COMPRESSOR UNIT OF CRYOCOOLER

Abstract

A compressor unit of a cryocooler includes: a compressor motor; an inverter that converts, into drive power of the compressor motor, AC power input to the compressor unit from an external power source; a transformer that converts the AC power into drive power of a cold head of the cryocooler of which a voltage is different from a voltage of the AC power, and a control panel on which the inverter and the transformer are mounted.

Claims

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

2. The compressor unit according to claim 1, wherein the inverter includes an inverter exhaust port serving as an outlet for cooling air flowing from the inverter and is mounted on the control panel such that the inverter exhaust port is positioned above the transformer.

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

4. The compressor unit according to claim 1, further comprising: a switching power source that converts the AC power into DC power, wherein the switching power source is mounted on the control panel.

5. The compressor unit according to claim 4, wherein the inverter includes an inverter exhaust port serving as an outlet for cooling air flowing from the inverter and is mounted on the control panel such that the inverter exhaust port is positioned above the switching power source.

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

7. The compressor unit according to claim 6, wherein the inverter includes an inverter exhaust port serving as an outlet for cooling air flowing from the inverter and is mounted on the control panel such that the inverter exhaust port is positioned above the noise filter and the DC reactor.

8. 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 compressor unit according to claim 1, wherein the inverter includes an inverter exhaust port serving as an outlet for cooling air flowing from the inverter, the compressor unit further comprises a compressor unit casing that includes a casing exhaust port serving as an outlet for the cooling air flowing from the compressor unit and that accommodates the compressor motor and the control panel, and the control panel includes an exhaust duct that defines a flow path for the cooling air flowing from the inverter exhaust port to the casing exhaust port.

10. The compressor unit according to claim 9, wherein the compressor unit casing includes a casing intake port that is disposed below the casing exhaust port and that serves as an inlet for the cooling air flowing into the compressor unit.

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

12. The compressor unit according to claim 9, wherein the exhaust duct includes a duct inlet component adjacent to the inverter exhaust port and a duct outlet component adjacent to the casing exhaust port, and the duct inlet component is removable from the duct outlet component and the inverter.

13. The compressor unit according to claim 1, wherein a footprint of the compressor unit falls within a region having a width of about 600 mm or less and a length of about 500 mm or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a view schematically showing a cryocooler according to an embodiment.

[0007] FIG. 2 is a view schematically showing an appearance of a compressor unit of a cryocooler according to the embodiment.

[0008] FIG. 3 is a view schematically showing the appearance of the compressor unit of the cryocooler according to the embodiment.

[0009] FIG. 4 is a schematic top view showing the arrangement of devices in the compressor unit of the cryocooler according to the embodiment.

[0010] FIG. 5 is a block diagram schematically showing a control panel of the compressor unit according to the embodiment.

[0011] FIG. 6 is a view schematically showing the appearance of the compressor unit according to the embodiment.

[0012] FIG. 7 is a view schematically showing the arrangement of devices on the control panel of the compressor unit according to the embodiment.

[0013] FIG. 8 is a view schematically showing the appearance of the compressor unit of the cryocooler according to the embodiment.

[0014] FIG. 9 is a view schematically showing the arrangement of devices on the control panel of the compressor unit according to the embodiment.

[0015] FIG. 10 is a view schematically showing another example of an exhaust duct mounted on the control panel according to the embodiment.

DETAILED DESCRIPTION

[0016] In a certain cryocooler, a motor that drives the compressor is operated at a constant rotation rate.

[0017] It is desirable to improve energy saving properties of a cryocooler.

[0018] The inverter may include an inverter exhaust port serving as an outlet for cooling air flowing from the inverter and be mounted on the control panel such that the inverter exhaust port is positioned above the transformer.

[0019] The transformer may be disposed below the inverter.

[0020] The compressor unit may further include a switching power source that converts the AC power into DC power. The switching power source may be mounted on the control panel.

[0021] The inverter may include an inverter exhaust port serving as an outlet for cooling air flowing from the inverter and be mounted on the control panel such that the inverter exhaust port is positioned above the switching power source.

[0022] The compressor unit may further include a noise filter and a DC reactor that are connected to the inverter. The noise filter and the DC reactor may be mounted on the control panel.

[0023] The inverter may include an inverter exhaust port serving as an outlet for cooling air flowing from the inverter and be mounted on the control panel such that the inverter exhaust port is positioned above the noise filter and the DC reactor.

[0024] The noise filter and the DC reactor may be disposed below the inverter and above the transformer.

[0025] The inverter may include an inverter exhaust port serving as an outlet for cooling air flowing from the inverter. The compressor unit may further include a compressor unit casing that includes a casing exhaust port serving as an outlet for the cooling air flowing from the compressor unit and that accommodates the compressor motor and the control panel. The control panel may include an exhaust duct that defines a flow path for the cooling air flowing from the inverter exhaust port to the casing exhaust port. The exhaust duct may include a duct inlet component adjacent to the inverter exhaust port and a duct outlet component adjacent to the casing exhaust port and the duct inlet component may be removable from the duct outlet component and the inverter.

[0026] The compressor unit casing may include a casing intake port that is disposed below the casing exhaust port and that serves as an inlet for the cooling air flowing into the compressor unit.

[0027] The inverter may be disposed closer to the casing exhaust port than the transformer is and the transformer may be disposed closer to the casing intake port than the inverter is.

[0028] A footprint of the compressor unit may fall within a region having a width of about 600 mm or less and a length of about 500 mm or less.

