JPH06630Y2 - Turbo molecular pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a turbo molecular pump which is equipped with an inert gas purging mechanism and an atmospheric leak mechanism and realizes an oil-free ultra-high vacuum.

[Prior Art] A turbo-molecular pump achieves an ultra-high vacuum by mechanical exhausting action of rotor blades and stator blades alternately arranged in the pump chamber. As a support structure for a drive shaft (rotor shaft) that firmly supports a rotor, the drive shaft is generally supported by a pair of upper and lower oil bearings in a machine chamber that applies a rotational drive force. And in this kind of turbo molecular pump,
Although the drive shaft has a seal at the shaft penetrating part that penetrates from the machine room side to the pump room side, there is a gap for inserting the drive shaft in a non-contact manner, so the pump room and the machine room are completely sealed. However, various measures have been taken to compensate for this structural defect.

For example, when a turbo molecular pump is used in an exhaust system for exhaust gas containing corrosive gas such as in a dry etching device, part of the exhaust gas enters from the pump chamber through the gap of the shaft penetration part, and It may corrode and deteriorate indoor motors, bearings, and even oil. Therefore,
In such a case, for example, as shown in Japanese Patent Laid-Open No. 58-74898, an inert gas for gas purging is continuously supplied into the machine chamber to bring the elements in the machine chamber into contact with the exhaust gas. A gas purge mechanism to cut off is adopted.

In addition, the turbo molecular pump usually has a rough pump such as an oil rotary pump connected in series at the rear side of its exhaust, but when the turbo molecular pump is stopped in such a system, high vacuum Exhaust gas may flow backward from the downstream pump side into the normal pump chamber, and the pump chamber may be contaminated with oil vapor. Therefore, it is also generally adopted that the turbo molecular pump is provided with an atmospheric leak mechanism that introduces the atmosphere into the pump chamber when the operation is stopped to prevent backflow. When these two mechanisms are adopted at the same time, if they are configured separately from each other, a supply system passage for the gas purging inert gas and an introduction system passage for the atmospheric leak are separately installed, and each Since a switching valve that switches at a predetermined timing must be provided in the system path, the structure and control may be complicated. Therefore, the inventor of the present invention is
No.), a single switching valve having two inflow ports capable of switching between a gas supply system passage for supplying an inert gas for gas purging to a machine chamber and an atmosphere introduction system passage for leaking the pump chamber to the atmosphere. We have proposed a turbo-molecular pump that is shared by a gas inflow system that connects the start end to the outflow port. That is, with such a configuration, only by providing a single gas inflow passage in the pump, it is possible to selectively perform the gas purging for the necessary machine chamber and the atmospheric leak for the pump chamber, and to switch between them. This is because there is an advantage in that it can be conveniently performed by operating the switching valve.

[Problems to be Solved by the Invention] However, the above-mentioned proposal has the following disadvantages in promoting the oil-free turbo molecular pump. That is, according to this prior art example, as shown in FIG. 3, a common gas inflow system passage 24 for supplying or introducing an inert gas or atmosphere into the pump is bored in the pump base 4 to allow the gas flow. Since the terminal end 24B of the inlet is opened in the oil tank 2, the inflowing gas flows from the oil tank 2 to the oil return hole 1 as shown by the arrow in the figure.
The flow path follows a gas flow path that flows into the machine room M through the gas passage 9 and further flows into the pump room P through the gap of the shaft penetrating portion 13. However, when such a gas flow is generated, particularly when an air leak to the pump chamber P is performed, the leak gas entrains the oil in the oil tank 2 or the machine chamber M (for example, the motor 11 thereof or particularly the upper oil bearing 9) to pump the oil. The chamber P and the evacuated container evacuated by the turbo molecular pump are contaminated with oil, making it impossible to obtain a clean ultrahigh vacuum.

[Means for Solving the Problems] The present invention is intended to solve the problems in the above prior art from the viewpoint of promoting the oil-free turbo molecular pump, and separates the machine room and the pump room. A drive shaft extending from the machine chamber to the pump chamber penetrates the holding plate through a minute gap, and a seal fixed to the drive shaft between the end face of the holding plate on the machine chamber side and the oil bearing. A ring is provided, and the seal ring, the bearing holder that holds the oil bearing, and the pressing plate form a labyrinth seal portion having a narrow labyrinth-shaped labyrinth gap, and the end of the gas inflow system path is It is characterized in that it is opened at a position facing the seal ring through the labyrinth gap, which is an end face of the pressing plate on the machine room side.

[Operation] According to the present invention, when the machine room is purged with an inert gas, the exhaust gas (the exhaust gas to be discharged by the inert gas supplied from the end of the common gas inflow passage opening to the labyrinth seal portion) Corrosive gas) can be prevented from entering the machine room, and at the same time, diffusion of oil vapor from the machine room to the pump room can be prevented.

