Cryopump and control device

Abstract

The invention relates to a cryopump adapted to a radiation environment. A cryopump (10) is provided with: a cold head motor (16a); a frequency converter (32b) disposed away from the cold head motor (16a) and configured to output a PWM voltage capable of driving the cold head motor (16a) at the determined operating frequency; and at least one converter (34) connected between the inverter (32b) and the cold head motor (16a). The converter (34) is configured to receive the PWM voltage from the inverter (32b), convert the PWM voltage into a cold-head motor drive voltage for driving the cold-head motor (16a) at the determined operating frequency, and output the cold-head motor drive voltage to the cold-head motor (16a). The cold-head motor drive voltage has a waveform in which a high-frequency component is reduced compared to the PWM voltage.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2024-155359, filed on September 9, 2024. The entire contents of that Japanese application are incorporated herein by reference. Technical Field

[0002] This invention relates to a cryogenic pump and its control device. Background Technology

[0003] A cryogenic pump is a vacuum pump that captures gas molecules onto a cryogenic plate cooled to ultra-low temperatures through condensation or adsorption and then exhausts the gas. Cryogenic pumps are typically installed in the vacuum chamber of a vacuum processing unit or other vacuum apparatus, providing a vacuum environment within the chamber.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2022-83523

[0005] Cryogenic pumps are sometimes mounted in vacuum devices that may generate radiation, such as accelerators. Radiation can have adverse effects on cryogenic pumps, such as causing malfunctions or damage to their control equipment. Summary of the Invention

[0006] One exemplary objective of one embodiment of the present invention is to adapt cryogenic pumps to radiation environments.

[0007] According to one embodiment of the present invention, a cryogenic pump includes: a cold head motor; a frequency converter disposed remotely from the cold head motor and configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency; and at least one converter connected between the frequency converter and the cold head motor. The converter is configured to receive the PWM voltage from the frequency converter, convert the PWM voltage into a cold head motor drive voltage to drive the cold head motor at the determined operating frequency, and output the cold head motor drive voltage to the cold head motor. The cold head motor drive voltage has a waveform with reduced high-frequency components compared to the PWM voltage.

[0008] According to one embodiment of the present invention, the control device includes: a frequency converter disposed remotely from the cold head motor and configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency; and at least one converter connected between the frequency converter and the cold head motor. The converter is configured to receive the PWM voltage from the frequency converter, convert the PWM voltage into a cold head motor drive voltage to drive the cold head motor at the determined operating frequency, and output the cold head motor drive voltage to the cold head motor. The cold head motor drive voltage has a waveform with reduced high-frequency components compared to the PWM voltage.

[0009] Invention Effects

[0010] According to the present invention, cryogenic pumps can be adapted to radiation environments. Attached Figure Description

[0011] Figure 1 This is a schematic diagram showing the cryogenic pump involved in the embodiment.

[0012] Figure 2 This diagram schematically illustrates an example of the control output from the frequency converter to the cold head motor in an embodiment.

[0013] Figure 3 This is a schematic diagram showing a portion of the control device for the cryogenic pump in an embodiment.

[0014] Figure 4 This is a schematic diagram showing a portion of the control device for the cryogenic pump in an embodiment.

[0015] In the picture:

[0016] 10-Cryogenic pump, 12-Cryogenic pump body, 14-Ultra-low temperature refrigerator, 16-Cold head, 16a-Cold head motor, 18-Compressor, 30-Cryogenic pump controller, 32-I / O device, 32a-I / O circuit, 32b-Inverter, 34-Converter, 34a-First converter, 34b-Second converter, 36-Cable, 42-Noise reduction component, 100-Vacuum device, 102-Vacuum container, 106-Radiation management area. Detailed Implementation

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description and drawings, the same or equivalent constituent elements, components, and processes are labeled with the same symbols, and repeated descriptions are omitted where appropriate. For ease of explanation, the proportions or shapes of the parts are appropriately set in each drawing, and unless otherwise specifically stated, this is not intended to be limiting. The embodiments are illustrative and do not limit the scope of the invention. All features or combinations thereof described in the embodiments are not necessarily essential to the invention.

