JPH034016A - Gas bearing - Google Patents

Abstract

PURPOSE:To form a pressure gas layer between a support portion and an accepted member on one side and prevent the escape of gas with an air barrier on the other side by guiding gas from a gas guide path to the support portion with the rotation of the accepted member and separating the flow of gas into two after guided. CONSTITUTION:A cylindrical partitioning member 11 with a cap is arranged between the vacuum room 4 and the drive room 8 of a casing 1 and a loose through hole 12 is provided for a rotation axis 9 at the center of the cap to form a bearing portion 13 with the axis 9 and the hole 13. A dynamic pressure groove is engraved in a portion opposite to the bearing portion 13 of the rotation axis 9 to enhance air pressure and undertake radial load at the bearing portion 13. The partitioning member 11 has a gas guide path 16 penetrated into the upper and lower sides and a thrust bearing portion 17 provided on the upper face, and the bearing portion 17 are partitioned with grooves 20, 21 into two area, a gas layer forming area and a gas seal portion area in the outer periphery thereof, in the space to the outer periphery edge portion of the loose through hole 12. Accordingly, the pressure gas layer is formed in the groove 20 to float a rotor 7 and pressure is retained in the seal formed groove 21.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to gas bearings.

[Prior Art] Conventionally, in a turbo-molecular pump, a rotor is supported by a ball bearing, and a lubricant such as oil or grease is used in combination with this bearing to ensure smooth rotation of the rotor. Due to the use of oil lubrication, oil mist tends to get mixed into the vacuum, making it impossible for the turbo molecular pump to perform its original function. Shortened the service life of lubricating oil.

In order to avoid the above-mentioned inconvenience, JP-A-63-25559
No. 3, an improved turbomolecular pump is disclosed. In this pump, a magnetic liquid is sealed between the rotor and the bearing, and by controlling this magnetic liquid with a magnet, the rotor can be moved while maintaining good balance in the thrust and radial directions of the rotor. This ensures stable high-speed operation by maintaining the float.

[Problem to be solved by the invention] However, in this turbo-molecular pump, it is necessary to use a magnetic liquid and a magnet to control it, which not only makes the configuration complicated and complicated to manufacture, but also increases the number of parts. There is a problem in that the number increases, leading to a rise in manufacturing costs.

This invention was made to solve the above-mentioned problems, and its purpose is to make it possible to use it in a vacuum atmosphere created by a turbo-molecular pump, etc., and to keep manufacturing costs low by making it simple and easy to manufacture. The objective is to provide a gas bearing that allows for

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a gas bearing that includes a support portion that rotatably supports a supported member when the supported member is rotated. Based on the rotation of and a power generating section that generates a pressure gas film between the support member and the supported member, and further generates an air barrier to prevent the gas forming the pressure gas film from escaping by the flow of the other side. This is the summary.

[Operation] By employing the above-mentioned means, the present invention allows gas to be introduced from the gas introduction path to the support part by rotation of the supported member, and then the flow of this gas is divided into parts, so that one flow flows into the support part and the support part. A pressure gas film is formed between the supported members, and an air barrier formed by the other flow prevents the gas forming the pressure gas film from escaping.

[Example] Hereinafter, an example in which the present invention is embodied in a turbo-molecular pump will be described in detail with reference to the drawings.

The casing 1 of the turbomolecular pump shown in FIG. Stator blades 6 protrude inward from the member 5 in a multi-stage manner.

In the cylindrical portion of the casing l, a rotor 7 having a bottomed cylindrical shape is disposed coaxially therewith, and a plurality of rotor blades 7a formed on the outer peripheral surface of the rotor 7 protrude between the stator blades 6, respectively. A rotating shaft 9 extending from a drive chamber 8 provided at the lower part of the casing 1 is fixedly connected to the bottom of the rotor 7, and a plurality of contact plates 10 are arranged at equal angular intervals on the bottom surface.
is installed. When the rotor 7 is rotated with the rotation of the rotating shaft 9, air is discharged from the suction port 2 through the vacuum chamber 4 to the discharge port 3, and the pressure inside the vacuum chamber 4 is reduced to 10-2.
The value is ~10”LOkg/cri.

A thick cylindrical partition member 11 with a lid is disposed between the vacuum chamber 4 and the drive chamber 8 of the casing 1, and the partition member 11 has a free space through which the rotating shaft 9 passes through the center of the lid. Through hole 1
2, and the radial bearing constitutes a portion 13 on the inner circumferential surface of the free through hole 12. On the outer circumferential surface of the rotating shaft 9, the radial bearing has a herringbone-shaped dynamic pressure groove 14 carved in the part facing the part 13, and as the rotating shaft 9 rotates, the action of the dynamic pressure 'a14 causes the bearing to Part 1
The pressure of the gas in the pressure chamber 15 between the rotating shaft 9 and the outer peripheral surface of the rotating shaft 9 is increased, and the radial load of the rotating shaft 9 is supported.

