Compressor unit of cryogenic refrigerator

Abstract

To improve energy saving properties of a cryogenic refrigerator.SOLUTION: A compressor unit of a cryogenic refrigerator comprises: a compressor motor; an inverter 60 that converts AC power, input into a compressor unit from an external power source, to drive power for the compressor motor; a transformer 62 that converts the AC power to drive power for a cold head of the cryogenic refrigerator having a voltage different from a voltage of the AC power; and a control panel 50 that is mounted with the inverter 60 and the transformer 62. The transformer 62 can also be arranged below the inverter 60.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a compressor unit for a cryogenic refrigerator. [Background technology]

[0002] Generally, cryogenic refrigerators, such as Gifford-McMahon (GM) refrigerators, have a refrigerant gas compressor to supply high-pressure refrigerant gas to the cold head. The compressor has components such as the compressor body, oil separator, adsorber, storage tank, and control device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-74326 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned cryogenic refrigerator, the motor that drives the compressor is operated at a constant rotation speed.

[0005] One exemplary object of an embodiment of the present invention is to improve the energy efficiency of a cryogenic refrigerator. [Means for solving the problem]

[0006] According to one aspect of the present invention, a compressor unit of a cryogenic refrigerator includes a compressor motor, an inverter that converts AC power input to the compressor unit from an external power source into drive power for the compressor motor, a transformer that converts the AC power into drive power for a cold head of the cryogenic refrigerator having a voltage different from that of the AC power, and a control panel equipped with the inverter and transformer.

[0007] According to this embodiment, the rotation speed of the compressor motor can be adjusted using an inverter, thereby improving the energy saving of the compressor unit of the cryogenic refrigerator. Also, although the AC power input may have different voltages depending on the country or region where the cryogenic refrigerator is used, the voltage can be converted to a suitable voltage for the cold head using a transformer, and the compressor unit can be used as a power source for the cold head.

[0008] The inverter may have an inverter exhaust port that serves as an outlet for cooling air from the inverter, and may be mounted on the control panel so that the inverter exhaust port is positioned above the transformer.

[0009] The transformer may be located below the inverter.

[0010] The compressor unit may further include a switching power supply that converts AC power to DC power. The control panel may include the switching power supply mounted thereon.

[0011] The inverter has an inverter exhaust port that serves as an outlet for cooling air from the inverter, and may be mounted on the control panel so that the inverter exhaust port is located above the switching power supply.

[0012] The compressor unit may further include a noise filter and a DC reactor connected to the inverter. The control panel may include the noise filter and the DC reactor mounted thereon.

[0013] The inverter has an inverter exhaust port that serves as an outlet for cooling air from the inverter, and may be mounted on the control panel so that the inverter exhaust port is located above the noise filter and the DC reactor.

[0014] The noise filter and the reactor may be disposed below the inverter and above the transformer.

[0015] The inverter may have an inverter exhaust port through which cooling air exits the inverter. The compressor unit may further include a compressor unit housing having a housing exhaust port through which cooling air exits the compressor unit and accommodating a compressor motor and a control panel. The control panel may include an exhaust duct defining a flow path for cooling air from the inverter exhaust port to the housing exhaust port. The exhaust duct may include a duct inlet part adjacent to the inverter exhaust port and a duct outlet part adjacent to the housing exhaust port, and the duct inlet part may be removable from the duct outlet part and the inverter.

[0016] The compressor unit housing may have a housing inlet that is located below the housing outlet and serves as an inlet for cooling air to the compressor unit.

[0017] The inverter may be arranged closer to the housing air outlet than the transformer, and the transformer may be arranged closer to the housing air inlet than the inverter.

[0018] The compressor unit footprint may be contained within an area no larger than 600mm in width and 500mm in length. [Effects of the Invention]

[0019] According to the present invention, the energy saving performance of a cryogenic refrigerator can be improved. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram schematically illustrating a cryogenic refrigerator according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an external view of a compressor unit of a cryogenic refrigerator according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating an external view of a compressor unit of a cryogenic refrigerator according to an embodiment. [Figure 4] FIG. 2 is a schematic top view illustrating the arrangement of devices in a compressor unit of the cryogenic refrigerator according to the embodiment. [Figure 5]FIG. 3 is a block diagram illustrating a control panel of the compressor unit according to the embodiment. [Figure 6] FIG. 2 is a diagram illustrating an external appearance of a compressor unit according to an embodiment. [Figure 7] FIG. 2 is a diagram illustrating an arrangement of devices on a control panel of a compressor unit according to an embodiment. [Figure 8] FIG. 2 is a diagram illustrating an external view of a compressor unit of a cryogenic refrigerator according to an embodiment. [Figure 9] FIG. 2 is a diagram illustrating an arrangement of devices on a control panel of a compressor unit according to an embodiment. [Figure 10] FIG. 10 is a diagram illustrating another example of an exhaust duct mounted on a control panel according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description and drawings, identical or equivalent components, parts, and processes are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience to facilitate explanation, and should not be interpreted as limiting unless otherwise specified. The embodiments are merely examples and do not limit the scope of the present invention in any way. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0022] FIG. 1 is a schematic diagram of a cryogenic refrigerator according to an embodiment. The cryogenic refrigerator 10 is used to provide cryogenic cooling to an object or medium. For example, the cryogenic refrigerator 10 may be used as a cooling source for a superconducting magnet device. The superconducting magnet device is installed in high-magnetic-field devices (not shown) as a magnetic field source for, for example, a single-crystal pulling device, a nuclear magnetic resonance (NMR) system, a magnetic resonance imaging (MRI) system, an accelerator such as a cyclotron, a high-energy physics system such as a nuclear fusion system, or other high-magnetic-field devices, and can generate the high magnetic fields required for the devices.

