KR20140023958A - Vacuum pump - Google Patents

Abstract

The vacuum pump 10 of the present invention is rotated at both ends by a pump casing 56 having an inlet port 54a, an exhaust port 54b, and pump chambers 50a to 50f formed therein, and bearings 84a and 84b. Rotating shaft 60 which is supported and extends in the longitudinal direction of pump casing 56, and rotors 62a to 62f housed in pump chambers 50a to 50f and connected to rotating shaft 60 to rotate integrally with rotating shaft 60. ). The pump casing 56 is provided with an air opening chamber 52 in fluid communication with the exhaust port 54b of the pump casing 56 and open to the atmosphere.

Description

Vacuum pump {VACUUM PUMP}

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

The vacuum pump connected to the vacuum chamber and exhausting the process gas introduced into the vacuum chamber generally includes a pump casing having an intake port, an exhaust port and a pump chamber formed therein, and a rotor rotatably housed 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 to each rotating shaft extending through the pump casing. Each rotating shaft has both ends rotatably supported by each bearing arrange | positioned in each bearing chamber of each side of a pump casing.

Therefore, the vicinity of the intake port of the pump casing of the vacuum pump connected to the vacuum chamber is in the same level of vacuum as the vacuum in the vacuum chamber, and the vicinity of the exhaust port of the pump casing is opened to the atmosphere and maintained at almost atmospheric pressure. Both ends of the rotating shaft are rotatably supported by each bearing, and are sealed by a contact seal or a non-contact seal, in order to prevent damage to the bearing due to a product produced by the process gas introduced into the bearing. Non-contact seals are widely used for seals of a rotating shaft to prevent damage due to contact of the rotating shaft.

For example, when the vacuum chamber or the like is evacuated using a multistage vacuum pump having a plurality of pump chambers in multiple stages, depending on the flow through a continuous pump chamber in the vacuum pump, for example, a first pump chamber, a second pump chamber, a third pump chamber, or the like, The pressure of the process gas in the vacuum pump increases step by step. 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 almost equal to the atmospheric pressure at the outlet side (exhaust vent) and is lower than the atmospheric pressure at the inlet side. When a non-contact seal is used for 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 accommodating the bearing therein is equal to the pressure (average pressure) in the final stage pump chamber. Corresponds. For example, when the pressure at the outlet side (exhaust port) of the final stage pump chamber is almost 760 Torr at atmospheric pressure, and the pressure at the inlet side of the final stage pump chamber is 200 Torr lower than atmospheric pressure, the pressure of the bearing chamber adjacent to the final stage pump chamber is about 480 Torr [= (760 + 200) / 2].

The pressure at the inlet side of the last stage pump chamber is changed by the inflow of process gas from the vacuum chamber or the like. For example, when the process gas flows 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, since the outlet side communicates with the atmosphere via the pump exhaust pipe, the pressure at the outlet side of the final stage pump chamber is hardly changed from the atmospheric pressure. 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)] Increased to Torr.

As such, the average pressure in the final stage pump chamber If the pressure is higher than the pressure in the bearing chamber adjacent to the pump chamber, the process gas introduced into the final stage pump chamber tends to leak into the bearing chamber. When 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 in the lubricating oil used to lubricate the bearings and the bearings disposed in the bearing chamber. It may damage the bearing.

In order to keep the temperature of the lubricating oil in the lubricating oil compartment effectively and to minimize the vaporization of the lubricating oil, while maintaining the temperature of the pump chamber high to be suitable for the exhaust of gas such as condensable gas or sublimable gas, Between relatively low temperature lubricating oil chambers, a dry pump including a hollow intermediate heat insulating chamber and a cooling passage through which a refrigerant is passed is proposed (see Japanese Patent Laid-Open No. 2005-105829).

Patent Document 1: Japanese Patent Application Laid-Open No. 2005-105829

The dry pump disclosed in Japanese Patent Laid-Open No. 2005-105829 effectively maintains the temperature of the lubricating oil in the lubricating oil chamber while maintaining the temperature of the pump chamber high so as to be suitable for the exhaust of gas such as condensable gas or sublimable gas. To minimize vaporization of the lubricant. However, the disclosed vacuum pump does not protect the bearing disposed in the bearing chamber located to the side of the pump casing from the process gas. It is also widely used to introduce a purge gas such as N ₂ gas into the non-contact seal of the rotating shaft to prevent the process gas from leaking into the bearing. However, increasing the amount of purge gas introduced into the non-contact seal of the rotating shaft lowers the pressure in the pump chamber, so that the amount of purge gas introduced into the non-contact seal of the rotating 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 that can protect a bearing from a process gas by effectively preventing the process gas introduced into the pump chamber from leaking into the bearing.