In addition, a plurality of channel-shaped gas introduction passages 16 are formed vertically through the partition member 11 in accordance with its cross-sectional shape. 17 are provided. In this thrust bearing, as shown in FIG. A gas seal formation region 19 is provided outside the gas introduction path 16 in the formation region 18 .

The thrust bearing has a plurality of positive pressure grooves 20 in the gas film forming region 18 of the portion 17 extending in a spiral shape from the outer peripheral edge of the free through hole 12 in the outer circumferential direction, and in the gas seal forming region 19, A plurality of seal forming grooves 21 are formed in a spiral shape in the same direction as the positive pressure groove 20 and extending in the outer circumferential direction.

As shown in FIG. 3, the air flowing through the rotation of the rotary shaft 9, that is, the rotor, generates positive pressure toward the center along the positive pressure groove 20, and applies upward pressure to the bottom of the rotor. . At the same time, a negative pressure is generated near the outlet of the gas introduction path 16, and air is introduced into the gas introduction path 16 from the outside, and this air flow flows through the positive pressure groove 20 and the seal forming groove 20.
The air that is diverted to the side and pressurized in the positive pressure groove 20 generates pressure gas 111A to keep the rotor 7 floating. In addition, the air flow in the seal forming groove 21 is reduced in pressure to almost the same level as the pressure value in the vacuum chamber 4, and due to the counterbalance of this pressure value, a gas seal S is generated above the seal forming groove 21, and the air flow is reduced to the same level as the pressure value in the vacuum chamber 4. The thrust bearing blocks air flow between the upper part 17 and the upper part 17.

A disk-shaped mounting section 22 is fixed to the lower end of the rotating shaft 9 in the drive chamber 8, and a plurality of magnet plates 23 are embedded in the lower surface of the mounting section 22, and a stator 2 is disposed opposite thereto.
The rotating shaft 9 is rotated by changing the polarity of the rotating shaft 4.

Now, when the rotating shaft 9 is not driven, the rotor 7 is moved to its contact plate 1.
The thrust bearing 0 is in contact with the portion 17 and is supported by the partition member 11. When the stator 24 in the drive chamber 8 is energized, the rotating shaft 9 is rotated as the polarity of the stator 24 changes. Then, the air flow generated by the rotation of the rotor 7 becomes a positive pressure acting in the center direction by the positive pressure groove 20 of the partition member 11, causing the rotor 7 to float.

Further, air is introduced into the gas introduction path 16 from the outside, and this air is divided from the outlet of the introduction path 16 to the positive pressure groove 20 side and the seal forming groove 21 side. The air flow flowing along the positive pressure groove 20 is a pressure gas II! A is generated between the rotor 7 and the partition member 11, and this gas film A supports the thrust load of the rotor to keep the rotor 7 floating. On the other hand, air flow between the vacuum chamber 4 and the thrust bearing portion 17 is blocked by the gas seal S formed by the air flow along the seal forming groove 21, so that air does not flow into the vacuum chamber 4. The pressure distribution state set to support the rotor 7 in a floating manner is maintained to ensure smooth rotation of the rotating shaft 9.

As described above, in this embodiment, the air flow introduced into the gas introduction passage 16 based on the air flow generated by the rotation of the rotor 7 is formed into an air seal by the seal forming groove 21, and a positive pressure is formed by the positive pressure groove 20. By adopting a configuration in which the rotor 7 is supported in a floating manner by receiving the thrust load of the rotating shaft 9 as an air film, a gas bearing can be formed in a vacuum atmosphere, and the configuration can be simplified and the number of parts can be reduced. It is possible.

[Effects] As described above in detail, the present invention exhibits the excellent effect of simplifying manufacturing and keeping manufacturing costs low.

[Brief explanation of the drawing]

FIG. 1 is a sectional view embodying the present invention, FIG. 2 is a partial plan sectional view showing a thrust bearing, and FIG. 3 is an enlarged sectional view showing the main part of FIG. 1. The rotor 7 and the rotating shaft 9 as supported members, the gas introduction path 16, the thrust bearing as the support part 17, the positive pressure groove 20 and the seal forming groove 21 as the dynamic pressure generating part, the pressure gas film A, and the air barrier. Closed Gas Seal S.

Claims (1)

[Claims] 1. When the supported members (7, 9) rotate, the supported members (7, 9)
7, 9), the gas bearing includes a support portion (17) that rotatably supports the support member (7, 9), and a gas introduction path that introduces gas into the support portion (17) based on the rotation of the supported member (7, 9). (16), and a gas introduction path (16) provided in the support portion (17).
) into the supporting part (17), one flow is used to connect the supporting part (17) and the supported members (7, 9).
) to generate a pressure gas film (A), and further generate an air barrier (S) to prevent the gas forming the pressure gas film (A) from escaping by the flow of the other side. A gas bearing characterized in that it consists of parts (20, 21).