[0023] The cryogenic refrigerator 10 includes a compressor 12 and a cold head 14. The compressor 12 is configured to recover refrigerant gas from the cryogenic refrigerator 10 through the cold head 14, pressurize the recovered refrigerant gas, and then supply the refrigerant gas back to the cold head 14. The compressor 12 is also referred to as a compressor unit. The cold head 14 is also referred to as an expander and includes a room-temperature section 14a and a low-temperature section 14b, also referred to as a cooling stage. The refrigerant gas, also referred to as a working gas, is typically helium gas, although other suitable gases may be used. The compressor 12 and the cold head 14 form a refrigeration cycle of the cryogenic refrigerator 10, thereby cooling the low-temperature section 14b to a desired cryogenic temperature. The low-temperature section 14b can cool a target object, such as a superconducting magnet.

[0024] Cryogenic refrigerator 10 is, by way of example, a single-stage or two-stage Gifford-McMahon (GM) refrigerator, but may also be a pulse tube refrigerator, a Stirling refrigerator, or other types of cryogenic refrigerator. While cold head 14 has a different configuration depending on the type of cryogenic refrigerator 10, compressor 12 may have the configuration described below regardless of the type of cryogenic refrigerator 10.

[0025] Generally, the pressure of the refrigerant gas supplied from the compressor 12 to the cold head 14 and the pressure of the refrigerant gas recovered from the cold head 14 to the compressor 12 are both significantly higher than atmospheric pressure and can be referred to as the first high pressure and the second high pressure, respectively. For ease of explanation, the first high pressure and the second high pressure are also simply referred to as the high pressure and the low pressure, respectively. Typically, the high pressure is, for example, 2 to 3 MPa. The low pressure is, for example, 0.5 to 1.5 MPa, e.g., approximately 0.8 MPa.

[0026] Compressor 12 is an oil-lubricated compressor for a cryogenic refrigerator, and includes a compressor main body 16, a refrigerant gas line 18, and an oil circulation line 20. For ease of understanding, in Fig. 1, refrigerant gas line 18 is shown by a solid line, and oil circulation line 20 is shown by a dashed line. Compressor 12 also includes a compressor unit housing 24 that houses each of the components of compressor 12, such as compressor main body 16, refrigerant gas line 18, and oil circulation line 20.

[0027] The compressor body 16 is configured to compress the refrigerant gas drawn in through its suction port and discharge it from its discharge port. The compressor body 16 uses oil for cooling and lubrication, and the drawn refrigerant gas is directly exposed to this oil inside the compressor body 16. Therefore, the refrigerant gas is discharged from the discharge port with a small amount of oil mixed in.

[0028] The compressor body 16 may be, for example, a scroll, rotary, or other pump that pressurizes the refrigerant gas. The compressor body 16 may be configured to discharge a fixed, constant refrigerant gas flow rate. Alternatively, the compressor body 16 may be configured to discharge a variable refrigerant gas flow rate. The compressor body 16 may also be referred to as a compression capsule.

[0029] The refrigerant gas line 18 includes a discharge port 30, a suction port 31, a discharge passage 32, and a suction passage 33. The discharge port 30 is a refrigerant gas outlet provided in the compressor unit housing 24 for sending refrigerant gas pressurized to a high pressure by the compressor body 16 from the compressor 12, and the suction port 31 is a refrigerant gas inlet provided in the compressor unit housing 24 for receiving low-pressure refrigerant gas into the compressor 12. The discharge passage 32 and the suction passage 33 are housed in the compressor unit housing 24. The discharge port of the compressor body 16 is connected to the discharge port 30 by the discharge passage 32, and the suction port 31 is connected to the suction port of the compressor body 16 by the suction passage 33.

[0030] The refrigerant gas line 18 is connected to the cold head 14. A high-pressure port 40 and a low-pressure port 41 are provided in the room-temperature section 14a of the cold head 14. The high-pressure port 40 is connected to the discharge port 30 by a high-pressure pipe 42, and the low-pressure port 41 is connected to the suction port 31 by a low-pressure pipe 43.

[0031] An oil separator 34 and an advertiser 35 are provided in the discharge flow path 32. The oil separator 34 is provided to separate oil from the refrigerant gas that becomes mixed with the refrigerant gas as it passes through the compressor body 16. The advertiser 35 is provided to remove contaminants remaining in the refrigerant gas, such as vaporized oil, from the refrigerant gas by adsorption. The oil separator 34 and advertiser 35 are connected in series. In the discharge flow path 32, the oil separator 34 is located on the compressor body 16 side, and the advertiser 35 is located on the discharge port 30 side.

[0032] An oil return line 21 is provided to connect the oil separator 34 to the compressor body 16. The oil recovered in the oil separator 34 can be returned to the compressor body 16 through the oil return line 21. A filter for removing dust contained in the oil separated in the oil separator 34 and an orifice for controlling the amount of oil returned to the compressor body 16 may be provided midway along the oil return line 21.

[0033] On the other hand, a storage tank 36 is provided in the suction passage 33. The storage tank 36 is provided as a volume for removing pulsation contained in the low-pressure refrigerant gas returning from the cold head 14 to the compressor 12.

[0034] The refrigerant gas line 18 is also provided with a bypass valve 38 that connects the discharge passage 32 to the suction passage 33 so as to bypass the compressor body 16. As an example, the bypass valve 38 branches off from the discharge passage 32 between the oil separator 34 and the adsorber 35, and is connected to the suction passage 33 between the compressor body 16 and the storage tank 36. The bypass valve 38 is provided for refrigerant gas flow rate control and / or for equalizing the pressures in the discharge passage 32 and the suction passage 33 when the compressor 12 is stopped.