[0018] Figure 1 This is a schematic diagram showing the cryogenic pump 10 according to the embodiment. Figure 1 The same shows a vacuum device 100 equipped with a cryogenic pump 10.

[0019] The vacuum device 100 includes a vacuum container 102 and a main controller 104 for controlling the vacuum device 100. The vacuum device 100 may include an accelerator capable of generating radiation (such as proton rays, neutron rays, etc.) or a radiation therapy device.

[0020] The cryogenic pump 10 includes a cryogenic pump body 12 and an ultra-low temperature refrigerator 14. The ultra-low temperature refrigerator 14 includes a cold head 16 and a compressor 18. The cold head 16 includes a cold head motor 16a for driving the cold head 16.

[0021] The cryogenic pump body 12 is installed in the vacuum container 102 of the vacuum device 100 to raise the vacuum level of the vacuum container 102 to the level required for the desired vacuum treatment. An ultra-low temperature surface (not shown), also referred to as a cryogenic plate, is housed within the cryogenic pump body 12. Gas entering from the suction port of the cryogenic pump body 12 is captured on this ultra-low temperature surface by condensation or adsorption. Various known structures can be appropriately adopted for the configuration of the cryogenic pump body 12, such as the arrangement and shape of the cryogenic plate, and therefore will not be described in detail here.

[0022] The compressor 18 of the cryogenic refrigerator 14 is configured to recover the working gas of the cryogenic refrigerator 14 from the cold head 16, pressurize the recovered working gas, and supply the working gas back to the cold head 16. The working gas is usually helium, but other suitable gases can be used.

[0023] The cryogenic refrigerator 14 includes a high-pressure line 20a and a low-pressure line 20b. The high-pressure line 20a connects the compressor 18 to the cold head 16, allowing high-pressure working gas compressed by the compressor 18 to be supplied from the compressor 18 to the cold head 16. The low-pressure line 20b connects the compressor 18 to the cold head 16, allowing low-pressure working gas, depressurized by expansion within the cold head 16, to be recovered from the cold head 16 back to the compressor 18. The cold head 16 is also referred to as the expander of the cryogenic refrigerator 14.

[0024] The working gas circulation loop, i.e., the refrigeration cycle of the cryogenic refrigerator 14, is formed by the cold head 16, the compressor 18, and the high-pressure pipeline 20a and low-pressure pipeline 20b connecting them, thereby cooling the cooling platform of the cold head 16. A low-temperature plate is mounted on the cooling platform of the cold head 16, and the low-temperature plate is also cooled by the cooling of the cold head 16. As an example, the cryogenic refrigerator 14 is a two-stage Gifford-McMahon (GM) refrigerator, but it can also be other types of cryogenic refrigerators.

[0025] Furthermore, the cryogenic pump 10 includes a control device comprising a cryogenic pump controller 30, an input / output device (hereinafter also referred to as an I / O device 32), and a converter 34.

[0026] The cryogenic pump controller 30 is configured to control the cryogenic pump 10 either according to instructions received from the main controller 104 or autonomously. Furthermore, the cryogenic pump controller 30 is configured to send information related to the cryogenic pump 10 to the main controller 104. The cryogenic pump controller 30 is connected to communicate with the cryogenic pump body 12 via an I / O device 32, and is also connected to communicate directly with the compressor 18.

[0027] The I / O device 32 may be, for example, an I / O module or a remote I / O unit, and includes an I / O circuit 32a. The I / O circuit 32a is configured to connect between the cryogenic pump body 12 and the cryogenic pump controller 30, and to integrate the transmission and reception between the cryogenic pump body 12 and the cryogenic pump controller 30. The I / O circuit 32a is connected to various electrical devices (e.g., temperature sensors, pressure sensors, valves, etc.) installed on the cryogenic pump body 12, including the cold head motor 16a, to transmit and receive signals with these devices.