In order to achieve the above object, the vacuum pump of the present invention has a pump casing having an intake port, an exhaust port, and a pump chamber formed therein, and both ends rotatably supported by a bearing and extending in the longitudinal direction in the pump casing. And a rotor accommodated in the pump chamber and connected to the rotary shaft to integrally rotate with the rotary shaft. The pump casing is provided with an atmospheric open chamber in fluid communication with the exhaust port of the pump casing and open to the atmosphere.

Since an open air chamber in fluid communication with the exhaust port of the pump casing and open to the atmosphere is provided near the exhaust port, even if the pressure in the pump chamber changes and a non-contact seal is used for the seal of the rotational shaft, it is located outside the air open chamber and internally The chamber containing the bearing is always kept at almost atmospheric pressure. Therefore, the process gas introduced from the vacuum pump into the pump chamber is reliably prevented from leaking into the chamber located outside the atmospheric open chamber and accommodating the bearing therein. Thus, the bearing is protected from the process gas.

In a preferred aspect of the present invention, the pump chamber includes a plurality of pump chambers in fluid communication with each other, and the rotor includes a plurality of rotors each arranged to rotate integrally with the rotation shaft in the pump chamber.

In the case where the vacuum pump is a multi-stage vacuum pump, the pressure on the inlet side of the final stage pump chamber is lower than the atmospheric pressure even when 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, i.e., rises. However, since the atmospheric open chamber is arranged outside the final stage pump chamber, this change in pressure (average pressure) in the final stage pump chamber affects the pressure in the chamber located outside the atmospheric open chamber and accommodating the bearing therein. To prevent it.

In a preferred aspect of the present invention, the vacuum pump further includes a side panel disposed on an end wall of the pump casing, wherein the rotation shaft extends through the side panel and the purge gas is disposed in the side panel. A purge gas flow path for supplying a part of is formed in the side panel.

Since a purge gas flow path for supplying a purge gas to a part of the rotating shaft disposed in the side panel is formed in the side panel through which the rotating shaft extends, a non-contact seal between the side panel and the rotating shaft to protect the rotating shaft from abrasion by contact. Is provided.

According to the present invention, even if the pressure in the pump chamber is changed, because the chamber located outside the atmospheric open chamber and accommodating the bearing therein is always kept at atmospheric pressure, the process gas flowing into the pump chamber is located outside the atmospheric open chamber. Prevents leakage into the chamber that houses the bearings therein. Thus, the bearing is reliably protected from the process gas.

1 is a longitudinal front view showing a vacuum pump according to an embodiment of the present invention.
FIG. 2 is a longitudinal side view of the first stage pump chamber of the main pump provided in the vacuum pump shown in FIG. 1.

EMBODIMENT OF THE INVENTION Below, preferred embodiment of this invention is described with reference to drawings. 1 is a vertical front view showing a vacuum pump 10 according to an embodiment of the present invention. As shown in FIG. 1, the vacuum pump 10 includes a booster pump 12 disposed on the vacuum side and a main pump 14 disposed on the atmospheric side, which are connected to each other by a connecting pipe 16. Connected. In the present embodiment, the main pump 14 is composed of a six-stage Roots vacuum pump, and the booster pump 12 is composed of a single Roots vacuum pump.

The booster pump 12 is arranged through a pump casing 22 having a substantially cylindrical outer cylinder 20 having a pump chamber 18 therein, and a pump casing 22, and is driven by the electric motor 24. It comprises a pair of rotary shafts 26 rotatable in synchronization with each other in a reverse direction about the axis. A pair of rotors 28, such as a two-lobed rotor, are rotatably housed in the pump chamber 18 with a predetermined gap therebetween. The rotors 28 are fixedly mounted to the rotary shafts 26, respectively. The outer cylinder 20 is formed in the wall and connected to a discharge pipe (not shown) which is extended from a vacuum chamber or the like exhausted by the vacuum pump 10, and is formed in the wall and connected to the piping 16. It is provided with the exhaust port 20b connected to. When the rotor 28 rotates in synchronization with each other in the opposite direction about the axis by the drive 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 the pump chamber 18 After compression by the rotor 28 in the (), it is discharged to the connecting pipe 16 through the exhaust port (20b). In FIG. 1, only one mechanism for driving the rotary shaft 26 based on the driving force from the rotary shaft 26, the rotor 28, and the electric motor 24 is shown. The rotating shaft, the rotor, and the other side of the mechanism are located on the opposite side of FIG. 1.