[0035] The oil circulation line 20 connects the oil outlet of the compressor body 16 to the oil inlet so that the oil flowing out from the compressor body 16 is returned to the compressor body 16. The oil circulation line 20 may be provided with an orifice that controls the amount of oil flowing therethrough. The oil circulation line 20 may also be provided with a filter that removes dust particles contained in the oil.

[0036] The compressor 12 is further provided with a heat exchanger 22 housed in a compressor unit housing 24 and cooling the compressor 12. The heat exchanger 22 includes a refrigerant gas cooler 22a that cools the refrigerant gas line 18 by heat exchange between the refrigerant gas and a cooling medium (e.g., cooling water), and an oil cooler 22b that cools the oil circulation line 20 by heat exchange between the oil and the cooling medium.

[0037] The refrigerant gas cooler 22a is disposed in the discharge flow path 32 between the compressor body 16 and the oil separator 34. It cools the high-pressure refrigerant gas heated by the heat of compression generated by the compression of the refrigerant gas in the compressor body 16. The refrigerant gas cooler 22a cools the refrigerant gas by heat exchange between the refrigerant gas and a cooling medium. The cooled refrigerant gas is purified in the oil separator 34 and the absorber 35. The oil cooler 22b cools the oil flowing from the oil outlet of the compressor body 16 to the oil circulation line 20 by heat exchange between the oil and the cooling medium. The cooled oil is returned to the compressor body 16 through the oil inlet of the compressor body 16. The cooling medium is supplied to the compressor 12 from the outside through the cooling medium intake port 44, passes through the refrigerant gas cooler 22a and the oil cooler 22b, and is discharged to the outside of the compressor 12 through the cooling medium outlet 45. The cooling medium may be a coolant, such as water. In this way, the heat of compression generated in the compressor body 16 is removed together with the cooling medium to the outside of the compressor 12. Note that the cooling medium may be cooled, for example, by a chiller (not shown), and then supplied again.

[0038] The cryogenic refrigerator 10 also includes a control panel 50. The control panel 50 is mounted on the compressor 12 as a control device that controls the cryogenic refrigerator 10. The control panel 50 may include a control circuit configured to receive outputs from various sensors provided in the cryogenic refrigerator 10 and control various devices of the cryogenic refrigerator 10 based on the sensor outputs. A plurality of electrical components including sensors may be housed in the compressor unit housing 24 together with the control panel 50. Each sensor may be connected to the control panel 50 by a communication cable. Examples of electrical components controlled based on the sensor outputs may include the compressor motor 28 that drives the compressor main body 16, the bypass valve 38, and a cold head motor that drives the cold head 14.

[0039] The compressor 12 may be provided with various sensors such as a pressure sensor and a temperature sensor to grasp the state of the compressor 12. For example, a first pressure sensor 37a may be disposed in the discharge passage 32 to measure the pressure of the refrigerant gas flowing through the discharge passage 32. The first pressure sensor 37a is configured to output a first measured pressure signal PH representing the measured pressure to the control panel 50. Furthermore, a second pressure sensor 37b may be disposed in the suction passage 33 to measure the pressure of the refrigerant gas flowing through the suction passage 33. The second pressure sensor 37b is configured to output a second measured pressure signal PL representing the measured pressure to the control panel 50.

[0040] The temperature sensors may include a refrigerant gas temperature sensor provided in the refrigerant gas line 18, an oil temperature sensor provided in the oil circulation line 20, a coolant temperature sensor provided in the coolant piping of the heat exchanger 22, and a cooling temperature sensor provided in the low-temperature section 14b of the cold head 14. The temperature sensors are configured to output signals representing the measured temperatures to the control panel 50.

[0041] 1 , a first temperature sensor 46 is provided on the discharge passage 32 of the refrigerant gas line 18 upstream of the heat exchanger 22 and measures the temperature of the refrigerant gas flowing from the compressor body 16 into the heat exchanger 22. A second temperature sensor 47 is provided on the refrigerant gas line 18 downstream of the heat exchanger 22 and measures the temperature of the refrigerant gas flowing from the heat exchanger 22 into the oil separator 34. A third temperature sensor 48 is provided on the oil circulation line 20 upstream of the heat exchanger 22 and measures the temperature of the oil flowing from the compressor body 16 into the heat exchanger 22. A fourth temperature sensor 49 is provided on the oil circulation line 20 downstream of the heat exchanger 22 and measures the temperature of the oil flowing from the heat exchanger 22 into the compressor body 16.

[0042] During operation of the cryogenic refrigerator 10, refrigerant gas is supplied from the compressor 12 to the cold head 14, and a refrigeration cycle (e.g., a GM cycle) is formed by periodic volume fluctuations in the expansion space of the refrigerant gas in the cold head 14 and synchronized pressure fluctuations of the refrigerant gas in the expansion space, thereby cooling the low-temperature section 14b of the cold head 14 to a desired cryogenic temperature. If the cold head 14 is, for example, a two-stage system, the first cooling stage is cooled to a first cooling temperature in the range of, for example, about 30 K to about 80 K, and the second cooling stage is cooled to a second cooling temperature lower than the first cooling temperature, for example, 1 K to 20 K. The second cooling temperature may be the liquid helium temperature of about 4.2 K or a temperature lower than that.

[0043] Refrigerant gas recovered from the cold head 14 to the compressor 12 flows from the low-pressure port 41 through the low-pressure piping 43 into the suction port 31 of the compressor 12. The refrigerant gas passes through the storage tank 36 on the suction passage 33 and is recovered to the suction port of the compressor body 16. The refrigerant gas is compressed and pressurized by the compressor body 16. At this time, the refrigerant gas is heated by the heat of compression. The refrigerant gas discharged from the discharge port of the compressor body 16 is cooled by the refrigerant gas cooler 22a of the heat exchanger 22, passes through the oil separator 34 and the advertiser 35, and leaves the compressor 12 through the discharge port 30. The refrigerant gas is supplied to the inside of the cold head 14 through the high-pressure piping 42 and the high-pressure port 40.

