Heating device for cryogenic refrigerator

Abstract

A heating device for a cryogenic refrigerator is configured to be inserted into a cylinder of the cryogenic refrigerator. The heating device includes a heater block configured to be accommodated in the cylinder, and an urging member configured to press the heater block against a cylinder inner bottom surface of the cylinder.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This Application is a national stage filing under 35 U.S.C. 371 of International Patent Application Serial No PCT / JP2024 / 033293, filed, Sep. 18, 2024, which claims priority to Japanese application number 2023-161945, filed, Sep. 26, 2023. The entire contents of these applications are incorporated herein by reference in their entireties.TECHNICAL FIELD

[0002] The present disclosure relates to a heating device for a cryogenic refrigerator.BACKGROUND ART

[0003] A heating device for a cryogenic refrigerator includes a first heating block, a second heating block, and flanges. The flanges hold the first heating block and the second heating block. The first heating block and the second heating block are arranged next to each other in the direction in which the flanges are arranged.

[0004] The heating device is inserted into a cylinder included in the cryogenic refrigerator. The cylinder includes a first cooling stage and a second cooling stage. The first cooling stage and the second cooling stage are arranged next to each other in the direction in which the cylinder extends. When the heating device is inserted into the cylinder, the first heating block is located in the vicinity of the first cooling stage, and the second heating block is located in the vicinity of the second cooling stage. Helium gas is supplied between the first heating block and the first cooling stage and between the second heating block and the second cooling stage. The helium gas conducts heat from each heating block toward the cooling stage located in the vicinity of the heating block (refer to, for example, Patent Literature 1).

[0005] Patent Literature 1: JP2022-30736ASUMMARY

[0006] In a heating device for a cryogenic refrigerator, it is desirable that the efficiency for conducting heat from the heating device to the cylinder, which is the subject of heating, be increased.

[0007] In one general aspect, a heating device for a cryogenic refrigerator is configured to be inserted into a cylinder of the cryogenic refrigerator. The heating device includes a heater block configured to be accommodated in the cylinder, and an urging member configured to press the heater block against a cylinder inner bottom surface of the cylinder.

[0008] With the heating device described above, the urging member presses the heater block against the cylinder inner bottom surface. Thus, the heater block directly contacts the cylinder inner bottom surface. This increases the efficiency for conducting heat from the heater block to the cylinder inner bottom surface.

[0009] The heating device may further include a tube configured to be accommodated in the cylinder and having an open part to which the heater block is coupled, and the tube may have a thermal conductivity that is lower than that of the heater block.

[0010] In the heating device described above, the tube has a lower thermal conductivity than the heater block. This reduces the heat conducted from the heater block to the tube, and limits loss in the amount of heat conducted from the heater block to the cylinder inner bottom surface.

[0011] In the heating device, the heater block may be formed from copper or aluminum, and the tube may be formed from stainless steel.

[0012] In the heating device described above, the tube has a lower thermal conductivity than the heater block to which the tube is coupled.

[0013] In the heating device, the cylinder inner bottom surface is a first cylinder inner bottom surface, the heater block is a first heater block, and the urging member is a first urging member. The heating device may further include a second heater block configured to be accommodated in the cylinder and located at a side of the first heater block opposite the first urging member, and a second urging member located between the first heater block and the second heater block and configured to press the second heater block against a second cylinder inner bottom surface of the cylinder.

[0014] With the heating device described above, the heating device includes the second urging member that presses the second heater block against the second cylinder inner bottom surface. This increases the efficiency for conducting heat from the heating device to the cylinder.

[0015] The heating device may further include a second tube configured to be accommodated in the cylinder and having an open part to which the second heater block is coupled, and the second tube may have a thermal conductivity that is lower than that of the second heater block.

[0016] In the heating device described above, the second tube has a lower thermal conductivity than the second heater block. This reduces the heat conducted from the second heater block to the second tube, and limits loss in the amount of heat conducted from the second heater block to the second cylinder inner bottom surface.

[0017] In the heating device, the tube configured to be accommodated in the cylinder is a first tube. The first heater block and the first tube may be included in a first tubular body, the second heater block and the second tube may be included in a second tubular body, and the first tubular body and the second tubular body may be configured such that the second tubular body is adjustable in position relative to the first tubular body in an axial direction of the first tubular body.