[0028] Furthermore, the I / O device 32 includes an inverter 32b for controlling the cold head motor 16a. The cold head motor 16a receives power from a power source 40, such as a commercial power supply (three-phase AC power), via the inverter 32b. The cold head motor 16a can be an electric motor with a variable operating frequency (i.e., the rotational speed of the cold head motor 16a), and can operate at an operating frequency corresponding to the output frequency of the inverter 32b. The operating frequency of the cold head motor 16a determines the number of thermal cycles (or GM cycles if the cryogenic refrigerator 14 is a GM refrigerator) per unit time in the cold head 16, i.e., the frequency of the thermal cycles. As an example, the output frequency of the inverter 32b (i.e., the operating frequency of the cold head motor 16a) can vary within the range of 30Hz to 100Hz or within the range of 40Hz to 70Hz.

[0029] Figure 2 This diagram schematically illustrates an example of the control output from the inverter 32b to the cooling head motor 16a in an embodiment. The inverter 32b is configured to generate a PWM voltage based on the input voltage from the power supply 40 via PWM (Pulse Width Modulation) control and output it to the cooling head motor 16a. Known PWM control methods can also be installed in the inverter 32b.

[0030] like Figure 2 As shown, in the waveform of the PWM voltage output from the inverter 32b, the duty cycle of each pulse of the PWM voltage waveform is adjusted by the inverter 32b so that the time-averaged voltage of the PWM voltage becomes a sine wave waveform with an operating frequency determined by the cryogenic pump controller 30. Therefore, when the PWM voltage is input from the inverter 32b to the cold head motor 16a, the cold head motor 16a can be driven at an operating frequency determined by the cryogenic pump controller 30.

[0031] The cryogenic pump controller 30 can determine the operating frequency of the cold head motor 16a in such a way that the cooling temperature of the cryogenic plate in the cryogenic pump body 12 follows the target temperature value, and control the frequency converter 32b to make the cold head motor 16a operate at the determined operating frequency.

[0032] For example, the cooling temperature of the cryogenic plate can be measured by a temperature sensor located on the cryogenic pump body 12. The cryogenic pump controller 30 can acquire a measured temperature signal representing the measured temperature from the temperature sensor via I / O circuit 32a. The cryogenic pump controller 30 can determine the output frequency of the inverter 32b through feedback control to minimize the deviation between the measured temperature and the target temperature value. The cryogenic pump controller 30 can determine the output frequency of the inverter 32b as a function of the deviation between the measured temperature and the target temperature value (e.g., through PID control). The cryogenic pump controller 30 can send a motor control signal representing the determined output frequency of the inverter 32b to the I / O device 32. The inverter 32b can generate a PWM voltage based on the motor control signal and output it to the cold head motor 16a.

[0033] Regarding the internal structure of the cryogenic pump controller 30 and the I / O device 32, as a hardware structure, it is implemented by components or circuits, represented by a computer's CPU or memory; as a software structure, it is implemented by computer programs, etc., but it is appropriately drawn in the figure as a functional module implemented through the cooperation of these. Those skilled in the art will understand that these functional modules can be implemented in various forms through a combination of hardware and software.

[0034] During operation, if the vacuum device 100 is a device that may generate radiation from the vacuum container 102, the vacuum container 102 is disposed in the radiation management area 106. The cryogenic pump body 12 is also disposed in the radiation management area 106 together with the vacuum container 102 of the vacuum device 100. The cold head motor 16a is part of the cryogenic pump body 12 and is therefore also disposed in the radiation management area 106. The radiation management area 106 is pre-defined around the vacuum container 102 as an area where radiation levels exceeding a reference level may be generated, and access to this area is restricted, at least during operation of the vacuum device 100. To prevent radiation that may be generated in the vacuum container 102 from leaking outward, the radiation management area 106 may be surrounded, for example, by a thick radiation shielding wall 108 such as a concrete wall or a lead wall, and separated from the outer safety area.

