Vacuum pump, vacuum exhaust device, and method of operating vacuum pump

Abstract

[Object] To provide a vacuum pump, a vacuum exhaust device, and a method of operating a vacuum pump that are capable of achieving a stable exhausting operation without causing a step-out. [Solving Means] Provided is a method of operating a vacuum pump including a rotor ( 21, 22 ), a drive motor ( 35 ), and a magnetic coupling ( 50 ) configured to transmit a rotational force of the drive motor to the rotor at a rotational torque equal to or smaller than a first threshold value (Th 1 ). The method includes detecting a load torque of the drive motor ( 35 ). The number of revolutions of the drive motor ( 35 ) is increased when the load torque is equal to or smaller than a second threshold value (Th 2 ) that is smaller than the first threshold value (Th 1 ). The number of revolutions of the drive motor ( 35 ) is reduced when the load torque exceeds the second threshold value (Th 2 ) and is equal to or smaller than the first threshold value (Th 1 ).

1 . A vacuum pump, comprising:
 a pump unit including
 a pump chamber including an intake port and an exhaust port, and 
 a rotor that is arranged in the pump chamber and transfers gas from the intake port to the exhaust port; 
   a drive unit including
 a motor chamber adjacent to the pump chamber, and 
 a drive motor that is arranged in the motor chamber and rotates the rotor; 
   a magnetic coupling including
 a partition member that airtightly partitions the pump chamber and the motor chamber, 
 a first magnet attached to the rotor, and 
 a second magnet that is attached to the drive motor and is magnetically connected to the first magnet via the partition member, the magnetic coupling being configured to transmit a rotational force of the drive motor to the rotor at a rotational torque equal to or smaller than a first threshold value; and 
   a controller including
 a detection section that detects a load torque of the drive motor, and 
 a revolution control section that controls the number of revolutions of the drive motor, the controller increasing the number of revolutions of the drive motor when the load torque is equal to or smaller than a second threshold value that is smaller than the first threshold value and reducing the number of revolutions of the drive motor when the load torque exceeds the second threshold value and is equal to or smaller than toe first threshold value. 
   
     
     
         2 . The vacuum pump according to  claim 1 , wherein
 the controller puts the drive motor into a free running state when the load torque exceeds the first threshold value.   
     
     
         3 . The vacuum pump according to  claim 1  or  claim 2 , wherein
 the second threshold value is a rated torque of the drive motor. 
 
     
     
         4 . A vacuum exhaust device, comprising:
 a first vacuum pump including
 a pump chamber including an intake port and an exhaust port, 
 a rotor that is arranged in the pump chamber and transfers gas from the intake port to the exhaust port, 
 a drive motor, and 
 a magnetic coupling configured to transmit a rotational force of the drive motor to the rotor at a rotational torque equal to or smaller than a first threshold value; 
   a second vacuum pump that exhausts the gas transferred to the exhaust port; and   a controller including
 a detection section that detects a load torque of the drive motor, and 
 a revolution control section that controls the number of revolutions of the drive motor, the controller increasing the number of revolutions of the drive motor when the load torque is equal to or smaller than a second threshold value that is smaller than the first threshold value and reducing the number of revolutions of the drive motor when the load torque exceeds the second threshold value and is equal to or smaller than the first threshold value. 
   
     
     
         5 . A method of operating a vacuum pump including a rotor, a drive motor, and a magnetic coupling configured to transmit a rotational force of the drive motor to the rotor at a rotational torque equal to or smaller than a first threshold value, the method comprising:
 detecting a load torque of the motor; and   increasing the number of revolutions of the drive motor when the load torque is equal to or smaller than a second threshold value that is smaller than the first threshold value and reducing the number of revolutions of the drive motor when the load torque exceeds the second threshold value and is equal to or smaller than the first threshold value.