[0018] The difference in machining precision or the difference in thermal contraction, which is caused by temperature distribution, may result in the distance between the first cylinder inner bottom surface and the second cylinder inner bottom surface differing from the distance between the bottom surface of the first heater block and the bottom surface of the second heater block. With the heating device described above, in such a case, the position of a second tubular body relative to a first tubular body in the axial direction of the first tubular body may be adjusted in order to press the first heater block against the first cylinder inner surface and press the second heater block against the second cylinder inner bottom surface at the same time.

[0019] In the heating device, the second heater block may be formed from copper or aluminum, and the second tube may be formed from stainless steel.

[0020] In the heating device described above, the second tube has a lower thermal conductivity than the second heater block to which the second tube is coupled.BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1 is a schematic diagram showing the structure of a superconducting magnet to which a cryogenic refrigerator heated during maintenance is attached.

[0022] FIG. 2 is a cross-sectional view showing the structure of a heating device.

[0023] FIG. 3 is a cross-sectional view showing the structure of a cylinder into which the heating device is inserted.

[0024] FIG. 4 is a cross-sectional view showing the structure of the heating device inserted into the cylinder.DESCRIPTION OF EMBODIMENTS

[0025] With reference to FIGS. 1 to 4, a heating device 10 of a cryogenic refrigerator 100 in accordance with one embodiment will now be described.Superconducting Magnet

[0026] With reference to FIG. 1, a superconducting magnet 100 will now be described. The superconducting magnet 100 is one example of a device to which the cryogenic refrigerator 110 is applied. The cryogenic refrigerator 110 of the present embodiment is a two-stage Gifford-McMahon refrigerator.

[0027] As shown in FIG. 1, the superconducting magnet 100 includes a cryostat 101, a heat shield 102, a superconducting coil 103, a coil support 104, and an inner tube 105. The cryostat 101 defines an open space for accommodation of the heat shield 102. The heat shield 102 defines an open space for accommodation of the superconducting coil 103, which is supported by the coil support 104. The superconducting coil 103 is accommodated in the heat shield 102 in a state supported by the coil support 104. The inner tube 105 extends through the cryostat 101 and the heat shield 102 in a direction in which the inner tube 105 extends. The superconducting coil 103 is located outside the inner tube 105 in the radial direction of the inner tube 105.

[0028] The cryogenic refrigerator (hereafter, referred to as the refrigerator) 110 includes a cylinder 111 and a main body 112. The cylinder 111 is accommodated in the cryostat 101. The cylinder 111 is connected to the heat shield 102 and the coil support 104. The main body 112 is inserted into the cylinder 111. The refrigerator 110 is a two-stage refrigerator, and the cylinder 111 include two cooling stages. The first cooling stage cools the heat shield 102. The second cooling stage cools the superconducting coil 103, which is supported by the coil support 104.

[0029] When the refrigerator 110 undergoes maintenance, the main body 112 is first separated from the cylinder 111. Then, the main body 112 is removed from the cylinder 111. Further, the heating device 10 of the refrigerator 110 (refer to FIG. 2) is inserted into the cylinder 111. The heating device 10 for the cryogenic refrigerator in accordance with the present disclosure (hereafter, referred to as the heating device 10) is used when the refrigerator 110 undergoes maintenance. The heating device 10 is inserted into the cylinder 111 to increase the temperature of the cylinder 111. This limits condensation in the cylinder 111 and allows for the elimination of moisture, produced before the temperature is increased, from the cylinder 111.The Heating Device and the Cylinder

[0030] With reference to FIGS. 2 to 4, the structure of the heating device 10 and the cylinder 111, into which the heating device 10 is inserted, will now be described. FIG. 2 shows the structure of the heating device 10 prior to insertion into the cylinder 111. FIG. 3 shows the structure of the cylinder 111, into which the heating device 10 is inserted. FIG. 4 shows the structure of the heating device 10, which is inserted in the cylinder 111, and the structure of the cylinder 111.

[0031] The heating device 10 of the cryogenic refrigerator 110 shown in FIG. 2 is inserted into the cylinder 111 of the cryogenic refrigerator 110. The heating device 10 includes a first heater block 11 and a first urging member 12. The first heater block 11 is accommodated in the cylinder 111. The first urging member 12 presses the first heater block 11 against a first cylinder inner bottom surface 121AB of the cylinder 111 (refer to FIG. 3).