[0035] However, some existing cryogenic pumps are designed such that the housing of the cryogenic pump controller 30 and / or the housing of the I / O device 32 are threadedly fixed to the outer surface of the cold head 16, meaning that at least a portion of the control device of the cryogenic pump 10 is directly mounted on the cryogenic pump body 12. In this case, the control device of the cryogenic pump 10, together with the cryogenic pump body 12, is located in the radiation management area 106, and may be exposed to radiation exceeding the reference dose during the operation of the vacuum device 100. Radiation may cause adverse effects such as malfunction or damage to the control device.

[0036] To avoid the effects of radiation that may be generated in the vacuum container 102, the control device of the cryogenic pump 10 can be configured remotely from the cryogenic pump body 12, preferably outside the radiation management area 106. The cryogenic pump controller 30 and I / O device 32 can also be configured outside the radiation management area 106. However, the compressor 18 can also be configured outside the radiation management area 106. The main controller 104 of the vacuum device 100 can also be configured outside the radiation management area 106.

[0037] Thus, the inverter 32b can be configured away from the cold head motor 16a and outside the radiation management area 106. The inverter 32b can be connected to the cold head motor 16a via cable 36. Cable 36 can have a core wire for transmitting power and an electromagnetic shield surrounding the core wire, and the electromagnetic shield can be grounded.

[0038] Cable 36 can, for example, have a length of 1m or more, or 5m or more, or 10m or more. Furthermore, cable 36 can, for example, have a length of less than 100m, or less than 50m, or less than 20m. In this way, cable 36 can have sufficient length to connect the inverter 32b and the cold head motor 16a, which are separated by the radiation shielding wall 108 and are configured at a relatively long distance.

[0039] However, the inventors discovered through experiments that the following disadvantages can be observed: simply configuring the inverter 32b away from the cold head motor 16a and connecting it only through the cable 36 may not enable the cold head motor 16a to operate at the determined operating frequency, or the cold head motor 16a may not move at all.

[0040] One reason is believed to be that the adverse effects of leakage current become significant. Leakage current may, for example, be generated in the electromagnetic shielding of cable 36. Due to the influence of leakage current, the waveform of the PWM voltage transmitted in cable 36 is disturbed, and when input to the cold head motor 16a, it may no longer have the expected waveform.

[0041] Alternatively, the issue might be due to the specifications of the inverter 32b. The inverter 32b can be configured to detect the normal operation of the cold head motor 16a (i.e., operation at a determined operating frequency). The inverter 32b can be configured to continuously increase the current supplied to the cold head motor 16a before detecting normal operation. If the cold head motor 16a does not operate normally at this time, it may cause the inverter 32b and the cold head motor 16a to stop operating due to overcurrent.

[0042] Therefore, in this embodiment, as Figure 1As shown, converter 34 is connected between inverter 32b and cold head motor 16a. Converter 34, like I / O device 32, is located outside radiation management area 106. Converter 34 is connected to cold head motor 16a via the aforementioned cable 36.

[0043] The converter 34 is configured closer to the inverter 32b than the cold head motor 16a. The converter 34 and the inverter 32b can be connected via a cable 38 shorter than the cable 36. Alternatively, the converter 34 can be integrated into the I / O device 32, forming part of the I / O device 32. This close configuration of the converter 34 and the inverter 32b helps suppress PWM voltage waveform disturbances between them.

[0044] The converter 34 is configured to receive a PWM voltage from the inverter 32b, convert the PWM voltage into a cold head motor drive voltage, and output the cold head motor drive voltage to the cold head motor 16a. The cold head motor drive voltage is configured to drive the cold head motor 16a at a determined operating frequency (i.e., the operating frequency of the cold head motor 16a represented by the PWM voltage). Therefore, when the cold head motor drive voltage is input from the converter 34 to the cold head motor 16a, the cold head motor 16a can be driven at the determined operating frequency.