[0029] Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the drawings. In the description and the drawings, the same or equivalent components, members, and processes will be represented by the same reference numerals, and repetitive description will be omitted as appropriate. The scale and the shape of each of parts shown in the drawings are set conveniently to make the description easy to understand, and are not to be interpreted as limiting unless stated otherwise. The embodiment is merely an example and does not limit the scope of the present invention. All features or combinations thereof described in the embodiment are not essential to the invention.

[0030] FIG. 1 is a diagram schematically showing a cryocooler according to the embodiment. A cryocooler 10 is used to provide cryogenic cooling for an object or a medium. For example, the cryocooler 10 may be used as a cooling source for a superconducting magnet device. The superconducting magnet device is mounted on, for example, a high magnetic field using device as a magnetic field source of an accelerator such as a single crystal pulling device, a nuclear magnetic resonance (NMR) system, a magnetic resonance imaging (MRI) system, and a cyclotron, a high energy physical system such as a nuclear fusion system, or other high magnetic field using devices (not shown) and can generate a high magnetic field required for the devices.

[0031] The cryocooler 10 includes a compressor 12 and a cold head 14. The compressor 12 is configured to collect a refrigerant gas of the cryocooler 10 from the cold head 14, to pressurize the collected refrigerant gas, and to supply the refrigerant gas to the cold head 14 again. The compressor 12 may be referred to as a compressor unit. The cold head 14 may be referred to as an expander and includes a room temperature section 14a and a low-temperature section 14b which may be referred to as a cooling stage. The refrigerant gas may be referred to as a working gas, and other suitable gases may also be used although a helium gas is typically used. The compressor 12 and the cold head 14 constitute a refrigeration cycle of the cryocooler 10, whereby the low-temperature section 14b is cooled to a desired cryogenic temperature. The low-temperature section 14b can cool an object to be cooled such as a superconducting magnet.

[0032] Although the cryocooler 10 is, for example, a single-stage or two-stage Gifford-McMahon (GM) cryocooler, the cryocooler 10 may also be a pulse tube cryocooler, a Stirling cryocooler, or another type of cryocooler. Although the configuration of the cold head 14 differs depending on the type of the cryocooler 10, for the compressor 12, a configuration described below can be adopted regardless of the type of the cryocooler 10.

[0033] In general, both a pressure of a refrigerant gas supplied from the compressor 12 to the cold head 14 and a pressure of a refrigerant gas collected from the cold head 14 to the compressor 12 are considerably higher than the atmospheric pressure, and can be referred to as a first high pressure and a second high pressure, respectively. For convenience of description, the first high pressure and the second high pressure may be simply referred to as a high pressure and a low pressure, respectively. Typically, the high pressure is, for example, a pressure of 2 to 3 MPa. The low pressure is, for example, a pressure of 0.5 to 1.5 MPa and is, for example, a pressure of approximately 0.8 MPa.

[0034] The compressor 12 is an oil-lubricated cryocooler compressor, and includes a compressor main body 16, a refrigerant gas line 18, and an oil circulation line 20. In FIG. 1, in order to facilitate understanding, the refrigerant gas line 18 is shown by a solid line, and the oil circulation line 20 is shown by a broken line. In addition, the compressor 12 includes a compressor unit casing 24 that accommodates each component of the compressor 12, such as the compressor main body 16, the refrigerant gas line 18, and the oil circulation line 20.

[0035] The compressor main body 16 is configured to internally compress a refrigerant gas sucked through a suction port of the compressor main body 16 and to discharge the refrigerant gas through a discharge port. Oil is used in the compressor main body 16 for the sake of cooling and lubrication, and the sucked refrigerant gas is directly exposed to the oil in the compressor main body 16. Accordingly, the refrigerant gas is delivered through the discharge port in a state of being slightly mixed with the oil.

[0036] The compressor main body 16 may be, for example, a scroll type pump, a rotary type pump, or another pump that pressurizes a refrigerant gas. The compressor main body 16 may be configured to discharge the refrigerant gas at a fixed and constant flow rate. Alternatively, the compressor main body 16 may be configured such that a flow rate at which the refrigerant gas is discharged is variable. The compressor main body 16 may be referred to as a compression capsule.

[0037] The refrigerant gas line 18 includes a discharge port 30, a suction port 31, a discharge flow path 32, and a suction flow path 33. The discharge port 30 is an refrigerant gas outlet that is installed in the compressor unit casing 24 to deliver, from the compressor 12, a refrigerant gas that is pressurized to a high pressure by the compressor main body 16 and the suction port 31 is a refrigerant gas inlet that is installed in the compressor unit casing 24 to introduce a low-pressure refrigerant gas into the compressor 12. The discharge flow path 32 and the suction flow path 33 are accommodated in the compressor unit casing 24. The discharge port of the compressor main body 16 is connected to the discharge port 30 by the discharge flow path 32, and the suction port 31 is connected to the suction port of the compressor main body 16 by the suction flow path 33.

[0038] The refrigerant gas line 18 is connected to the cold head 14. The room temperature section 14a of the cold head 14 is provided with a high-pressure port 40 and a low-pressure port 41. 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.

[0039] The discharge flow path 32 is provided with an oil separator 34 and an adsorber 35. The oil separator 34 is provided in order to separate oil, which is mixed with a refrigerant gas when passing through the compressor main body 16, out from the refrigerant gas. The adsorber 35 is provided in order to remove, for example, vaporized oil and other contaminants remaining in the refrigerant gas from the refrigerant gas through adsorption. The oil separator 34 and the adsorber 35 are connected in series. In the discharge flow path 32, the oil separator 34 is disposed on the compressor main body 16 side, and the adsorber 35 is disposed on the discharge port 30 side.

