KR101760550B1 - Vacuum pump - Google Patents

Abstract

The vacuum pump 10 of the present invention is provided with a pump casing 56 having an intake port 54a and an exhaust port 54b and pump chambers 50a to 50f formed therein and a pump casing 56 having bearings 84a and 84b, And rotors 60a to 60f connected to the rotary shaft 60 so as to rotate integrally with the rotary shaft 60. The rotary shaft 60 is supported in the pump chamber 50a to 50f and extends in the longitudinal direction of the pump casing 56, ). The pump casing 56 is provided with an atmospheric opening chamber 52 which is in fluid communication with the exhaust port 54b of the pump casing 56 and is open to the atmosphere.

Description

Vacuum pump {VACUUM PUMP}

The present invention relates to a vacuum pump used in a process such as a CVD process or an etching process, which is one of manufacturing methods for the production of semiconductors, liquid crystals, solar cells, LEDs and the like, and more particularly to a vacuum pump in which a sublimable gas or a corrosive gas And more particularly to a vacuum pump used in a process which can be used for a vacuum pump.

The vacuum pump connected to the vacuum chamber for exhausting the process gas introduced into the vacuum chamber generally includes a pump casing having an inlet port, an exhaust port and a pump chamber formed therein, and a rotor rotatably received in the pump casing. When the rotor rotates about its axis in the pump chamber, the process gas introduced into the pump chamber through the intake port is compressed by the rotor, and then exhausted out of the pump chamber through the exhaust port. The rotor is fixedly mounted on each of the rotating shafts extending through the pump casing. Each of the rotary shafts has both ends rotatably supported by the respective bearings disposed in the respective bearing chambers on the respective sides of the pump casing.

Therefore, the vicinity of the intake port of the pump casing of the vacuum pump connected to the vacuum chamber is in a vacuum state at the same level as the vacuum in the vacuum chamber, and the vicinity of the exhaust port of the pump casing is kept open atmospheric pressure. Both ends of the rotary shaft are rotatably supported by respective bearings and sealed by a contact seal or a noncontact seal in order to prevent damage to the bearing caused by the product gas caused by the process gas introduced into the bearing. A contactless seal is widely used to prevent damage due to the contact of the rotating shaft with the seal of the rotating shaft.

For example, when a vacuum chamber or the like is exhausted by using a multi-stage vacuum pump having a plurality of multi-stage pump chambers, in accordance with the flow through the continuous pump chamber in the vacuum pump, for example, the first pump chamber, the second pump chamber, The pressure of the process gas in the vacuum pump increases stepwise. In each pump chamber, the process gas has a higher pressure at the outlet side than at the inlet side. Therefore, the pressure of the process gas in the final stage pump chamber is substantially equal to the atmospheric pressure at the outlet side (exhaust port), and is lower than the atmospheric pressure at the inlet side. When a non-contact seal is used on the seal of the rotary shaft to prevent excessive wear of the rotary shaft, the pressure of the process gas in the bearing chamber adjacent to the final stage pump chamber and receiving the bearing therein, Corresponding. For example, when the pressure on the outlet side (exhaust port) of the final stage pump chamber is approximately 760 Torr at the atmospheric pressure, and the pressure at the inlet side of the final stage pump chamber is 200 Torr lower than the atmospheric pressure, the pressure of the bearing chamber adjacent to the final stage pump chamber is approximately 480 Torr [= (760 + 200) / 2].

The pressure at the inlet side of the final stage pump chamber is changed by influx of process gas from the vacuum chamber or the like. For example, when process gas is introduced from the vacuum chamber into the final stage pump chamber, the pressure at the inlet side of the final stage pump chamber rises from 200 Torr to 300 Torr. On the other hand, the pressure on the outlet side of the final stage pump chamber is hardly changed from the atmospheric pressure because the outlet side communicates with the atmosphere through the pump exhaust pipe. When the pressure at the inlet side of the final stage pump chamber rises from 200 Torr to 300 Torr, the pressure (average pressure) in the final stage pump chamber is 530 [= (760 + 300) higher than 480 Torr, which is the pressure in the bearing chamber adjacent to the final stage pump chamber ) / 2)] Torr.