[0044] 2 and 3 are diagrams illustrating the outline of the appearance of the compressor unit of the cryogenic refrigerator according to the embodiment. Fig. 2 shows a perspective view of the compressor 12 as seen from the rear. Fig. 3 shows the front of the compressor 12.

[0045] As shown in Figure 2, the compressor unit housing 24 has a rectangular parallelepiped shape with six sides and includes a front panel 24a, a rear panel 24b, a top panel 24c, a bottom panel 24d, and two side panels 24e and 24f. The rear panel 24b faces away from the front panel 24a. Between the front panel 24a and the rear panel 24b, the top panel 24c is located above, the bottom panel 24d is located below, and the side panels 24e and 24f are located on the left and right. These panels are thin plate-like members made of metal such as stainless steel or other appropriate materials.

[0046] The front panel 24a is configured to provide a user interface. As shown in Fig. 3, the front panel 24a is provided with a discharge port 30, a suction port 31, a cooling medium intake port 44, and a cooling medium exhaust port 45. The front panel 24a also has an input power connector 51, a communication cable connector 52, a cold head connector 53, and a main switch 54.

[0047] In an exemplary configuration, the front panel 24a may include two panel portions, specifically, a first panel portion 24a1 and a second panel portion 24a2, that combine to form the front panel 24a. The second panel portion 24a2 is attached to the first panel portion 24a1. As shown in FIG. 3, the second panel portion 24a2 may be provided on the left side of the front panel 24a.

[0048] In this example, the first panel portion 24a1 provides the piping connections. That is, the discharge port 30, the suction port 31, the cooling medium inlet 44, and the cooling medium outlet 45 are provided in the first panel portion 24a1. The discharge port 30 and the suction port 31 are located in the upper part of the first panel portion 24a1, and the cooling medium inlet 44 and the cooling medium outlet 45 are located in the lower part of the first panel portion 24a1. In this way, the inlets and outlets for fluids such as refrigerant gas in the compressor 12 are concentrated in the first panel portion 24a1. The second panel portion 24a2 is not provided with such fluid inlets and outlets.

[0049] In consideration of the ease of operation when connecting the high-pressure pipe 42 and the low-pressure pipe 43 to the discharge port 30 and the suction port 31, respectively, the discharge port 30 and the suction port 31 are arranged with a center-to-center distance of, for example, 5 cm to 20 cm.

[0050] Cooling medium intake 44 and cooling medium outlet 45 are disposed at a position lower than input power connector 51 and communication cable connector 52 in the height direction (the vertical direction in FIG. 3).

[0051] In addition, the first panel portion 24a1 is provided with a communication cable connector 52. The communication cable connector 52 is connected to an external device via a communication cable, thereby enabling communication between the compressor 12 and the external device. The communication cable connector 52 is disposed above the discharge port 30 and the suction port 31 on the first panel portion 24a1.

[0052] The second panel portion 24a2 also provides power connections. An input power connector 51, a cold head connector 53, and a main switch 54 are provided on the second panel portion 24a2. The input power connector 51 is connected to an external power source, such as a commercial power source, and powers the cryogenic refrigerator 10. Electrical wiring for supplying power to and controlling the cold head 14 is connected to the cold head connector 53. This electrical wiring establishes an electrical connection between the compressor 12 and the cold head 14. The main switch 54 is a switch for turning the cryogenic refrigerator 10 on and off. When the main switch 54 is on, the compressor 12 and the cold head 14 operate, and when the main switch 54 is off, the compressor 12 and the cold head 14 stop operating. The cold head connector 53 is located on the upper part of the second panel portion 24a2, and the input power connector 51 and the main switch 54 are located on the lower part of the second panel portion 24a2.

[0053] 2, casters 26 may be attached to the bottom panel 24d to facilitate movement and transportation of the compressor 12. Four casters 26 may be provided at the four corners of the bottom panel 24d.

[0054] Fig. 4 is a schematic top view showing the arrangement of equipment in the compressor unit of the cryogenic refrigerator according to the embodiment. Fig. 4 shows the compressor unit housing 24 with the top panel 24c removed. For simplicity, the piping connecting the components of the compressor 12 is omitted from each drawing.

[0055] As described above, the compressor 12 includes the compressor body 16, the heat exchanger 22, the oil separator 34, the absorber 35, the storage tank 36, and the control panel 50, which are housed in the compressor unit housing 24. The front panel 24a of the compressor unit housing 24 has a first panel portion 24a1 and a second panel portion 24a2.

[0056] 4, the oil separator 34, the adsorber 35, and the storage tank 36 are disposed on the side panel 24e side between the front panel 24a and the rear panel 24b. In other words, the oil separator 34, the adsorber 35, and the storage tank 36 are disposed between the first panel portion 24a1 of the front panel 24a and the rear panel 24b. The compressor main body 16 and the control panel 50 are disposed on the side panel 24f side between the front panel 24a and the rear panel 24b. The compressor main body 16 and the control panel 50 are disposed between the second panel portion 24a2 of the front panel 24a and the rear panel 24b.

[0057] The control panel 50 is attached to the second panel portion 24a2 of the front panel 24a and is supported by the compressor unit housing 24. The control panel 50 may be attached to the side panel 24f. The compressor body 16, the oil separator 34, the adder 35, and the storage tank 36 are installed on the bottom panel 24d and are supported by the compressor unit housing 24.

