Compressor for cryogenic refrigerating machine

Abstract

To provide heat exchanger arrangement capable of reducing footprint of a heat exchanger in a compressor for a cryogenic refrigerating machine.SOLUTION: A compressor 12 for a cryogenic refrigerating machine includes: a compressor housing 24; and a double pipe-type heat exchanger 22 housed in the compressor housing 24 and cooling the compressor 12. The double pipe-type heat exchanger 22 includes a double pipe 28 disposed along at least one surface of the compressor housing 24. The double pipe 28 may be bent into a spiral shape along at least one surface of the compressor housing 24. The double pipe 28 may be bent along at least two sides adjacent to at least one surface of the compressor housing 24.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

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

[0003] [Patent Document 1] JP 2001-74326 A Summary of the Invention [Problem to be solved by the invention]

[0004] In addition to the above components, a compressor for a cryogenic refrigerator is typically provided with a heat exchanger to cool the compressor. These compressor components are housed in a compressor housing. In existing designs, the heat exchanger occupies a relatively large footprint in the compressor housing. Therefore, the heat exchanger can be one of the obstacles to miniaturization of the compressor.

[0005] One exemplary objective of an embodiment of the present invention is to propose a heat exchanger arrangement that allows for a reduced footprint of the heat exchanger in a compressor for a cryogenic refrigerator. [Means for solving the problem]

[0006] According to one embodiment of the present invention, a compressor for a cryogenic refrigerator includes a compressor housing and a double-pipe heat exchanger housed in the compressor housing and cooling the compressor. The double-pipe heat exchanger includes a double pipe disposed along at least one surface of the compressor housing. Effect of the Invention

[0007] According to the present invention, it is possible to provide a heat exchanger arrangement that enables a reduction in the footprint of a heat exchanger in a compressor for a cryogenic refrigerator. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic diagram of a cryogenic refrigerator according to an embodiment; [Diagram 2] 1 is a schematic perspective view showing an appearance of a compressor according to an embodiment; [Diagram 3] FIG. 2 is a schematic perspective view showing an arrangement of equipment inside a compressor according to an embodiment. [Figure 4] 1 is a schematic front view of a heat exchanger according to an embodiment; [Diagram 5] FIG. 5(a) is a schematic top view showing the arrangement of devices in a compressor according to the embodiment, and FIG. 5(b) is a schematic top view showing the arrangement of devices in a compressor according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processes are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience in order to facilitate the description, and are not to be interpreted as being 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.

[0010] FIG. 1 is a schematic diagram of a cryogenic refrigerator 10 according to an embodiment. The cryogenic refrigerator 10 is utilized 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 mounted in a high magnetic field device 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 device (not shown), and can generate a high magnetic field required for the device.

[0011] The cryogenic refrigerator 10 includes a compressor 12 and a cold head 14. The compressor 12 is configured to recover the refrigerant gas of the cryogenic refrigerator 10 from the cold head 14, pressurize the recovered refrigerant gas, and supply the refrigerant gas to the cold head 14 again. The compressor 12 is also called a compressor unit. The cold head 14 is also called an expander and has a room temperature section 14a and a low temperature section 14b, also called a cooling stage. The refrigerant gas is also called a working gas, and is typically helium gas, but 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 an object to be cooled, such as a superconducting magnet.

[0012] 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 type of cryogenic refrigerator. Cold head 14 has a different configuration depending on the type of cryogenic refrigerator 10, but compressor 12 may have the configuration described below regardless of the type of cryogenic refrigerator 10.

[0013] 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 called the first high pressure and the second high pressure, respectively. For convenience of explanation, the first high pressure and the second high pressure are also simply called 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., about 0.8 MPa.

[0014] The compressor 12 is an oil-lubricated compressor for a cryogenic refrigerator, and includes a compressor body 16, a refrigerant gas line 18, and an oil circulation line 20. In order to facilitate understanding, the refrigerant gas line 18 is indicated by a solid line, and the oil circulation line 20 is indicated by a dashed line in Fig. 1. The compressor 12 also includes a compressor housing 24 that houses each of the components of the compressor 12, such as the compressor body 16, the refrigerant gas line 18, and the oil circulation line 20.

