JP2698430B2 - Gas bearing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas bearing.

[Related Art] Conventionally, in a turbo-molecular pump, a rotor is supported by a ball bearing or the like, and a lubricant such as oil or grease is used in combination with the bearing to assure smooth rotation of the rotor. The use of this oil lubrication makes it easy for oil mist to be mixed into the vacuum, which not only prevents the turbo molecular pump from fulfilling its original function, but also causes hydrocarbons such as lubricant vapor generated by heat generation due to solid contact with the bearing. The service life of lubricating oil has been shortened.

In order to avoid the above-mentioned disadvantages, an improved turbo-molecular pump is disclosed in JP-A-63-255593. In this pump, a magnetic liquid is sealed between a rotor and a bearing, and the magnetic liquid is controlled by a magnet, thereby maintaining a good balance in the thrust direction and the radial direction of the rotor while maintaining the rotor in good condition. This ensures stable high-speed operation by maintaining the levitation.

[Problems to be Solved by the Invention] However, in this turbo molecular pump, it is necessary to use a magnetic liquid and a magnet for controlling the magnetic liquid.
Not only does the configuration become complicated and the manufacturing becomes complicated, but also the number of parts increases and the manufacturing cost rises.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has an object to be used in a vacuum atmosphere formed by a turbo-molecular pump or the like, and furthermore, it is possible to simplify the manufacturing and to reduce the manufacturing cost. It is to provide a simple gas bearing.

Means for Solving the Problems In order to achieve the above object, the present invention provides a gas bearing provided with a support portion for rotatably supporting a supported member when the supported member rotates. Based on the rotation of the gas, a gas introduction path for introducing a gas into the support portion, and a flow of the gas provided in the support portion and introduced from the gas introduction path to the support portion is divided into two, and the flow of the support portion is divided into two flows. And a power generation unit for generating a pressure gas film between the support member and the support member, and further generating an air barrier for preventing escape of gas forming the pressure gas film by the other flow. This is the gist.

[Operation] By adopting the above-described means, the present invention employs the above-described means. After the gas is introduced from the gas introduction path to the support by the rotation of the supported member, the flow of the gas is divided into two, and the flow of the support and the support is caused by one flow. A pressure gas film is formed between the supported members, and escape of the gas forming the pressure gas film is prevented by an air barrier formed by the other flow.

Embodiment An embodiment in which the present invention is embodied in a turbo-molecular pump will be described below in detail with reference to the drawings.

The casing 1 of the turbo-molecular pump shown in FIG. 1 has a suction port 2 and a discharge port 3 which are respectively opened at an upper part and a lower part, and further has a plurality of annularly fixedly arranged vertically so as to cover an inner peripheral wall of a vacuum chamber 4. Stationary blade 6 inward from member 5
Project in a multi-step manner.

A cylindrical bottomed rotor 7 is disposed coaxially with the inside of the cylindrical portion of the casing 1, and a plurality of moving blades 7 a formed on the outer peripheral surface of the rotor 7 protrude between the stationary blades 6. A rotating shaft 9 extending from a driving chamber 8 provided at a lower portion of the casing 1 is fixedly connected to the bottom of the rotor 7, and a plurality of contact plates 10 are arranged on the bottom surface at equal angular intervals. When the rotor 7 rotates with the rotation of the rotating shaft 9, air is discharged from the suction port 2 to the discharge port 3 through the vacuum chamber 4, and the pressure in the vacuum chamber 4 becomes 10 ⁻² to 10 −10.
The value is ^-10 kg / cm ² .

Between the vacuum chamber 4 and the driving chamber 8 of the casing 1, there is provided a thick-walled partitioning member 11 having a closed cylindrical shape. A radial bearing 13 is formed on the inner peripheral surface of the through hole 12. A herringbone-shaped dynamic pressure groove 14 is formed in a portion of the outer peripheral surface of the rotary shaft 9 facing the radial bearing portion 13, and the bearing portion is formed by the action of the dynamic pressure groove 14 as the rotary shaft 9 rotates. The pressure of the gas in the pressure chamber 15 between the outer peripheral surface of the rotary shaft 9 and the rotary shaft 9 is increased.
Is supported.