That is, according to the configuration of the present invention, a labyrinth seal portion having a labyrinth gap is provided between the pump chamber and the oil bearing of the machine chamber, not only the gap formed between the pressing plate and the drive shaft. Will be done. Moreover, if the end of the gas inflow path is opened at the position as described above, the inert gas will bypass the outer circumference of the seal ring and will be in a labyrinth gap that is continuous in a labyrinth-like shape, at a site near the pump chamber. Will be supplied. Therefore, it becomes difficult for the oil vapor from the oil bearing to pass through the labyrinth gap to reach the gap between the holding plate and the drive shaft, and the oil vapor is pushed back by the inert gas and does not easily leak from the machine room. On the other hand, part of the inert gas supplied to the position near the pump chamber in the labyrinth gap reaches the gap and flows out into the pump chamber. Therefore, it is possible to effectively prevent the corrosive gas from entering the machine room from the pump room. Similarly, when the atmosphere is introduced from the end of the shared gas inflow path, the atmosphere preferentially flows out of the gap into the pump chamber while suppressing the oil vapor from entering the gap.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the entire structure of a turbo-molecular pump equipped with an inert gas purging mechanism that also functions as an atmospheric leak according to the present invention, and FIG. 2 shows the structure of the main part thereof. The turbo-molecular pump is an air-cooled type, and is constructed by attaching an oil tank 2 equipped with an air-cooling fan (not shown) to the bottom of the pump body 1, and further providing an inert gas supply means 3 outside.

In the pump body 1, a motor housing 5 is provided upright in the center of the pump base 4 to form a machine room M therein, and the outer periphery is surrounded by an outer frame case 6 so that the intake port 7 is located upward. To form a pump chamber P having an exhaust port 8 below. Then, the drive shaft S is inserted through the center of the machine room M, and is rotatably supported by a pair of upper and lower oil bearings 9 and 10, and the drive shaft S is rotated at an extremely high speed by the internal motor 11. ing. On the other hand, in the pump chamber P, one end of the drive shaft S extends with a minute gap 14 formed in a shaft penetrating portion (shaft penetrating hole) 13 provided in a holding plate 12 attached to the motor housing 5. A hanging bell-shaped rotor R is fixedly supported at this one end. The rotor blades 15 projecting from the outer circumference of the rotor R in multiple stages are alternately arranged with the opposite stator blades 16 fixed to the spacer 17 from the inner circumference of the case 6 and projecting in the opposite direction. In P, a turbine blade row that performs a mechanical exhaust action is formed.

Further, the oil tank 2 attached to the pump body 1 stores therein oil O for lubricating and cooling which is injected into the oil bearings 9 and 10 in the machine chamber M. The other end nozzle portion Sn of the drive shaft S is immersed in the oil tank 2, and the drive shaft S is driven from the nozzle portion Sn while the pump is operating.
After continuously supplying oil to the oil bearings 9 and 10 through the oil passage 18 in the inside and utilizing the oil flowing out from the bearings 9 and 10 to cool the machine room M, return holes 19 and 20 opened in the base 4 are provided. It is configured to be returned to the oil tank 2 more.

As shown in FIG. 2, in this case, from the oil passage 18 formed inside the drive shaft S to the oil bearings 9, 10
The oil supply ports 21, 21 for supplying oil to the lower oil bearing 10 are conventionally opened at the upper position thereof, while those for the upper oil bearing 9 are capable of controlling the amount of oil leaching to the upper end side of the bearing 9. In order to reduce the amount only, it is opened just below it. In addition, in the figure, 22 is a bearing holder, and 23 is an oil reflection frame.