[0032] In the heating device 10 of the present disclosure, since the first urging member 12 presses the first heater block 11 against the first cylinder inner bottom surface 121AB, the first heater block 11 directly contacts the first cylinder inner bottom surface 121AB. This increases the efficiency for conducting heat from the first heater block 11 to the first cylinder inner bottom surface 121AB. As a result, the cylinder 111, which is the subject heated by the heating device 10, is efficiently heated.

[0033] The heating device 10 further includes a first tube 13. The first tube 13 includes an open part 13A to which the first heater block 11 is coupled. The first tube 13 is accommodated in the cylinder 111. Preferably, the first tube 13 has a lower thermal conductivity than the first heater block 11. When the thermal conductivity of the first tube 13 is lower than the thermal conductivity of the first heater block 11, the heat conducted from the first heater block 11 to the first tube 13 is reduced. This limits loss in the amount of heat conducted from the first heater block 11 to the first cylinder inner bottom surface 121AB. As a result, the cylinder 111, which is in contact with the first heater block 11, is efficiently heated.

[0034] In an example, the first heater block 11 may be formed from copper or aluminum, and the first tube 13 may be formed from stainless steel. This allows the first tube 13 to have a lower thermal conductivity than the first heater block 11, which is coupled to the first tube 13. In this case, the heat conducted from the first tube 13 to the first heater block 11 is limited. This limits increases in the temperature of the first tube 13, which may be touched by a person, and facilitates handling of the heating device 10.

[0035] The first tube 13 includes a top surface 13B at the end opposite to the open part 13A. The first urging member 12 contacts the top surface 13B of the first tube 13 to urge the first tube 13 toward the first cylinder inner bottom surface 121AB of the cylinder 111. This presses the first heater block 11, which is coupled to the open part 13A of the first tube 13, against the first cylinder inner bottom surface 121AB.

[0036] The first tube 13 includes a guide 13C extending away from the first heater block 11 in the direction in which the first tube 13 extends. The first urging member 12 is fitted to the guide 13C. The first tube 13 includes a pushing portion 13D. The pushing portion 13D is fitted to the guide 13C. The first urging member 12 is held between the pushing portion 13D and the top surface 13B in the direction in which the first tube 13 extends. The pressing force that presses the first urging member 12 against the top surface 13B is varied in accordance with the position of the pushing portion 13D in the direction in which the first tube 13 extends. As the pushing portion 13D becomes closer to the top surface 13B in the direction in which the first tube 13 extends, the pressing force acting on the first urging member 12 increases. As a result, when the heating device 10 is inserted into the cylinder 111, the position of the pushing portion 13D in the direction in which the first tube 13 extends varies the force with which the first urging member 12 presses the first heater block 11 against the first cylinder inner bottom surface 121AB.

[0037] The heating device 10 may include one or more first urging members 12. For example, in the present embodiment, the heating device 10 includes three first urging members 12. As viewed from a side facing the top surface 13B of the first tube 13, each first urging member 12 urges a part of the top surface 13B that is not in contact with another first urging member 12.

[0038] The first heater block 11 includes a first surface (upper surface as viewed in FIG. 2), which is in contact with the first tube 13, and a second surface (bottom surface as viewed in FIG. 2), which is located at the opposite side and which faces the first cylinder inner bottom surface 121AB shown in FIG. 3. The pressing force of the first urging member 12 is set to allow the second surface of the first heater block 11 to contact the first cylinder inner bottom surface 121AB. For example, the pressing force of the first urging member 12 is set to avoid the formation of a gap between the first heater block 11 and the first cylinder inner bottom surface 121AB that may be caused by the dimensional tolerance of the heating device 10 in the direction in which the first tube 13 extends.

[0039] The heating device 10 includes a plurality of first heaters 14. In the example shown in FIG. 2, the heating device 10 includes six first heaters 14 (two shown in FIG. 2). Each first heater 14 is located in the first tube 13 and inserted into the first heater block 11. Current is supplied to the first heaters 14 to heat the first heaters 14, which, in turn, heat the first heater block 11.