[0040] An oil return line 21 that connects the oil separator 34 to the compressor main body 16 is provided. Oil collected by the oil separator 34 can be returned to the compressor main body 16 through the oil return line 21. In the middle of the oil return line 21, a filter that removes dust included in the oil separated out by the oil separator 34 and an orifice that controls the amount of the oil returning to the compressor main body 16 may be provided.

[0041] Meanwhile, the suction flow path 33 is provided with a storage tank 36. The storage tank 36 is provided to have a volume for removal of pulsation included in a low-pressure refrigerant gas returning from the cold head 14 to the compressor 12.

[0042] In addition, a bypass valve 38 that connects the discharge flow path 32 to the suction flow path 33 to bypass the compressor main body 16 is provided at the refrigerant gas line 18. For example, the bypass valve 38 branches off from the discharge flow path 32 at a position between the oil separator 34 and the adsorber 35 and is connected to the suction flow path 33 at a position between the compressor main body 16 and the storage tank 36. The bypass valve 38 is provided in order to control the flow rate of a refrigerant gas and/or in order to equalize the pressure in the discharge flow path 32 and the pressure in the suction flow path 33 at the time of stoppage of the compressor 12.

[0043] The oil circulation line 20 connects an oil outlet of the compressor main body 16 to an oil inlet in order to return, to the compressor main body 16, oil flowing out from the compressor main body 16. The oil circulation line 20 may be provided with an orifice that controls the flow rate of oil flowing in the oil circulation line 20. In addition, the oil circulation line 20 may be provided with a filter that removes dust included in oil.

[0044] In addition, the compressor 12 further includes a heat exchanger 22 that is accommodated in the compressor unit casing 24 and that cools the compressor 12. The heat exchanger 22 includes a refrigerant gas cooler 22a that cools the refrigerant gas line 18 through heat exchange between a refrigerant gas and a cooling medium (for example, cooling water), and an oil cooler 22b that cools the oil circulation line 20 through heat exchange between oil and the cooling medium.

[0045] The refrigerant gas cooler 22a is disposed between the compressor main body 16 and the oil separator 34 in the discharge flow path 32, and cools a high-pressure refrigerant gas heated by compression heat generated due to the compression of the refrigerant gas in the compressor main body 16. The refrigerant gas cooler 22a cools a refrigerant gas through heat exchange between a refrigerant gas and the cooling medium. The cooled refrigerant gas is purified by the oil separator 34 and the adsorber 35. In addition, the oil cooler 22b cools oil through heat exchange between oil flowing out from the oil outlet of the compressor main body 16 to the oil circulation line 20 and the cooling medium. The cooled oil is returned into the compressor main body 16 through the oil inlet of the compressor main body 16. The cooling medium is supplied from the outside to the compressor 12 through a cooling medium intake port 44, and is discharged to the outside of the compressor 12 through a cooling medium discharge port 45 after passing through the refrigerant gas cooler 22a and the oil cooler 22b. The cooling medium may be a coolant, for example, water. In this manner, compression heat generated at the compressor main body 16 is removed to the outside of the compressor 12 together with the cooling medium. Note that the cooling medium may be supplied again after being cooled by, for example, a chiller (not shown).

[0046] In addition, the cryocooler 10 includes a control panel 50. The control panel 50 is mounted in the compressor 12 as a control device that controls the cryocooler 10. The control panel 50 may include a control circuit configured to receive an output from various sensors provided in the cryocooler 10 and to control various devices of the cryocooler 10 based on the sensor output. A plurality of electric components including the sensors may be accommodated in the compressor unit casing 24 together with the control panel 50. Each sensor may be connected to the control panel 50 by a communication cable. Electric components controlled based on the sensor output may include, for example, a 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.

[0047] Various sensors such as pressure sensors and temperature sensors may be provided in the compressor 12 to figure out the state of the compressor 12. For example, a first pressure sensor 37a may be disposed in the discharge flow path 32 to measure a pressure of a refrigerant gas flowing through the discharge flow path 32. The first pressure sensor 37a is configured to output a first measured pressure signal PH indicating the measured pressure to the control panel 50. In addition, a second pressure sensor 37b may be disposed in the suction flow path 33 to measure a pressure of a refrigerant gas flowing through the suction flow path 33. The second pressure sensor 37b is configured to output a second measured pressure signal PL indicating the measured pressure to the control panel 50.

[0048] 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 a coolant pipe of the heat exchanger 22, a cooling temperature sensor provided in the low-temperature section 14b of the cold head 14, and the like. The temperature sensors are configured to output a signal indicating a measured temperature to the control panel 50.

[0049] For example, as shown in FIG. 1, a first temperature sensor 46 is provided upstream of the heat exchanger 22 on the discharge flow path 32 of the refrigerant gas line 18, and measures the temperature of a refrigerant gas flowing into the heat exchanger 22 from the compressor main body 16. A second temperature sensor 47 is provided downstream of the heat exchanger 22 on the refrigerant gas line 18, and measures the temperature of a refrigerant gas flowing into the oil separator 34 from the heat exchanger 22. A third temperature sensor 48 is provided upstream of the heat exchanger 22 on the oil circulation line 20, and measures the temperature of oil flowing into the heat exchanger 22 from the compressor main body 16. A fourth temperature sensor 49 is provided downstream of the heat exchanger 22 on the oil circulation line 20, and measures the temperature of oil flowing into the compressor main body 16 from the heat exchanger 22.

