Method for operation control of vacuum pump and control system for vacuum pump

Abstract

A vacuum pump has an alternating current motor, a rotary shaft and a gas transferring body. The alternating current motor runs at a certain speed based on frequency of alternating current and is sufficiently supplied with the alternating current. Gas is transferred from a certain space by the gas transferring body driven by the alternating current motor through the rotary shaft. A method for controlling a vacuum pump includes keeping a rotational speed of the alternating current motor at a second predetermined rotational speed, detecting a value of the alternating current to the alternating current motor, keeping the rotational speed at a first predetermined rotational speed that is higher than the second predetermined rotational speed when the detected alternating current value exceeds a first predetermined value, and keeping the rotational speed at the second predetermined rotational speed when the detected alternating current value becomes equal to a second predetermined value.

What is claimed is:  
     
         1 . A method for controlling a vacuum pump that has an alternating current motor, a rotary shaft and a gas transferring body, the alternating current motor running at a certain speed based on frequency of alternating current, the alternating current motor being sufficiently supplied with the alternating current, gas being transferred from a certain space by the gas transferring body that is driven by the alternating current motor through the rotary shaft, the method comprising the steps of: 
 keeping a rotational speed of the alternating current motor at a second predetermined rotational speed;    detecting a value of the alternating current to the alternating current motor;    keeping the rotational speed at a first predetermined rotational speed that is higher than the second predetermined rotational speed when the detected value of the alternating current exceeds a first predetermined value; and    keeping the rotational speed at the second predetermined rotational speed when the detected value of the alternating current becomes equal to a second predetermined value.    
     
     
         2 . The method according to  claim 1 , wherein the second predetermined value is lower than the first predetermined value.  
     
     
         3 . The method according to  claim 1 , wherein the second predetermined value is equal to the first predetermined value.  
     
     
         4 . A method for controlling a vacuum pump that has an alternating current motor, a rotary shaft and a gas transferring body, the alternating current motor running at a certain speed based on frequency of alternating current, the alternating current motor being sufficiently supplied with the alternating current, gas being transferred from a certain space by the gas transferring body that is driven by the alternating current motor through the rotary shaft, the method comprising the steps of: 
 detecting a value of the alternating current to the alternating current motor; and    changing a rotational speed of the alternating current motor to eliminate a variation of the alternating current such that the detected value of the alternating current becomes a predetermined value.    
     
     
         5 . The method according to  claim 4 , wherein the changing step further includes the additional steps of: 
 continuously increasing the rotational speed of the alternating current motor until the detected value of the alternating current becomes equal to a first predetermined value, when the detected value of the alternating current exceeds a second predetermined value; and    continuously decreasing the rotational speed of the alternating current motor until the detected value of the alternating current becomes equal to the second predetermined value, when the detected value of the alternating current becomes equal to or lower than the first predetermined value.    
     
     
         6 . The method according to  claim 5 , wherein the first predetermined value is lower than the second predetermined value.  
     
     
         7 . The method according to  claim 5 , wherein the first predetermined value is equal to the second predetermined value.  
     
     
         8 . The method according to  claim 4 , further comprising the steps of: 
 keeping the rotational speed of the alternating current motor at a first predetermined rotational speed when the rotational speed reaches the first predetermined rotational speed; and    keeping the rotational speed of the alternating current motor at a second predetermined rotational speed when the rotational speed reaches the second predetermined rotational speed.    
     
     
         9 . The method according to  claim 8 , wherein the first predetermined rotational speed is higher than the second predetermined rotational speed.  
     
     
         10 . The method according to  claim 8 , wherein the first predetermined rotational speed is equal to the second predetermined rotational speed.  
     
     
         11 . A control system for controlling pump torque on a vacuum pump having an alternating current motor, a rotary shaft and a gas transferring body, the alternating current motor being actuated by an external power source, the alternating current motor running at a certain speed based on frequency of alternating current, the alternating current motor being sufficiently supplied with the alternating current, gas being transferred from a certain space by the gas transferring body that is driven by the alternating current motor through the rotary shaft, the control system comprising: 
 a rotational speed adjuster electrically connected to the alternating current motor, the rotational speed adjuster changing the value of the alternating current supplied to the alternating current motor in response to the pump torque in order to keep the rotational speed of the alternating current motor at a predetermined rotational speed; and    a controller electrically connected to the rotational speed adjuster, the controller detecting a value of the alternating current to the alternating current motor from the rotational speed adjuster, the controller comparing the detected value of the alternating current with a predetermined value, the controller changing the rotational speed of the alternating current motor in such a manner that the detected value approaches the predetermined value when the detected value is different from the predetermined value.    
     
     
         12 . The control system according to  claim 11 , wherein the controller changes the rotational speed of the alternating current motor by changing frequency of alternating current supplied to the alternating current motor.  
     
     
         13 . The control system according to  claim 11 , wherein the predetermined value includes a first predetermined value and a second predetermined value, the rotational speed adjuster keeping the rotational speed of the alternating current motor at a first predetermined rotational speed when the detected value of the alternating current exceeds the first predetermined value, the rotational speed adjuster keeping the rotational speed of the alternating current motor at a second predetermined rotational speed that is smaller than the first predetermined rotational speed when the detected value of the alternating current becomes equal to the second predetermined value.  
     
     
         14 . The control system according to  claim 13 , wherein the second predetermined value is lower than the first predetermined value.  
     