[0040] The heating device 10 further includes a second heater block 15 and a second urging member 16. The second heater block 15 is located at the side of the first heater block 11 opposite the first urging member 12 and is accommodated in the cylinder 111. The second urging member 16 is located between the first heater block 11 and the second heater block 15 and configured to press the second heater block 15 against a second cylinder inner bottom surface 121BB of the cylinder 111 (refer to FIG. 3). The heating device 10 includes the second urging member 16, which presses the second heater block 15 against the second cylinder inner bottom surface 121BB. Thus, the efficiency for conducting heat from the heating device 10 to the cylinder 111 is increased in the cylinder 111 at both the first cylinder inner bottom surface 121AB and the second cylinder inner bottom surface 121BB.

[0041] The first urging member 12, the first heater block 11, the second urging member 16, and the second heater block 15 are arranged in this order in the direction in which the heating device 10 extends. In the direction in which the heating device 10 extends, the first heater block 11 is located at the side of the second urging member 16 opposite the second heater block 15. In the direction in which the heating device 10 extends, the first urging member 12 is located at the side of the first heater block 11 opposite the second urging member 16.

[0042] The heating device 10 further includes a second tube 17. The second tube 17 is accommodated in the cylinder 111 and includes an open part 17A, to which the second heater block 15 is coupled. Preferably, the second tube 17 has a lower thermal conductivity than the second heater block 15. When the thermal conductivity of the second tube 17 is lower than the thermal conductivity of the second heater block 15, the heat conducted from the second heater block 15 to the second tube 17 is reduced. This limits loss in the amount of heat conducted from the second heater block 15 to the second cylinder inner bottom surface 121BB.

[0043] In an example, the second heater block 15 may be formed from copper or aluminum, and the second tube 17 may be formed from stainless steel. In the heating device 10, the second tube 17 has a lower thermal conductivity than the second heater block 15 to which the second tube 17 is coupled.

[0044] The second tube 17 includes a guide 17B at the end opposite the open part 17A. Since the second tube 17 includes the guide 17B, the end of the second tube 17 opposite the open part 17A is closed. The guide 17B includes a step 17BA in the radial direction of the second tube 17 to receive a first end of the second urging member 16.

[0045] The first heater block 11 includes a fitting portion 11H. The fitting portion 11H is a socket that opens in the second surface (bottom surface as viewed in FIG. 2) of the first heater block 11. The fitting portion 11H has a bottom located in the first heater block 11 between the second surface and the first surface (upper surface as viewed in FIG. 2 in the thickness direction. The fitting portion 11H includes a groove 11HA that receives the second end of the second urging member 16. The guide 17B of the second tube 17, in a state in which the second urging member 16 is arranged thereon, is fitted to the fitting portion 11H.

[0046] The guide 17B includes an elongated hole 17BG that hollows out in the radial direction of the second tube 17 and extends in the axial direction of the second tube 17. The first heater block 11 includes fastening pins 11P that extend in the radial direction of the first tube 13. The end of each fastening pin 11P that is located toward the center axis of the first tube 13 in the radial direction of the first tube 13 projects into the fitting portion 11H of the first heater block 11. The fastening pins 11P and the elongated hole 17BG are configured to allow the second tube 17 to be fastened to the first heater block 11 by the fastening pins 11P at any position in the elongated hole 17BG in the axial direction of the second tube 17.

[0047] Thus, in the heating device 10, a second tubular body is configured to be adjustable in position relative to a first tubular body in an axial direction of the first tubular body. In the heating device 10, the first heater block 11 and the first tube 13 are included in the first tubular body, and the second heater block 15 and the second tube 17 are included in the second tubular body.

[0048] The difference in machining precision or the difference in thermal contraction, which is caused by temperature distribution, may result in the distance between the first cylinder inner bottom surface 121AB (refer to FIG. 3) and the second cylinder inner bottom surface 121BB (refer to FIG. 3) differing from the distance between the bottom surface of the first heater block 11 and the bottom surface of the second heater block 15. The bottom surface of the first heater block 11 is the surface of the first heater block 11 pressed against the first cylinder inner bottom surface 121AB. The bottom surface of the second heater block 15 is the surface of the second heater block 15 pressed against the second cylinder inner bottom surface 121BB.