Thus, the average pressure in the final stage pump chamber When the pressure in the bearing chamber adjacent to the pump chamber becomes higher than the pressure in the bearing chamber adjacent to the pump chamber, the process gas introduced into the final pump chamber tends to leak into the bearing chamber. In the case where the process gas contains a sublimable gas or the like, since the bearing chamber is generally kept at a low temperature, the product produced by the process gas is deposited on the bearing disposed in the bearing chamber and the lubricant used for lubricating the bearing , Causing damage to the bearings.

In order to effectively keep the temperature of the lubricating oil in the lubricating oil chamber at a low level and to minimize the vaporization of the lubricating oil while maintaining the temperature of the pump chamber at a high level so as to be suitable for exhausting gases such as condensable gas or sublimable gas, There has been proposed a dry pump including a hollow heat insulating intermediate chamber and a cooling channel for passing a coolant between lubricating oil chambers having relatively low temperatures (see Japanese Patent Application Laid-Open No. 2005-105829).

Patent Document 1: JP-A-2005-105829

The dry pump disclosed in Japanese Patent Application Laid-Open No. 2005-105829 maintains the temperature of the lubricating oil in the lubricating oil chamber at a low level effectively while maintaining the temperature of the pump chamber at a high level so as to be suitable for exhausting a gas such as a condensable gas or a sublimable gas Thereby minimizing the vaporization of the lubricating oil. However, the disclosed vacuum pump does not protect the bearing disposed in the bearing chamber located on the side of the pump casing from the process gas. It is widely used to introduce a purge gas such as N ₂ gas to prevent the process gas from leaking into the bearing in the noncontact state of the rotating shaft. However, if the amount of the purge gas introduced into the noncontact seal of the rotary shaft is increased, the pressure in the pump chamber deteriorates. Therefore, the amount of the purge gas introduced into the noncontact seal of the rotary shaft has a certain limit.

The present invention has been made in view of the above circumstances. It is an object of the present invention to provide a vacuum pump capable of effectively protecting a bearing from a process gas by effectively preventing a process gas introduced into a pump chamber from leaking to a bearing.

In order to achieve the above object, a vacuum pump according to the present invention comprises: a pump casing having therein a plurality of stages of pump chambers each having an intake port and an exhaust port and communicating with each other and divided by partition walls; And a plurality of rotors supported rotatably and arranged along the longitudinal direction of the pump casing, and a plurality of rotors respectively accommodated in the pump chamber and connected to the rotatable shaft and rotating in accordance with rotation of the rotatable shaft, Side partition wall and an exhaust-side end wall, and a side panel is provided on a side of the end wall on the exhaust side, and between the end wall and the side panel, Wherein the pump casing is provided with an inner wall and an outer wall disposed at a predetermined distance from the inner wall Is a vacuum pump, characterized in that a characteristic of the double-wall structure.

Even when a pressure in the pump chamber changes and a noncontact seal is used to seal the rotary shaft, an atmospheric opening chamber that is in fluid communication with the exhaust port of the pump casing and is open to the atmosphere is provided near the exhaust port. The chamber housing the bearing is always kept at atmospheric pressure. Therefore, the process gas introduced from the vacuum pump into the pump chamber is surely prevented from leaking into the chamber located outside the atmospheric release chamber and receiving the bearing therein. Thus, the bearing is protected from the process gas.

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When the vacuum pump is a multi-stage vacuum pump, the pressure at the inlet side of the final stage pump chamber is lower than the atmospheric pressure even if the outlet side (exhaust port) of the final stage pump chamber is almost atmospheric pressure. When the process gas flows from the vacuum pump into the final stage pump chamber, the pressure (average pressure) in the final stage pump chamber changes, that is, increases. However, since the atmospheric opening chamber is disposed outside the final-stage pump chamber, such a change in the pressure (average pressure) in the final-stage pump chamber is located outside the atmospheric opening chamber and affects the pressure in the chamber, .

According to a second aspect of the invention, there is provided the vacuum pump according to the first aspect, wherein the side panel has the rotation shaft inserted therein, and the purge gas passage for supplying the purge gas to the insertion penetration portion of the rotation shaft is provided .
The invention according to claim 3 is the vacuum pump according to claim 1 or 2, wherein the atmospheric opening chamber has a constant width.

Since the purge gas flow path for supplying the purge gas to a part of the rotary shaft disposed in the side panel is formed in the side panel in which the rotary shaft extends through the side panel, a noncontact seal for protecting the rotary shaft from abrasion due to contact, .