In a turbo molecular pump having such a configuration,
From the external inert gas supply means 3 through the gas inflow system passage 24 bored in the pump body 1, the shaft penetrating portion 13 corresponding to the adjacent boundary portion between the machine chamber M and the pump chamber is filled with N ₂ or the like. An inert gas or atmosphere for gas purging is supplied or introduced. The inert gas supply means 3 is composed of a tank 25 for storing the inert gas, an adjusting valve 26 for adjusting the flow rate thereof, and a switching valve 27. As the switching valve 27, a 3-port switching valve capable of selectively connecting the inflow port I or II to the outflow port III is used.
Is connected to the storage tank 25 side, while the inflow port
II is released to the atmosphere through a filter. And
A start end (inflow port) 24A of the gas inflow system passage 24 is connected to the outflow port III. Therefore, when the inflow port of the switching valve 27 is switched to the I position, the tank 25
The inert gas whose pressure has been reduced by the adjusting valve 26 is supplied to the gas inflow passage 24, and conversely, when the position is switched to the II position, the atmosphere for leaking is introduced into the gas inflow passage 24. The gas inflow system passage 24 includes a gas passage 28 formed in the pump base 4, a gas passage 29 formed in the motor housing 5, and a gas passage 30 formed in the holding plate 12. Are connected to each other, and the start end 24A is connected to the outflow port III of the switching valve 27 as described above, while the end (outflow port) 24B is connected to the upper oil bearing 9
Is opened near the. More specifically, in this turbo molecular pump, a seal ring 33 that creates a narrow labyrinth-like labyrinth gap 32 between the bearing holder 22 and the holding plate 12 is fixed to the drive shaft S at the shaft penetrating portion 13. Thus, the labyrinth reel portion 34 is provided above the oil bearing 9. Then, the end 24B of the gas inflow system passage 24 extends from the middle of the labyrinth gap 32 to the bearing 9
It is opened toward. That is, the gas inflow path 24
As shown in FIG. 2, the terminal end 24B of the end of the pressing plate 12 is an end face of the pressing plate 12 on the machine room M side and is opened at a position facing the seal ring 33 via the labyrinth gap 32. is there.

Next, the operation of this turbo molecular pump will be described. Switching valve 2 incorporated in the inert gas supply means 3
When the inflow port of 7 is switched to the I position and gas purging is performed on the machine room M during pump operation, a small amount of inert gas from the storage tank 25 passes through the gas inflow system passage 24 to the labyrinth gap 32 and ends 24B. Continuously supplied from. At this time, a part of the inert gas is used for the upper oil bearing 9
Is supplied into the machine room M through the seal ring 33, and the rest flows through the gap 14 to the pump chamber P side. Therefore, this inert gas purge can completely prevent the exhausted gas from entering the machine chamber M from the pump chamber P side. At the same time, it is possible to effectively prevent the phenomenon that the oil vapor diffuses and leaks from the machine room M side to the pump room P side and the pump room P is contaminated with oil. That is, according to the configuration described above, the pressing plate 1 is provided between the pump chamber P and the oil bearing 9 of the machine chamber M.
2 as well as the gap 14 formed between the drive shaft S and
A labyrinth seam portion 34 having a labyrinth gap 32 is interposed. Moreover, the end 2 of the gas inflow system passage 24
If 4B is opened at the position as described above, the inert gas is supplied to the portion near the pump chamber P in the labyrinth gap 32 that continues in a labyrinth-like manner so as to bypass the outer periphery of the seal ring 33. become. Therefore, it becomes difficult for the oil vapor from the oil bearing 9 to pass through the labyrinth gap 32 to reach the gap 14 between the pressing plate 12 and the drive shaft S, and is pushed back by the inert gas to be kept in the machine room M.
Will be difficult to leak from. On the other hand, a part of the inert gas supplied to the position near the pump chamber P in the labyrinth gap 32 reaches the gap 14 and flows out into the pump chamber P. Therefore, it is possible to effectively prevent the corrosive gas from entering the machine room M from the pump room P.

In particular, this one has a special effect because the end 24B of the gas inflow passage 24 is opened not in the gap 14 but in the labyrinth gap 32 to face the seal ring 33. That is, temporarily, the end 2 of the gas inflow system passage 24
When 4B is opened in the gap 14 between the retainer plate 12 and the drive shaft S, the gap 14 is made relatively large in order to secure the flow rate of the inert gas ejected from the gas inflow passage 24 to some extent. I have to keep it. However, if this gap 14 is made large, the oil vapor on the machine room M side and the corrosive gas on the pump room P side easily flow, and in order to prevent this, a high pressure inert gas is used for comparison. There is a dilemma of having to supply an extremely large amount. On the other hand, like the present turbo molecular pump, the gas inflow passage 24
If the end 24B of the gas flow passage 24 is opened in the middle of the labyrinth gap 32 to face the seal ring 33,
It is also possible to design the gap 14 to be as small as possible without causing a problem of substantially closing the terminal end 24B. As a result, most of the inert gas ejected from the gas inflow system passage 24 will flow to the machine room M side and prevent the oil vapor from trying to move to the pump room P side. In this case, the inert gas injected from the gas inflow system passage 24 comes into contact with the seal ring 33 rotating at a high speed, is given a rotational force, and is urged in the outer peripheral direction of the seal ring 33 by the centrifugal force. The force that pushes back the oil vapor becomes even stronger. It should be noted that a part of the inert gas injected from the gas inflow passage 24, of course, passes through the gap 14 and flows out to the pump chamber P side, but as described above, the gap 14 should be made small without any problem. Therefore, even if only a small amount of the inert gas leaks from the gap 14, it becomes possible to prevent the corrosive gas in the pump chamber P from passing through the gap 14 and entering the machine chamber M. . Therefore, both the inconvenience that the oil vapor in the machine room M leaks to the pump room P side and the problem that the corrosive gas in the pump room P enters the machine room M are both effective with a minimum of inert gas. It can be suppressed or prevented.