[0050] During an operation of the cryocooler 10, a refrigerant gas is supplied from the compressor 12 to the cold head 14, a refrigeration cycle (for example, a GM cycle) is configured by a periodic volume fluctuation of an expansion space of the refrigerant gas in the cold head 14 and a pressure fluctuation of the refrigerant gas in the expansion space synchronized with the periodic volume fluctuation, and the low-temperature section 14b of the cold head 14 is cooled to a desired cryogenic temperature. In a case where the cold head 14 is, for example, a two-stage type, a first cooling stage is cooled to a first cooling temperature that falls in a range of, for example, approximately 30 K to approximately 80 K, and a 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 a liquid helium temperature of approximately 4.2 K or a temperature lower than the liquid helium temperature.

[0051] The refrigerant gas collected by the compressor 12 from the cold head 14 flows into the suction port 31 of the compressor 12 through the low-pressure port 41 and the low-pressure pipe 43. The refrigerant gas is collected to the suction port of the compressor main body 16 after passing through the storage tank 36 on the suction flow path 33. The refrigerant gas is compressed and pressurized by the compressor main body 16. In this case, the temperature of the refrigerant gas is increased by compression heat. The refrigerant gas delivered through the discharge port of the compressor main body 16 is cooled by the refrigerant gas cooler 22a of the heat exchanger 22 and exits the compressor 12 through the discharge port 30 after passing through the oil separator 34 and the adsorber 35. The refrigerant gas is supplied into the cold head 14 via the high-pressure pipe 42 and the high-pressure port 40.

[0052] FIGS. 2 and 3 are views schematically showing the appearance of a compressor unit of a cryocooler according to the embodiment. FIG. 2 is a perspective view showing the compressor 12 as seen from a rear side. FIG. 3 shows a front surface of the compressor 12.

[0053] As shown in FIG. 2, the compressor unit casing 24 of the compressor 12 has a rectangular parallelepiped-like shape with six surfaces, and includes a front panel 24a, a back panel 24b, an upper panel 24c, a bottom panel 24d, and two side panels 24e and 24f on right and left sides. The back panel 24b faces a side opposite to a side that the front panel 24a faces. Between the front panel 24a and the back panel 24b, the upper panel 24c is disposed on an upper side, the bottom panel 24d is disposed on a lower side, and the side panels 24e and 24f are disposed on the right and left sides. The panels are thin plate-shaped members formed of a metal such as stainless steel or other appropriate materials.

[0054] The front panel 24a is configured to provide a user interface. As shown in FIG. 3, the front panel 24a is provided with the discharge port 30, the suction port 31, the cooling medium intake port 44, and the cooling medium discharge port 45. In addition, the front panel 24a is provided with an input power source connector 51, a communication cable connector 52, a cold head connector 53, and a main switch 54.

[0055] As an exemplary configuration, the front panel 24a may include two panel portions that are combined with each other to form the front panel 24a, specifically, a first panel portion 24a1 and a second panel portion 24a2. 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 a left side as seen in a direction toward the front panel 24a.

[0056] In this example, the first panel portion 24a1 provides pipe connection. That is, the first panel portion 24a1 is provided with the discharge port 30, the suction port 31, the cooling medium intake port 44, and the cooling medium discharge port 45. The discharge port 30 and the suction port 31 are disposed at an upper portion of the first panel portion 24a1, and the cooling medium intake port 44 and the cooling medium discharge port 45 are disposed at a lower portion of the first panel portion 24a1. In this way, an outlet and an inlet for a fluid such as a refrigerant gas in the compressor 12 are disposed together at the first panel portion 24a1. The second panel portion 24a2 is not provided with such an outlet and an inlet for a fluid.

[0057] In consideration of workability at the time of connection between the discharge port 30 and the high-pressure pipe 42 and connection between the suction port 31 and the low-pressure pipe 43, the discharge port 30 and the suction port 31 are disposed with an interval of, for example, 5 cm to 20 cm provided between the centers thereof.

[0058] The cooling medium intake port 44 and the cooling medium discharge port 45 are disposed at positions lower than the input power source connector 51 and the communication cable connector 52 in a height direction (a vertical direction in FIG. 3).

[0059] In addition, the first panel portion 24a1 is provided with the communication cable connector 52. The communication cable connector 52 is connected to an external device by a communication cable, so that communication between the compressor 12 and the external device is possible. The communication cable connector 52 is disposed above the discharge port 30 and the suction port 31 at the first panel portion 24a1.

[0060] In addition, the second panel portion 24a2 provides power connection. The second panel portion 24a2 is provided with the input power source connector 51, the cold head connector 53, and the main switch 54. The input power source connector 51 is connected to an external power source such as a commercial power source, so that the cryocooler 10 is supplied with power. An electric wire for supply of power to the cold head 14 and for the controlling of the cold head 14 is connected to the cold head connector 53. Electrical connection between the compressor 12 and the cold head 14 is established by the electric wire. The main switch 54 is a switch for the switching on and off of the cryocooler 10. When the main switch 54 is turned on, the compressor 12 and the cold head 14 are operated, and when the main switch 54 is turned off, the operation of the compressor 12 and the cold head 14 is stopped. The cold head connector 53 is disposed at an upper portion of the second panel portion 24a2 and the input power source connector 51 and the main switch 54 are disposed at a lower portion of the second panel portion 24a2.

[0061] As shown in FIG. 2, casters 26 may be attached to the bottom panel 24d in order to facilitate movement and transportation of the compressor 12. Four casters 26 may be respectively provided at four corners of the bottom panel 24d.

