JPWO2005042979A1 - Rotary dry vacuum pump - Google Patents

Abstract

When a canned motor is used as a drive unit in the rotary dry vacuum pump, there is a problem that the reaction product gas is mixed into the can motor and the motor fails, and therefore the rotary dry vacuum pump fails. In order to solve this problem, one or a plurality of rotors housed in a housing, bearings for supporting the rotation shafts of these rotors, a fluid inlet and outlet formed in the housing, and the one or more rotors In a rotary dry vacuum pump having a rotary rotor composed of a motor that rotationally drives at least one of a plurality of rotors, the motor has a stator core fixed inside the motor housing and is mounted on the inner diameter side of the stator The partition wall is fixed to the housing to seal the inside of the partition wall, and the rotor is fixed to the rotating shaft in the partition wall so as to be rotatable, and a gas injection port for flowing purge gas into the partition wall is provided. The rotary dry vacuum pump is configured.

Description

  The present invention relates to a rotary dry vacuum pump having a structure in which a reaction product gas hardly flows into a canned motor, which is a power unit of a rotary dry vacuum pump used in a device for flowing a reaction product gas such as a semiconductor manufacturing apparatus. .

In the semiconductor manufacturing process, a problem is that impurities such as oil are mixed in the reaction chamber and the semiconductor is contaminated. In particular, mixing of oil from a vacuum pump for exhausting the gas in the reaction chamber becomes a problem. Therefore, a rotary dry vacuum pump has been conventionally used. Examples of the rotary dry vacuum pump include a screw type, a root type, and a scroll type. However, such a rotary dry vacuum pump has a rotating shaft for rotating the rotor, and a bearing is used to support the rotating shaft. Lubricating oil is usually attached to the bearing, and a shaft seal is disposed between the exhaust chamber and the bearing portion to prevent oil molecules of the lubricating oil from entering the exhaust chamber of the rotary dry vacuum pump. It was. However, when this shaft seal is worn, it may leak through the shaft seal into the reaction chamber from the exhaust chamber of the rotary dry vacuum pump. This is because the motor for rotating the rotor is in the atmosphere and the pressure difference between the motor side and the vacuum exhaust chamber side is large. For this reason, if the shaft seal is worn away to create a gap, the air leaks into the exhaust chamber, which causes a reduction in pump performance. In view of this, a canned motor capable of having the same pressure in the motor as in the exhaust chamber has been used for a rotary dry vacuum pump having a rotary drive unit. The structure of the canned motor includes a stator winding that generates a rotating magnetic field in the stator core, and the inside of the partition is sealed with a metal thin cylindrical partition (can) mounted on the frame, side plate, and stator inner diameter side. A rotating shaft supported by a bearing fixed to the bracket is configured to have a rotor and a rotatable structure. (Patent Document 1)
JP 2003-189529 A

  However, when the canned motor is used as a driving unit of a rotary dry vacuum pump for a semiconductor manufacturing apparatus that flows reaction product gas, the inside of the partition in which the rotor is housed is evacuated during operation. Therefore, when the motor is stopped and returned to atmospheric pressure, the reaction product gas is mixed into the motor from the exhaust chamber, and the reaction product adheres to the components in the canned motor partition wall, causing the motor to malfunction. There was a problem that. In addition, if reaction products adhere to the bearings and shaft seals at that time, the pump itself may be damaged.

In order to solve this problem, in the present invention, according to the first aspect of the present invention, one or a plurality of rotors housed in a housing, bearings for supporting the rotating shafts of these rotors, and the housing are formed. In a rotary dry vacuum pump having a rotary rotor constituted by a motor for rotating and driving at least one of the one or more rotors, the motor includes a stator core and is fixed. A partition wall mounted on the inner diameter side of the rotor is fixed to the housing and seals the partition wall, and a rotor is rotatably disposed in the partition wall. A rotating shaft and a rotor of at least one of the plurality of rotors The rotary shaft is fixed to drive the rotor to rotate, and a gas injection port is provided in the partition to allow purge gas to flow. If the purge gas inlet is formed in the flange of the motor, it is easy to process. The partition walls can be made of a magnetic metal. The purge gas can also flow to a bearing that rotatably supports the rotating shaft of the rotor.

  In a second aspect of the present invention, the rotating shaft of the motor and the rotating shaft of the rotor are integrally formed. As an example of assembly, after fixing the rotor to the flange constituting the housing, the rotor of the motor is fixed to the end of the rotor by a predetermined means on the rotating shaft, and the end is provided with a cylindrical member constituting the partition wall. The inside of the partition is sealed by fixing to the flange and then covering with a flange constituting the partition. Note that an O-ring is disposed in a portion that needs to be sealed.