On the other hand, when the inflow port of the switching valve 27 is switched to the II position and air is leaked to the pump chamber P when the pump is stopped, the air introduced from the inflow port II is supplied to the gas inflow passage 2
4 through the end 24B and is introduced into the labyrinth gap 32 at once. At this time, the atmosphere flowing into the pump chamber P is
Instead of passing through the machine room M, it flows directly into the pump room P through the gap 14 of the shaft penetrating portion 13 as shown by the arrow in the figure. For this reason, when there is an air leak as before, the machine room M
It is possible to prevent the phenomenon that oil vapor is blown out from the pump chamber and pollutes the pump chamber P.

As described above, in the turbo molecular pump according to the present invention,
It is possible to effectively suppress the phenomenon in which oil vapor leaks from the machine room M to the pump room P and is entrained in either case of performing the inert gas purge during operation or performing the atmospheric leak at the time of stoppage. Therefore, it will be effective for making the turbo molecular pump oil-free. The advantage of being able to provide the necessary gas purging mechanism of inert gas and the atmospheric leak mechanism by the installation and switching operation of the single gas inflow passage 24 and the single switching valve 27 is retained as it is. .

[Effects of the Invention] As described above, the turbo molecular pump of the present invention is equipped with the necessary inert gas purging mechanism and atmospheric leak mechanism for a simple structure and easy switching operation. It is possible to effectively solve the problem of oil pollution in and to realize a clean high vacuum. That is, as in the present invention, if the labyrinth seal portion is formed between the clearance of the shaft penetrating portion and the oil bearing, and the starting end of the gas inflow passage is opened at the position as described above, It is possible to effectively prevent the oil vapor from approaching the gap between the holding plate and the drive shaft. Then, a part of the inert gas supplied from the end thereof preferentially passes through the gap and flows out into the pump chamber. Therefore, it is possible to effectively prevent the corrosive gas from entering the machine chamber from the pump chamber without leaking the oil vapor in the machine chamber to the pump chamber. In particular, in the present invention, since the end of the gas inflow system passage is opened in the middle of the labyrinth gap and faces the seal ring, centrifugal force can be used to remove the oil vapor, and at the same time as the pressing plate. The gap between the drive shaft and the drive shaft can be narrowed without difficulty, and the inconvenience that the oil vapor in the machine chamber M leaks to the pump chamber P side using the minimum amount of inert gas, and It is possible to effectively suppress or prevent the problem that the corrosive gas enters the machine room M, respectively. Similarly, when the atmosphere is introduced from the end of the gas inflow path, the atmosphere preferentially flows out of the gap into the pump chamber while suppressing the invasion of the oil vapor into the gap. Therefore, according to the present invention, the gas purge and the atmospheric leak can be performed while effectively suppressing the oil vapor in the machine room from leaking to the pump room.

[Brief description of drawings]

FIG. 1 is a sectional view of a partially broken turbo molecular pump showing an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a main part thereof. FIG. 3 is an enlarged sectional view of a main part of a turbo molecular pump showing a conventional example. S ... Drive shaft P ... Pump chamber M ... Machine room 1 ... Pump body 2 ... Oil tank 3 ... Inert gas supply means 4 ... Pump base 5 ... Motor housing 9 ... Oil 12 ... Presser plate 13 ... Shaft penetrating portion 14 ... Gap 22 ... Bearing holder 24 ... Gas inflow system passage 24A ... Start end 24B ... End end 27 ... Switching valve 32 ... Labyrinth gap 33 ... Seal ring 34 ... Labyrinth seal part

Claims (1)

[Scope of utility model registration request] 1. A single switching valve having two inflow ports capable of switching between a gas supply system path for supplying an inert gas for gas purging to a machine room and an atmosphere introduction path for leaking the pump room to the atmosphere. A turbo molecular pump that is commonly used in a gas inflow system path whose start end is connected to an outflow port,
A drive shaft extending from the machine chamber to the pump chamber is passed through a holding plate that divides the machine chamber and the pump chamber through a minute gap, and the end face of the holding plate on the machine chamber side and the oil bearing are separated from each other. A seal ring fixed to the drive shaft is disposed between the seal ring, the bearing holder that holds the oil bearing, and the holding plate to form a labyrinth seal portion having a labyrinth-shaped narrow labyrinth gap. A turbo molecular pump, characterized in that the end of the gas inflow passage is opened at a position facing the seal ring through the labyrinth gap, which is an end surface of the pressing plate on the machine chamber side.