[0062] FIG. 4 is a schematic top view showing the arrangement of devices in the compressor unit of the cryocooler according to the embodiment. FIG. 4 shows a state where the upper panel 24c is removed from the compressor unit casing 24. In addition, for the sake of simplicity, a pipe connecting the components of the compressor 12 to each other is not shown in each drawing.

[0063] As described above, the compressor 12 includes the compressor main body 16, the heat exchanger 22, the oil separator 34, the adsorber 35, the storage tank 36, and the control panel 50 and the compressor main body 16, the heat exchanger 22, the oil separator 34, the adsorber 35, the storage tank 36, and the control panel 50 are accommodated in the compressor unit casing 24. The front panel 24a of the compressor unit casing 24 includes the first panel portion 24a1 and the second panel portion 24a2.

[0064] As shown in FIG. 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 back 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 back panel 24b. In addition, 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 back 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 back panel 24b.

[0065] The control panel 50 is attached to the second panel portion 24a2 of the front panel 24a, and is supported by the compressor unit casing 24. The control panel 50 may be attached to the side panel 24f. The compressor main body 16, the oil separator 34, the adsorber 35, and the storage tank 36 are installed on the bottom panel 24d and are supported by the compressor unit casing 24.

[0066] The heat exchanger 22 is disposed close to the back panel 24b. The heat exchanger 22 is disposed along the back panel 24b behind the compressor main body 16 and the oil separator 34. Note that as another disposition example of the heat exchanger 22, for example, the heat exchanger 22 may be disposed so as to surround a component of the compressor 12 that is disposed in the compressor unit casing 24 like the storage tank 36. For example, the heat exchanger 22 may be wound around the storage tank 36.

[0067] FIG. 5 is a block diagram schematically showing a control panel of the compressor unit according to the embodiment. An inverter 60, a transformer 62, a noise filter 64, a DC reactor 66, a switching power source 68, and a controller 70 are mounted to the control panel 50.

[0068] The inverter 60 converts, into drive power of the compressor motor 28, AC power that is input to the compressor 12 from the external power source. The external power source is connected to the input power source connector 51 as described above. The inverter 60 can convert, into AC power of which the voltage and the frequency are suitable for the driving of the compressor motor 28, AC power input to the inverter 60 from the input power source connector 51. The frequency may be selected within, for example, a range of 30 Hz to 78 Hz. The rotation rate of the compressor motor 28 can be adjusted by means of the inverter 60 and thus it is possible to improve the energy saving properties of the compressor 12.

[0069] In order to reduce high-frequency noises of the inverter 60, the noise filter 64 may be connected to the inverter 60. The noise filter 64 is connected between the input power source connector 51 and the inverter 60. In addition, the DC reactor 66 may be connected to the inverter 60 in order to suppress harmonic currents of the inverter 60.

[0070] The transformer 62 converts, into drive power of the cold head 14, AC power input to the compressor 12 from the external power source. The cold head 14 is connected to the cold head connector 53 as described above. Depending on a country or region where the cryocooler is used, the AC power input to the compressor 12 may have a different voltage (for example, any of a plurality of voltage values within a range of 380V to 480V). The transformer 62 can convert, into AC power having a voltage (for example, 200 V) suitable for the driving of the cold head 14, AC power input to the transformer 62 from the input power source connector 51. The transformer 62 is may be referred to as a voltage conversion transformer. Since the transformer 62 is mounted, the compressor 12 can also be used as a power source for the cold head 14. In addition, the transformer 62 is also useful for insulation of the cold head 14 from power source noises.

[0071] The switching power source 68 converts, into DC power, the AC power input to the compressor 12 from the external power source. As shown in FIG. 5, the switching power source 68 may be connected between the transformer 62 and the controller 70. The switching power source 68 may convert AC power output from the transformer 62 into DC power and supply the DC power to the controller 70.

[0072] In this embodiment, the switching power source 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 source 68. The switching power source 68 can be disposed to be separated from the transformer 62 on the control panel 50. Therefore, in comparison with a case where a transformer that can output both of AC power and DC power is used, the transformer 62 can secure an insulation distance inside and improve insulation performance.

[0073] The controller 70 may receive an output from various sensors provided in the cryocooler 10, such as the pressure sensors and the temperature sensors described above, and control the inverter 60 based on the sensor output.

[0074] FIG. 6 is a view schematically showing the appearance of the compressor unit of the cryocooler according to the embodiment. FIG. 6 shows the side panel 24f of the compressor unit casing 24. In addition, for the sake of understanding, in FIG. 6, the control panel 50 disposed inside the side panel 24f is represented by broken lines.

[0075] As shown in FIG. 6, the compressor unit casing 24 includes a casing intake port 72 and a casing exhaust port 74. The casing intake port 72 is an inlet for cooling air flowing from the surrounding environment into the compressor 12, and the casing exhaust port 74 is an outlet for cooling air flowing from the compressor 12 to the surrounding environment. The components of the compressor 12 accommodated in the compressor unit casing 24 are cooled by air that is taken into the compressor unit casing 24 through the casing intake port 72. Air of which the temperature has been increased due to the cooling of the compressor 12 is discharged to the outside of the compressor 12 through the casing exhaust port 74.