  According to invention of Claim 3, the said motor was arrange | positioned at the inlet side. In this case, grease may be used instead of the lubricating oil in order to reduce the amount of the lubricating oil leaked into the motor from the bearing disposed between the exhaust chamber and the motor. Further, the effect can be further improved by placing the rotary dry vacuum pump vertically and arranging the bearing and the motor at the top. Lubricating oil can be installed vertically by a rotary dry vacuum pump having a plurality of rotating shafts, a timing gear requiring lubrication for synchronization is arranged on the lower discharge port side, and a motor is arranged on the intake side. Prevents exhaust chamber contamination from

According to the invention of claim 4, the flow rate adjusting means is provided in the piping for sending the purge gas to the purge gas inlet. As the flow rate adjusting means, there are means for restricting the flow rate of the purge gas through a purge gas flow hole of a predetermined size in the purge gas flow path, a manual valve if necessary, and an electromagnetic valve is installed on the N2 supply side. When the pump stopped, before and after and during operation, the gas flow rate changed, especially when the pressure in the exhaust chamber became higher than the pressure in the motor partition, the solenoid valve was opened and adjusted by the valve By flowing the flow rate as a purge gas, the process gas is prevented from entering the bearing unit and the motor unit.
If the flow rate is determined, an adjustment valve can be eliminated by installing an orifice in the pipe that allows the same amount of gas to flow instead of the valve.
Moreover, when adjusting the amount of gas inflow, it can adjust by the time which opens an electromagnetic valve, or can use the electromagnetic valve with a flow volume adjustment function.

  According to invention of Claim 5, the pressure measuring instrument for measuring the pressure in the said partition, and / or the pressure measuring instrument for measuring the pressure in the said exhaust chamber were provided. The difference between the two pressure values may be taken, and the flow rate may be adjusted by an electromagnetic valve so that the pressure in the partition wall is the same as or greater than the pressure in the exhaust chamber. In addition, the inflow amount and flow rate of the purge gas can be adjusted with only one pressure. Examples of the pressure measuring device include a thin film semiconductor detector. In addition, the inflow amount and flow rate of the purge gas can be adjusted by measuring the pressure in the chamber of a semiconductor manufacturing apparatus or the like exhausted by a vacuum pump. The inflow amount and flow rate of the gas may be adjusted only by changing the pressure in the chamber, but may be adjusted according to the pressure in the partition wall.

  According to invention of Claim 6, the measurement means for measuring the rotation speed of the rotor of a motor or a rotor was provided. As the rotational speed measuring means, the rotational speed is detected by attaching an encoder to the rotor of the motor, or detecting the magnetism of the permanent magnet of the rotor at a specific position. The inflow amount and flow rate of the purge gas are adjusted according to the rotational speed. For example, when the rotational speed decreases, the purge gas can be controlled to flow, or the inflow amount and flow rate of the gas can be adjusted by the rate of increase / decrease in the rotational speed.

  According to invention of Claim 7, the means for measuring the power consumption of a motor was provided. The gas flow rate is adjusted by the power consumption. For example, when the power consumption fluctuates due to an increase in the amount of intake gas during operation, the purge gas can be controlled to flow, or the inflow amount and flow rate of the purge gas can be adjusted according to the amount of change in power consumption when stopped.

  According to the invention of claim 8, the reaction product gas flow meter is provided in the vicinity of the intake port or the exhaust port. The flow rate of the purge gas is adjusted according to the change in the flow rate of the reaction product gas. For example, when the flow rate of the reaction product gas is increased, control is performed such as increasing the flow rate of the purge gas. Further, the flow rate of the purge gas may be adjusted according to the flow rate of the gas flowing through the chamber.

  According to the first aspect of the present invention, the rotor or rotors housed in the housing, the bearings that support the rotating shafts of these rotors, the fluid inlet and outlet ports formed in the housing, In a rotary dry vacuum pump having a rotary rotor composed of a motor that rotationally drives at least one of a single or a plurality of rotors, the motor includes a stator core fixed inside the motor housing, and the stator inner diameter side A partition wall attached to the housing is fixed to the housing to seal the inside of the partition wall, and a rotary shaft in the partition wall is configured to have a rotor fixed and rotatable, and a gas inlet for pouring purge gas into the partition wall is provided. As a result, the reaction product gas in the vacuum exhaust chamber leaks into the partition from the exhaust chamber when the vacuum exhaust chamber and the partition returns to atmospheric pressure when the pump is stopped. The product accumulates in the motor components such rotor, so that the motor is not faulty or stuck, it is possible to prevent flowing the reaction product gas into the partition wall from the vacuum exhaust chamber poured purge gas. In addition, by flowing the purge gas in the same manner to the bearing, it is possible to prevent the bearing from causing a reaction product to be damaged due to adhesion.