     
         15 . The control system according to  claim 13 , wherein the second predetermined value is equal to the first predetermined value.  
     
     
         16 . The control system according to  claim 11 , wherein the predetermined value includes a first predetermined value and a second predetermined value, the controller adjusting the rotational speed of the alternating current motor to a first predetermined rotational speed when the detected value of the alternating current exceeds the first predetermined value, the controller adjusting the rotational speed of the alternating current motor to a second predetermined rotational speed that is slower than the first predetermined rotational speed when the detected value of the alternating current becomes equal to or lower than the second predetermined value.  
     
     
         17 . The control system according to  claim 16 , wherein the second predetermined value is lower than the first predetermined value.  
     
     
         18 . The control system according to  claim 16 , wherein the second predetermined value is equal to the first predetermined value.  
     
     
         19 . The control system according to  claim 11 , wherein the certain space is a load lock chamber, the control system further comprising a valve through which the vacuum pump communicates with the load lock chamber, the rotational speed of the alternating current motor being kept at the first predetermined rotational speed in a state that the electric control valve is open while the pressure in the load lock chamber is reduced to a predetermined pressure value, the electric control valve being closed at the time when the value of the alternating current reaches a value that corresponds to the predetermined pressure value.  
     
     
         20 . A method of controlling pressure in a chamber using a vacuum pump having a motor, the vacuum pump being connected to the chamber via an adjustable valve, comprising the steps of: 
 running the motor at a predetermined slow rotational speed and a predetermined low current level with the adjustable valve in an open state to maintain a chamber pressure at a first predetermined pressure;    closing the adjustable valve for a first time to modify the chamber pressure to a second predetermined pressure above the first predetermined pressure;    opening the adjustable valve to modify the chamber pressure towards the first predetermined pressure;    continuously monitoring electric current to the motor to compare the electric current to a first predetermined electric current valve;    changing the slow rotational speed to a predetermined fast rotational speed if the electric current exceeds the first predetermined electric current value;    continuously monitoring the chamber pressure;    closing the adjustable valve for a second time when the chamber pressure reaches the first predetermined pressure; and    changing the predetermined fast rotational speed to the predetermined slow rotational speed when the electric current reaches the predetermined low current level.    
     
     
         21 . The method of controlling pressure according to  claim 20 , wherein the first predetermined pressure is under the atmospheric pressure.  
     
     
         22 . The method of controlling pressure according to  claim 20 , wherein the second predetermined pressure is near the atmospheric pressure.  
     
     
         23 . The method of controlling pressure according to  claim 20 , wherein a first predetermined task is performed when the chamber pressure is at the first predetermined pressure.  
     
     
         24 . The method of controlling pressure according to  claim 20 , wherein a second predetermined task is performed when the chamber pressure is at the second predetermined pressure.  
     
     
         25 . The method of controlling pressure according to  claim 20 , further comprising an additional step of opening the adjustable valve to run the monitor at the predetermined slow rotational speed and the predetermined low current so that the chamber pressure is maintained at the first predetermined pressure.  
     
     
         26 . The method of controlling pressure according to  claim 20 , wherein pressure near the adjustable valve is below the first predetermined pressure and at a third predetermined pressure when the electric current reaches the predetermined low current level after closing the adjustable valve for the second time.  
     
     
         27 . A system for controlling pressure in a chamber, comprising: 
 a vacuum pump having a motor connected to the chamber, the motor initially running at a predetermined slow rotational speed and a predetermine low current level to maintain a chamber pressure at a first predetermined pressure;    an adjustable valve connected to and placed between the chamber and the vacuum pump for opening and closing a passage between the chamber and the vacuum pump;    a switching control device connected to the adjustable valve, the switching control device closing the adjustable valve for a first time to modify the chamber pressure to a second predetermined pressure above the first predetermined pressure, the switching control device opening the adjustable valve to modify the chamber pressure towards the first predetermined pressure;    a controller operationally connected to the vacuum pump for continuously monitoring electric current to the motor to compare the electric current to a first predetermined electric current value, the controller changing the slow rotational speed to a predetermined fast rotational speed if the electric current exceeds the first predetermined electric current value; and    a pressure detector connected to the switching control device and the chamber for continuously monitoring the chamber pressure, the switching control device closing the adjustable valve for a second time when the chamber pressure reaches the first predetermined pressure, wherein the controller changing the predetermined fast rotational speed to the predetermined slow rotational speed when the electric current reaches the predetermined low current level.    
     
     
         28 . The system for controlling pressure according to  claim 27 , wherein the first predetermined pressure is under the atmospheric pressure.  
     
     
         29 . The system for controlling pressure according to  claim 27 , wherein the second predetermined pressure is near the atmospheric pressure.  
     
     
         30 . The system for controlling pressure according to  claim 27 , wherein a first predetermined task is performed when the chamber pressure is at the first predetermined pressure.  
     
     
         31 . The system for controlling pressure according to  claim 27 , wherein a second predetermined task is preformed when the chamber pressure is at the second predetermined pressure.  
     
     
         32 . The system for controlling pressure according to  claim 27 , wherein the motor runs at the predetermined slow speed and the predetermined low current so that the chamber pressure is maintained at the first predetermined pressure when the adjustable valve is open.  
     
     
         33 . The system for controlling pressure according to  claim 27 , wherein pressure near the adjustable valve is below the first predetermined pressure and at a third predetermined pressure when the electric current reaches the predetermined low current level after the adjustable valve is closed for the second time.