JP2014176120A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: Switching a filter with a relay switch deteriorates the relay switch.SOLUTION: A switching control section 483 outputs a switching signal to a switcher 40 and switches connection of a power input line from a connection state of a line filter 41 for low load to connection of a line filter 42 for high load. In switching the switcher 40, because no electric power is output from a DC-DC converter 44, no arc discharge is generated at a relay switch of the switcher 40 and hence a problem that deterioration of the relay switch shortens the service life of the relay switch can be avoided.

Description

  The present invention relates to a vacuum pump used in a semiconductor manufacturing apparatus, an analysis apparatus, or the like.

  A power supply device for driving a turbo molecular pump used in a semiconductor manufacturing apparatus, an analysis apparatus or the like includes a high power switching circuit such as a DC-DC converter, and emits a large amount of electromagnetic noise. For this reason, a line filter is provided on the power input line side of the power supply device so as not to release electromagnetic noise generated in the power supply device to the outside. For example, Patent Document 1 describes an electric device that switches between a plurality of line filters in consideration of the power consumption of the line filters.

JP 2006-280135 A

  However, when a plurality of filters are switched by a relay switch while the electrical equipment is in a load state, there is a problem that arc discharge occurs in the relay switch, which deteriorates the relay switch and shortens the life of the relay switch.

  The vacuum pump according to the present invention includes a motor that is powered and rotated by a power input line, a rotating body that rotates by the motor and performs vacuum exhaust, and a plurality of filters that suppress noise intrusion into the power input line. A switch that selects and switches the plurality of filters, a detection unit that detects a switching timing of the switch according to an operating state of the motor, and the switching when the switching timing is detected by the detection unit A motor control unit that switches the motor from normal drive to regenerative drive prior to switching of the switch, and switching that causes the switch to switch the filter when the motor is driven to regenerate and the generated power from the motor is fed. A control unit is provided.

  The present invention prevents deterioration of the switching device that switches the filter, suppresses generation of a surge voltage, and suppresses generation of noise.

Sectional drawing which shows schematic structure of pump unit Block diagram showing schematic configuration of control unit Flow chart showing line filter switching operation Diagram showing changes in motor power The block diagram which shows the modification of schematic structure of a control unit

Hereinafter, an embodiment for implementing a vacuum pump according to the present invention as a turbo molecular pump will be described with reference to the drawings.
-First embodiment-
The turbo molecular pump includes a pump unit that performs evacuation and a control unit that drives and controls the pump unit. FIG. 1 is a cross-sectional view showing a schematic configuration of the pump unit 1. The turbo molecular pump shown in FIG. 1 is a magnetic bearing type pump, and the rotor 30 is supported in a non-contact manner by magnetic bearings 37 and 38 constituting a 5-axis control type magnetic bearing. The rotor 30 magnetically levitated by the magnetic bearings 37 and 38 is rotated by a motor 36. For example, a DC brushless motor is used as the motor 36.

  The rotor 30 is formed with a plurality of stages of rotating blades 32 and a cylindrical screw rotor 31 as an exhaust function unit. On the other hand, on the fixed side, a plurality of stages of fixed blades 33 arranged alternately with the rotary blades 32 in the axial direction and a screw stator 39 provided on the outer peripheral side of the screw rotor 31 are provided as exhaust function units. . The fixed wings 33 are stacked so as to be sandwiched from above and below in the axial direction by a pair of spacer rings 35 and placed on the base 20. When the pump casing 34 in which the inlet flange 21 is formed is fixed to the base 20, the stacked spacer ring 35 is sandwiched between the base 20 and the pump casing 34, and each fixed blade 33 is positioned.

  The base 20 is provided with an exhaust port 22, and a back pump is connected to the exhaust port 22. By rotating the rotor 30 at high speed by the motor 36 while magnetically levitating, the gas molecules on the intake port side are exhausted to the exhaust port 22 side.

  FIG. 2 is a block diagram showing a schematic configuration of the control unit 2 and a diagram showing the motor 36. The control unit 2 constitutes a power supply device for the motor 36, and an AC input from the outside is input to the switch 40 from the power input line. The switch 40 is configured by a relay switch, a semiconductor element, or the like, and switches the connection of the power input line to the low load line filter 41 or the high load line filter 42. The low load line filter 41 and the high load line filter 42 are composed of an LC filter, a T-type filter, a π-type filter, and the like that shield a specific frequency.