  According to the invention of claim 2, by adopting a configuration in which the rotating shaft of the motor and the rotating shaft of the rotor are integrally formed, a joining part of the two rotating shafts becomes unnecessary, and the two rotating shafts are aligned. There is no need to do.

  According to a third aspect of the present invention, by arranging the motor on the intake port side, a portion that normally needs lubricating oil to prevent the exhaust chamber from being contaminated with oil is located on the discharge port side. Be placed. Therefore, by arranging the motor on the intake port side where the lubricating oil is not used much, it is possible to minimize the lubricating oil from entering the partition wall.

  According to the invention of claim 4, the flow rate adjusting means is provided in the pipe for sending the gas to the purge gas inlet. By adopting such a configuration, it is possible to flow the minimum amount of purge gas necessary for the process gas not to enter the partition wall during stoppage, and useless N2 is suppressed, and it adheres to the bearing portion. Diffusion of lubricant into the exhaust chamber can be minimized.

  According to invention of Claim 5, the pressure measuring instrument for measuring the pressure in the said partition, and / or the pressure measuring instrument for measuring the pressure in the said exhaust chamber were provided. With this configuration, the purge gas flow rate can be controlled by an electromagnetic valve or the like so that the pressure in the partition wall is slightly higher than the pressure in the exhaust chamber.

  According to the invention of claim 6, by providing a measuring means for measuring the rotational speed of the rotor or rotor of the motor, it becomes possible to control the flow of only the necessary purge gas, and it is possible to waste gas or exhaust gas. The purge gas does not leak into the room and the exhaust capacity is not deteriorated.

  According to the seventh aspect of the present invention, since the means for measuring the power consumption of the motor is provided, it becomes possible to control the flow of only the necessary purge gas, so that the waste of gas or the purge gas leaks into the exhaust chamber. The exhaust capacity will not be deteriorated.

  According to the invention of claim 8, by providing a gas flow meter in the vicinity of the intake port or the exhaust port, it becomes possible to control only the necessary purge gas to flow, and waste of gas or purge gas leaks into the exhaust chamber. The exhaust capacity will not be deteriorated.

  FIG. 1 shows a screw type vacuum pump as an example of the rotary dry vacuum pump in the present invention.

The vacuum pump 200 includes two screw rotors 202 and 204.
The screw rotors 202 and 204 are housed inside the housing 210. More specifically, the screw rotor 202 is rotatably supported on the housing 210 by bearings 231 and 233, and the screw rotor 204 is rotatably supported on the housing 210 by bearings 234 and 236. Timing gears 251 and 253, a motor 241, and seals 237, 238, 239, and 240 are arranged as shown. Here, the seals 237 and 238 isolate the bearings 231 and 233 from the rotor storage chamber 210b, prevent the lubricating oil of the bearings 231 and 233 from leaking into the screw rotor storage chamber 210b, and from the screw rotor storage chamber 210b. Foreign matter is prevented from entering the bearings 231 and 233. Similarly, the seals 239 and 240 isolate the bearings 234 and 236 from the rotor storage chamber 210b, prevent the lubricating oil of the bearings 234 and 236 from leaking into the screw rotor storage chamber 210b, and from the screw rotor storage chamber 210b. Foreign matter is prevented from entering the bearings 234 and 236. The seals 237, 238, 239, and 240 include contact seals, non-contact seals such as magnetic fluid seals and labyrinths.

  Timing gears 251 and 253 that rotate the screw rotor 202 as the screw rotor 204 rotates are fixed to one end portions of the screw rotor 202 and the screw rotor 204 so as to mesh with each other. Further, a motor 241 is integrally connected to the other end of the screw rotor 202.

  The screw rotor storage chamber 210 b is formed in the wall portion of the housing 210, and is external to the housing 210 through an intake port (not shown) for sucking compressive fluid from the outside of the housing 210 into the housing 210. The screw rotor storage chamber 210b is formed in the wall portion of the housing 210 and communicates with the housing 210 through a discharge port (not shown) for discharging a compressive fluid from the inside of the housing 210 to the outside of the housing 210. Communicates with the outside. Here, the intake port communicates with a vacuum container (not shown), and the discharge port communicates with an exhaust gas processing device (not shown).

