Method of controlling the stopping operation of vacuum pump and device therefor

Abstract

A method for controlling the operation of a vacuum pump when stopping the gas transferring operation thereof, the vacuum pump having a housing in which a pump chamber is formed and a gas transferring body which is rotatably disposed in the pump chamber for transferring gas, the method comprises the steps of reducing rotational speed of the gas transferring body to a first preset speed below a second preset speed that is lower than a normal speed of the gas transferring body during normal gas transferring operation of the vacuum pump, maintaining the speed of the gas transferring body below the second preset speed, and stopping the rotation of the gas transferring body when the temperature of the housing reaches a predetermined temperature which is lower than that of the housing during the normal gas transferring operation of the vacuum pump.

1 . A method for controlling the operation of a vacuum pump when stopping the gas transferring operation thereof, the vacuum pump having a housing in which a pump chamber is formed and a gas transferring body which is rotatably disposed in the pump chamber for transferring gas, comprising the steps of: 
 reducing rotational speed of the gas transferring body to a first preset speed below a second preset speed that is lower than a normal speed of the gas transferring body during normal gas transferring operation of the vacuum pump;    maintaining the speed of the gas transferring body below the second preset speed; and    stopping the rotation of the gas transferring body when the temperature of the housing reaches a predetermined temperature which is lower than that of the housing during the normal gas transferring operation of the vacuum pump.    
     
     
         2 . The method according to  claim 1 , wherein the vacuum pump further has a cooling passage through which coolant flows for cooling the housing and the step further includes the additional step of: 
 flowing the coolant in the cooling passage before the speed of the gas transferring body is reduced to the speed below the second preset speed.    
     
     
         3 . The method according to  claim 1 , wherein the step further includes the additional steps of: 
 rapidly increasing the rotational speed of the gas transferring body in the range below the second preset speed while the gas transferring body is being rotated at the speed below the second preset speed after the reducing the rotational speed of the gas transferring body; and    reducing the rotational speed of the gas transferring body below the second preset speed.    
     
     
         4 . A device for controlling the operation of a vacuum pump when stopping the gas transferring operation thereof, the vacuum pump having a housing in which a pump chamber is formed, a gas transferring body rotatably provided in the pump chamber for transferring gas, the device comprising: 
 means for controlling the stopping operation of the vacuum pump; and    detection means for detecting the temperature of the housing and generating a detection signal when the temperature of the housing reaches a predetermined temperature which is lower than a temperature of the housing during normal operation of the vacuum pump when gas is being transferred by the gas transferring body;    wherein the controlling means is operable to reduce rotating speed of the gas transferring body to a speed below a second preset speed that is lower than a normal speed of the gas transferring body during normal gas transferring operation of the vacuum pump in response to a pump-stop command signal for stopping the gas transferring body and also to stop the rotation of the gas transferring body in response to the detection signal from the detection means.    
     
     
         5 . The device according to  claim 4 , the vacuum pump further having a cooling passage being formed therein through which coolant for cooling the housing passes and a means for opening and closing the cooling passage, wherein the means for controlling the stopping operation of the vacuum pump is operable to open the means for opening and closing the cooling passage before the rotational speed of the gas transferring body is reduced to the speed below the second preset speed.  
     
     
         6 . The device according to  claim 4 , wherein the means for controlling the stopping operation of the vacuum pump is operable to rapidly increase the rotational speed of the gas transferring body in the range below the second preset speed while the gas transferring body is being rotated at the speed below the second preset speed after the reducing the rotational speed of the gas transferring body and also to reduce the rotational speed of the gas transferring body below the second preset speed after the rapid increase of the rotational speed.