The low load line filter 41 reduces noise corresponding to a switching frequency of a DC-DC converter 44 described later when the turbo molecular pump is in a low load state, so that the noise is not emitted to the outside from the power input line. Is provided.
The high load line filter 42 is provided so as to reduce noise corresponding to the switching frequency of the DC-DC converter 44 and prevent the noise from being emitted to the outside from the power input line when the turbo molecular pump is in a high load state. ing. Since strong noise is generated from the DC-DC converter 44 when the turbo molecular pump is in a high load state, the high load line filter 42 has a filter configuration that reduces noise more strongly than the low load line filter 41. And

  In the turbo molecular pump of the first embodiment, the switching frequency of the DC-DC converter 44 is a fixed value set in advance.

  An AC input from the outside is converted into a DC voltage by an AC-DC converter 43 through a low load line filter 41 or a high load line filter 42. The DC voltage is input to the DC-DC converter 44, where a DC voltage for the motor 36 is generated and input to the inverter 46 via the diode 45. Further, the DC voltage of the DC-DC converter 44 is supplied to the control unit 48 as an operating voltage. The inverter 46 rotationally drives the motor 36 by PWM (Pulse Width Modulation) control. The diode 45 is connected in a forward direction to a path from the DC-DC converter 44 to the inverter 46.

  The currents flowing through the U, V, and W phase coils provided in the motor stator of the motor 36 are detected by a current sensor (not shown), and the detected current value is input to the control unit 48 via the signal detection line 401. .

  The control unit 48 is a digital arithmetic unit that controls the motor 36, and includes, for example, an FPGA (Field Programmable Gate Array). The control unit 48 outputs a signal for setting the output voltage to the DC-DC converter 44 via the control signal line 402 and causes the DC-DC converter 44 to output a preset voltage. The control unit 48 has a function of controlling the inverter 46 and outputs a control signal for driving the switching element of the inverter 46 via the control signal line 403.

  The control unit 48 includes a load detection unit 481, a motor control unit 482, a switching control unit 483, and a filter storage unit 484. The load detection unit 481 receives the current value detected by the current sensor as described above, and calculates the electric power of the motor 36 based on this current value, thereby detecting the load state of the turbo molecular pump. The motor control unit 482 selectively controls regenerative driving and normal driving of the motor 36.

  That is, when a regenerative drive control signal is output to the control signal line 403 to the inverter 46, the motor 36 is regeneratively driven and enters a brake operation state. Therefore, the motor 36 serves as a generator to generate electric power, and the electric power is supplied from the inverter 46 to the control unit 48 from the cathode side of the diode 45 via the power supply line 405. Since the diode 45 is provided, the power extracted by the regenerative operation is not supplied to the DC-DC converter 44.

  On the other hand, when a control signal for normal driving control is output to the control signal line 403 for the inverter 46, the motor 36 is normally driven. The normal driving means that the motor 36 is driven to rotate in the forward direction by the electric power supplied from the DC-DC converter 44.

  The switching control unit 483 outputs a switching signal to the switch 40 via the switching signal line 404 and switches the connection of the power input line to the low load line filter 41 or the high load line filter 42. The filter storage unit 484 stores a table indicating the correspondence between the output voltage of the DC-DC converter 44 and the line filter to be selected by the switch 40. Specifically, the high load line filter 42 is selected when the output voltage of the DC-DC converter 44 is high, and the low load line filter is selected when the output voltage of the DC-DC converter 44 is low. The line filter type corresponding to the load state is stored so that 41 is selected.

  FIG. 3 is a flowchart showing the line filter switching operation in the control unit 48. The control shown in FIG. 3 is repeatedly executed at predetermined intervals while power is supplied to the control unit 48. This operation will be described below with reference to the block diagram of FIG. 2 based on the flowchart shown in FIG.

  In step S01, it is detected whether the turbo molecular pump has changed from a low load state to a high load state. That is, the current value detected by the current sensor is input to the load detection unit 481, and the load detection unit 481 calculates the electric power of the motor 36 based on this current value. FIG. 4 shows an example of a diagram in which the electric power w of the motor 36 changes with time t. At point a in FIG. 4, the load detector 481 detects that the power has risen to the threshold value N watts or more. That is, the switching timing of the switch 40 is detected.