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

The booster pump 12 is generally low temperature because the internal vacuum level is kept high (low pressure level) and the heat of compression is not generated much. Therefore, even if the pressure in the pump chamber 18 is low, the sublimable substance or the like contained in the process gas flowing into the pump chamber 18 may be precipitated on the inner circumferential surface of the pump chamber 18. However, as mentioned above, by raising the temperature in the pump chamber 18 by the heater jacket 30, the sublimable substance etc. contained in the process gas which flows into the pump chamber 18 precipitate on the inner peripheral surface of the pump chamber 18. As shown in FIG. Prevent it.

At the shaft end of the pump casing 22, two side panels 32a and 32b are disposed, respectively. 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 attached to the side panels 32a and 32b, respectively. On each outer side surface of the side panels 32a and 32b, two lubricant housings 40a and 40b for holding lubricant therein are disposed. The motor housing of the electric motor 24 is connected to one lubricating oil housing 40b.

In order to prevent the process gas introduced into the pump chamber 18 from flowing out to the bearings 36a and 36b, the side panels 32a and 32b are configured to pass purge gas such as N ₂ gas or the like into the rotating shafts in the side panels 32a and 32b. Each of the purge gas flow paths 42a and 42b for supplying to a part of 26 is provided. The purge gas supplied from the purge gas flow paths 42a and 42b provides a non-contact seal between the side panels 32a and 32b and the rotation shaft 26 to protect the rotation shaft 26 from contact wear.

The main pump 14 of the present embodiment is composed of a six-stage Roots type vacuum pump, and six pump chambers 50a to 50f, that is, a first stage pump chamber 50a to a sixth stage pump chamber 50f are formed in the substantially The pump casing 56 provided with the cylindrical outer cylinder 54, the atmospheric opening chamber 52 formed adjacent to the 6th-stage pump chamber 50f, and the pump casing 56 are arrange | positioned, and the electric motor 58 is carried out. It includes a pair of rotary shafts (60) rotatable in synchronization with each other about the axis in accordance with the driving of the reverse direction. As shown in FIG. 2, a pair of rotors 62a, such as a three-lobe rotor, are rotatably housed in the first stage pump chamber 50a disposed on the suction side of the main pump 14. Similarly, a pair of rotors 62b, such as a three-lobed rotor, is rotatably housed inside the second stage pump chamber 50b, and a pair of rotors 62c, such as a three-lobed rotor, is installed in the third stage pump chamber 50c. It is housed rotatably inside. A pair of rotors 62d, such as a three-lobe rotor, is rotatably housed in the fourth stage pump chamber 50d, and a pair of rotors 62e, such as a three-lobed rotor, is installed inside the fifth stage pump chamber 50e. It is rotatably received, and a pair of rotors 62f, such as a three-lobe rotor, is rotatably housed in the sixth stage pump chamber 50f disposed on the discharge side of the main pump 14. The rotors 62a to 62f arranged in one straight line are fixedly mounted on one of the rotation shafts 60, and the rotors 62a to 62f arranged in the other straight line are fixedly mounted to the other one of the rotation shafts 60.

The pump casing 56 includes end walls 64a and 64b for closing both ends of the outer cylinder 54, and five, i.e., first, partitioning walls 66a to fifth to divide the inner portion of the outer cylinder 54. It has a wall 66e. The first stage pump chamber 50a is formed between the end wall 64a and the first partition wall 66a in the outer cylinder 54. The second stage pump chamber 50b is formed between the first end wall 66a and the second dividing wall 66b in the outer cylinder 54. The third stage pump chamber 50c is formed between the second end wall 66b and the third dividing wall 66c in the outer cylinder 54. The fourth stage pump chamber 50d is formed between the third end wall 66c and the fourth dividing wall 66d in the outer cylinder 54. The fifth stage pump chamber 50e is formed between the fourth end wall 66d and the fifth partition wall 66e in the outer cylinder 54. The sixth stage pump chamber 50f is formed between the fifth dividing wall 66e and the end wall 64b in the outer cylinder 54. An atmospheric open chamber 52 is formed between the end wall 64b and the side panel 80b disposed adjacent to the end wall 64b and spaced apart in the axial direction.