[0058] The heat exchanger 22 is disposed adjacent to the rear panel 24b. The heat exchanger 22 is disposed along the rear panel 24b behind the compressor body 16 and the oil separator 34. As an alternative arrangement example, the heat exchanger 22 may be disposed so as to surround components of the compressor 12 disposed within the compressor unit housing 24, such as the storage tank 36. For example, the heat exchanger 22 may be wrapped around the storage tank 36.

[0059] 5 is a block diagram showing a control panel 50 of the compressor unit according to the embodiment. The control panel 50 includes an inverter 60, a transformer 62, a noise filter 64, a DC reactor 66, a switching power supply 68, and a controller 70.

[0060] The inverter 60 converts AC power input from an external power source to the compressor 12 into power to drive the compressor motor 28. The external power source is connected to the input power connector 51 as described above. The inverter 60 can convert the AC power input from the input power connector 51 into AC power having a voltage and frequency suitable for driving the compressor motor 28. The frequency may be selected from the range of 30 Hz to 78 Hz, for example. The inverter 60 can be used to adjust the rotation speed of the compressor motor 28, thereby improving the energy efficiency of the compressor 12.

[0061] A noise filter 64 may be connected to the inverter 60 to reduce high-frequency noise from the inverter 60. The noise filter 64 is connected between the input power connector 51 and the inverter 60. A DC reactor 66 may be connected to the inverter 60 to suppress harmonic currents in the inverter 60.

[0062] The transformer 62 converts AC power input from an external power source to the compressor 12 into power for driving the cold head 14. The cold head 14 is connected to the cold head connector 53 as described above. Depending on the country or region in which the cryogenic refrigerator is used, the AC power input to the compressor 12 may have a different voltage (e.g., one of multiple voltage values ranging from 380 V to 480 V). The transformer 62 can convert the AC power input from the input power connector 51 to AC power having a voltage suitable for driving the cold head 14 (e.g., 200 V). The transformer 62 is also called a voltage conversion transformer. By installing the transformer 62, the compressor 12 can be used as a power source for the cold head 14. The transformer 62 also helps to insulate the cold head 14 from power supply noise.

[0063] The switching power supply 68 converts AC power input from an external power supply to the compressor 12 into DC power. As shown in Fig. 5, the switching power supply 68 may be connected between the transformer 62 and the controller 70. The switching power supply 68 may convert the AC power output from the transformer 62 into DC power and supply the DC power to the controller 70.

[0064] In this embodiment, a switching power supply 68 is provided separately from the transformer 62. AC power is output from the transformer 62, and DC power is output from the switching power supply 68. The switching power supply 68 can be placed away from the transformer 62 on the control panel 50. Therefore, compared to using a transformer that can output both AC power and DC power, the transformer 62 can ensure an internal insulation distance and improve insulation performance.

[0065] The controller 70 may receive outputs from various sensors provided in the cryogenic refrigerator 10, such as the pressure sensor and temperature sensor described above, and control the inverter 60 based on the sensor outputs.

[0066] Fig. 6 is a diagram illustrating the outline of the appearance of the compressor unit of the cryogenic refrigerator according to the embodiment. Fig. 6 shows the side panel 24f of the compressor unit housing 24. For ease of understanding, Fig. 6 also shows the control panel 50 arranged inside the side panel 24f by a dashed line.

[0067] As shown in Fig. 6, the compressor unit housing 24 has a housing inlet 72 and a housing outlet 74. The housing inlet 72 is an inlet for cooled air from the ambient environment to the compressor 12, and the housing outlet 74 is an outlet for cooled air from the compressor 12 to the ambient environment. The components of the compressor 12 housed in the compressor unit housing 24 are cooled by air taken into the compressor unit housing 24 from the housing inlet 72. The air that has been heated by cooling the compressor 12 is discharged outside the compressor 12 from the housing outlet 74.

[0068] The housing inlet 72 is disposed below the housing outlet 74. Therefore, natural convection that occurs as a result of the air temperature rising due to cooling of the compressor 12 is utilized to generate an air flow from the housing inlet 72 to the housing outlet 74, thereby effectively cooling the compressor 12. In this example, the housing inlet 72 and the housing outlet 74 are provided in the side panel 24f of the compressor unit housing 24. The housing inlet 72 and the housing outlet 74 are disposed on the side panel 24f close to the front panel 24a.

[0069] The housing air inlet 72 is formed in the lower part of the side panel 24 f, and the housing air outlet 74 is formed in the upper part of the side panel 24 f. As described above, the control panel 50 is disposed adjacent to the side panel 24 f within the compressor unit housing 24. Therefore, the housing air inlet 72 is adjacent to the lower part of the control panel 50, and the housing air outlet 74 is adjacent to the upper part of the control panel 50.

[0070] Fig. 7 is a diagram showing the schematic arrangement of devices on a control panel of a compressor unit according to an embodiment. Fig. 7 shows the arrangement of devices on the control panel 50 when viewed from the front with the front panel 24a removed from the compressor unit housing 24, and also shows the flow of cooling air with arrows for ease of understanding.

[0071] As described above, the control panel 50 is equipped with the inverter 60, the transformer 62, the noise filter 64, the DC reactor 66, the switching power supply 68, and the controller 70.

[0072] In this embodiment, the transformer 62 is disposed below the inverter 60. The noise filter 64 and the DC reactor 66 are disposed below the inverter 60 but above the transformer 62. Therefore, the inverter 60 is disposed at the highest position on the control panel 50 among the inverter 60, the transformer 62, the noise filter 64, and the DC reactor 66. The transformer 62 is disposed at the lowest position on the control panel 50 among the inverter 60, the transformer 62, the noise filter 64, and the DC reactor 66. The switching power supply 68 and the controller 70 are disposed next to the inverter 60, i.e., at the same height as the inverter 60.