[0076] The casing intake port 72 is disposed below the casing exhaust port 74. Therefore, it is possible to generate an air stream from the casing intake port 72 to the casing exhaust port 74 and to effectively cool the compressor 12 by using natural convection that is generated as a result of an increase in temperature of air attributable to the cooling of the compressor 12. In this example, the casing intake port 72 and the casing exhaust port 74 are provided in the side panel 24f of the compressor unit casing 24. The casing intake port 72 and the casing exhaust port 74 are disposed close to the front panel 24a on the side panel 24f.

[0077] The casing intake port 72 is formed in a lower portion of the side panel 24f, and the casing exhaust port 74 is formed in an upper portion of the side panel 24f. As described above, the control panel 50 is disposed adjacent to the side panel 24f in the compressor unit casing 24. Therefore, the casing intake port 72 is adjacent to a lower portion of the control panel 50, and the casing exhaust port 74 is adjacent to an upper portion of the control panel 50.

[0078] FIG. 7 is a view schematically showing the arrangement of devices on the control panel of the compressor unit according to the embodiment. FIG. 7 shows the arrangement of the devices on the control panel 50 that is seen when the control panel 50 is seen in a direction toward a front surface in a state where the front panel 24a has been removed from the compressor unit casing 24 and how cooling air flows is represented by arrows for the sake of understanding.

[0079] As described above, the inverter 60, the transformer 62, the noise filter 64, the DC reactor 66, the switching power source 68, and the controller 70 are mounted on the control panel 50.

[0080] In the 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 and above the transformer 62. Therefore, of the inverter 60, the transformer 62, the noise filter 64, and the DC reactor 66, the inverter 60 is disposed at the highest place on the control panel 50. Of the inverter 60, the transformer 62, the noise filter 64, and the DC reactor 66, the transformer 62 is disposed at the lowest place on the control panel 50. The switching power source 68 and the controller 70 are disposed adjacent to the inverter 60, that is, at the same height as the inverter 60.

[0081] The inverter 60 includes an inverter casing 60a and an inverter circuit 60b accommodated in the inverter casing 60a. The inverter circuit 60b operates to convert, into the drive power of the compressor motor 28, the AC power input to the compressor 12 from the external power source.

[0082] The inverter casing 60a includes an inverter intake port 76 and an inverter exhaust port 78. The inverter intake port 76 is an inlet for cooling air flowing from the control panel 50 into the inverter 60, and the inverter exhaust port 78 is an outlet for cooling air flowing from the inverter 60 to the control panel 50.

[0083] The inverter intake port 76 is disposed below the inverter exhaust port 78. As shown in the drawing, the inverter intake port 76 is provided in a lower portion of the inverter casing 60a, and the inverter exhaust port 78 is provided in an upper portion of the inverter casing 60a. Therefore, the inverter intake port 76 is positioned above the transformer 62, the noise filter 64, and the DC reactor 66. The inverter exhaust port 78 is positioned above the transformer 62, the noise filter 64, the DC reactor 66, the switching power source 68, and the controller 70.

[0084] In addition, the control panel 50 includes an exhaust duct 80 that defines a flow path of cooling air flowing from the inverter exhaust port 78 to the casing exhaust port 74. The exhaust duct 80 is mounted on the control panel 50 above the inverter 60. Therefore, the exhaust duct 80 is disposed at the uppermost portion at the control panel 50. The exhaust duct 80 includes a duct inlet adjacent to the inverter exhaust port 78 and a duct outlet adjacent to the casing exhaust port 74.

[0085] As described above, the casing intake port 72 is disposed below the casing exhaust port 74, and the transformer 62 is disposed below the inverter 60. Therefore, the inverter 60 is disposed closer to the casing exhaust port 74 than the transformer 62 is. The transformer 62 is disposed closer to the casing intake port 72 than the inverter 60 is. The casing intake port 72 is adjacent to the transformer 62 disposed at the lower portion of the control panel 50.

[0086] Therefore, as represented by dashed arrows in FIG. 7, cooling air is taken into the control panel 50 in the compressor unit casing 24 through the casing intake port 72 from the outside of the compressor 12 to cool the transformer 62 first. The air that has cooled the transformer 62 flows upward in the control panel 50 to cool the noise filter 64 and the DC reactor 66. Then, the cooling air further flows upward, is taken into the inverter casing 60a through the inverter intake port 76, and cools the inverter circuit 60b. The air that has cooled the inverter 60 in this manner exits the inverter casing 60a through the inverter exhaust port 78 and flows into the exhaust duct 80 through the duct inlet. An air stream is directed to the duct outlet in the exhaust duct 80, and is discharged to the outside of the compressor 12 through the duct outlet and the casing exhaust port 74.

[0087] In this embodiment, the inverter 60 generates a large amount of heat during operation in comparison with devices on the control panel 50 like the transformer 62, the noise filter 64, the DC reactor 66, the switching power source 68, and the controller 70. Air that has passed through the inverter 60 and has cooled the inverter 60 may have a high temperature of, for example, 50 C. When the high-temperature air that exits the inverter 60 comes into contact with other devices, the other devices may be heated instead of being cooled. However, according to the embodiment, the inverter 60 is disposed closest to a downstream side in a direction in which cooling air flows and air that has cooled the inverter 60 is discharged to the outside of the compressor 12 through the casing exhaust port 74 as it is. Therefore, it is possible to avoid a problem in which high-temperature air from the inverter 60 may hinder the cooling of other devices.

[0088] In addition, since a flow path of cooling air from the inverter exhaust port 78 to the casing exhaust port 74 is defined by the exhaust duct 80, air from the inverter 60 is guided to the outside of the compressor 12 through the exhaust duct 80. The exhaust duct 80 is useful in preventing high-temperature air exiting the inverter 60 from leaking into the control panel 50.