According to the present invention, even if the pressure in the pump chamber changes, since the chamber located outside the atmospheric release chamber and receiving the bearing therein is always kept at atmospheric pressure, the process gas introduced into the pump chamber is located outside the atmospheric release chamber To prevent leakage into the chamber housing the bearing therein. Therefore, the bearing is reliably protected from the process gas.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal elevation view showing a vacuum pump according to an embodiment of the present invention; FIG.
Fig. 2 is a longitudinal side view of the pump chamber of the first stage of the main pump provided in the vacuum pump shown in Fig. 1. Fig.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 is a longitudinal elevation view showing a vacuum pump 10 according to an embodiment of the present invention. 1, the vacuum pump 10 includes a booster pump 12 disposed on the vacuum side and a main pump 14 disposed on the atmosphere side, which are connected to each other by a connection pipe 16 Respectively. In this embodiment, the main pump 14 is a six-stage roots vacuum pump, and the booster pump 12 is a single roots vacuum pump.

The booster pump 12 includes a pump casing 22 having a substantially cylindrical outer cylinder 20 having a pump chamber 18 formed therein and a pump casing 22 disposed through the pump casing 22 and driven by the electric motor 24 And a pair of rotation shafts 26 that are rotatable in synchronism with each other in the reverse direction about an axis. A pair of rotors 28 such as a bipolar rotor are rotatably received in the pump chamber 18 with a predetermined clearance therebetween. The rotors 28 are fixedly mounted on the rotary shaft 26, respectively. The outer cylinder 20 includes an inlet port 20a formed in the wall and connected to a discharge pipe (not shown) extending from a vacuum chamber or the like exhausted by the vacuum pump 10, And an exhaust port 20b connected to the exhaust port 20b. When the rotor 28 is rotated synchronously in the reverse direction about its axis by the driving of the electric motor 24, the process gas in the vacuum chamber or the like flows into the pump chamber 18 through the intake port 20a, And is discharged to the connection pipe 16 through the exhaust port 20b. 1 shows only one mechanism for driving the rotary shaft 26 on the basis of the driving force from the rotary shaft 26, the rotor 28 and the electric motor 24. The other side of the rotating shaft, the rotor and the mechanism is located on the opposite side of the view of Fig.

In the present embodiment, the outer circumferential surface of the outer casing 22 of the pump casing 22 is surrounded by a substantially hollow cylindrical heater jacket 30, except for the intake port 20a and the exhaust port 20b. When power is supplied, the heater jacket 30 heats the inside of the pump chamber 18.

The booster pump 12 is generally kept at a low vacuum because the internal vacuum level is kept high (the pressure level is low) and a lot of compression heat is not generated. Therefore, even if the pressure in the pump chamber 18 is low, sublimable substances contained in the process gas flowing into the pump chamber 18 may be deposited on the inner peripheral surface of the pump chamber 18. However, as described above, by raising the temperature in the pump chamber 18 by the heater jacket 30, the sublimable substances contained in the process gas flowing into the pump chamber 18 are precipitated from the inner peripheral surface of the pump chamber 18 .

At the shaft end of the pump casing 22, two side panels 32a and 32b are respectively disposed. The rotary shaft 26 is rotatably supported at its outer end by the bearings 36a and 36b housed in the bearing housings 34a and 34b respectively mounted to the side panels 32a and 32b. Two lubricating oil housings 40a and 40b for holding lubricating oil are disposed on the outer side surfaces of the side panels 32a and 32b, respectively. The motor housing of the electric motor 24 is connected to one of the lubricating oil housings 40b.

Rotating shaft within the process gas flows into the pump chamber 18, the bearing (36a, 36b), side panels (32a, 32b) to prevent the outflow of silver, N ₂ purge gas to the side panels (32a, 32b) such as a gas ( And purge gas flow paths 42a and 42b for supplying the purge gas flow paths 42a and 42b. The purge gas supplied from the purge gas flow paths 42a and 42b provides a noncontact seal between the side panels 32a and 32b and the rotary shaft 26 to protect the rotary shaft 26 from abrasion due to contact.

