JPH04353296A - Vacuum pump - Google Patents

Abstract

PURPOSE:To sufficiently heighten pumping performance without increasing required power and additionally to effectively seal a bearing. CONSTITUTION:A screw rotor 9 forming an exhaust passage 10 communicating through to a gas passage 4 is provided free to rotate integrally with a pump rotor on the side of an exhaust port 12 of the pump rotor 3 arranged free to rotate on the gas passage 4 of a pump stator 2. Upper and lower clearances against the pump stator 2 are set large by communicating the exhaust passage 10 formed between the screw, rotor 9 and a face 2a which the pump stator 2 faces through to the exhaust port 12. Additionally a bearing 8 is effectively sealed by discharging gas in the gas passage 4 to the exhaust port 12 and communicating the exhaust passage 10 through to the bearing 8 supporting a drive shaft 71 on a bulkhead 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump used in semiconductor manufacturing equipment and the like.

0002

2. Description of the Related Art Conventionally, this type of vacuum pump is already known, as disclosed in, for example, Japanese Patent Laid-Open No. 1-237397. As shown in FIG. 3, this conventional vacuum pump is equipped with an intake port connected to a semiconductor manufacturing room or the like at the top.
Further, a motor-side casing E containing a motor is provided at the bottom of a pump-side casing D having a partition wall B having an exhaust port A at the bottom and a pump stator C therein,
A plurality of upper and lower vortex rotors G are freely rotatably arranged in the gas flow path F of the pump stator C, and the drive shaft H of the motor is inserted into the pump side casing D and coupled to the vortex rotor G. On the other hand, the partition wall B is provided with an oil-lubricated bearing J that supports the drive shaft H, and the gas flow path F is communicated with the exhaust port A, so that the rotation of the vortex rotor G causes gas to flow from the intake port. evacuating the gas introduced into the flow path F to the exhaust port A;
It is configured to maintain the semiconductor manufacturing room and the like in a clean state. Further, in this vacuum pump, a screw seal L is provided in the drive shaft receiving shaft hole K on the exhaust port A side of the pump stator C, and the pump stator C is provided with a threaded seal L at the outlet in the gas flow path F and the exhaust port A. A part of the gas discharged from the gas flow path F to the exhaust port A is provided with a discharge passage N that communicates with the exhaust passage N, and a branch passage P that branches from the discharge passage N and opens into the shaft hole K. A part of this gas is supplied from the branch path P to the shaft hole K and used as a seal gas, and the bearing J is sealed with this seal gas.

0003

[Problem to be Solved by the Invention] However, as described above, it is desirable to rotate the vortex rotor G disposed in multiple stages above and below in the gas flow path F of the pump stator C to move the gas in the gas flow path F to the exhaust port. In the case of a vacuum pump designed to discharge air to A, in order to avoid deterioration in pump performance, it is necessary to reduce the vertical clearance between the final stage vortex rotor G closest to the exhaust port A and the pump stator C. If the gap is made too small, an accident will occur where the vortex rotor G comes into contact with the pump stator C due to thermal expansion, so it is difficult to manage the above-mentioned vertical gap, and the manufacturing cost of the pump stator C and the vortex rotor G is reduced accordingly. There is a problem that the pump performance becomes high, and since it is necessary to provide a gap necessary to eliminate the above-mentioned contact accident, there is a problem that the pump performance cannot be sufficiently improved. In addition, in the above configuration, in order to sufficiently improve the pump performance, it is conceivable to increase the rotation speed of the vortex rotor G, but if the rotation speed is increased, the required power will increase accordingly, and the running speed will increase. There is a problem of high cost. On the other hand, when the vortex rotor G rotates within the gas flow path F of the pump stator C, there is a low pressure region on the intake side and a high pressure region on the exhaust side in the circumferential direction of the gas flow path F, that is, Since there is a pressure distribution in the circumferential direction, the shaft sealing gas for sealing the bearing J becomes a local flow from the shaft hole K to the low pressure region side of the gas flow path F where the swirl rotor G rotates, and the gas Since the flow returns to the flow path F, the lubricating oil in the bearing J is lifted up to the gas flow path F side together with the recirculated seal gas, and a sufficient shaft seal cannot be achieved, resulting in poor reliability of the shaft seal. There was a problem.

