JP5062964B2 - Molecular pump - Google Patents

Description

  The present invention relates to a molecular pump such as a turbo molecular pump, a composite molecular pump, and a thread groove molecular pump, and more particularly to a molecular pump that prevents a product from being unable to restart.

This type of molecular pump is used as a pump for evacuating in a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, etc., and has a structure in which a rotor is rotatably provided in a pump case having an intake port and an exhaust port, and is rotated by a motor. (For example, refer to Patent Document 1).
JP-A-10-73088

  However, this type of conventional molecular pump has the following problems.

  When this type of molecular pump is used in a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, or the like, reaction products may adhere to and accumulate inside the pump. Therefore, in order to prevent product deposition, the inside of the molecular pump is heated with a heater, an induction coil, or the like, or the inside of the molecular pump is heated using frictional heat due to an exhaust gas load. Even so, it is difficult to reliably suppress product adhesion, and product adhesion remains.

  On the other hand, according to the past operation results, even if the product adheres and accumulates inside the molecular pump, this type of pump does not cause rotor lock as long as the operation is continued. However, in order to maintain equipment, valves, vacuum pipes, etc. connected to the inlet side or exhaust side of the molecular pump, it is necessary to stop this type of pump and release the interior to the atmosphere. .

  At this time, the physical and chemical changes suddenly progress due to the temperature drop inside the molecular pump due to the stop of the molecular pump and the moisture absorption of the product due to release to the atmosphere, and the product adheres to the gap between the stator and the rotor, Rotor lock may occur. Once the rotor lock has occurred, there is a case where the molecular pump cannot be restarted because the starting torque of the motor that drives the rotor is small even if it is attempted to restart it.

  As a method for removing the product adhering at the time of restarting, there are a method of scraping the product by swinging a rotor supported, levitated and controlled by a magnetic bearing by the control means, and a stator at 100 ° C. A method of sublimating the product by heating to ˜180 ° C. has been proposed (see, for example, Patent Document 1). However, when the rotor and the stator are firmly fixed by the product, the above-mentioned swinging method cannot sufficiently exert the effect, and the substances that can be sublimated by heating the stator at 100 ° C. to 180 ° C. are limited. There are many substances that cannot be sublimated at a temperature, and this heating method may not be fully effective.

  The present invention has been made in view of the above, and an object of the present invention is to provide a molecular pump that reliably prevents a restart from being impossible even when the vacuum exhaust is stopped.

  The molecular pump of the present invention includes a rotor that is rotated by a motor in a pump case having an intake port and an exhaust port. The molecular pump that performs vacuum exhaust has a maintenance mode, and the molecular pump is in operation in the maintenance mode. Sometimes, the brake operation is performed to set the motor to a very low speed at a predetermined first specified rotational speed, and when the molecular pump is not in operation, the starting torque is increased and the motor is restarted to restart the motor. If the motor does not reach the first specified rotational speed even after a predetermined set time has elapsed with the first specified rotational speed being an ultra-low speed rotation, the rotation direction opposite to the normal direction is stopped after the motor stops rotating Then, the motor is restarted, and the motor is set to the ultra-low speed rotation of the second specified rotation speed lower than the first specified rotation speed, and the second specified rotation speed is reached. It performs a stop operation, when it is first prescribed rotational speed to rotate up again, as it is operated at a first predetermined rotational speed, it was decided to terminate the execution of the maintenance mode.

  The molecular pump of the present invention has a maintenance mode, and when the molecular pump is in operation in the maintenance mode, the motor is braked to rotate the motor at a predetermined ultra-low speed. Even if the rotor is stopped, it can be reliably prevented that the rotor continues to rotate at an ultra-low speed that can rotate in the atmosphere and cannot be restarted.

  In addition, the molecular pump of the present invention has a maintenance mode. When the molecular pump is not in operation in the maintenance mode, the starting torque is increased and the motor is restarted. The motor is restarted in the direction of rotation of the motor, or the motor is restarted by rotating the motor forward and backward at a minute angle, so that the product adhered between the rotor and the stator can be easily scraped off. It is possible to reliably prevent the inability to restart.