[0015] The compressor body 16 is configured to compress the refrigerant gas drawn in from 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.

[0016] 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 deliver a fixed, constant flow rate of refrigerant gas. Alternatively, the compressor body 16 may be configured to deliver a variable flow rate of refrigerant gas. The compressor body 16 may also be referred to as a compression capsule.

[0017] 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 an outlet port of the refrigerant gas provided in the compressor housing 24 for sending out the refrigerant gas pressurized to a high pressure by the compressor body 16 from the compressor 12, and the suction port 31 is an inlet port of the refrigerant gas provided in the compressor housing 24 for receiving the low-pressure refrigerant gas into the compressor 12. The discharge passage 32 and the suction passage 33 are housed in the compressor 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.

[0018] 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.

[0019] 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 that is mixed into the refrigerant gas as it passes through the compressor body 16 from the refrigerant gas. 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 the advertiser 35 are connected in series. In the discharge flow path 32, the oil separator 34 is disposed on the compressor body 16 side, and the advertiser 35 is disposed on the discharge port 30 side.

[0020] 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 in the oil return line 21.

[0021] 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.

[0022] In addition, the refrigerant gas line 18 is 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 controlling the flow rate of the refrigerant gas and / or for equalizing the pressure in the discharge passage 32 and the suction passage 33 when the compressor 12 is stopped.

[0023] The oil circulation line 20 connects an oil outlet of the compressor body 16 to an oil inlet so as to return the oil flowing out from the compressor body 16 to the compressor body 16. The oil circulation line 20 may be provided with an orifice that controls the flow rate of oil flowing therethrough. The oil circulation line 20 may also be provided with a filter that removes dust contained in the oil.

[0024] The compressor 12 further includes a heat exchanger 22 that is housed in a compressor housing 24 and cools 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, and an oil cooler 22b that cools the oil circulation line 20 by heat exchange between the oil and the cooling medium.

[0025] The refrigerant gas cooler 22a is disposed between the compressor body 16 and the oil separator 34 in the discharge passage 32, and 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 by the oil separator 34 and the absorber 35. The oil cooler 22b cools the oil by heat exchange between the oil flowing out from the oil outlet of the compressor body 16 to the oil circulation line 20 and the cooling medium. The cooled oil is returned to the compressor body 16 from 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 from the cooling medium discharge port 45. The cooling medium may be a cooling liquid, for example, water. In this manner, 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 supplied again.

[0026] In this embodiment, the heat exchanger 22 is a double-tube type heat exchanger. Thus, the heat exchanger 22 has an outer tube and an inner tube inserted therein. A cooling medium is supplied to one of the outer tube and the inner tube, and a fluid to be cooled is supplied to the other, whereby heat exchange between the cooling medium and the target fluid is performed, and the fluid can be cooled. For example, in the refrigerant gas cooler 22a, cooling water may be supplied to the outer tube, and refrigerant gas may be supplied to the inner tube. In the oil cooler 22b, cooling water may be supplied to the outer tube, and oil may be supplied to the inner tube.

[0027] The compressor housing 24 may also house a control device 50 for controlling the cryogenic refrigerator 10. The control device 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. The sensors may include, for example, a refrigerant gas temperature sensor and a refrigerant gas pressure sensor provided in the refrigerant gas line 18, an oil temperature sensor provided in the oil circulation line 20, and a cooling temperature sensor provided in the low-temperature section 14b of the cold head 14. Devices controlled based on the sensor outputs may include, for example, a compressor motor that drives the compressor main body 16, a bypass valve 38, and a cold head motor that drives the cold head 14. The control device 50 may include a compressor inverter for controlling the rotation speed of the compressor motor and / or a cold head inverter for controlling the rotation speed of the cold head motor.