The main pump 14 of this embodiment is constituted by a six-stage roots vacuum pump and includes six pump chambers 50a to 50f, that is, a first pump chamber 50a to a sixth pump chamber 50f, An atmospheric opening chamber 52 formed adjacent to the sixth stage pump chamber 50f and a pump casing 56 disposed through the pump casing 56 and connected to the electric motor 58. The pump casing 56 includes a cylindrical outer cylinder 54, And a pair of rotation shafts 60 that are rotatable in synchronism with each other in the reverse direction about the axis in accordance with the driving of the shafts. As shown in Fig. 2, a pair of rotors 62a such as a three-leaf rotor is rotatably received in the first-stage pump chamber 50a disposed on the suction side of the main pump 14. Likewise, a pair of rotors 62b such as a three-leaf rotor are rotatably housed in the second-stage pump chamber 50b, and a pair of rotors 62c such as a three-leaf rotor are accommodated in the third-stage pump chamber 50c And is rotatably received inside. A pair of rotors 62d such as a three-leaf rotor is rotatably received in the fourth-stage pump chamber 50d and a pair of rotors 62e such as a three-rotor rotor are accommodated in the fifth-stage pump chamber 50e And a pair of rotors 62f such as a three-leaf rotor are rotatably housed in a sixth-stage pump chamber 50f disposed on the discharge side of the main pump 14. [ One of the rectilinearly arranged rotors 62a to 62f is fixedly mounted on one of the rotating shafts 60 and the other rectilinearly arranged rotors 62a to 62f are fixedly mounted on the other one of the rotating shafts 60. [

The pump casing 56 includes end walls 64a and 64b for closing both end portions of the outer cylinder 54 and five divided portions that divide the inside of the outer cylinder 54 from the first divided wall 66a to the fifth divided portion And a wall 66e. A first stage pump chamber 50a is formed in the outer cylinder 54 between the end wall 64a and the first partition wall 66a. A second stage pump chamber 50b is formed in the outer cylinder 54 between the first end wall 66a and the second partition wall 66b. A third stage pump chamber 50c is formed in the outer cylinder 54 between the second end wall 66b and the third partition wall 66c. A fourth-stage pump chamber 50d is formed in the outer cylinder 54 between the third end wall 66c and the fourth partition wall 66d. A fifth-stage pump chamber 50e is formed in the outer cylinder 54 between the fourth end wall 66d and the fifth partition wall 66e. A sixth-stage pump chamber 50f is formed in the outer cylinder 54 between the fifth partition wall 66e and the end wall 64b. An atmospheric opening chamber 52 is formed between the end wall 64b and the axially spaced side panel 80b disposed adjacent to the end wall 64b.

2, when the rotor 62a of the first-stage pump chamber 50a is rotated synchronously in the reverse direction about its axis by the electric motor 56, the process gas is connected to the connection pipe 16 Stage pump chamber 50a from the upper inlet side and is compressed by the rotor 62a in the first stage pump chamber 50a and then discharged from the first stage pump chamber 50a to the lower outlet side. Thereafter, the process gas is equally compressed in the second-stage pump chamber 50b to the sixth-stage pump chamber 50f.

The outer cylinder 54 is provided with an intake port 54a formed on the side wall and connected to the connection pipe 16 and in fluid communication with the upper inlet side of the first stage pump chamber 50a, And an exhaust port 54b in fluid communication with the lower outlet side of the pump chamber 50f. The exhaust port 54b is in fluid communication with the atmospheric release chamber 52 through the end wall 64b. With this structure, the atmospheric opening chamber 52 is opened to the atmosphere through the exhaust port 54b. The outer casing 54 of the pump casing 56 has a double wall structure including an inner wall 68 and an outer wall 70 disposed outside at a predetermined distance from the inner wall 68, A first gas passage 72a to a fifth gas passage 72e are formed between the outer wall 68 and the outer wall 68. [ Specifically, the first gas passage 72a is formed around the first-stage pump chamber 50a, and the second gas passage 72b is formed around the second-stage pump chamber 50b. The third gas passage 72c is formed around the third pump chamber 50c and the fourth gas passage 72d is formed around the fourth pump chamber 50d and the fifth gas passage 72e is formed around the fifth But is formed around the pump chamber 50e. In addition, the fifth gas passage 70e is formed around the sixth-stage pump chamber 50f.