[0045] However, the cold head motor drive voltage has a waveform with reduced high-frequency components compared to the PWM voltage. Therefore, the converter 34 can be equipped with a low-pass filter that removes or reduces high-frequency components from the PWM voltage. The reduced high-frequency components may be, for example, frequency components exceeding the operating frequency of the cold head motor 16a determined by the cryogenic pump controller 30, or frequency components exceeding twice the determined operating frequency of the cold head motor 16a, or frequency components exceeding five times the determined operating frequency of the cold head motor 16a.

[0046] As an example structure, converter 34 may include a sine wave filter. The sine wave filter converts the PWM voltage into a cold head motor drive voltage, so that the cold head motor drive voltage has a sine wave waveform with a determined operating frequency. In other words, the sine wave filter converts the PWM voltage into... Figure 2 The time-averaged voltage shown is used as the driving voltage for the cold head motor 16a. The sine wave filter can be, for example, a known sine wave filter with an LC circuit or an LCR circuit.

[0047] The leakage current is considered to be more significant the more high-frequency components are included in the PWM voltage. According to the embodiment, the cold head motor drive voltage has a waveform with reduced high-frequency components compared to the PWM voltage, thus reducing or ignoring the effect of leakage current. Therefore, the above-mentioned problem can be addressed, and the cold head motor 16a can operate at the determined operating frequency. The control device of the cryogenic pump 10 can be configured outside the radiation management area 106, and the adverse effects of radiation on the control device can also be reduced or prevented. In this way, the cryogenic pump 10 can be adapted to a radiation environment.

[0048] Figure 3 This diagram schematically illustrates a portion of the control device for the cryogenic pump 10 according to an embodiment. The cryogenic pump 10 may also include at least one noise reduction component 42 disposed between the inverter 32b and the power supply 40 of the inverter 32b. The noise reduction component 42 can employ various known noise reduction components. For example, the noise reduction component 42 may include a noise filter 42a such as an LC filter, a line noise filter 42b such as a radio noise filter, and a ferrite core 42c. In this way, common-mode noise and other noise can be reduced, enabling stable operation of the control device for the cryogenic pump 10, such as the I / O device 32.

[0049] Figure 4 This diagram schematically illustrates a portion of the control device for the cryogenic pump 10 according to an embodiment. The converter 34 may include a first converter 34a and a second converter 34b. The first converter 34a may be configured near the inverter 32b, and the second converter 34b may be configured near the cold head motor 16a. The first converter 34a and the second converter 34b can be connected via the aforementioned cable 36. The first converter 34a and the inverter 32b can be connected via a cable 38 shorter than cable 36, and the second converter 34b and the cold head motor 16a can be connected via a cable 39 shorter than cable 36.

[0050] The first converter 34a is configured to receive a PWM voltage from the inverter 32b and convert the PWM voltage into an intermediate voltage. The intermediate voltage has a waveform with reduced high-frequency components compared to the PWM voltage. The second converter 34b is configured to receive the intermediate voltage from the first converter 34a, convert the intermediate voltage into a cold head motor drive voltage, and output the cold head motor drive voltage to the cold head motor 16a. For example, the intermediate voltage can be a DC voltage, the first converter 34a can be an AC-DC converter that converts the PWM voltage into an intermediate voltage (DC voltage), and the second converter 34b can be a DC-AC converter that converts the intermediate voltage (DC voltage) into an AC voltage to drive the cold head motor 16a. Even so, compared with the reference... Figure 1 Similarly, the described implementation method also enables the cold head motor 16a to operate at the determined operating frequency.

[0051] The present invention has been described above with reference to embodiments. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various design changes and modifications are possible, and these modifications are also within the scope of the present invention. Various features described in conjunction with one embodiment can also be applied to other embodiments. New embodiments resulting from combinations possess the effects of each of the combined embodiments.