The present invention was devised in view of the above-mentioned problems, and its purpose is to sufficiently improve pump performance without increasing the required power, and to eliminate the risk of contact accidents between the pump rotors. The purpose of this invention is to enable sufficient sealing of the bearing.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a pump-side casing 1 having an intake port 11 and an exhaust port 12, a pump stator 2 inside, a motor 7 inside, and a partition wall. A motor-side casing 6 is partitioned from the exhaust port 12 via a motor-side casing 6, and the pump rotor 3 is rotatably arranged in the gas flow path 4 of the pump stator 2, while the drive shaft 71 of the motor 7 In the vacuum pump, the exhaust port 12 of the pump rotor 3 is inserted into the pump side casing 1 and coupled to the pump rotor 3, and the partition wall 5 is provided with a bearing 8 that supports the drive shaft 71. A screw rotor 9 is provided on the side thereof with a screw 91 facing the inner circumferential surface of the pump stator 2, and has an exhaust passage 10 communicating with the gas flow passage 4, and is rotatable with the pump rotor 3. An exhaust passage 10 formed between the screw rotor 9 and the facing surface 2a of the pump stator 2 is communicated with the exhaust port 12 and with the bearing 8.

[0006] Also, an exhaust passage 10 formed in the screw rotor 9
A purge gas supply passage 1 is provided in the communication passage 13 between the bearing 8 and the bearing 8.
It is preferable to communicate 4.

[0007]

[Operation] When the pump rotor 3 is driven to rotate to perform evacuation, the screw rotor 9 rotates together with the pump rotor 3, and the gas in the gas passage 4 communicating with one end of the screw rotor 9 in the axial direction is transferred to the screw rotor. Since the screw rotor 9 is disposed on the exhaust port 12 side of the pump rotor 3 which communicates with the other end in the axial direction of the pump rotor 9, the vertical clearance between the pump rotor 3 and the pump stator 2 is reduced. can be set large, and therefore, the vertical clearance can be easily managed, making it easy to manufacture the pump rotor 3 and pump stator 2, and reducing costs accordingly. Since the screw rotor 9 is provided on the side and the gas in the gas flow path 4 is discharged to the exhaust port 12, the pump performance can be sufficiently enhanced without increasing the required power. Since the vertical clearance can be set large, it is possible to eliminate the risk of a contact accident in which the pump rotor 3 comes into contact with the pump stator 2. Also,
In the exhaust passage 10 formed between the screw rotor 9 and the pump stator 2, a low pressure side communicating with the gas flow path 4 and a high pressure side communicating with the exhaust port 12 are displaced in the axial direction of the screw rotor 9. Since no circumferential pressure distribution occurs at the outlet of the exhaust passage 10, by communicating the exhaust passage 10 with the bearing 8 that supports the drive shaft 71 on the partition wall 5,
The seal of the bearing 8 can be made effective, and the lubricating oil of the bearing 8 can be prevented from flowing out to the gas flow path 4 side.

[0008] Furthermore, an exhaust passage 10 formed in the screw rotor 9
A purge gas supply passage 14 is provided in the communication passage 13 between the bearing 8 and the bearing 8.
By supplying purge gas to the communicating path 13, even if the gas coming out of the exhaust path 10 contains corrosive gas components, the flow of this gas toward the bearing 8 side can be prevented. This can reliably prevent corrosion of the bearing 8.

[0009]

[Embodiment] The vacuum pump shown in FIGS. 1 and 2 has a jig burn type pump element 2 in a cylindrical pump side casing 1.
00 and a vortex type pump element 300 are arranged vertically, and a motor side casing 6 in which a motor 7 is installed is coupled to the lower end of the pump side casing 1 via a partition 5. , the drive shaft 71 of the motor 7 is inserted into the pump side casing 1 through the shaft hole 51 provided in the partition wall 5, and the respective pump elements 200, 30 are inserted.
0 rotor is rotated.

Further, an intake port 11 connected to a semiconductor manufacturing room or the like is provided in the upper part of the pump side casing 1, and an exhaust port 12 opened to the outside is provided in the partition wall 5. 51 is provided with a bearing 8 that supports the drive shaft 71.

[0011] Also, the jig burn type pump element 200
has gas flow paths 4 in two stages, upper and lower, so as to be able to communicate with each other,
A disk-shaped jig burn stator 21 fixed in the pump side casing 1, and upper and lower parts 2 having spiral blades and freely rotatable in the gas flow path 4 of the jig burn stator 21.
The vortex-type pump element 300 has gas flow passages 4 in two stages, upper and lower, so as to be able to communicate with each other, and is located below the jig-burn stator 21 in the pump-side casing 1. It consists of a vortex stator 22 fixed to a part, and two upper and lower vortex rotors 32 having a large number of blades 32a on the outer periphery and freely rotatable in the gas flow path 4 of the vortex stator 22, and each of the jig burn stators 21 and each vortex stator 22 constitute a pump stator 2, and each jig burn rotor 31 and each vortex rotor 32 constitute a pump rotor 3, and the drive shaft 71 is coupled to this pump rotor 3. There is. Note that the gas flow path 4 of the jig burn stator 21, the gas flow path 4 of the vortex stator 22, and the exhaust port 12 are in communication with each other.