The gas passages 72a to 72e have respective portions that are in fluid communication with the respective pump chambers 50a to 50e via respective lower outlet sides and are in fluid communication with the respective pump chambers 50b to 50f through the respective upper inlet sides And have respective portions. 2, the process gas introduced into the first pump chamber 50a from the suction port 54a through the upper inlet side is compressed in the first pump chamber 50a, And then flows into the first gas passage 72a from the pump chamber 50a through the lower outlet side. Then, the process gas flows upward in the first gas passage 72a and reaches the upper inlet side of the second-stage pump chamber 50b. The process gas flows into the second stage pump chamber 50b through the upper inlet side and is compressed in the second stage pump chamber 50b and then flows from the second stage pump chamber 50b to the second gas flow path 72b. Then, the process gas flows upward in the second gas flow path 72b and reaches the upper inlet side of the third stage pump chamber 50c. Thereafter, the process gas is compressed and passes through the third-stage pump chamber 50c to the sixth-stage pump chamber 50f. Thereafter, the process gas is discharged from the lower outlet side of the sixth pump chamber 50f through the exhaust port 54b and out of the main pump 14. [

According to the present embodiment, since the outer cylinder 54 of the pump casing 56 has the double wall structure including the gas flow channels 72a to 72e therein, the high-temperature process gas flowing through the gas flow channels 72a to 72e The interior of the pump chambers 50a to 50f is reliably thermally isolated from the outside so that the interior of the main pump 14 is kept at a high temperature so that the sublimable gas or the like contained in the process gas is converted into solid, 14, that is, from the inner circumferential surface of the pump casing 56, can be prevented. Particularly, the high-temperature process gas flowing from the lower outlet side of the pump chambers 50a to 50e to the upper inlet side of the next pump chambers 50b to 50f through the gas channels 72a to 72e causes the pump chambers 50a to 50f to be heated It is effective in doing.

The outer peripheral surface of the outer cylinder 54 of the pump casing 56 is surrounded by a heater jacket 74 of a substantially hollow cylindrical shape except for the intake port 54a and the exhaust port 54b. The heater jacket 74 keeps the inside of the pump chambers 50a to 50f at a constant temperature by interrupting the inside of the pump chambers 50a to 50f with the outside.

Two side panels 80a and 80b are disposed on the end walls 64a and 64b of the pump casing 56, respectively. The rotary shaft 60 is rotatably supported at its outer end by the bearings 84a and 84b housed in the bearing housings 82a and 82b respectively mounted to the side panels 80a and 80b. Two lubricating oil housings 88a and 88b for holding lubricating oil are disposed on the outer side surfaces of the side panels 80a and 80b, respectively. The motor housing of the electric motor 58 is connected to one of the lubricating oil housings 88b. Pump chamber (50a~50f) the process gas is introduced into the bearing (84a, 84b), side panels (80a, 80b) to prevent the outflow of silver, N ₂ gas purge gas side panel (80a, 80b), such as in the And purge gas passages 90a and 90b for supplying the purge gas to a part of the rotary shaft 60, respectively. The purge gas supplied from the purge gas passages 90a and 90b provides a noncontact seal between the side panels 80a and 80b and the rotary shaft 60 to protect the rotary shaft 60 from abrasion due to contact. Further, the purge gas flowing through the purge gas flow path 90b flows into the atmospheric opening chamber 52.

According to the present embodiment, between the end wall 64b near the sixth (final stage) pump chamber 50f where the process gas becomes the highest pressure and the side panel 80b located adjacent to the end wall 64b An atmospheric opening chamber 52 is provided which is in fluid communication with the exhaust port 54b and is open to the atmosphere. The lubricating oil housing 88b housing the bearing housing 82b in which the bearing 84b is disposed is mounted on the side panel 80b. Therefore, even when the pressure in the sixth stage (final stage) pump chamber 50f is changed, the pressure in the chamber R, i.e., the side panel 80b, which is located outside the atmospheric release chamber 52 and accommodates the bearing 84b, The chamber R surrounded by the housing 88b is always kept at almost atmospheric pressure. Therefore, the process gas introduced into the pump chambers 50a to 50f is surely prevented from leaking into the chamber R, which is positioned outside the atmospheric opening chamber 52 and accommodates therein the bearing 84b. Therefore, the bearing 84b is protected from the process gas.