[0089] It can be deduced that the transformer 62 is next in heat generation amount to the inverter 60. Since the transformer 62 is adjacent to the casing intake port 72, the transformer 62 can be effectively cooled by fresh air from the casing intake port 72. In addition, since the transformer 62 is heavy, it is possible to improve stability by lowering the center of gravity of the compressor 12 with the transformer 62 installed at a lower portion of the control panel 50.

[0090] In this embodiment, the footprint of the compressor 12 falls within a region having a width of 600 mm or less and a length of 500 mm or less. Here, the width of the footprint of the compressor 12 corresponds to a width W of the compressor unit casing 24 as shown in FIG. 2. The length of the footprint of the compressor 12 corresponds to a length L of the compressor unit casing 24. In this case, the footprint of the compressor 12 can be made equal to the footprint of a compressor for an existing cryocooler.

[0091] In addition, a height H of the compressor 12 may be 700 mm or less. In this case, the height H of the compressor 12 can be made equal to the height of a compressor for an existing cryocooler in a case where the heat exchanger 22 of the compressor 12 is a water-cooled type.

[0092] The present invention has been described hereinbefore based on the examples. It will be understood by those skilled in the art that the present invention is not limited to the embodiment, various modification examples are possible, and such modification examples are also within the scope of the present invention. Various features described in relation to a certain embodiment are also applicable to other embodiments. New embodiments resulting from combinations have the effect of each of embodiments which are combined.

[0093] In the above-described embodiment, a case where the compressor 12 includes the water-cooled type heat exchanger 22 has been described as an example. However, as shown in FIG. 8, the compressor 12 may include an air-cooled type heat exchanger 90 together with the water-cooled type heat exchanger 22 or instead of the water-cooled type heat exchanger 22. The air-cooled type heat exchanger 90 may be installed on the compressor unit casing 24. In this case, the height H of the compressor 12 may be 1000 mm or less. In this case, the height H of the compressor 12 can be made equal to the height of a compressor for an existing cryocooler.

[0094] In addition, FIG. 9 is a view schematically showing the arrangement of devices on the control panel 50 of the compressor unit according to the embodiment. FIG. 9 shows the schematic internal structures of the inverter 60 and the exhaust duct 80 on the control panel 50 shown in FIG. 7.

[0095] The control panel 50 may be provided with an air cooling fan 60c so that the inverter 60 is effectively cooled. The air cooling fan 60c may be mounted in the inverter 60 such that an air stream that cools the inverter circuit 60b is generated in the inverter casing 60a. In FIG. 9, for the sake of understanding, how cooling air flows in the exhaust duct 80 is represented by an arrow as with FIG. 7.

[0096] The air cooling fan 60c may be disposed in the inverter casing 60a to be close to the inverter exhaust port 78 of the inverter casing 60a. For example, the air cooling fan 60c may be disposed between the inverter circuit 60b and the inverter exhaust port 78 of the inverter casing 60a. Alternatively, the air cooling fan 60c may be attached to an outer surface of the inverter casing 60a to be disposed between the inverter exhaust port 78 and the exhaust duct 80. The air cooling fan 60c may be a unit that can be attached to and detached from the inverter 60.

[0097] In examples shown in FIGS. 7 and 9, the exhaust duct 80 is a single duct component. As described above, the exhaust duct 80 is mounted on the inverter casing 60a to be adjacent to the inverter exhaust port 78 on an inlet side thereof. In addition, the exhaust duct 80 is attached to the side panel 24f to be adjacent to the casing exhaust port 74 on an outlet side thereof. In this manner, the inverter exhaust port 78 is connected to the casing exhaust port 74 by the exhaust duct 80 and air cooling the inverter 60 is discharged to the outside of the compressor 12 through the exhaust duct 80 and the casing exhaust port 74.

[0098] The inlet of the exhaust duct 80 may be in close contact with the inverter casing 60a so that high-temperature exhaust air discharged through the inverter exhaust port 78 is prevented from leaking into the control panel 50. For example, the inlet of the exhaust duct 80 may be attached to the inverter casing 60a by being screwed. Alternatively, the inlet of the exhaust duct 80 may be attached to the inverter casing 60a by means of an adhesive tape such as an aluminum tape. Alternatively, a sealing material such as a rubber material may be interposed between the inlet of the exhaust duct 80 and the inverter casing 60a. Similarly, the outlet of the exhaust duct 80 may be in close contact with the side panel 24f so that high-temperature exhaust air discharged through the outlet of the exhaust duct 80 is prevented from leaking into the control panel 50. For example, the outlet of the exhaust duct 80 may be attached to the side panel 24f by being screwed.

[0099] It is known that a failure of the air cooling fan 60c like a malfunction of a drive motor, which is caused due to long-term use, is likely to occur in comparison with other electric components, the air cooling fan 60c being one of various devices mounted on the control panel 50. In a case where a failure of the air cooling fan 60c occurs, maintenance such as replacement or repair of the air cooling fan 60c is performed. Typically, at least one edge (an upper edge in an example shown in FIG. 9) of a casing panel constituting the compressor unit casing 24 such as the side panel 24f is provided with a bent portion 82 for improvement in structural strength or attachment to another panel. The bent portion 82 is provided above an attachment portion of the exhaust duct 80 (that is, the outlet of the exhaust duct 80) with respect to the side panel 24f so that the attachment portion is covered and hidden by the bent portion 82.