[0073] The inverter 60 includes an inverter housing 60a and an inverter circuit 60b housed in the inverter housing 60a. The inverter circuit 60b operates to convert AC power input to the compressor 12 from an external power source into power for driving the compressor motor 28.

[0074] The inverter housing 60a has an inverter intake port 76 and an inverter exhaust port 78. The inverter intake port 76 is an inlet for cooling air from the control panel 50 to the inverter 60, and the inverter exhaust port 78 is an outlet for cooling air from the inverter 60 to the control panel 50.

[0075] The inverter air inlet 76 is disposed below the inverter exhaust port 78. As shown in the figure, the inverter air inlet 76 is provided in the lower part of the inverter housing 60a, and the inverter exhaust port 78 is provided in the upper part of the inverter housing 60a. Therefore, the inverter air inlet 76 is located above the transformer 62, the noise filter 64, and the DC reactor 66. The inverter exhaust port 78 is located above the transformer 62, the noise filter 64, the DC reactor 66, the switching power supply 68, and the controller 70.

[0076] The control panel 50 also includes an exhaust duct 80 that defines a flow path for cooling air from the inverter exhaust port 78 to the chassis exhaust port 74. The exhaust duct 80 is mounted on the control panel 50 above the inverter 60. Thus, the exhaust duct 80 is located at the top of the control panel 50. The exhaust duct 80 has a duct inlet adjacent to the inverter exhaust port 78 and a duct outlet adjacent to the chassis exhaust port 74.

[0077] As described above, the housing air inlet 72 is disposed below the housing exhaust port 74, and the transformer 62 is disposed below the inverter 60. Therefore, the inverter 60 is disposed closer to the housing exhaust port 74 than the transformer 62. The transformer 62 is disposed closer to the housing air inlet 72 than the inverter 60. The housing air inlet 72 is adjacent to the transformer 62, which is disposed at the bottom of the control panel 50.

[0078] 7, cooling air is drawn from outside the compressor 12 through the housing inlet 72 into the control panel 50 in the compressor unit housing 24, where it first cools the transformer 62. After cooling the transformer 62, the air rises within the control panel 50 and cools the noise filter 64 and the DC reactor 66. The cooling air then continues to rise, is drawn into the inverter housing 60a through the inverter inlet 76, and cools the inverter circuit 60b. After cooling the inverter 60 in this way, the air exits the inverter housing 60a through the inverter outlet 78 and flows from the duct inlet to the exhaust duct 80. The air is directed within the exhaust duct 80 toward the duct outlet, and is then exhausted through the duct outlet to the outside of the compressor 12 through the housing outlet 74.

[0079] In this embodiment, the inverter 60 generates a greater amount of heat during operation than the other components on the control panel 50, such as the transformer 62, noise filter 64, DC reactor 66, switching power supply 68, and controller 70. The air that passes through the inverter 60 and cools it can reach high temperatures, for example, as high as 50°C. If the high-temperature air exiting the inverter 60 comes into contact with other equipment, it may heat rather than cool that equipment. However, in this embodiment, the inverter 60 is positioned at the most downstream position in the cooling air flow, and the air that has cooled the inverter 60 is directly discharged from the housing exhaust port 74 to the outside of the compressor 12. This avoids the problem of the high-temperature air exiting the inverter 60 interfering with the cooling of other equipment.

[0080] Additionally, the exhaust duct 80 defines a cooling air flow path from the inverter exhaust port 78 to the housing exhaust port 74, so that the air from the inverter 60 is guided out of the compressor 12 through the exhaust duct 80. The exhaust duct 80 helps prevent the hot air from the inverter 60 from leaking into the control panel 50.

[0081] The transformer 62 is expected to have the second largest heat generation after the inverter 60. The transformer 62 is adjacent to the housing air intake 72, so it can be effectively cooled by fresh air from the housing air intake 72. In addition, since the transformer 62 is heavy, by installing it below the control panel 50, the center of gravity of the compressor 12 can be lowered and stability can be improved.

[0082] In this embodiment, the footprint of compressor 12 is within an area in which the width is 600 mm or less and the length is 500 mm or less. Here, the width of the footprint of compressor 12 corresponds to the width W of compressor unit housing 24, as shown in FIG. 2. The length of the footprint of compressor 12 corresponds to the length L of compressor unit housing 24. In this way, the footprint of compressor 12 can be made equivalent to that of compressors for existing cryogenic refrigerators.

[0083] Furthermore, the height H of the compressor 12 may be 700 mm or less. In this way, when the heat exchanger 22 of the compressor 12 is water-cooled, the height H of the compressor 12 can be made equivalent to that of compressors for existing cryogenic refrigerators.

[0084] The present invention has been described above based on examples. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, and that various design changes and modifications are possible, and that such modifications are also within the scope of the present invention. Various features described in relation to one embodiment can also be applied to other embodiments. A new embodiment created by combining embodiments will have the combined effects of the respective combined embodiments.

[0085] In the above-described embodiment, the compressor 12 has been described as having a water-cooled heat exchanger 22. However, as shown in FIG. 8 , the compressor 12 may be provided with an air-cooled heat exchanger 90 in addition to or instead of the water-cooled heat exchanger 22. The air-cooled heat exchanger 90 may be installed on top of the compressor unit housing 24. In this case, the height H of the compressor 12 may be 1000 mm or less. In this way, the height H of the compressor 12 can be made equivalent to that of compressors for existing cryogenic refrigerators.