[0052] In the above embodiment, the example shown is that the cryogenic pump 10 has one cryogenic pump body 12, but the cryogenic pump 10 may also have multiple cryogenic pump bodies 12, for example, several to dozens, or more cryogenic pump bodies 12. Furthermore, in order to supply and discharge refrigerant gas to the cold heads 16 of these cryogenic pump bodies 12, multiple compressors 18 may be provided in the cryogenic pump 10.

[0053] In the above embodiments, the case of vacuum device 100 being used as a radiation therapy device has been described as an example, but vacuum device 100 may also be a device used for other purposes. For example, vacuum device 100 may be a device configured to process a workpiece such as a wafer in a vacuum environment within a vacuum container 102, for example, using a desired vacuum process, such as an ion implantation device, a sputtering device, or a vapor deposition device.

[0054] In the above embodiments, the invention has been described using the application of the invention to a cryogenic pump as an example; however, the invention can also be applied to an ultra-low temperature refrigerator instead of a cryogenic pump. In one embodiment, the ultra-low temperature refrigerator may include: a cold head motor; a frequency converter disposed remotely from the cold head motor and configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency; and at least one converter connected between the frequency converter and the cold head motor. The converter may be configured to receive the PWM voltage from the frequency converter, convert the PWM voltage into a cold head motor drive voltage that drives the cold head motor at the determined operating frequency, and output the cold head motor drive voltage to the cold head motor. The cold head motor drive voltage may have a waveform with reduced high-frequency components compared to the PWM voltage.

[0055] The invention has been described using specific language according to the embodiments, but the embodiments are merely one aspect illustrating the principles and applications of the invention. Various modifications or configuration changes are permitted in the embodiments without departing from the spirit of the invention as defined in the claims.

Claims

1. A cryogenic pump, characterized by, Possessing: a cold head motor; a frequency converter configured distally from the cold head motor and configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency; and at least one converter connected between the frequency converter and the cold head motor, the converter configured to receive the PWM voltage from the frequency converter and convert the PWM voltage into a cold head motor drive voltage that drives the cold head motor at the determined operating frequency and output the cold head motor drive voltage to the cold head motor, the cold head motor drive voltage having a waveform with reduced high frequency components compared to the PWM voltage.

2. The cryopump of claim 1, wherein the at least one converter possesses a sine wave filter that converts the PWM voltage into the cold head motor drive voltage, the cold head motor drive voltage possesses a sine wave waveform having the determined operating frequency.

3. The cryopump of claim 2, wherein the sine wave filter is configured closer to the frequency converter than the cold head motor.

4. The cryopump of claim 2, wherein the sine wave filter is connected to the cold head motor by a cable having a length of 1 m to 100 m.

5. The cryopump of claim 2, wherein the cold head motor is configured within a radiation management area, the frequency converter and the sine wave filter are configured outside the radiation management area.

6. The cryopump of claim 1, wherein the at least one converter possesses: a first converter configured to receive the PWM voltage from the frequency converter and convert the PWM voltage into an intermediate voltage; and a second converter configured to receive the intermediate voltage from the first converter and convert the intermediate voltage into the cold head motor drive voltage and output the cold head motor drive voltage to the cold head motor, the intermediate voltage having a waveform with reduced high frequency components compared to the PWM voltage.

7. The cryopump of claim 6, wherein the intermediate voltage is a direct current voltage.

8. The cryopump of any of claims 1 to 7, wherein, a noise reduction component disposed between the frequency converter and a power supply of the frequency converter is further possessed.

9. A control device characterized by comprising: Possessing: a frequency converter configured distally from a cold head motor and configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency; and at least one converter connected between the frequency converter and the cold head motor, the converter configured to receive the PWM voltage from the frequency converter and convert the PWM voltage into a cold head motor drive voltage that drives the cold head motor at the determined operating frequency and output the cold head motor drive voltage to the cold head motor, the cold head motor drive voltage having a waveform with reduced high frequency components compared to the PWM voltage.

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