[0028] 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 pressure fluctuations of the refrigerant gas in the expansion space synchronized therewith, and the low-temperature section 14b of the cold head 14 is cooled to a desired cryogenic temperature. When the cold head 14 is, for example, of a two-stage type, 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.

[0029] The 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 temperature of the refrigerant gas is raised 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, and then passes through the oil separator 34 and the adsorber 35 to leave the compressor 12 from 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.

[0030] Fig. 2 is a schematic perspective view showing the appearance of the compressor 12 according to the embodiment. Fig. 3 is a schematic perspective view showing the arrangement of internal equipment of the compressor 12 according to the embodiment. Both Fig. 2 and Fig. 3 show perspective views of the compressor 12 as seen from the rear. Fig. 3 shows a state in which some panels of the compressor housing 24 have been removed in order to show the arrangement of the internal equipment of the compressor 12.

[0031] 2, the compressor housing 24 of the compressor 12 has a rectangular parallelepiped shape with six faces, 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 the opposite side to the front panel 24a. Between the front panel 24a and the rear panel 24b, the top panel 24c is disposed above, the bottom panel 24d is disposed below, and the side panels 24e and 24f are disposed on the left and right.

[0032] The front panel 24a may be configured to provide a user interface and piping connections. Thus, an operation panel 25 may be provided on the front side of the front panel 24a for receiving inputs for controlling the cryogenic refrigerator 10 from a user of the cryogenic refrigerator 10 and / or for displaying information about the cryogenic refrigerator 10. The front panel 24a may be equipped with a control device 50, for example, the control device 50 may be attached to the rear side of the front panel 24a. The front panel 24a may also be provided with a discharge port 30, a suction port 31, a cooling medium inlet 44, and a cooling medium outlet 45, although they are not shown in Figs. 2 and 3 because they are inverted.

[0033] The bottom panel 24d may be provided with casters 52 to facilitate movement and transportation of the compressor 12.

[0034] As shown in Fig. 3, the compressor housing 24 includes a frame structure 26 that supports the above-mentioned panels and provides structural strength. The panels are removably attached to the frame structure 26. When the panels are attached to the frame structure 26, the equipment inside the compressor 12 is covered by the panels as shown in Fig. 2. The panels may be attached to the frame structure 26 by an appropriate method, such as by screw fastening. When the panels are removed from the frame structure 26, a user or worker can easily access the equipment inside the compressor 12 through the openings in the frame structure 26, and can efficiently perform maintenance or manufacturing work on the compressor 12.

[0035] For example, a rectangular rear outer frame 26a is provided on the rear surface of the compressor housing 24, surrounding the rear surface and constituting a part of the frame structure 26. The rear panel 24b has four rectangular sides that are removably attached to the rear outer frame 26a. The upper ends of the rear outer frame 26a are connected to the upper edge ends of the front panel 24a by two side frames 26b, and the lower part of the rear outer frame 26a is connected to the rear edge of the bottom panel 24d. The lower edge of the front panel 24a is connected to the front edge of the bottom panel 24d. The upper panel 24c has four sides that are removably attached to the rear outer frame 26a and the upper part of the front panel 24a and the two side frames 26b. The side panels 24e and 24f have four sides that are removably attached to the rear outer frame 26a, the side parts of the front panel 24a, the side frames 26b, and the bottom panel 24d.

[0036] As described above, the main components of the compressor 12, such as the compressor body 16, the heat exchanger 22, the oil separator 34, the adder 35, the storage tank 36, and the control device 50, are housed in the compressor housing 24. The oil separator 34, the adder 35, and the storage tank 36 are installed on the bottom panel 24d in close proximity to one side panel 24e and are arranged in the compressor housing 24. The adder 35, the storage tank 36, and the oil separator 34 are arranged in this order from the front panel 24a to the rear panel 24b. The compressor body 16 and the control device 50 are arranged in close proximity to the other side panel 24f in the compressor housing 24. As described above, the control device 50 may be attached to the front panel 24a, and the compressor body 16 is installed on the bottom panel 24d between the control device 50 and the rear panel 24b.