[0086] 9 is a diagram illustrating an arrangement of devices on a control panel 50 of the compressor unit according to the embodiment. FIG. 9 illustrates a schematic internal structure of the inverter 60 and the exhaust duct 80 on the control panel 50 illustrated in FIG.

[0087] The control panel 50 may be provided with an air-cooling fan 60c for effective cooling of the inverter 60. The air-cooling fan 60c may be mounted on the inverter 60 so as to generate an air flow within the inverter housing 60a that cools the inverter circuit 60b. For ease of understanding, in Fig. 9, as in Fig. 7, the flow of cooling air within the exhaust duct 80 is indicated by arrows.

[0088] The air-cooling fan 60c may be disposed inside the inverter housing 60a in proximity to the inverter exhaust port 78 of the inverter housing 60a, for example, between the inverter circuit 60b and the inverter exhaust port 78 of the inverter housing 60a. Alternatively, the air-cooling fan 60c may be attached to the outer surface of the inverter housing 60a and disposed between the inverter exhaust port 78 and the exhaust duct 80. The air-cooling fan 60c may be a unit that is detachable from the inverter 60.

[0089] 7 and 9, the exhaust duct 80 is a single duct component. As described above, the exhaust duct 80 is attached to the inverter housing 60a at its inlet side adjacent to the inverter exhaust port 78. The exhaust duct 80 is also attached to the side panel 24f at its outlet side adjacent to the housing exhaust port 74. In this way, the inverter exhaust port 78 is connected to the housing exhaust port 74 by the exhaust duct 80, and the air that has cooled the inverter 60 is discharged through the exhaust duct 80 and from the housing exhaust port 74 to the outside of the compressor 12.

[0090] To prevent high-temperature exhaust gas from the inverter exhaust port 78 from leaking into the control panel 50, the inlet of the exhaust duct 80 may be tightly attached to the inverter housing 60a. For example, the inlet of the exhaust duct 80 may be attached to the inverter housing 60a by screwing. Alternatively, the inlet of the exhaust duct 80 may be attached to the inverter housing 60a by adhesive tape such as aluminum tape. Alternatively, a sealant such as rubber may be sandwiched between the inlet of the exhaust duct 80 and the inverter housing 60a. Similarly, to prevent high-temperature exhaust gas from leaking into the control panel 50 from the outlet of the exhaust duct 80, the outlet of the exhaust duct 80 may be tightly attached to the side panel 24f. For example, the outlet of the exhaust duct 80 may be attached to the side panel 24f by screwing.

[0091] Among the various devices mounted on the control panel 50, the air-cooled fan 60c is known to be more susceptible to breakdowns over long periods of use, such as malfunctioning of the drive motor, than other electrical components. When a breakdown occurs, maintenance is performed, such as replacement or repair of the air-cooled fan 60c. Typically, a housing panel constituting the compressor unit housing 24, such as the side panel 24f, has a bent portion 82 on at least one edge of the panel (the upper edge in the illustrated example) to improve structural strength and for attachment to other panels. The bent portion 82 is provided above the attachment portion of the exhaust duct 80 to the side panel 24f (i.e., the outlet of the exhaust duct 80) like a canopy that conceals this attachment portion.

[0092] To access the air-cooled fan 60c for maintenance, the top panel 24c must first be removed and the exhaust duct 80 must be removed. However, if the outlet of the exhaust duct 80 is obscured by the bent portion 82, even if a worker removes the top panel 24c, it may be difficult to access the attachment portion, making it difficult to remove the exhaust duct 80 from the side panel 24f. Furthermore, even if an attempt is made to remove the exhaust duct 80 upward, the outlet of the exhaust duct 80 may interfere with the bent portion 82, making it impossible to remove. If various components of the compressor 12 are densely arranged within the compressor unit housing 24, removing the exhaust duct 80 may be even more difficult due to interference with not only the bent portion 82 but also these components.

[0093] To address this issue, it is conceivable to remove the control panel 50 itself from the compressor unit housing 24, and then remove the exhaust duct 80 from the control panel 50 to access the air-cooled fan 60c. However, such extensive disassembly work on the compressor 12 is undesirable because it complicates the maintenance work process and increases the amount of work required.

[0094] Therefore, as will be described below, in order to improve maintainability, the exhaust duct 80 may be made up of a plurality of duct parts.

[0095] FIG. 10 is a diagram schematically illustrating another example of an exhaust duct 80 mounted on a control panel 50 according to an embodiment. The exhaust duct 80 includes a duct inlet part 80a and a duct outlet part 80b. The duct inlet part 80a is attached to the inverter housing 60a adjacent to the inverter exhaust port 78. The duct inlet part 80a is detachable from the duct outlet part 80b and the inverter 60. For example, the duct inlet part 80a may be detachably attached to the duct outlet part 80b by screw fastening. The duct outlet part 80b is attached to the side panel 24f adjacent to the housing exhaust port 74.

[0096] The duct inlet part 80a may be a cover that covers the end of the duct outlet part 80b opposite the housing exhaust port 74 and the inverter exhaust port 78. Comparing Figures 9 and 10, it can be seen that the length of the duct inlet part 80a in the duct length direction is shorter than that of the exhaust duct 80 (single duct part) in Figure 9. Here, the duct length direction refers to the extension direction of the exhaust duct 80 (left and right direction in the figure). The duct length direction corresponds to the direction in which the bent portion 82 extends from the side panel 24f.

[0097] The length of the duct inlet part 80a in the duct length direction is determined so that when the duct inlet part 80a is attached to the duct outlet part 80b, the end of the duct inlet part 80a on the duct outlet part 80b side does not overlap with the bent part 82. In other words, the duct inlet part 80a is not covered by the bent part 82.