The reason why the bearing 84b is protected from the process gas will be explained below. When the sixth stage (final stage) pump chamber 50f is positioned immediately adjacent to the side panel 80b, in other words, when the air in the atmospheric opening chamber 52 The pressure in the chamber R that is located outside the open chamber 52 and accommodates the bearing 84b, that is, the pressure in the chamber R surrounded by the side panel 80b and the lubricant housing 88b, The pressure is almost equal to the average pressure in the sixth (final stage) pump chamber 50f. For example, when the pressure on the outlet side of the sixth pump chamber 50f is atmospheric pressure 760 Torr and the pressure on the inlet side is lower than the atmospheric pressure, for example, 200 Torr, the side panel 80b and the lubricant housing 88b The pressure in the enclosed chamber R is about 480 Torr [= (760 + 200) / 2]. When the pressure at the inlet side of the sixth-stage pump chamber 50f changes from 200 Torr to 300 Torr, that is, by the inflow of the process gas from the vacuum chamber, the average pressure in the sixth-stage pump chamber 50f becomes 530 Torr [ = (760 + 300) / 2]. The process gas is introduced into the chamber R through the gap between the side panel 80b and the rotary shaft 60 from the sixth stage pump chamber 50f until the pressure in the chamber R rises to 530 Torr .

According to the present embodiment, between the end wall 64b near the sixth (final stage) pump chamber 50f and the side panel 80b disposed adjacent to the end wall 64b is provided an exhaust port 54b There is provided an atmospheric opening chamber 52 which is in fluid communication and is open to the atmosphere. Therefore, even if the pressure (average pressure) in the sixth-stage pump chamber 50f changes or rises, the pressure in the atmospheric release chamber 52 does not change from the atmospheric pressure, The pressure in the chamber R surrounded by the chamber R and the side panel 80b and the lubricating oil housing 88b which are positioned on the outer side and accommodate the bearing 84b on the outside, It is kept at atmospheric pressure without being affected by a change in pressure.

The vacuum pump 10 constructed as described above is driven by the electric motor 24 of the booster pump 12 and the electric motor 58 of the main pump 14 to drive the booster pump 12 and the main pump 14 For example, to evacuate the process gas introduced into the vacuum chamber from the vacuum chamber. The pressure in the chamber R surrounded by the chamber R and the side panel 80b and the lubricating oil housing 88b located outside the atmospheric opening chamber 52 and receiving the bearing 84b outside is always almost By maintaining the atmospheric pressure, the process gas introduced into the main pump 14 is surely prevented from leaking to the bearing 84b. Therefore, the bearing 84b is protected from the process gas.

Although a preferred embodiment of the present invention has been described, the present invention is not limited to the above-described embodiments, but should be understood within the scope of the technical concept included herein. For example, in the present embodiment, the present invention is applied to a multi-stage Roots vacuum pump. However, the technical scope of the present invention is not limited to a vacuum pump including at least two types of vacuum pump, single vacuum vacuum pump, screw vacuum pump, Roots type vacuum cleaner, It may be applied to a vacuum pump combined on a rotary shaft.

Industrial availability

The present invention can be applied to a vacuum pump used in a process in which a sublimable gas or a corrosive gas can be introduced into a vacuum pump.

Claims (4)

A pump casing having an intake port and an exhaust port and communicating with each other and having a plurality of stages of pump chambers divided into partition walls,
A rotating shaft rotatably supported at both ends by a bearing and disposed along the longitudinal direction of the pump casing,
A plurality of rotors that are respectively received in the pump chambers and connected to the rotors to rotate in accordance with rotation of the rotors;
Lt; / RTI >
The pump chamber in the final stage is formed by a partition wall on the intake side and an end wall on the exhaust side,
A side panel is provided on the side of the end wall on the exhaust side,
An atmospheric opening chamber communicating with the exhaust port and being open to the atmosphere is provided between the end wall and the side panel,
Wherein the pump casing has a double wall structure including an inner wall and an outer wall disposed at a predetermined distance from the inner wall. The vacuum pump according to claim 1, wherein the side panel has a rotation shaft inserted therein, and a purge gas passage for supplying a purge gas to the insertion hole of the rotation shaft is provided. The vacuum pump according to claim 1 or 2, wherein the atmospheric opening chamber has a constant width. delete

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