[0037] The heat exchanger 22 includes a double tube 28 disposed along at least one surface of the compressor housing 24, in this embodiment, the rear surface of the compressor housing 24. The double tube 28 is supported by the rear outer frame 26a. When the rear panel 24b is attached to the rear outer frame 26a, the heat exchanger 22 is covered by the rear panel 24b.

[0038] Fig. 4 is a schematic front view of the heat exchanger 22 according to the embodiment. Fig. 4 shows the heat exchanger 22 and the rear outer frame 26a as viewed from inside the compressor 12 (i.e., from inside the compressor housing 24) with the rear panel 24b removed.

[0039] 3 and 4, the double pipe 28 includes a first portion 28a and a second portion 28b. The first portion 28a of the double pipe 28 functions as the refrigerant gas cooler 22a of the heat exchanger 22 shown in FIG. 1, and the second portion 28b functions as the oil cooler 22b.

[0040] As shown in FIG. 4, a refrigerant gas inlet 54a and a first cooling medium outlet 56b are provided at one end of the first portion 28a of the double pipe 28, and a refrigerant gas outlet 54b and a first cooling medium inlet 56a are provided at the other end. As shown in FIG. 1, the refrigerant gas inlet 54a is connected to the discharge port of the compressor body 16, and high-temperature and high-pressure refrigerant gas pressurized by the compressor body 16 flows into the refrigerant gas cooler 22a (i.e., the first portion 28a) through the refrigerant gas inlet 54a. The cooling medium (e.g., cooling water as described above) supplied to the compressor 12 from the cooling medium intake 44 flows into the refrigerant gas cooler 22a from the first cooling medium inlet 56a, cools the refrigerant gas by heat exchange, and flows out from the first cooling medium outlet 56b. The refrigerant gas outlet 54b is connected to the oil separator 34, and the cooled high-pressure refrigerant gas is supplied to the oil separator through the first cooling medium outlet 56b.

[0041] The first portion 28a of the double pipe 28 is bent along at least two adjacent sides of the back surface of the compressor housing 24, and in this embodiment, three adjacent sides. As shown in Figures 3 and 4, the first portion 28a is bent in a substantially C-shape along the upper and side edges of the back surface outer frame 26a and the rear edge of the bottom panel 24d. In this way, the first portion 28a is arranged so as to leave the center of the back surface of the compressor housing 24 open.

[0042] In addition, an oil inlet 58a and a second cooling medium outlet 60b are provided at one end of the second portion 28b of the double pipe 28, and an oil outlet 58b and a second cooling medium inlet 60a are provided at the other end. The oil inlet 58a is connected to the oil outlet of the compressor body 16 as shown in FIG. 1, and the oil flowing out from the compressor body 16 flows into the oil cooler 22b (i.e., the second portion 28b) through this oil inlet 58a. The second cooling medium inlet 60a is connected to the first cooling medium outlet 56b as shown in FIG. 4, and the cooling medium flows from the first portion 28a to the second portion 28b, cools the oil by heat exchange, and flows out from the second cooling medium outlet 60b. The second cooling medium outlet 60b is connected to the cooling medium outlet 45 as shown in FIG. 1, and the cooling medium used to cool the refrigerant gas and the oil is discharged from the compressor 12 through the cooling medium outlet 45. The oil outlet 58b is connected to the oil inlet of the compressor body 16, and the cooled oil is returned to the compressor body 16.

[0043] The second portion 28b of the double pipe 28 is bent in a spiral shape along the back surface of the compressor housing 24. The second portion 28b is disposed inside the first portion 28a on the back surface of the compressor housing 24. In this manner, the second portion 28b is disposed so as to leave the center of the back surface of the compressor housing 24 open. Inside the second portion 28b, i.e., at the center of the back surface of the compressor housing 24, an opening 62 is formed where the double pipe 28 is not disposed.