  If the electric power exceeds the threshold value N watts, a brake operation is performed by the motor control unit 482 in step S02. That is, a regeneration control signal is output to the inverter 46 via the control signal line 403, and the motor 36 that has been normally driven is driven to regenerate to reduce the motor rotation speed. At this time, the motor 36 serves as a generator to generate electric power, and the electric power from the inverter 46 is supplied to the control unit 48 via the feeder line 405. The electric power extracted from the motor 36 by the regenerative operation is not supplied to the DC-DC converter 44 because the diode 45 is provided.

  In the next step S03, the control unit 48 outputs a signal for stopping the output voltage to the DC-DC converter 44 via the control signal line 402, and stops the output voltage of the DC-DC converter 44.

  In step S04, the switching control unit 483 outputs a switching signal to the switching unit 40 via the switching signal line 404, and changes the connection of the power input line from the connection state of the low load line filter 41 to the high load line filter 42. Switch to connection. In step S03, the supply of power from the DC-DC converter 44 to the control unit 48 is stopped. However, as described above, the power extracted by the regenerative operation is supplied to the control unit 48. Thus, the connection to the high load line filter 42 is switched by the switch 40.

  In addition, since no power is output from the DC-DC converter 44 during the switching operation of the switching device 40, arc discharge does not occur in the relay switch of the switching device 40, and the life of the relay switch is reduced due to the deterioration of the relay switch. The problem of shortening can be avoided. Further, when the switcher 40 is switched, it is possible to prevent a surge voltage from being generated due to the inductance in the control unit 2 and to suppress the generation of noise.

  In the next step S05, the control unit 48 outputs a signal for setting an output voltage to the DC-DC converter 44 via the control signal line 402, and a voltage corresponding to a high load is output from the DC-DC converter 44. Output from. On the other hand, the motor control unit 482 outputs a control signal for normal driving from the control signal line 403 to the inverter 46. As a result, the output voltage of the DC-DC converter 44 is supplied to the motor 36 via the diode 45 and the inverter 46, and the motor 36 performs normal operation and accelerates.

  If it is not detected in step S01 that the low load state has changed to the high load state, it is detected in step S06 whether the high load state has changed to the low load state. As shown at point b in FIG. 4, the load detector 481 detects that the power has dropped below the threshold value N watts. That is, the switching timing of the switch 40 is detected.

  If the power drops below the threshold N watts, a brake operation is performed by the motor control unit 482 in step S07. This operation is the same as that in step S02. In the next step S08, the control unit 48 provides a stop signal to the DC-DC converter 44 via the control signal line 402. As a result, the DC-DC converter 44 stops its driving and the output voltage becomes zero. This operation is the same as that in step S03.

  In step S09, the switching control unit 483 outputs a switching signal to the switch 40 via the switching signal line 404, and changes the connection of the power input line from the connection state of the high load line filter 42 to the low load line filter 41. Switch to connection. In step S08, the supply of power from the DC-DC converter 44 to the control unit 48 is stopped. However, as described above, the power extracted by the regenerative operation is supplied to the control unit 48. Thus, the connection to the low load line filter 41 is switched by the switch 40. In addition, since no power is output from the DC-DC converter 44 during the switching operation of the switching device 40, arc discharge does not occur in the relay switch of the switching device 40, and the life of the relay switch is reduced due to the deterioration of the relay switch. The problem of shortening can be avoided. Further, when the switcher 40 is switched, it is possible to prevent a surge voltage from being generated due to the inductance in the control unit 2 and to suppress the generation of noise.

  In the next step S10, the control unit 48 outputs a signal for setting the output voltage to the DC-DC converter 44 via the control signal line 402, and the motor control unit 482 causes the inverter 46 to perform normal driving. A control signal is output to the control signal line 403. As a result, a predetermined voltage is output from the DC-DC converter 44, and the motor 36 is accelerated through the diode 45 and the inverter 46. As described above, when the flow rate of gas flowing into the turbo molecular pump decreases and the load becomes low, the output voltage of the DC-DC converter 44 decreases. As a result, the noise of the DC-DC converter 44 decreases. Switching to the filter 41 reduces noise.