  The housing 210 includes a first housing member 211, a second housing member 212, a third housing member 213, a fourth housing member 214, and a fifth housing member 215. Here, the first housing member 211 forms an intake side flange and also serves as a housing for the canned motor 241. The second housing member 212, the third housing member 213, and the fourth housing member 214 constitute a housing body, and the second housing member 212, the third housing member 213, and the fourth housing member 214 constitute a vacuum exhaust chamber. Has been. Bearings 231 and 234 and shaft seals 237 and 239 are fixed to the second housing member 212. Further, bearings 233 and 236 and shaft seals 238 and 240 are fixed to the fourth housing member 214.

  Next, the configuration of the canned motor 241 that is a drive unit of the vacuum pump 200 according to the present embodiment will be described. The canned motor 241 is provided with a stator winding that generates a rotating magnetic field in the stator core 261. On the inner diameter side of the stator, a rotor 265 is fixed to a rotating shaft portion 263 of a canned motor 241 integrated with the rotor 202. A partition wall (can) 281 is provided between the stator core 261 and the rotor 265, and the partition wall 281 is closely fixed to the second housing member 212. A flange 267 of the canned motor 241 is closely fixed to the partition wall 281 and the rotor 265 is sealed from the outside air. A purge gas (for example, nitrogen gas or argon gas) is allowed to flow through the flange 267 through the partition 281 whose joint is sealed with an O-ring or the like (not shown), the housing second member 212, and the canned motor 241 sealed with the flange 267. The injection hole 269 for this is vacant. The injection hole 269 is provided with a flow passage 271 for introducing a purge gas. The flow passage 271 has a flow rate adjusting means (for example, a manual valve, an orifice, etc.) 273 and an electromagnetic valve 275 for adjusting the flow rate of the purge gas. Is installed.

Next, the operation of the vacuum pump 200 according to this embodiment will be described.
First, when the canned motor 241 rotates the screw rotor 202, the timing gears 253 and 251 are fixed to one end portions of the screw rotor 204 and the screw rotor 202 so as to mesh with each other. Along with this, the screw rotor 204 rotates. As the screw rotor 202 and the screw rotor 204 rotate, the compressible fluid in the screw rotor storage chamber 210b is transferred from the intake port side to the communication path 210c and discharged through the communication path 210c. Further, when the compressive fluid in the screw rotor storage chamber 210b is discharged out of the screw rotor storage chamber 210b through the communication path 210c, the screw rotor storage chamber 210b is newly supplied from the vacuum container through the intake port. Compressible fluid is inhaled.
At this time, the inside of the canned motor 241 sealed by the housing first member 211, the housing second member 212, and the flange 267 is evacuated.
Therefore, when the vacuum pump is stopped, the pressure in the exhaust chamber 210c rises, and the gas in the exhaust chamber 210c is inside the canned motor 241 sealed by the housing first member 211, the housing second member 212, and the flange 267 whose pressure is low. Will flow backwards. When the gas in the exhaust chamber is a corrosive gas or a reaction product gas, the rotor 265 and the rotary shaft 263 are corroded, and the can motor 241 may be damaged due to the product adhering thereto. Therefore, when corrosive gas or reaction product gas is flowed, the pressure inside the canned motor 241 sealed by the housing first member 211, the housing second member 212, and the flange 267 becomes higher than the pressure inside the exhaust chamber 210c. Purge gas is flowed. Therefore, the flow rate of the purge gas may be set such that P1 ≧ P2 after the pump is stopped, assuming that the pressure P1 inside the canned motor and the pressure in the exhaust chamber 210c closest to the canned motor 241 are P2. As an operation sequence, when the pump is stopped or before and after that, the solenoid valve is opened, and the flow rate L adjusted by the valve (manual valve or solenoid valve or orifice) is allowed to flow as a purge gas. Prevent entry of process gas. If the time T until P1 reaches atmospheric pressure is measured in advance, the electromagnetic valve can be opened and the flow rate L can flow only during the time T.
Therefore, the minimum necessary purge gas can be flowed, the use of unnecessary purge gas can be suppressed, and the diffusion of the lubricant adhering to the bearing portion to the exhaust chamber can be minimized.