[0012] As shown in FIG.
In addition, a screw 91 is provided on the exhaust port 12 side of the vortex rotor 22 to face the inner peripheral surface of the lumen 23 of the pump stator 2, and the vortex stator The screw rotor 9 having an exhaust passage 10 communicating with the lowermost gas flow passage 4 of 22 is attached to the vortex rotor 32.
The body is rotatably provided, and an exhaust passage 10 formed between the screw rotor 9 and the inner circumferential surface (2a) of the inner cavity 23 is communicated with the exhaust port 12, and the exhaust passage 10 and the A part of the gas discharged from the exhaust passage 10 is supplied to the bearing 8 by communicating with the shaft hole 51 through the communication passage 13, so that the lubricating oil in the bearing 8 flows out to the exhaust passage 10 side. I am trying to prevent this.

The screw rotor 9 is formed into a bottomed cylindrical shape with an open lower end, and the screw 91 having a plurality of spiral grooves opening from one end in the axial direction to the other end is formed on the outer periphery of the screw rotor 9. The communication path 13 is formed between the screw rotor 9 and the partition wall 5. Further, although the screw rotor 9 has its bottom portion connected to the lower end of the vortex rotor 32 with a mounting screw, it may be formed integrally with the vortex rotor 32.

Further, the partition wall 5 is provided with an annular purge chamber 15 in the shaft hole 51, and a purge gas supply passage 14 extending from the outer peripheral surface toward the center in the radial direction and opening into the purge chamber 15. Purge gas can be supplied from this purge gas supply passage 14 to the purge chamber 15.

In the vacuum pump constructed as described above, the jig burn rotor 31, the vortex rotor 32, and the screw rotor 9 are rotated at a high speed of, for example, several tens of thousands of times per minute by the drive of the motor 7. 31 and vortex rotor 3
2, the gas flowing into the gas flow path 4 from the intake port 11 is discharged to the exhaust path 10 side, and the pressure at the entrance side of the exhaust path 10 becomes close to 400T0 rr. The gas discharged to the inlet side of the exhaust passage 10 is discharged from the exhaust passage 10 to the exhaust port 12 by the rotation of the screw rotor 9, and at the exit of the exhaust passage 10, the gas reaches atmospheric pressure (760T0 rr
) and is discharged to the outside from the exhaust port 12 at this atmospheric pressure. Thus, the screw rotor 9 has one axial end communicating with the gas flow path 4 and the other end communicating with the exhaust port 12 to drain the gas in the gas flow path 4 from the one axial end of the screw rotor 9. Because it is discharged to the other end,
The vortex rotor 32 and the jig burn rotor 31 can be arranged on the low pressure side where the influence of the vertical clearance on the vortex stator 22 and the jig burn stator 21 is reduced,
The vertical clearance between the vortex rotor 32 and the jig burn rotor 31 relative to the vortex stator 22 and the jig burn stator 21 can be set large. Therefore, since it is easy to manage the vertical clearance, it is easy to manufacture the screw rotor 9, the swirl rotor 32, the jig burn rotor 31, the swirl stator 22, and the jig burn stator 21,
This allows for cost reduction. At the same time, a screw rotor 9 is attached to the exhaust port 12 side of the vortex rotor 32.
Since the gas in the gas flow path 4 is discharged to the exhaust port 12, the pump performance can be sufficiently improved without increasing the required power. In addition, since the vertical clearance can be set large, the vortex rotor 3
There is no risk of a contact accident in which the rotor 2 and the jig burn rotor 31 come into contact with the vortex stator 22 and the jig burn stator 21.

Further, the communication passage 13 that communicates the outlet of the exhaust passage 10 with the bearing 8 becomes atmospheric pressure, and the pressure difference between the atmospheric pressure inside the motor side casing 6 and the atmospheric pressure in the communication passage 13, which is at atmospheric pressure, increases. Therefore, the bearing 8 can be sealed by the gas discharged from the exhaust passage 10, and the exhaust passage 10 has a low pressure side communicating with the gas flow passage 4 and a high pressure side communicating with the exhaust port 12. are displaced in the axial direction of the screw rotor 9, and no pressure distribution in the circumferential direction occurs at the outlet of the exhaust passage 10, so that the shaft sealing gas for sealing the bearing 8 is returned to the exhaust passage 10. Therefore, the lubricating oil in the bearing 8 is not lifted up into the exhaust passage 10 together with the seal gas, and the sealing of the bearing 8 can be made effective.