[0044] The double pipe 28 is supported by the rear outer frame 26a. As an example, as shown in FIG. 4, the double pipe 28 may be fixed to the rear outer frame 26a using a support member 64. In this example, two support members 64 are attached to each of the left and right sides of the rear outer frame 26a. One end of the support member 64 is attached to the rear outer frame 26a by an appropriate method such as screwing, and the other end extends horizontally toward the opening 62. A hole into which the double pipe 28 is inserted is formed in the support member 64, and the double pipe 28 is inserted into this hole of the support member 64 and attached to the support member 64 by an appropriate method such as brazing.

[0045] Fig. 5(a) is a schematic top view showing the arrangement of equipment in the compressor 12 according to the embodiment, and Fig. 5(b) is a schematic top view showing the arrangement of equipment in the compressor 12 according to a comparative example. Figs. 5(a) and 5(b) show a state in which the top panel 24c is removed from the compressor housing 24. For simplicity, the piping connecting the components of the compressor 12 is omitted in each drawing.

[0046] As described above, the compressor 12 includes the compressor body 16, the heat exchanger 22, the oil separator 34, the adder 35, the storage tank 36, and the control device 50. As shown in Fig. 5(a), the compressor body 16 and the control device 50 are arranged in half of the area between the front panel 24a and the rear panel 24b of the compressor housing 24, and the oil separator 34, the adder 35, and the storage tank 36 are arranged in the remaining half of the area. The heat exchanger 22 is arranged along the rear panel 24b.

[0047] On the other hand, in the compressor 112 of the existing design shown in Fig. 5(b), the compressor body 16, the heat exchanger 122, and the control device 50 are arranged in half the area between the front panel 24a and the rear panel 24b of the compressor housing 24, and the oil separator 34, the adsorber 35, and the storage tank 36 are arranged in the remaining half of the area. The heat exchanger 122 is arranged between the compressor body 16 and the control device 50, and may be, for example, a plate-type heat exchanger.

[0048] In the equipment arrangement of the compressor 112 shown in Fig. 5(b), in order to provide a desired cooling performance, the heat exchanger 122 occupies a relatively large footprint between the compressor body 16 and the control device 50. Therefore, as can be understood by comparing Fig. 5(a) and Fig. 5(b), the footprint allowed for the compressor body 16 and the control device 50 is restricted.

[0049] In contrast, according to the embodiment, as shown in FIG. 5(a), the heat exchanger 22 is arranged along at least one surface, for example the back surface, of the compressor housing 24. The space adjacent to the surface of the compressor housing 24 is not used as dead space in the existing design. By using this space to accommodate the heat exchanger 22, the footprint for other devices such as the compressor body 16 and the control device 50 can be expanded. Therefore, the degree of freedom in device arrangement within the compressor 12 is increased, which is advantageous. In addition, in recent years, there is a tendency to require the compressor 12 to be equipped with a large control device 50 in order to implement advanced control. According to the embodiment, in response to such a request, it is easy to secure a sufficient installation space for the control device 50, which is advantageous.

[0050] Also, according to the embodiment, the double tube 28 of the heat exchanger 22 is bent along the outer periphery of the surface of the compressor housing 24. For example, as described above, the first portion 28a is bent along at least two adjacent sides of the back surface of the compressor housing 24, and the second portion 28b is bent in a spiral shape along the back surface of the compressor housing 24. By using a bent tube of such a shape, it is possible to easily increase the overall length of the heat exchanger 22 while suppressing an increase in the footprint of the heat exchanger 22. In particular, the heat exchanger 22 according to the embodiment can reduce the footprint compared to a plate-type heat exchanger that can be mounted on an existing compressor. Suppressing an increase in the footprint helps to improve the degree of freedom in arranging other devices in the compressor 12, as described above. Increasing the overall length of the heat exchanger 22 helps to improve the cooling performance of the double-tube type heat exchanger 22.