[0049] In such a case, the position of the second tubular body relative to the first tubular body in the axial direction of the first tubular body is adjusted in order to press the first heater block 11 against the first cylinder inner bottom surface 121AB and press the second heater block 15 against the second cylinder inner bottom surface 121BB at the same time.

[0050] The pressing force of the second urging member 16 is set to allow the surface of the second heater block 15 opposite the surface contacting the second tube 17 to contact the second cylinder inner bottom surface 121BB. The pressing force of the second urging member 16 is set to, for example, avoid the formation of a gap between the second heater block 15 and the second cylinder inner bottom surface 121BB that would be caused by dimension tolerance of the heating device 10 or thermal contraction, which is caused by temperature distribution, in the direction in which the second tube 17 extends.

[0051] The heating device 10 includes a plurality of second heaters 18. In the example shown in FIG. 2, the heating device 10 includes two second heaters 18 (one shown in FIG. 2). The second heaters 18 are located in the second tube 17 and inserted into the second heater block 15. Current is supplied to the second heaters 18 to heat the second heaters 18, which, in turn, heat the second heater block 15.

[0052] The heating device 10 further includes a flange 10F, a gas supply pipe 10G1, a gas discharge pipe 10G2, and wiring portion 10W. The flange 10F is supported by the guide 13C of the first tube 13.

[0053] The gas supply pipe 10G1 extends in the direction in which the first tube 13 extends. The gas supply pipe 10G1 extends over a length from the flange 10F to the distal end of the second tube 17. The gas supply pipe 10G1 is connected to, for example, a helium gas tank. The gas discharge pipe 10G2 is inserted into an insertion hole of the flange 10F.

[0054] The gas discharge pipe 10G2 extends from the flange 10F toward the side opposite the second heater block 15. The gas discharge pipe 10G2 discharges the gas supplied to the cylinder 111 from the gas supply pipe 10G1 out of the cylinder 111.

[0055] The wiring portion 10W is supported by the flange 10F. The wiring portion 10W includes wires connected to the first heaters 14 and wires connected to the second heaters 18.

[0056] As shown in FIG. 3, the cylinder 111 includes a main body 121, a first cooling stage 122, and a second cooling stage 123. The main body 121 includes a first cylinder portion 121A and a second cylinder portion 121B. The first cylinder portion 121A and the second cylinder portion 121B are arranged next to each other in the direction in which the main body 121 extends. Further, the second cylinder portion 121B is connected to the first cylinder portion 121A. The second cylinder portion 121B has a smaller diameter than the first cylinder portion 121A. The first cylinder portion 121A has a first cylinder end from which the flange 121F extends, and a second cylinder end defining the first cylinder inner bottom surface 121AB. The first cylinder inner bottom surface 121AB has a closed annular shape. The second cylinder portion 121B has a first cylinder end connected to the first cylinder portion 121A, and a second cylinder end defining the second cylinder inner bottom surface 121BB.

[0057] The first cooling stage 122 is coupled to the second cylinder end of the first cylinder portion 121A. The first cooling stage 122 may have a higher thermal conductivity than the main body 121. When the cylinder 111 is mounted on the superconducting magnet 100, the first cooling stage 122 contacts the heat shield 102 of the superconducting magnet 100.

[0058] The second cooling stage 123 is coupled to the second cylinder end of the second cylinder portion 121B. The second cooling stage 123 may have a higher thermal conductivity than the main body 121. When the cylinder 111 is mounted on the superconducting magnet 100, the second cooling stage 123 contacts the coil support 104 of the superconducting magnet 100.

[0059] As shown in FIG. 4, the heating device 10 is inserted into the cylinder 111. As a result, the heating device 10 is coupled to the cylinder 111 so that the flange 121F of the cylinder 111 contacts the flange 10F of the heating device 10. In this state, the bottom surface of the second heater block 15 opposite the surface contacting the second tube 17 contacts the second cylinder inner bottom surface 121BB. As a result, the force of the second urging member 16 pressing the second heater block 15 against the second cylinder inner bottom surface 121BB acts on the second heater block 15.

