gas bearing 16 includes a plurality of nozzles 23, a plurality of spiral grooves 33, 35, and lands 34, 36. The annular land portion 36 is provided continuously in the circumferential direction at a central portion between the inner and outer ends of the gas bearing 16. Each of the plurality of spiral grooves 33, 35 extends from the inner and outer ends of the gas bearing 16 to the central land portion 36, and the spiral grooves 33, 35 are configured so as not to communicate with each other. And the adjacent spiral groove 3
3 and between adjacent spiral grooves 35 are formed land portions 34, respectively. The ratio of the circumferential width G of the spiral grooves 33 and 35 to the circumferential width R of the land portion 34, that is, the groove width ratio G / R is set to 1/3 to 1/4. A plurality of air supply nozzles 23 are provided at substantially the center of the central land portion 36 and substantially at the center between the adjacent spiral grooves 33 and 35.

In this embodiment constructed as described above, the gap width G / R is set to 1/3 to 1/4 in both of the composite type thrust gas bearing and the radial gas bearing, so that the gap is increased. The area occupied by the part of the groove where
The G / R is 1 or less than that of the conventional bearing shown in FIGS. 3 to 5, and the area occupied by the land portion having a small gap is increased to 1.5 times or more of the conventional bearing. Accordingly, the overall clearance of the bearing is reduced, the effective area of the land is increased, the characteristics of the hydrostatic bearing are improved, and the bearing load capacity and rigidity during low-speed rotation with a small dynamic pressure effect are improved.

On the other hand, the groove width ratio G / R is 1/3 as described above.
Since it is set to １ ／, and the area of the groove portion is secured, the characteristics as the dynamic pressure bearing are not reduced.

As described above, the nozzles 17, 23
Are land portions 46, 3 which are respectively continuous in the central circumferential direction.
6, a spiral groove 4 substantially at the center and adjacent to the spiral groove 4
3, 45; provided at a substantially central position between 33, 35, and the spiral grooves 43, 45, 33 do not communicate with each other. Thus, each nozzle is located at the center of the center land and at the same time, each of the spiral grooves 43, 45;
Since it is provided at the center position of the nozzles 33 and 35, the spiral grooves 43 and 45 and the nozzles 2
The distance from the groove 3 to the spiral grooves 33, 35, that is, the land seal length is about 1.5 times longer than that of the conventional apparatus shown in FIGS. Therefore, the gas flowing out of the nozzles 17 and 23 does not directly flow into the spiral grooves 43, 45 and 33, 35, but the gas from the nozzles 17 and 23 has the spiral groove 4.
The gas flowing to 3, 45 and 33, 35 passes over the central land portions 46 and 34, and then flows into the spiral groove, the gas streamline length increases, and the gas flows as a hydrostatic bearing. The load characteristics are improved.

A gap particularly affecting this kind of bearing characteristic is considered as an equivalent gap determined by an area ratio occupied by each gap between the groove portion and the land portion. A groove gap of 40 μm and a land gap of 20 μm are generally adopted. Comparing the conventional gaps shown in FIGS. 3 to 5 with the equivalent gaps of this embodiment, the values are as follows. Equivalent gap = groove gap × groove area ratio + land groove area ratio Conventional equivalent gap = 40 μm × １ ／ + 20 μm × １ ／ = 30 μm Equivalent gap of this embodiment = 40 μm × １ ／ + 20 μm × 3/4 = 25 μm equivalent gap Is reduced to about 5/6 . The static pressure load capacity (bearing supportable load) when air is supplied to the nozzle is as follows. Static pressure load capacity = Proportional coefficient x (Land seal length) x (Land area) x (1 / equivalent clearance) squared Compare the static pressure load capacity of the present invention with that of the present invention. = 1.5 × 1.5 × (6/5) square = 3.2 times, and this embodiment has a remarkable effect of improving the static pressure load capacity.

In the above embodiment, the composite type thrust bearing and the radial bearing are used in combination, but it goes without saying that the present invention can be applied to any one of them.

[0022]

[Effects of the Invention] As described above, the present invention has the following features.
Because of the configuration 1, the static pressure load capability as a static bearing can be improved without deteriorating the characteristics as a dynamic pressure bearing, and the bearing load capability and rigidity at low speed rotation with a small dynamic pressure effect are small. Can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a portion of a composite type thrust gas bearing according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a portion of a composite radial gas bearing of the embodiment.

FIG. 3 is a sectional view of an example of a conventional composite gas bearing.

FIG. 4 is a sectional view taken along the line X ₂ -X _{2 in} FIG. 3;

FIG. 5 is a sectional view taken along the line YY of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Rotating body 12 Rotating slide disk 13 Upper plate of thrust gas bearing 14 Spacer 15 Lower plate of thrust gas bearing 16 Radial gas bearing 17,23 Nozzle 33,35 Spiral groove 34,36 Land part 43,45 Spiral Groove 44, 46, 47 Land

Claims (1)

(57) [Scope of request for utility model registration] 1. A composite gas bearing in which a static pressure type gas bearing having a plurality of air supply nozzles and a dynamic pressure type gas bearing having a land portion and a spiral groove are combined. A land portion is provided, and a plurality of spiral grooves that do not communicate with each other are provided from the inner and outer ends of the bearing to the central land portion. place each air supply nozzles of the plurality of hydrostatic gas bearing in a position, before
The circumferential width G of the spiral groove and the spiral shape
Ratio between the circumferential width R of the land portion having no groove between the grooves G and G /
A composite gas bearing, wherein R is set to 1/3 to 1/4 .