[0051] According to the embodiment, the heat exchanger 22 is arranged so as to leave the center of the surface of the compressor housing 24 where the double tube 28 is arranged open. As a result, an opening 62 where the double tube 28 is not arranged is formed in the center of this surface of the compressor housing 24. In the manufacturing process of the compressor 12 or in maintenance work on the compressor 12 at the site where the compressor 12 is used, workers can easily access the equipment inside the compressor 12 from the opening 62. For example, manufacturing work such as pipe welding and joint fastening, and various maintenance work (for example, replacement of consumables such as filters, replacement of equipment such as broken sensors, repairs, etc.) can be performed through the opening 62. In this way, the arrangement of the double tube 28 with the center open helps to improve the efficiency of manufacturing and maintenance of the compressor 12.

[0052] In existing compressors, the panels that form each side of the compressor housing are designed to provide structural strength, so the panels tend to be thick and heavy. This makes it difficult to install the panels during the manufacturing process or to remove them during maintenance, which is one of the factors that reduces workability for workers.

[0053] In contrast, according to the embodiment, the compressor housing 24 includes a frame structure 26 that provides structural strength, and therefore each panel, such as the rear panel 24b attached to the frame structure 26, can be made thinner and lighter. This housing structure also contributes to improved workability. Also, making the panels thinner helps to ensure storage space for the heat exchanger 22.

[0054] 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, that various design changes are possible, that various 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 resulting from a combination has the combined effects of each of the combined embodiments.

[0055] In the above embodiment, the heat exchanger 22 is disposed along the rear surface of the compressor housing 24, but this is merely an example and the present invention is not limited thereto. The heat exchanger 22 may be disposed along other surfaces (e.g., the top surface or side surface) of the compressor housing 24.

[0056] In addition, in the above embodiment, the heat exchanger 22 is disposed along only a single surface (i.e., the back surface) of the compressor housing 24, but other arrangements are possible for the heat exchanger 22. For example, the heat exchanger 22 may be disposed along at least two adjacent surfaces (e.g., the back surface and the top surface, or the back surface and the side surface) of the compressor housing 24.

[0057] The bent shape of the double pipe 28 is not limited to a spiral shape. For example, the double pipe 28 may be bent in a serpentine shape along the surface of the compressor housing 24.

[0058] The present invention has been described using specific terms based on the embodiments, but the embodiments merely show one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0059] 10 cryogenic refrigerator, 12 compressor, 22 heat exchanger, 24 compressor housing, 24b rear panel, 26a rear outer frame, 28 double pipe.

Claims

1. A compressor for a cryogenic refrigerator, comprising: A compressor housing; A double-pipe heat exchanger is housed in the compressor housing and cools the compressor, The compressor for a cryogenic refrigerator, wherein the double-pipe type heat exchanger includes a double pipe arranged along at least one surface of the compressor housing.

2. 2. The compressor for a cryogenic refrigerator according to claim 1, wherein the double pipe is bent in a spiral shape along the at least one surface of the compressor housing.

3. 3. The compressor for a cryogenic refrigerator according to claim 2, wherein the double pipe is arranged so as to leave a central portion of the at least one surface of the compressor housing open.

4. 2. The compressor for a cryogenic refrigerator according to claim 1, wherein the double pipe is bent along at least two adjacent sides of the at least one surface of the compressor housing.

5. 5. The compressor for a cryogenic refrigerator according to claim 4, wherein the double pipe is arranged so as to leave a central portion of the at least one surface of the compressor housing open.

6. 6. The compressor for a cryogenic refrigerator according to claim 1, wherein the at least one surface includes a rear surface of the compressor housing.

7. 7. The compressor for a cryogenic refrigerator according to claim 6, wherein the compressor housing comprises: a rear outer frame that is arranged to surround the rear surface and supports the double pipe; and a rear panel that is removably attached to the rear outer frame so as to cover and conceal the double pipe type heat exchanger.

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