  A molecular pump according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view of a main body 1 of a typical molecular pump to which the present invention can be applied.

  As shown in FIG. 1, the main body 1 of the molecular pump according to the embodiment of the present invention is a complex molecular pump including a turbo molecular pump part A and a thread groove molecular pump part B.

  The main body 1 includes a pump case 1a having an intake port 2 and an exhaust port 3, a turbo molecular pump stator 4a and a thread groove molecular pump unit stator 4b provided in contact with the inner surface of the pump case 1a, and the stator 4a, The rotor 5 rotates within 4b, the rotary shaft 8 is supported by the inner housing 9 provided in the pump case 1a and the rotor 5 is fixed, and the motor 10 is provided in the inner housing 9. ing.

  A large number of blades 6 are radially formed on the outer peripheral surface of the rotor 5 of the turbo molecular pump part A in a multistage manner, and the inner surface of the turbo molecular pump part stator 4a has a space between these blades 6. A large number of stationary blades 7 located in the position are projected. The outer shape of the rotor 5 of the thread groove molecular pump part B is formed in a cylindrical shape, and the rotor 5 is inserted into a thread groove molecular pump part stator 4b having a thread groove 4b1 on the inner peripheral part. The motor 10 is a DC brushless motor, and the rotor 5 is rotated through the rotating shaft 8 by the rotational drive of the motor 10 to be evacuated.

  FIG. 2 shows a block diagram of the main body 1 and the controller 16 of the molecular pump according to the embodiment of the present invention.

  As shown in FIG. 2, the molecular pump according to the embodiment of the present invention includes a main body 1 and a controller 16. The main body 1 is configured as shown in FIG. 1, but as shown in FIG. 2, a rotation speed detector 11 that detects the rotation speed of the motor 10 is provided around the rotation shaft 8. The controller 16 converts a DC power source into an AC power source and drives the motor 10, a current detector 13 that detects an output current of the inverter 12, and an AD converter that converts the output of the current detector 13 into a digital signal 14, a storage unit 17 storing a maintenance mode program, and a signal from the current detector 13 through the AD converter 14 to perform rated current control, and a signal from the rotational speed detector 11 is input to rotate. The control unit 15 is configured to perform speed feedback control and perform control in the maintenance mode when an operation for executing the maintenance mode is performed. The maintenance mode is used when maintenance of devices, valves, vacuum pipes and the like connected to the molecular pump is performed, or when the molecular pump cannot be restarted. Further, the feedback control of the rotational speed performed by inputting the signal from the rotational speed detector 11 can be performed also in the operation at the normal rotational speed and the operation at the ultra-low rotational speed in the maintenance mode.

  FIG. 3 is a flowchart of Example 1 when the maintenance mode operation is performed in the molecular pump according to the embodiment of this invention.

  The operation when the maintenance mode operation is performed in the molecular pump according to the embodiment of the present invention will be described with reference to the flowchart of FIG. Here, the maintenance mode means that the molecular pump is rotated at an ultra-low speed for maintenance of devices, valves, vacuum pipes, etc. connected to the molecular pump, or the molecular pump is caused by adhesion and deposition of products. This is a special operation mode that is used when the rotor is locked and cannot be restarted.

  The molecular pump is usually operated at a predetermined rated rotational speed at which a predetermined exhaust speed is obtained. As shown in FIG. 3, when an operation switch (not shown) is used to execute the maintenance mode (step 21), when the molecular pump is in operation (yes in step 22), a brake operation is performed (step 23). ), The speed is reduced to a first specified rotational speed of, for example, 20 rps or less, which is an ultra-low speed that can rotate in atmospheric pressure (step 24), and when the speed is not reduced to the first specified rotational speed (no in step 24), the brake When the operation (step 23) is repeated and the vehicle is decelerated to the first specified rotational speed (yes in step 24), the operation is continued at the first specified rotational speed (step 25), and the execution of the maintenance mode is terminated.

  When the molecular pump is not in operation (no in step 22), it starts with a normal starting torque of 1.5 to 3 times (step 31), and when the first specified rotational speed is reached (yes in step 32), The operation is continued at the first specified rotational speed (step 25), and the execution of the maintenance mode is terminated. When the first specified rotational speed is not reached (no in step 32), the start-up is continued until a predetermined set time of, for example, 30 to 60 seconds is over (no in step 33), and the predetermined set time is reached. When the time is over (yes in step 33), a stop operation is performed (step 34), and rotation is started in the reverse direction with a normal starting torque 1.5 to 3 times (step 35), for example, 2 to 5 rps. When the second specified rotational speed is reached (yes in step 36), a stop operation is performed (step 39), and the engine is started again with a normal starting torque of 1.5 to 3 times (step 31). When the specified rotational speed is reached (Yes in step 32), the operation is continued at the first specified rotational speed (step 25), and the execution of the maintenance mode is terminated. When the first specified rotational speed is not reached (no in step 32), the steps after step 32 are repeated.

  When the second specified rotational speed is not reached in step 36 (no in step 36), the rotation start in the reverse direction is continued until a predetermined set time of, for example, 15 to 30 seconds is over (no in step 37). ) When a predetermined set time is over (yes in step 33), the operator determines whether to retry, and when the operator determines that the restart is impossible and does not retry (no in step 38), End maintenance mode execution. When retrying (yes in step 38), a series of steps from step 31 starting with a normal starting torque 1.5 to 3 times is repeated. The maintenance of the apparatus or the like can be performed during the operation of the maintenance mode of the molecular pump or before and after the execution of the maintenance mode. Moreover, since the increase in the starting torque of the motor is limited to the operation only for a short time, no abnormal heat is generated.

  As described above, the molecular pump according to the embodiment of the present invention normally operates at the rated rotation speed, and when in the maintenance mode during the operation, the molecular pump decelerates to an ultra-low speed specified rotation speed that can rotate even under atmospheric pressure. The rotation can be continued as it is to enable restarting.

  When the operation is stopped, 1.5 to 3 times the normal starting current is applied to generate a high starting torque to enable restarting. When restarting is impossible even if high starting torque is generated, starting in the reverse rotation direction Can be restarted.

  In the molecular pump according to the embodiment of the present invention, when the operation is stopped, a normal starting current of 1.5 to 3 times is flown to generate a high starting torque, which can be restarted. It is also possible to perform the activation in the rotation direction and enable the reactivation independently.

  Also, if the molecular pump can be accelerated to the specified rotational speed when the molecular pump is not in operation at first (22 step is no), the rotor lock (rotation of the rotor by the product) can be performed by yes in step 32 or yes in step 36. ) Can be determined to have been resolved. In that case, the operation may be stopped and terminated without performing continuous operation at an ultra-low speed.

  FIG. 4 is a flowchart of Example 2 when the maintenance mode operation is performed in the molecular pump according to the embodiment of this invention.

  The molecular pump is usually operated at a predetermined rated rotational speed. As shown in FIG. 4, when an operation switch (not shown) is used to execute the maintenance mode (step 21), when the molecular pump is in operation (yes in step 22), a brake operation is performed (step 23). ), The speed is reduced to a first specified rotational speed of, for example, 1 to 20 rps, which can rotate even under atmospheric pressure (step 24), and when the speed is not reduced to the first specified rotational speed (no in step 24), the brake operation ( When step 23) is repeated and the vehicle is decelerated to the first specified rotation speed (yes in step 24), the operation is continued at the first specified rotation speed (step 25), and the execution of the maintenance mode is terminated.

  When the molecular pump is not in operation (No in Step 22), it rotates forward and backward with a normal starting torque of 1.5 to 3 times (Step 40). As implementation conditions at this time, for example, the forward / reverse rotation speed is 9 to 11 Hz, the deflection angle is within ± 7 °, and the forward / reverse rotation time is 10 seconds.

  After that, if it is normally started and accelerated to the first specified rotational speed within 10 seconds (step 41), it is operated at the first specified speed as it is (step 25), and the execution of the maintenance mode is terminated. However, if the first specified rotational speed is not reached within 10 seconds (no in step 41), normal startup is continued until a predetermined set time of, for example, 30 to 60 seconds is over (no in step 42). When the preset set time has expired (yes in step 42), a stop operation is performed (step 43), the operator decides whether or not to retry, the operator judges that the restart is impossible, and does not retry Sometimes (no in step 44), the execution of the maintenance mode is terminated. When retrying (yes in step 44), the motor is rotated forward and backward by a small angle with a normal starting torque 1.5 to 3 times (step 40), and the above-described operation is repeated.

  In the molecular pump according to the embodiment of the present invention, the signal from the rotational speed detector 11 is input and the rotational speed feedback control is performed. However, the rotational frequency detector 11 is not provided and the output frequency from the controller 16 is not provided. The rotational speed can be controlled by the output current.

  Furthermore, the molecular pump according to the embodiment of the present invention can be applied to a turbo molecular pump, a thread groove molecular pump, and the like in addition to a composite molecular pump. In both the first and second embodiments, the rotating shaft 8 is only rotated by the motor while maintaining its mounting position, and it is not necessary to swing or the like by the magnetic bearing control. Applicable to not only magnetic bearing types but also ball bearing types and gas bearing types.

  The present invention is used in a molecular pump that exhausts a process gas that is easily condensed, such as a semiconductor manufacturing apparatus.

1 shows a cross-sectional view of a typical molecular pump body to which the present invention is applicable. The block diagram of the main body and controller of the molecular pump of embodiment of this invention is shown. The flowchart of Example 1 when operation of maintenance mode is performed with the molecular pump of embodiment of this invention is shown. The flowchart of Example 2 when operation of maintenance mode is performed with the molecular pump of embodiment of this invention is shown.

DESCRIPTION OF SYMBOLS 1 Main body 1a Pump case 2 Intake port 3 Exhaust port 4a Turbo molecular pump part stator 4b Thread groove molecular pump part stator 5 Rotor 6 Rotor blade 7 Stator blade 8 Rotating shaft 9 Internal housing 10 Motor 11 Rotation speed detector 12 Inverter 13 Current detection 14 AD converter 15 Control unit 16 Controller 17 Storage unit A Turbo molecular pump unit B Thread groove pump unit

Claims (3)

A molecular pump that has a rotor rotated by a motor in a pump case having an intake port and an exhaust port, and has a maintenance mode. When the molecular pump is in operation in the maintenance mode, a brake operation is performed. When the motor is rotated at an ultra-low speed with a predetermined first specified rotational speed and the molecular pump is not in operation, the starting torque is increased and the motor is restarted to make the motor operate at the first specified rotational speed. If the motor does not reach the first specified rotation speed even after a predetermined set time has elapsed, the motor is stopped and then restarted in the reverse rotation direction. Then, the motor is turned to an ultra-low speed with a second specified rotation speed lower than the first specified rotation speed, and when the second specified rotation speed is reached, a stop operation is performed, When it is first prescribed rotational speed and starting rotation, as it is operated at a first predetermined rotational speed, molecular pump, characterized in that to end the execution of the maintenance mode. In the maintenance mode, when the motor is restarted in the direction opposite to the normal rotation, if the motor does not reach the second specified rotation speed, the rotation in the reverse direction is started until a set time is exceeded. It continued, when the time is over, the molecular pump according to claim 1 you characterized in that it is configured to select whether to retry as determined by the operator. First rotational speed of very low speed rotation, the molecular pump according to claim 1, characterized in der Rukoto following 20rps a predetermined of said motor.

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