[0100] In order to access the air cooling fan 60c for maintenance, it is necessary to remove the upper panel 24c and to pull out the exhaust duct 80 before accessing the air cooling fan 60c. However, in a case where the outlet of the exhaust duct 80 is covered and hidden by the bent portion 82, it may be difficult for a worker to access the attachment portion and to detach the exhaust duct 80 from the side panel 24f even when the worker removes the upper panel 24c. In addition, the outlet of the exhaust duct 80 may interfere with the bent portion 82 such that the exhaust duct 80 cannot be pulled out even when there is an attempt to pull out the exhaust duct 80 upward. In a case where various components of the compressor 12 are densely disposed in the compressor unit casing 24, it may be more difficult to remove the exhaust duct 80 since the outlet of the exhaust duct 80 may interfere with not only the bent portion 82 but also such components.

[0101] It is also conceivable to access the air cooling fan 60c after removing the control panel 50 from the compressor unit casing 24 and removing the exhaust duct 80 from the control panel 50 in order to address such a problem. However, such a large-scale disassembly work on the compressor 12 makes a maintenance work process complicated and increases the time and effort to be taken, which is undesirable.

[0102] Therefore, as described below, the exhaust duct 80 may be composed of a plurality of duct components for improvement in maintainability.

[0103] FIG. 10 is a view schematically showing another example of the exhaust duct 80 mounted on the control panel 50 according to the embodiment. The exhaust duct 80 includes a duct inlet component 80a and a duct outlet component 80b. The duct inlet component 80a is mounted on the inverter casing 60a to be adjacent to the inverter exhaust port 78. The duct inlet component 80a is removable from the duct outlet component 80b and the inverter 60. For example, the duct inlet component 80a may be removably attached to the duct outlet component 80b by being screwed. The duct outlet component 80b is attached to the side panel 24f to be adjacent to the casing exhaust port 74.

[0104] The duct inlet component 80a may be a cover that covers an end portion of the duct outlet component 80b that is on a side opposite to the casing exhaust port 74 and the inverter exhaust port 78. When comparing FIGS. 9 and 10, it can be understood that the length of the duct inlet component 80a in a duct length direction is smaller than that of the exhaust duct 80 (the single duct component) in FIG. 9. Here, the duct length direction refers to a direction in which the exhaust duct 80 extends (a lateral direction in the drawings). The duct length direction corresponds to a direction in which the bent portion 82 extends from the side panel 24f.

[0105] The length of the duct inlet component 80a in the duct length direction is determined such that an end portion of the duct inlet component 80a that is on the duct outlet component 80b side does not overlap with the bent portion 82 when the duct inlet component 80a is attached to the duct outlet component 80b. That is, the duct inlet component 80a is not covered and hidden by the bent portion 82.

[0106] The duct outlet component 80b may be a cylinder (for example, a rectangular cylinder) extending from the side panel 24f in the duct length direction. The length of the duct outlet component 80b in the duct length direction is small in comparison with the exhaust duct 80 (the single duct component) in FIG. 9. In order to facilitate the attachment and removal of the duct inlet component 80a to and from the duct outlet component 80b, the length of the duct outlet component 80b may be larger than the length of the bent portion 82 as shown in the drawing. In addition, in order to prevent the duct outlet component 80b from blocking the inverter exhaust port 78, the length of the duct outlet component 80b may be determined such that the duct outlet component 80b does not overlap with the inverter exhaust port 78.

[0107] In this way, the inverter exhaust port 78 is connected to the casing exhaust port 74 by the duct inlet component 80a and the duct outlet component 80b, and air cooling the inverter 60 is discharged to the outside of the compressor 12 through the exhaust duct 80 and the casing exhaust port 74. In the example shown in FIG. 10 as well, the duct inlet component 80a may be in close contact with the inverter casing 60a so that high-temperature exhaust air discharged through the inverter exhaust port 78 is prevented from leaking into the control panel 50, as with the example shown in FIG. 9. In addition, the duct outlet component 80b may be in close contact with the side panel 24f.

[0108] For maintenance of the air cooling fan 60c, the upper panel 24c is removed first. Next, the duct inlet component 80a is removed from the duct outlet component 80b and the inverter 60. In the example shown in FIG. 10, unlike the example shown in FIG. 9, the duct inlet component 80a is not covered and hidden by the bent portion 82. Accordingly, as schematically represented by an upward arrow in FIG. 10, the duct inlet component 80a can be pulled out upward without interfering with the bent portion 82. In this manner, the duct inlet component 80a can be easily pulled out in comparison with the single duct component in FIG. 9. Although the duct outlet component 80b remains at the side panel 24f, a space sufficient for access to the air cooling fan 60c is secured since the duct inlet component 80a is removed. Therefore, the maintainability of the air cooling fan 60c can be improved.

[0109] In the above-described embodiment, a case where the casing intake port 72 and the casing exhaust port 74 are provided in the side panel 24f of the compressor unit casing 24 has been described as an example. However, the casing intake port 72 and the casing exhaust port 74 may be provided in another casing panel of the compressor unit casing 24. For example, the casing intake port 72 and the casing exhaust port 74 may be provided in the front panel 24a. In this case as well, as with the above-described embodiment, the control panel 50 may include the exhaust duct 80 that defines a flow path of cooling air flowing from the inverter exhaust port 78 to the casing exhaust port 74. The exhaust duct 80 may be a single duct component or may include a plurality of duct components.

[0110] Although the present invention has been described using specific phrases based on the embodiments, the embodiments merely show one aspect of the principles and applications of the present invention, and many modification examples and changes in disposition are allowed without departing from the scope of the present invention defined in the claims.

[0111] It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.