As shown in FIG. 2, when the rotor 62a of the 1st stage pump chamber 50a rotates synchronously reversely with respect to the axis by the electric motor 56, process gas is connected to the connection pipe 16. As shown in FIG. It flows into the 1st stage pump chamber 50a from the upper top inlet side, is compressed by the rotor 62a in the 1st stage pump chamber 50a, and is discharged out of the lower outlet side from the 1st stage pump chamber 50a. 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 formed in the side wall, is connected to the connection pipe 16, and is in the inlet port 54a which is in fluid communication with the upper inlet side of the first stage pump chamber 50a, and is formed in the side wall at the sixth end (final end). An exhaust port 54b in fluid communication with the lower outlet side of the pump chamber 50f is provided. In addition, the exhaust port 54b is in fluid communication with the atmospheric opening chamber 52 through the end wall 64b. By this structure, the atmospheric open chamber 52 is opened to the atmosphere through the exhaust port 54b. The outer cylinder 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, and the inner wall 66. The first gas passage 72a to the 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 stage pump chamber 50c, the fourth gas passage 72d is formed around the fourth stage pump chamber 50d, and the fifth gas passage 72e is formed around the fifth stage. However, it is formed around the pump chamber 50e. In addition, the fifth gas flow path 70e is formed around the sixth stage pump chamber 50f.

The gas flow paths 72a to 72e have respective portions in fluid communication with the respective pump chambers 50a to 50e through the respective lower outlet sides, and are in fluid communication with the respective pump chambers 50b to 50f through the respective upper inlet sides. Each part has it. Therefore, as shown in FIG. 2, the process gas introduced into the first stage pump chamber 50a from the inlet port 54a through the upper inlet side is compressed in the first stage pump chamber 50a and then the first stage. It flows into the 1st gas flow path 72a through the lower outlet side from the pump chamber 50a. The process gas flows upward in the first gas flow 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 the second gas flow path (2) is passed through the lower outlet side from the second stage pump chamber 50b. 72b). Then, the process gas flows upward in the second gas flow passage 72b to reach the upper inlet side of the third stage pump chamber 50c. Thereafter, the process gas is compressed to pass through the third stage pump chamber 50c to the sixth stage pump chamber 50f. Thereafter, the process gas is discharged out of the main pump 14 via the exhaust port 54b from the lower outlet side of the sixth stage pump chamber 50f.

According to the present embodiment, since the outer cylinder 54 of the pump casing 56 has a double wall structure having gas flow passages 72a to 72e therein, the high temperature process gas flowing through the gas flow passages 72a to 72e is used. As a result, the inside of the pump chambers 50a to 50f is reliably shut off from the outside, so that the inside of the main pump 14 is maintained at a high temperature, and the sublimable gas contained in the process gas is converted into a solid, and the main pump ( 14) can be prevented from being deposited in the inner circumferential surface of the pump casing 56. In particular, 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 pump chambers 50b to 50f of the next stage through the gas flow passages 72a to 72e heats the pump chambers 50a to 50f. Effective for doing

In the present embodiment, except for the inlet port 54a and the exhaust port 54b, the outer circumferential surface of the outer cylinder 54 of the pump casing 56 is surrounded by a substantially hollow cylindrical heater jacket 74. The heater jacket 74 keeps the inside of the pump chambers 50a to 50f at a constant temperature by thermally blocking the inside of the pump chambers 50a to 50f.

Two side panels 80a and 80b are disposed on the end walls 64a and 64b of the pump casing 56, respectively. The rotating shaft 60 is rotatably supported at the outer end by the bearings 84a and 84b accommodated in the bearing housings 82a and 82b respectively mounted to the side panels 80a and 80b. On each outer side surface of the side panels 80a and 80b, two lubricant housings 88a and 88b for holding lubricant therein are disposed. The motor housing of the electric motor 58 is connected to one lubricant housing 88b. In order to prevent the process gas introduced into the pump chambers 50a to 50f from flowing out to the bearings 84a and 84b, the side panels 80a and 80b may purge gas such as N ₂ gas into the side panels 80a and 80b. Each of the purge gas flow paths 90a and 90b for supplying a part of the rotating shaft 60 is provided. The purge gas supplied from the purge gas flow paths 90a and 90b provides a non-contact seal between the side panels 80a and 80b and the rotation shaft 60 to protect the rotation shaft 60 from abrasion by contact. In addition, the purge gas flowing through the purge gas flow path 90b flows into the atmospheric open chamber 52.

According to the present embodiment, between the end wall 64b near the sixth stage (final end) pump chamber 50f at which the process gas is at the highest pressure, and the side panel 80b disposed adjacent to the end wall 64b. The air opening chamber 52 which is in fluid communication with the exhaust port 54b and opened to the atmosphere is provided. The lubricating oil housing 88b which accommodated the bearing housing 82b in which the bearing 84b is arrange | positioned inside is attached to the side panel 80b. Therefore, even if the pressure in the sixth stage (final stage) pump chamber 50f is changed, the chamber R located outside the atmospheric open chamber 52 and containing the bearing 84b, that is, the side panel 80b and the lubricant oil The chamber R surrounded by the housing 88b is always maintained at almost atmospheric pressure. Therefore, the process gas flowing into the pump chambers 50a to 50f is reliably prevented from leaking into the chamber R located outside the atmospheric open chamber 52 and accommodating the bearing 84b therein. Thus, the bearing 84b is protected from the process gas.