A plurality of gas introduction passages 16 having a channel shape corresponding to the cross-sectional shape are formed in the partition member 11 so as to penetrate vertically, and a thrust bearing portion facing the bottom surface of the rotor 7 is provided on the upper surface thereof. 17 are provided. This thrust bearing 17 is, as shown in FIG.
Are disposed on the same circumference, a gas film forming region 18 is provided between the gas introduction passage 16 and the outer peripheral edge of the free passage hole 12, and a gas seal formation region 19 is provided outside the gas introduction passage. Is provided.

In the gas film forming region 18 of the thrust bearing portion 17, a plurality of positive pressure grooves 20 extending in the outer peripheral direction in a spiral shape from the outer peripheral edge of the through hole 12, and the positive pressure groove 20 in the gas seal forming region 19. A plurality of seal forming grooves 21 extending in the outer peripheral direction in a spiral shape in the same direction as the pressure grooves 20 are formed. Then, as shown in FIG. 3, the air flowing by the rotation of the rotating shaft 9, that is, the rotation of the rotor 7 generates a positive pressure in the center direction along the positive pressure groove 20, and the pressure acting upward against the bottom of the rotor 7. Add. At the same time, a negative pressure is generated in the vicinity of the outlet of the gas introduction passage 16, air is introduced into the gas introduction passage 16 from the outside, and this air flow is divided into the positive pressure groove 20 and the seal forming groove 21 side, and the positive pressure groove The air pressurized in 20 is a pressure gas film A
Is generated to keep the rotor 7 floating. In the seal forming groove 21, the air flow is reduced to almost the same level as the pressure value of the vacuum chamber 4.
A gas seal S is generated above 21 to block the flow of air between the vacuum chamber 4 and the thrust bearing 17.

A disc-shaped mounting portion 22 is fixed to the lower end of the rotating shaft 9 in the drive chamber 8, and a plurality of magnet plates 23 buried on the lower surface thereof, and a stator 24 disposed opposite to these. The rotation shaft 9 is rotated by the change in the polarity of.

Now, when the rotating shaft 9 is not driven, the rotor 7 is
10 contacts the thrust bearing 17 and is supported by the partition member 11. Then, the stator 24 in the drive room 8 is
Is turned on, the rotating shaft 9 is rotated with the change in the polarity of the stator 24. 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, and causes the rotor 7 to float.

Air is introduced into the gas introduction passage 16 from the outside, and the air is diverted from the outlet of the introduction passage 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 generates a pressurized gas film A between the rotor 7 and the partition member 11, and the gas film A supports the thrust load of the rotor 7 to keep the rotor 7 floating. . On the other hand, the seal forming groove
Since the 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 21, the rotor 7 floats without the air flowing into the vacuum chamber 4. The smoothness of rotation of the rotating shaft 9 is ensured by maintaining the pressure distribution state set to be supported.

As described above, in the present embodiment, the flow of air introduced into the gas introduction passage 16 based on the air flow generated by the rotation of the rotor 7 is applied to the air seal by the seal forming groove 21 and to the positive pressure groove.
By applying a thrust load to the rotating shaft 9 as a positive pressure air film by 20 and supporting the rotor 7 in a floating manner, a gas bearing can be formed in a vacuum atmosphere.
Moreover, the configuration can be simplified and the number of parts can be reduced.

[Effects] As described above in detail, the present invention exerts an excellent effect that the production is simplified and the production cost can be kept low.

[Brief description of the drawings]

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

Claims (1)

(57) [Claims] 1. A gas bearing comprising a support portion (17) for rotatably supporting a supported member (7, 9) when the supported member (7, 9) rotates, wherein the supported member (7, 9) A gas introduction path (16) for introducing gas into the support section (17) based on the rotation of 9); and a gas introduction path provided in the support section (17) and from the gas introduction path (16) to the support section (17). The flow of the introduced gas is divided into two, and one of the flows generates a pressure gas film (A) between the support part (17) and the supported members (7, 9). A dynamic pressure generator (2) for generating an air barrier (S) for preventing escape of gas forming the gas film (A)
0,21) A gas bearing comprising: