JP3978018B2 - Turbomolecular pump and method of operating turbomolecular pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a turbo molecular pump having a magnetic bearing and a method for operating the turbo molecular pump.
[0002]
[Prior art]
A pump unit of the turbo molecular pump will be described with reference to FIG. In FIG. 4A, reference numerals 1 and 16 denote an upper casing 1 and a lower casing 16 which are integrally assembled with bolts via an O-ring 15. The upper opening of the upper casing 1 serves as a gas inlet 2. On the inner peripheral surface side of the casing 1, a circular ring-shaped stationary blade group (fixed blade) 4 is vertically formed by a spacer 13.
[0003]
In addition, a seal ring 14 is disposed below the stationary blade group (fixed blade) 4 so as to surround the outer periphery of a thread groove pump stage 8 to be described later, thereby increasing the compression effect.
The lower casing 16 is provided with the exhaust port 3 on the side, and further has a connector 23 formed on the lower side thereof.
A cylindrical support cylinder 17 is suspended upward in the central area of the upper surface of the lower casing 16, and the upper protective bearing 19 and the upper part are arranged at a position facing the rotor shaft 7 on the inner peripheral side of the support cylinder 17 from above. A radial magnetic bearing 9, a motor stator 12, a lower bearing 10, a protective bearing 20, and a thrust magnetic bearing 11 are attached.
Reference numeral 6 denotes a pump rotating portion in which the rotor shaft 7 is suspended downward from the center lower surface. A large number of moving blade groups (rotating blades) 5 radially arranged on the outer periphery of the rotating portion 6 are arranged in the radial direction. A plurality of stages are arranged so as to alternately mesh with the stationary blades 4, and a spiral thread groove pump stage 8 is attached to the lower outer peripheral part of the rotating part 6.
The rotor shaft 7 fitted in the support cylinder 17 constitutes an AC motor 29 by fitting a motor rotor 21 at a position facing the motor stator 12, and an upper radial magnet is formed above the rotor 21. The distance between the bearing 9 and the protective bearing 19 is set at the upper part.
[0004]
Further, the lower radial magnetic bearing 10 is set at the lower part of the rotor 21, and the space between the lower part and the protective bearing 20 is set. A disc-shaped magnetic plate 22 is provided at the lower end of the rotor shaft 7, and the magnetic plate 22 penetrates into the thrust magnetic bearing 11 on the support cylinder 17 side, and is maintained in the air in the thrust direction (Z-axis). Control is in progress.
That is, as shown in FIG. 4B, the upper radial magnetic bearing 9 and the lower radial magnetic bearing 10 are paired in the left-right (X-axis) and front-rear (Y-axis) directions, respectively, in a cross section orthogonal to the axis. The rotor shaft 7 is configured so that the rotor shaft 7 can be kept hollow on the center axis without falling down. As a result, the thrust magnetic bearing 11 (Z-axis), the upper radial magnetic bearing 9 and the lower radial magnetic bearing 10 ( The X-axis and Y-axis) causes the rotor shaft 7 to be rotated in the air in the five-axis direction.
Further, when the magnetic control of the magnetic bearings 9, 10 and 11 is abnormal and the rotor shaft 7 is eccentric to one side, the rotation is compensated by contacting the upper or lower protective bearings 19 and 20.
[0005]
In the turbo molecular pump configured as described above, the motor is operated at, for example, 10,000 to 100,000 rpm while energizing each radial magnetic bearing 9 and maintaining the pump rotating portion 6 hollow via the rotor shaft 7. By rotating at a high speed, the moving blade 5 rotates in the stationary blade 4 and the thread groove pump stage 8 rotates while facing the seal ring 14, and the gas to be evacuated is discharged from the upper intake port 2 to the moving blade 5. After the first compression between the blades 4, the second compression is performed in the spiral groove passage of the thread groove pump stage 8, flows through the gas passage toward the exhaust port 3, and the suction port 2 side is evacuated. Is done.
And in each magnetic bearing 9,10,11 which concerns on this embodiment, the position sensors 24,25,26 are each arrange | positioned in the vicinity, The rotor shaft 7 and the support cylinder 17 in each magnetic bearing 9,10,11 position. And the deviation in the thrust direction are detected.
[0006]
FIG. 5 shows a pump unit A and a power supply unit B. As shown in FIG. 5, the pump unit A side and the power supply unit B side are electrically connected to each other, and the pump unit A side is directly connected to the rotor shaft 7 of the pump body rotating part (rotor part) 6. Motor 29 composed of the rotor 21 and the stator 12, upper and lower radial magnetic bearings 9, 10 positioned above and below the rotor 21, and a thrust magnetic bearing provided on the lower end of the rotor shaft 7 with a disc sandwiched therebetween. 11, position sensors 24 and 25 for detecting the gaps (X and Y axes) between the upper and lower radial magnetic bearings 9 and 10 and the rotor shaft 7 and the displacement between the radial magnetic bearing 9 and the disc in the thrust direction. , 26.
And it is comprised so that the signal from the said position sensors 24, 25, 26 can be transmitted to the power supply unit B side from the signal cable 40A via the converter 36.
[0007]
On the side of the power supply unit B, the motor drive circuit 34 for driving the motor 29 at high speed and the signals from the position sensors 24, 25, 26 are received to control the drive voltages of the magnetic bearings 9, 10, 11, and the rotor shaft 7 as a magnetic bearing control circuit 32 that holds the center 7 in the horizontal and thrust directions, and a transistor circuit that performs ON / OFF control of the drive voltage from the magnetic bearing drive power supply 31 in response to a signal from the calculator 51 A magnetic bearing drive circuit 33 including a magnetic bearing drive power source 31 is incorporated.
The number of the arithmetic units 51 and the magnetic bearing drive circuits 33 as the magnetic bearing control circuit 32 is provided corresponding to n pairs of electromagnets constituting the magnetic bearings 9, 10, and 11.
That is, as shown in FIG. 4B, the upper radial magnetic bearing 9 and the lower radial magnetic bearing 10 have one pair each in the X-axis direction, one pair each in the Y-axis direction (four pairs in total), and a thrust magnetic bearing. 11 is a pair on the top and bottom, and a total of 5 pairs are required, so that there are five position sensors 24, 25, 26 on the pump unit A side, and a magnetic bearing that is controlled / calculated based on this detection signal. Five control circuits 32 and five magnetic bearing drive circuits 33 are required.
Since the set constant data from the table 50 to be described later is a digital signal, the magnetic bearing control circuit 32 is constituted by a computing unit 51 such as a CPU so that a control value can be output by digital computation. Since the detection signals from the sensors 24, 25, and 26 and the drive control signal to the magnetic bearing drive circuit 33 are analog signals, an A / D conversion for digitally converting the position sensor signal to the input side of the computing unit 51 is performed. The D / A converter 46 is provided on the output side of the calculator 45, and the calculation output is converted into a control signal in an analog manner so that it can be sent to the magnetic bearing drive circuit 33.
[0008]
Next, the magnetic bearing control circuit 32 will be described.
In FIG. 6, reference numeral 60 denotes a PID control circuit to which a feedback signal based on detection signals from the position sensors 24, 25, and 26 is inputted. Reference numeral P denotes a proportional unit, I denotes an integrator, and D denotes a differentiator. After passing through this PID control circuit, after passing through a phase compensation circuit 63 for stabilizing the natural frequency of several orders due to the structure of the rotating body 6, a feedback control current is obtained through a circuit 65 for compensating the electromagnet characteristics. .
[0009]
[Problems to be solved by the invention]
Now, the turbo molecular pump can be freely selected between the vertical placement and the horizontal placement according to the installation situation.
In the vertical / horizontal placement, the direction in which the weight of the rotor 21 acts is different, so the currents flowing through the radial bearings 9 and 10 and the thrust bearing 11 are different. For this reason, the bearing rigidity differs between vertical installation and horizontal installation. For example, in the case of the upper radial bearing 9, the bearing rigidity is about three times greater when placed horizontally than when placed vertically. Since the rigidity and the gain are proportional, the gain increases as the bearing rigidity increases. As a result, the gain of high-frequency vibration components (for example, third-order and fourth-order eigenvalues) also increases, and the control becomes unstable. End up.
In addition, the eigenvalue varies depending on the bearing rigidity.
This is shown in FIG. At the rated speed, the eigenvalue is higher in the case of horizontal placement than in the case of vertical placement.
In order to stabilize the bearing control constant regardless of the installation state, phase compensation is performed for eigenvalues (from rigid body primary backward to rigid body secondary forward) up to the second order during vertical installation and horizontal installation. ing. For this reason, it is necessary to take a wider phase compensation region by the phase compensation circuit 63 than in the case of only the vertical placement or only the horizontal placement. Therefore, the gain also increases. When the gain is increased, there is a problem that the control becomes unstable as described above.
[0010]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a turbo molecular pump capable of stabilizing control and a method of operating the turbo molecular pump.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 includes a magnetic bearing, a magnetic bearing control device that controls the magnetic bearing, and a determination unit that provides the magnetic bearing control device with a control constant corresponding to an installation direction. The apparatus is provided with at least an integrator, and the determination means detects an installation direction based on a state of the integrator .
[0012]
In the present invention, it is possible to control the magnetic bearing using a control constant appropriate for the control in each case according to the difference in the installation direction of the turbo molecular pump (for example, vertical installation and horizontal installation). Furthermore, in the present invention, the installation direction is determined from the state of the integrator used to make the deviation of the rotation axis of the rotor zero. More specifically, the state of the load acting on the magnetic bearing is determined based on the output of the integrator in the case of a digital circuit and the voltage value of a capacitor provided in the integrator in the case of an analog circuit.
[0015]
Invention according to claim 2, in the turbo molecular pump according to claim 1, wherein the magnetic bearing control device is provided with a proportional circuit and the differentiator is the control constant is of the proportional circuit and the differentiator It is a set value.
[0016]
In the present invention, a control constant that makes the rigidity of the magnetic bearing appropriate according to the installation direction of the turbo molecular pump is given to the proportionalizer and the differentiator. As a result, it is possible to prevent an increase in the gain of the high-frequency vibration component caused by the increased rigidity.
[0017]
Invention according to claim 3, in the turbo molecular pump according to claim 1, wherein the magnetic bearing controller, a phase compensation circuit is provided, wherein the control constant is set value before Symbol position phase compensation circuit It is characterized by being.
[0018]
In the present invention, the phase compensation region of the phase compensation circuit can be changed according to the installation direction of the turbo molecular pump. Thereby, it is possible to prevent an increase in the gain of the high-frequency vibration component caused by the wide phase compensation region.
[0019]
According to a fourth aspect of the present invention, in the method for operating a turbo molecular pump including a magnetic bearing and a magnetic bearing control device that controls the magnetic bearing, the magnetic bearing control device includes an installation direction of the turbo molecular pump. It is detected from the state of the integrator, and the control constant of the magnetic bearing control device is changed according to the installation direction.
[0020]
In the present invention, it is possible to control the magnetic bearing using a control constant appropriate for the control in each case according to the difference in the installation direction of the turbo molecular pump (for example, vertical installation and horizontal installation).
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. In addition, about the structure same as the past, the same code | symbol is used and the description is abbreviate | omitted.
FIG. 1 is a control block diagram of a magnetic bearing control device for the upper radial bearing 9. Reference numeral 60 denotes a PID control circuit. Reference numeral P denotes a proportional device, I denotes an integrator, and D denotes a differentiator. Reference numeral 70 denotes determination means for determining whether the apparatus is placed vertically or horizontally, and reference numeral 71 denotes constant storage means in which control constants of the proportional device P and the differentiator D are stored.
Note that, in the initial state, the proportional constant P and the differentiator D are given control constants suitable for vertical installation.
[0022]
First, a turbo molecular pump is installed. The installation direction is arbitrary by the user, and may be either vertical or horizontal. At the first startup after that, the determination means 70 determines from the state of the integrator I whether the turbo molecular pump is installed vertically or horizontally. Specifically, the output of the integrator I is detected in the case of a digital circuit, and the voltage value of the capacitor in the integrator I is detected in the case of an analog circuit. Specifically, it is “small” in the vertical position and “large” in the horizontal position. Therefore, for example, a threshold value is determined in advance, and if it is equal to or greater than the threshold value, it can be determined to be horizontal, and if it is less than the threshold value, it can be determined to be vertical.
[0023]
Based on the determination result, the determination means 70 reads a control constant suitable for the horizontal placement from the constant storage means 71 when the turbo molecular pump is in the horizontal orientation, and gives it to the proportional device P and the differentiator D. By giving this control constant, in the proportional device P and the differentiator D, the bearing rigidity (gain) does not increase, and even in the horizontal position, the same rigidity as in the vertical position can be obtained. Therefore, high-frequency gain can be suppressed, and more stable control can be performed.
In the above description, the upper radial bearing 9 is shown. However, the control constants of other magnetic bearings (lower radial bearing 10 and thrust bearing 11) can be similarly changed according to the installation direction of the turbo molecular pump.
[0024]
Next, a second embodiment of the present invention will be described.
In the following, the case of a digital circuit will be described. Moreover, the same code | symbol is used about the same structure as the past, and the description is abbreviate | omitted.
2 is a control block diagram showing a magnetic bearing control device for the upper radial bearing 9. Reference numeral 60 is a PID control circuit, reference numeral P is a proportional unit, I is an integrator, and D is a differentiator. It is. Reference numeral 75 denotes a determination unit that determines whether the device is placed vertically or horizontally, and reference numeral 76 denotes a constant storage unit that stores a control constant of the phase compensation circuit 63.
In the initial state, the phase compensation circuit 63 is set to be suitable for vertical installation.
[0025]
First, a turbo molecular pump is installed. The installation direction is arbitrary by the user, and may be either vertical or horizontal. At the first startup after that, the determination means 75 determines from the state of the integrator I whether the turbo molecular pump is installed vertically or horizontally. Specifically, the output of the integrator I is detected in the case of a digital circuit, and the voltage value of the capacitor in the integrator I is detected in the case of an analog circuit. Specifically, it is “small” in the vertical position and “large” in the horizontal position. Therefore, for example, a threshold value is determined in advance, and if it is equal to or greater than the threshold value, it can be determined to be horizontal, and if it is less than the threshold value, it can be determined to be vertical.
[0026]
Based on the determination result, the determination means 75 reads the control constant suitable for the horizontal placement from the constant storage means 76 and gives it to the phase compensation circuit 63 when the turbo molecular pump is in the horizontal orientation.
Specifically, α1 (time constant) that was 0.76 during vertical installation is set to 0.9. As a result, the conventional phase compensation range that includes both vertical and horizontal placement is narrower than the conventional phase compensation range that is suitable for vertical placement when placed vertically, and narrower than conventional compensation that is suitable for horizontal placement when placed horizontally. It can be.
As described above, in this example, the phase compensation range is narrowed, so that a high-frequency gain can be suppressed, and more stable control can be performed.
[0027]
In the case of the digital circuit as described above, the control constant may be changed. In the case of the analog circuit (primary phase advance circuit) shown in FIG. 3, R1 = T1 / C, R2 = {α1 / ( Since 1−α1)} * R1, it can be realized by changing the value of the resistor R2.
In the above description, the upper radial bearing 9 is shown. However, the control constants of other magnetic bearings (lower radial bearing 10 and thrust bearing 11) can be similarly changed according to the installation direction of the turbo molecular pump.
Further, in each of the above examples, whether or not it is placed vertically or horizontally is determined not only based on the integrator I of the upper radial bearing 9 but also based on the integrators of the other magnetic bearings 10 and 11 and combinations thereof. It may be.
Furthermore, the installation direction is not limited to the time of initial activation, but may be when each activation or when the installation direction is changed, or when the user designates.
Further, the target to which the determination means 70 and 75 control constants are given may be only the proportional device P, the integrator I, and the differentiator D, or may be a combination thereof including the phase compensation circuit 63.
[0028]
As described above, in the present invention, stable control can be performed by increasing the stability margin of the high-frequency vibration component. The user himself can freely change the installation direction without adjusting the equipment.
[0029]
【The invention's effect】
As described above, in the present invention, the magnetic bearing can be controlled using a control constant appropriate for the control in each case according to the difference in the installation direction of the turbo molecular pump. It can be performed.
[Brief description of the drawings]
FIG. 1 is a magnetic bearing control block diagram of a turbo molecular pump shown as an embodiment of the present invention.
FIG. 2 is a magnetic bearing control block diagram of a turbo molecular pump shown as another embodiment of the present invention.
FIG. 3 is a diagram showing a part of a phase compensation circuit in an analog circuit.
4A and 4B are diagrams showing a configuration of a turbo molecular pump, where FIG. 4A is a longitudinal sectional view, and FIG. 4B is a transverse sectional view of a radial magnetic bearing portion.
FIG. 5 is a schematic view showing a control circuit of the turbo molecular pump.
FIG. 6 is a magnetic bearing control block of a conventional turbo molecular pump.
FIG. 7 is a diagram showing changes in eigenvalues when a turbo molecular pump is placed vertically and when it is placed horizontally.
[Explanation of symbols]
9 Upper radial magnetic bearing 10 Lower radial magnetic bearing 11 Thrust magnetic bearing 70, 75 Determination means P Proportional device I Integrator D Differentiator

Claims (4)

Magnetic bearings,
A magnetic bearing control device for controlling the magnetic bearing ;
Determining means for giving a control constant corresponding to the installation direction to the magnetic bearing control device;
With
The magnetic bearing control device is provided with at least an integrator,
The turbo molecular pump according to claim 1, wherein the determination unit detects an installation direction based on a state of the integrator . The turbo-molecular pump according to claim 1,
The magnetic bearing control device is provided with a proportional device and a differentiator, and the control constant is a set value of the proportional device and the differentiator . In the turbo molecular pump according to claim 1, wherein the magnetic bearing control device, the phase compensation circuit is provided, wherein the control constant is a turbo molecular pump, which is a set value of the phase compensation circuit. In a method of operating a turbo molecular pump comprising a magnetic bearing and a magnetic bearing control device for controlling the magnetic bearing,
  An operating method of a turbo molecular pump, wherein an installation direction of a turbo molecular pump is detected from a state of an integrator provided in the magnetic bearing control device, and a control constant of the magnetic bearing control device is changed according to the installation direction.

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