The reason why the bearing 84b is protected from the process gas is explained below. When there is a non-contact seal between the rotating shaft 60 and the side panel 80b, and the 6th stage (final end) pump chamber 50f is located directly adjacent to the side panel 80b, in other words, the atmospheric open chamber 52 ) In the chamber (R) located outside the open chamber (52) and surrounded by the pressure in the chamber (R) containing the bearing (84b), that is, surrounded by the side panel (80b) and the lubricant housing (88b). The pressure is almost equal to the average pressure in the sixth stage (final stage) pump chamber 50f. For example, when the pressure at the outlet side of the sixth stage pump chamber 50f is 760 Torr at atmospheric pressure, and the pressure at the inlet side is lower than atmospheric pressure, for example 200 Torr, the side panel 80b and the lubricating oil housing 88b are used. 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 due to the inflow of the process gas from the vacuum chamber, that is, the average pressure in the sixth stage pump chamber 50f is 530 Torr [ = (760 + 300) / 2]. Therefore, the process gas flows into the chamber R from the sixth stage pump chamber 50f through the gap between the side panel 80b and the rotary shaft 60 until the pressure in the chamber R rises to 530 Torr. .

According to the present embodiment, the exhaust port 54b is disposed between the end wall 64b near the sixth stage (final end) pump chamber 50f and the side panel 80b disposed adjacent to the end wall 64b. An atmospheric open chamber 52 is provided that is in fluid communication and is open to the atmosphere. Therefore, as described above, even if the pressure (average pressure) in the sixth stage pump chamber 50f changes, that is, rises, the pressure in the atmospheric opening chamber 52 does not change from the atmospheric pressure, The pressure in the chamber R, located outside and surrounded by the bearing 84b outside, i.e., surrounded by the side panel 80b and the lubricating oil housing 88b, is within the sixth stage pump chamber 50f. Unaffected by pressure changes, it is maintained at almost atmospheric pressure.

The vacuum pump 10 configured in this manner drives the booster pump 12 and the main pump 14 by driving the electric motor 24 of the booster pump 12 and the electric motor 58 of the main pump 14. Operating to, for example, evacuate the process gas introduced into the vacuum chamber from the vacuum chamber. The pressure in the chamber R, located outside the atmospheric open chamber 52 and surrounded by the bearing 84b, i.e., surrounded by the side panel 80b and the lubricating oil housing 88b, is almost always constant. By maintaining at atmospheric pressure, the process gas introduced into the main pump 14 is reliably prevented from leaking into the bearing 84b. Thus, the bearing 84b is protected from the process gas.

Although preferred embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It should be understood within the scope of the technical concept contained here. For example, in the present embodiment, the present invention is applied to a multistage Roots type vacuum pump. However, the technical scope of the present invention can be used in various ways, such as a single Roots vacuum pump, a claw vacuum pump, a screw vacuum pump, or a vacuum pump including at least two methods of Roots, claws, and screw. It may be applied to a vacuum pump combined on a rotating shaft.

Industrial availability

The present invention is applicable to a vacuum pump used in a process in which sublimable gas or corrosive gas may be introduced into the vacuum pump.

Claims (4)

A pump casing having an intake port, an exhaust port, and a pump chamber formed therein;
A rotating shaft rotatably supported at both ends by a bearing and extending in the longitudinal direction of the pump casing; and
A rotor housed in the pump chamber and connected to the rotary shaft to integrally rotate with the rotary shaft
The pump casing, wherein the pump casing is formed with an air opening chamber in fluid communication with the exhaust port of the pump casing and open to the atmosphere. The vacuum pump according to claim 1, wherein the pump chamber includes a plurality of pump chambers in fluid communication with each other, and the rotor includes a plurality of rotors each arranged to rotate integrally with the rotation shaft in the pump chamber. The purge of claim 1, further comprising a side panel disposed at an end wall of the pump casing, wherein the rotation shaft extends through the side panel and supplies purge gas to a portion of the rotation shaft disposed in the side panel. And a gas passage is provided in the side panel. The purge of claim 2, further comprising a side panel disposed on an end wall of the pump casing, wherein the rotation shaft extends through the side panel and supplies purge gas to a portion of the rotation shaft disposed in the side panel. And a gas passage is provided in the side panel.

Images