Further, the pressure inside the canned motor 241 sealed with the housing first member 211, the housing second member 212 and the flange 267 is measured with the pressure gauge P1, and the pressure inside the exhaust chamber 210c is measured with the pressure gauge P2. There is also a method of controlling the flow rate with an electromagnetic valve so that the pressure difference is P1 ≧ P2. (Instead of “valve + solenoid valve”, use an electromagnetic valve that can freely control the flow rate.) Control of the flow rate is not only at the time of stop, but even if the purge gas continues to flow slightly so that P1 ≧ P2 during operation. Moreover, if the flow rate of the reaction product gas changes even during operation, the pressure in the exhaust chamber may change, so the flow rate of the purge gas is controlled so that P1 ≧ P2.
Further, the pressure in the exhaust chamber can be replaced with the pressure in the semiconductor manufacturing apparatus chamber using the present vacuum pump.
In this embodiment, the flow rate of the purge gas is controlled by comparing the two pressures. However, the flow rate can be controlled by any one of the pressure in the motor partition, the pressure in the exhaust chamber, and the pressure in the chamber.

In this embodiment, the flow rate of the purge gas is controlled by measuring the pressure, but it can also be controlled by measuring the rotational speed of the motor or rotor, the power consumption, and the flow rate of the reaction product gas.
Further, in this embodiment, only the purge gas for the motor is shown. However, if the purge gas is allowed to flow also to the bearing, the reaction product adheres to the bearing, and the rotary dry vacuum pump does not move. It can also be prevented.

  Generally, a semiconductor manufacturing apparatus dislikes contamination by oil. However, as in the present embodiment, the vertical gear is used as a mold, the intake port is located on the upper side, the discharge port is located on the lower side, and timing gears 251 and 253 that always require lubricating oil. The can motor 241 which does not use the lubricating oil and dislikes the contamination with the lubricating oil is arranged on the intake side. Thereby, it can suppress as much as possible that the intake side is contaminated with oil. Further, the use of vacuum grease as a lubricant for the intake-side bearing further increases the effect.

In the present embodiment, the volume transfer type screw vacuum pump has been described. However, the present invention can be applied to a vacuum pump such as a claw type, a roots type, a scroll type or the like that drives a rotary shaft by a motor.
Moreover, each pump of a multi-stage type vacuum pump, for example, a two-stage screw type vacuum pump, can also be made into the structure of the rotary dry vacuum pump of this invention.
The pressure, gas flow rate, power consumption, and rotation speed are converted into a data electrical signal, sent to the signal processing means, the flow rate of the purge gas is determined from the previous data electrical signal by the previous signal processing means, and the determined amount is the output electrical signal And is transmitted to the flow rate adjusting means, and the flow rate of the purge gas is adjusted by an electromagnetic valve or the like.

  The present invention can be applied to a vacuum pump having a rotating shaft for flowing and exhausting an extremely dilute reaction product gas and a motor for driving the rotating shaft, such as a semiconductor manufacturing apparatus.

It is an axial sectional view of the screw type vacuum pump of the present invention.

Explanation of symbols

200 Vacuum pumps 202, 204 Screw rotor 210 Housing 210b Rotor storage chambers 231, 233, 234, 236 Bearings 251, 253 Timing gears 237, 238, 239, 240 Shaft seal 241 Canned motor 261 Stator core 263 Rotating shaft 265 Rotor 267 Flange 269 Injection hole 271 Flow passage

Claims (8)

  At least one of the rotor or rotors housed in the housing, the bearings that support the rotation shafts of these rotors, the fluid inlets and outlets formed in the housing, and the rotors In a rotary dry vacuum pump having a rotary rotor composed of a motor for rotating the motor, the motor includes a stator core, and a partition mounted on the inner diameter side of the stator is fixed to the housing to seal the inside of the partition. A rotor is rotatably disposed in the partition wall, and a rotation shaft of at least one of the plurality of rotors and a rotation shaft of the rotor are fixed to rotate the rotor, and purge gas is supplied into the partition wall. A rotary dry vacuum pump comprising a gas inlet for pouring.   The rotary dry vacuum pump according to claim 1, wherein the rotation shaft of the motor and the rotation shaft of the rotor are integrally formed.   The rotary dry vacuum pump according to claim 1 or 2, wherein the motor is disposed on an intake port side.   4. The rotary dry vacuum pump according to claim 1, wherein a flow rate adjusting means is provided in a pipe for sending purge gas to the purge gas inlet.   5. The rotary dry vacuum according to claim 1, further comprising a pressure measuring instrument for measuring the pressure in the partition wall and / or a pressure measuring instrument for measuring the pressure in the exhaust chamber. pump. 5. The rotary dry vacuum pump according to claim 1, further comprising measuring means for measuring the rotational speed of the rotor or rotor of the motor. 7. The rotary dry vacuum pump according to claim 1, further comprising means for measuring power consumption of the motor. The rotary dry vacuum pump according to claim 1, wherein a gas flow meter is provided in the vicinity of the intake port, the exhaust port, or in a vacuum chamber.

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