[0098] The duct outlet piece 80b may be a (e.g., rectangular) tube extending from the side panel 24f in the duct length direction. The length of the duct outlet piece 80b in this direction is shorter than that of the exhaust duct 80 (single duct piece) in FIG. 9. To facilitate attachment and detachment of the duct inlet piece 80a to the duct outlet piece 80b, the length of the duct outlet piece 80b may be longer than the length of the bent portion 82, as shown. Furthermore, to prevent the duct outlet piece 80b from blocking the inverter exhaust port 78, the length of the duct outlet piece 80b may be determined so as not to overlap the inverter exhaust port 78.

[0099] In this way, the inverter exhaust port 78 is connected to the housing exhaust port 74 by the duct inlet part 80a and the duct outlet part 80b, and the air that has cooled the inverter 60 is discharged from the housing exhaust port 74 through the exhaust duct 80 to the outside of the compressor 12. In the example shown in Fig. 10 , as in the example shown in Fig. 9 , the duct inlet part 80a may be tightly attached to the inverter housing 60a to prevent high-temperature exhaust air from the inverter exhaust port 78 from leaking into the control panel 50. Furthermore, the duct outlet part 80b may be tightly attached to the side panel 24f.

[0100] To perform maintenance on the air-cooled fan 60c, the top panel 24c is first removed. Next, the duct inlet part 80a is removed from the duct outlet part 80b and the inverter 60. In the example shown in FIG. 10 , unlike the example shown in FIG. 9 , the duct inlet part 80a is not obscured by the bent part 82. As a result, as indicated by the upward arrow in FIG. 10 , the duct inlet part 80a can be removed upward without interference from the bent part 82. Thus, the duct inlet part 80a can be removed more easily than the single duct part shown in FIG. 9 . Although the duct outlet part 80b remains on the side panel 24f, removing the duct inlet part 80a ensures sufficient space for access to the air-cooled fan 60c. This improves the ease of maintenance of the air-cooled fan 60c.

[0101] In the above-described embodiment, the case where the housing inlet 72 and the housing outlet 74 are provided on the side panel 24f of the compressor unit housing 24 has been described as an example, but the housing inlet 72 and the housing outlet 74 may also be provided on another housing panel of the compressor unit housing 24. For example, the housing inlet 72 and the housing outlet 74 may be provided on the front panel 24a. In this case, as in the above-described embodiment, the control panel 50 may also include an exhaust duct 80 that defines a flow path for cooling air from the inverter exhaust port 78 to the housing outlet 74. The exhaust duct 80 may be a single duct component, or may include multiple duct components.

[0102] The present invention has been described using specific terms based on the embodiments, but the embodiments merely illustrate one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments as long as they do not deviate from the concept of the present invention as defined in the claims. [Explanation of symbols]

[0103] 10 cryogenic refrigerator, 12 compressor, 14 cold head, 24 compressor unit housing, 28 compressor motor, 50 control panel, 60 inverter, 62 transformer, 64 noise filter, 66 DC reactor, 68 switching power supply, 72 housing intake port, 74 housing exhaust port, 78 inverter exhaust port, 80 exhaust duct.

Claims

1. A compressor unit of a cryogenic refrigerator, A compressor motor; an inverter that converts AC power input from an external power source to the compressor unit into drive power for the compressor motor; a transformer that converts the AC power into driving power for a cold head of the cryogenic refrigerator, the driving power having a voltage different from that of the AC power; a control panel on which the inverter and the transformer are mounted.

2. 2. The compressor unit according to claim 1, wherein the inverter has an inverter exhaust port which is an outlet for cooling air from the inverter, and the inverter exhaust port is mounted on the control panel so that it is positioned above the transformer.

3. The compressor unit according to claim 1 , wherein the transformer is disposed below the inverter.

4. a switching power supply that converts the AC power into DC power; 4. The compressor unit according to claim 1, wherein the control panel is equipped with the switching power supply.

5. 5. The compressor unit according to claim 4, wherein the inverter has an inverter exhaust port that serves as an outlet for cooling air from the inverter, and is mounted on the control panel so that the inverter exhaust port is located above the switching power supply.

6. a noise filter and a DC reactor connected to the inverter, 4. The compressor unit according to claim 1, wherein the noise filter and the DC reactor are mounted on the control panel.

7. 7. The compressor unit according to claim 6, wherein the inverter has an inverter exhaust port that serves as an outlet for cooling air from the inverter, and the compressor unit is mounted on the control panel so that the inverter exhaust port is located above the noise filter and the DC reactor.

8. 7. The compressor unit according to claim 6, wherein the noise filter and the DC reactor are disposed below the inverter and above the transformer.

9. the inverter has an inverter exhaust port that serves as an outlet for cooling air from the inverter, the compressor unit further includes a compressor unit housing having a housing exhaust port serving as an outlet for the cooling air from the compressor unit and accommodating the compressor motor and the control panel; 4. The compressor unit according to claim 1, wherein the control panel includes an exhaust duct that defines a flow path of the cooling air from the inverter exhaust port to the housing exhaust port.

10. The compressor unit according to claim 9, wherein the compressor unit housing has a housing inlet that is positioned below the housing outlet and serves as an inlet for the cooling air to the compressor unit.

11. the inverter is disposed closer to the housing exhaust port than the transformer; The compressor unit according to claim 10, wherein the transformer is disposed closer to the housing intake port than the inverter.

12. 10. The compressor unit of claim 9, wherein the exhaust duct comprises a duct inlet piece adjacent to the inverter outlet and a duct outlet piece adjacent to the enclosure outlet, the duct inlet piece being detachable from the duct outlet piece and the inverter.

13. 4. The compressor unit according to claim 1, wherein the footprint of the compressor unit is within an area of 600 mm or less in width and 500 mm or less in length.

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