Furthermore, by supplying purge gas from the purge gas supply passage 14 to the purge chamber 15, a purge gas atmosphere is created in the shaft hole 51 around the drive shaft 71, so that the gas flowing from the exhaust passage 10 into the communication passage 13 is The bearing 8
Since it is possible to reliably prevent the gas from flowing into the side, if the gas evacuated by each of the rotors 31, 32, and 9 contains a corrosive gas component, the gas containing the corrosive gas component Therefore, the bearing 8 and the built-in components inside the motor side casing 6 can be protected.

In the above embodiment, a composite vacuum pump is shown in which the jig burn type pump element 200 and the vortex type pump element 300 are provided in the pump side casing 1, but other than the above jig burn type pump element The structure may include only one of the pump element 200 and the swirl pump element 300.

[0019]

Effects of the Invention As described above, the present invention provides a pump rotor 3 rotatably disposed in a gas passage 4 of a pump stator 2.
A screw 91 facing the inner peripheral surface of the pump stator 2 is provided on the exhaust port 12 side of the pump stator 2, so that the screw rotor 9, which has an exhaust passage 10 communicating with the gas flow passage 4, can be rotated together with the pump rotor 3. An exhaust passage 10 formed between the screw rotor 9 and the opposing surface 2a of the pump stator 2 is connected to the exhaust port 12, so that the gas flow passage 4 in the gas flow passage 4, which communicates with one end of the screw rotor 9 in the axial direction, is connected to the exhaust port 12. Gas, screw rotor 9
Since the exhaust port 12 communicates with the other axial end of the pump stator 2 of the pump rotor 3,
Since the vertical gap can be set large, and the vertical gap can be easily managed, the pump rotor 3 and the pump stator 2 can be manufactured easily, and the cost can be reduced accordingly. Since the screw rotor 9 is provided on the exhaust port 12 side of the pump 3 to discharge the gas in the gas flow path 4 to the exhaust port 12, the pump performance can be sufficiently enhanced without increasing the required power. Moreover, since the vertical gap can be set large, there is no fear of a contact accident in which the pump rotor 3 comes into contact with the pump stator 2.

Furthermore, the exhaust passage 10 formed between the screw rotor 9 and the pump stator 2 has a low pressure side communicating with the gas passage 4 of the screw rotor 9 and a high pressure side communicating with the exhaust port 12. Since the screw rotor 9 is displaced in the axial direction and no pressure distribution in the circumferential direction occurs at the exit of the exhaust path, by making the exhaust path 10 communicate with the bearing 8 that supports the drive shaft 71 on the partition wall 5, The seal of the bearing 8 can be made effective, and the lubricating oil of the bearing 8 can be prevented from flowing out to the gas flow path 4 side.

Furthermore, an exhaust passage 10 formed in the screw rotor 9
A purge gas supply passage 14 is provided in the communication passage 13 between the bearing 8 and the bearing 8.
By supplying purge gas to the communicating path 13, even if the gas discharged from the exhaust path 10 contains corrosive gas components, the flow of this gas toward the bearing 8 side is prevented. It is possible to reliably prevent corrosion of the bearing 8 and the built-in components in the motor side casing 6.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a vacuum pump of the present invention.

FIG. 2 is a partial sectional view of only the essential parts.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

1 Pump side casing 2 Pump stator 3 Pump rotor 4 Gas flow path 5 Bulkhead 6 Motor side casing 7 Motor 8 Bearing 9 Screw rotor 10 Exhaust path 11 Intake port 12 Exhaust port 13　　　Communication path 14 Purge gas supply passage 71 Drive shaft 91 screw

Claims (2)

[Claims] 1. A pump side casing 1 having an intake port 11 and an exhaust port 12 and housing a pump stator 2 therein, and a motor side housing a motor 7 therein and partitioned from the exhaust port 12 through a partition wall 5. A casing 6 is provided, and the pump rotor 3 is rotatably disposed within the gas flow path 4 of the pump stator 2, while the drive shaft 71 of the motor 7 is inserted into the pump side casing 1 to rotate the pump rotor 3. In the vacuum pump, a bearing 8 for supporting the drive shaft 71 is provided on the partition wall 5, and a screw is provided on the exhaust port 12 side of the pump rotor 3, facing the inner circumferential surface of the pump stator 2. 91, and a screw rotor 9 having an exhaust path 10 communicating with the gas flow path 4 is provided so as to be rotatable with the pump rotor 3, and between the screw rotor 9 and the opposing surface 2a of the pump stator 2. The exhaust passage 10 to be formed is communicated with the exhaust port 12, and the bearing 8
A vacuum pump characterized by being connected to. 2. The vacuum pump according to claim 1, wherein a purge gas supply passage 14 is connected to a communication passage 13 between an exhaust passage 10 formed in the screw rotor 9 and the bearing 8.