  If it is not detected in step S01 that the low load state has changed to the high load state, and if it is not detected in step S06 that the high load state has changed to the low load state, that is, the low load state. Alternatively, when the high load state is maintained, the switching operation by the switch 40 is not performed.

  Whether it is in a low load state or a high load state is stored as a flag in a storage unit (not shown) in the control unit 48, and this flag is referred to or rewritten in steps S01 and S06. Detect load conditions. For example, when a threshold value of N watts or more is detected in a state where a low load state flag is stored, it is determined that a high load state has occurred, and the flag is rewritten to a high load state. When the flag of the high load state is stored and a value less than the threshold N watts is detected, it is determined that the low load state has been reached, and the flag is rewritten to the low load state.

According to 1st Embodiment described above, there can exist the following effects.
(1) When the flow rate of the gas flowing into the pump unit 1 of the turbo molecular pump increases and the motor 36 has a high load, the voltage output from the DC-DC converter 44 increases and noise increases. Therefore, when the load of the motor 36 becomes equal to or higher than the threshold, the low load line filter 41 is switched to the high load line filter 42. This reduces noise.
(2) When switching from the low load line filter 41 to the high load line filter 42, the motor 36 is regeneratively driven. The voltage output from the motor 36 is equal to or higher than the output voltage of the DC-DC converter 44. At this time, the switcher 40 is in a non-energized state. On the other hand, the regenerative electric power from the motor 36 is supplied to the control unit 48 via the feeder line 405. The switching control unit 483 sends a switching signal to the switching signal line 404 to switch the switch 40. Thereby, the high load line filter 42 is inserted into the power input line.
Therefore, since the switch 40 is in a non-energized state when switching the line filter, arc discharge does not occur in the switch of the switch 40, and the durability of the switch 40 can be improved.
Further, since the regenerative power from the motor 36 is used as the drive power for the control unit 48, the control unit 48 can supply a switching signal to the switch 40.

  The conventional vacuum pump has a problem that when a plurality of line filters are switched by a relay switch in a loaded state, a surge voltage is generated due to the inductance of a power supply device or the like, and thus noise is generated. On the other hand, in the turbo molecular pump of the first embodiment, the switching device 40 is in a non-energized state when the line filter is switched, and no surge voltage is generated, so that no noise is generated.

-Second Embodiment-
FIG. 5 is a modification of the block diagram showing the schematic configuration of the control unit 2 shown in FIG. The switch 49 switches whether the low load line filter 41 is connected or whether the low load line filter 41 and the high load line filter 42 are connected in series. Other configurations are the same as those in FIG. 2, and the same parts are denoted by the same reference numerals and the description thereof is omitted.

Also in the turbo molecular pump of the second embodiment, the filter switching control process is performed based on the flowchart shown in FIG.
In the turbo molecular pump of the second embodiment shown in FIG. 5, when it is detected in step S01 that the low load state is changed to the high load state, the low load line filter 41 and the high load line filter are used. 42 to be connected in series. Although the output voltage of the DC-DC converter 44 increases and the noise increases as the load increases, it can be reduced by the low load line filter 41 and the high load line filter 42.

  When it is detected in the above step S06 that the low load state has been changed from the high load state, only the low load line filter 41 is switched. Thereby, the noise of the DC-DC converter 44 is reduced by the low load line filter 41. When the high load state is detected, the low load line filter 41 and the high load line filter 42 are connected in series, so that there is an advantage that the high load line filter 42 can be made smaller.

The present invention can be implemented by modifying the first and second embodiments described above as follows.
(1) In the embodiment described above, the low load line filter 41 and the high load line filter 42 are switched according to the load state. However, three or more line filters may be provided and switched to a line filter corresponding to the detected load state. For example, a line filter for low load, a line filter for medium load, and a line filter for high load are provided, thresholds N1 watts and N2 watts (N2> N1) are set, and the load crosses each threshold by the load detection unit 481. This is detected and set as the switching timing to each line filter.

(2) In the first embodiment, the low load line filter 41 and the high load line filter 42 are switched according to the load state. However, the switching control unit 483 may be switched to connection of a line filter having a resonance frequency that does not match an integer multiple of the switching frequency of the DC-DC converter 44. In the turbo molecular pump driven in the energy saving mode at low load, the frequency of the DC-DC converter 44 is increased when the load becomes high, and the DC-DC converter 44 is used for power saving when the load becomes low. Reduce the frequency.

  In this case, since the noise frequency also changes, in order to reduce the noise corresponding to the switching frequency of the DC-DC converter 44, a line filter having a resonance frequency that does not coincide with an integer multiple of the switching frequency of the DC-DC converter 44 is selected. To switch. Specifically, a plurality of line filters are provided, and the filter storage unit 484 stores a table indicating the correspondence between the switching frequency of the DC-DC converter 44 and the line filter to be selected by the switch 40.

  Then, when the frequency of the DC-DC converter 44 is changed according to the load, the switching control unit 483 refers to the filter storage unit 484, and performs the control similar to the steps S02 and S03. The connection is switched to a line filter having a resonance frequency that does not coincide with an integral multiple of the switching frequency of the DC converter 44. Thereafter, the same control as in step S05 is performed. Even when the frequency of the DC-DC converter 44 is changed, there is an advantage that a line filter that reduces noise can be selected. As described above, the problem of shortening the life of the relay switch of the switch 40 can be avoided, and noise due to the surge voltage generated by the inductance in the control unit 2 can be suppressed when the switch 40 is switched.

(3) In the above-described embodiment, the magnetic bearing type pump is shown as an example of the turbo molecular pump. However, a ball bearing type turbo molecular pump may be used.
(4) Although the turbo molecular pump has been described as an example in the above-described embodiment, the present invention can also be applied to a vacuum pump without a screw pump stage.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Pump unit 2 Control unit 40 Switching device 41 Low load line filter 42 High load line filter 43 AC-DC converter 44 DC-DC converter 45 Diode 46 Inverter 48 Control part 49 Switch 481 Load detection part 482 Motor control part 483 Switching control unit 484 Filter storage unit

Claims (6)

A motor that is powered from a power input line and is driven to rotate;
A rotating body that is evacuated by rotating by the motor;
A plurality of filters for suppressing noise intrusion into the power input line;
A switch for selecting and switching the plurality of filters;
A detection unit for detecting a switching timing of the switch according to an operation state of the motor;
When the switching timing is detected by the detection unit, a motor control unit that switches the motor from normal driving to regenerative driving prior to switching of the switch;
A vacuum pump comprising a switching control unit that causes the switch to switch the filter when the motor is regeneratively driven and power generated by the motor is supplied. The vacuum pump according to claim 1, wherein
The detection unit detects that it is the switching timing when a load state of the motor becomes a high load or a low load,
When the detection unit detects a high-load load state, the switching control unit causes the switch to select and switch a high-load filter, and the detection unit detects a low-load load state. A vacuum pump that causes the switch to select and switch a low load filter. The vacuum pump according to claim 1 or 2,
A converter for converting a voltage supplied from the power input line;
A vacuum pump that stops the output of the converter when the switching control unit causes the switch to switch the filter. The vacuum pump according to claim 1 or 2,
A DC-DC converter for converting a voltage supplied from the power input line;
An inverter that is supplied with a voltage from the DC-DC converter and generates a voltage for driving the motor;
A diode connected in a forward direction to a path from the DC-DC converter to the inverter;
The vacuum pump further comprising a switching control unit and a power supply line that feeds power to the motor control unit from the cathode side of the diode. The vacuum pump according to claim 1 or 2,
A DC-DC converter for converting a voltage supplied from the power input line;
The switching control unit is a vacuum pump that selects a filter corresponding to a switching frequency of the DC-DC converter from the plurality of filters, and causes the switch to switch to the selected filter. The vacuum pump according to claim 5,
A converter control unit for switching a switching frequency of the DC-DC converter;
The plurality of filters include a plurality of filters having resonance frequencies that do not match an integer multiple of a switching frequency of the DC-DC converter,
The vacuum control unit, wherein the switching control unit selects a filter having a resonance frequency that does not match an integer multiple of a switching frequency of the DC-DC converter, and causes the switch to switch to the selected filter.

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