[0060] Further, the flange 10F of the heating device 10 contacts the flange 121F of the cylinder 111, and the bottom surface of the first heater block 11 contacts the first cylinder inner bottom surface 121AB. As a result, the force of the first urging member 12 pressing the first heater block 11 against the first cylinder inner bottom surface 121AB acts on the first heater block 11.

[0061] The heating device 10 for the cryogenic refrigerator 110 in accordance with one embodiment has the advantages described below.

[0062] The first urging member 12 presses the first heater block 11 against the first cylinder inner bottom surface 121AB. Thus, the first heater block 11 directly contacts the first cylinder inner bottom surface 121AB. This increases the efficiency for conducting heat from the first heater block 11 to the first cylinder inner bottom surface 121AB.

[0063] (2) When the thermal conductivity of the first tube 13 is lower than the thermal conductivity of the first heater block 11, the heat conducted from the first heater block 11 to the first tube 13 is reduced. This limits loss in the amount of heat conducted from the first heater block 11 to the first cylinder inner bottom surface 121AB.

[0064] (3) The heating device 10 includes the second urging member 16 that presses the second heater block 15 against the second cylinder inner bottom surface 121BB. Thus, the efficiency for conducting heat from the heating device 10 to the cylinder 111 is increased in the cylinder 111 at both the first cylinder inner bottom surface 121AB and the second cylinder inner bottom surface 121BB.

[0065] (4) When the thermal conductivity of the second tube 17 is lower than the thermal conductivity of the second heater block 15, the heat conducted from the second heater block 15 to the second tube 17 is reduced. This limits loss in the amount of heat conducted from the second heater block 15 to the second cylinder inner bottom surface 121BB.

[0066] (5) The position of the second tubular body is adjusted relative to the first tubular body so that the first heater block 11 is pressed against the first cylinder inner bottom surface 121AB at the same time as when the second heater block 15 is pressed against the second cylinder inner bottom surface 121BB.

[0067] (6) When the heater blocks 11 and 15 are each formed from copper or aluminum, and the tubes 13 and 17 are each formed from stainless steel, the thermal conductivity of the tubes 13 and 17 is lower than the thermal conductivity of the heater blocks 11 and 15, which are coupled to the tubes 13 and 17.

[0068] The embodiment may be modified as described below.Thermal Conductivity

[0069] The thermal conductivity of each of the heater blocks 11 and 15 may be less than or equal to the thermal conductivity of the tubes 13 and 17, which are coupled to the heater blocks 11 and 15. This also obtains advantages (1) and (3) since the heater blocks 11 and 15 are pressed against the cylinder inner bottom surfaces.

[0070] The first heater block 11 and the second heater block 15 may be formed from a metal other than copper or aluminum. Further, the first tube 13 and the second tube 17 may be formed from a metal other than stainless steel. Any metal may be used as long as the thermal conductivity of the metal forming the first tube 13 and the second tube 17 is sufficiently lower than the thermal conductivity of the metal forming the first heater block 11 and the second heater block 15.The Cryogenic Refrigerator

[0071] The cryogenic refrigerator including the superconducting magnet 100 may be of a single-stage type. In this case, the cylinder 111 includes only one tube. Thus, the heating device 10 applied to the cylinder 111 may also include only one heater block and one urging member. When the cryogenic refrigerator is of a single-stage type, the second heater block 15, the second urging member 16, and the second tube 17 may be omitted from the heating device 10. Alternatively, when the cryogenic refrigerator is of a single-stage type, the first heater block 11, the first urging member 12, and the first tube 13 may be omitted from the heating device 10. In this case, for example, the flange 10F of the heating device 10 may include a structure corresponding to the fitting portion 11H, which includes the first heater block 11.

Claims

1. A heating device for a cryogenic refrigerator, the heating device configured to be inserted into a cylinder of the cryogenic refrigerator, the heating device comprising:a heater block configured to be accommodated in the cylinder; andan urging member configured to press the heater block against a cylinder inner bottom surface of the cylinder.

2. The heating device according to claim 1, further comprising:a tube configured to be accommodated in the cylinder and including an open part to which the heater block is coupled,wherein the tube has a thermal conductivity that is lower than that of the heater block.

3. The heating device according to claim 2, whereinthe heater block is formed from copper or aluminum, andthe tube is formed from stainless steel.

4. The heating device according to claim 1, whereinthe cylinder inner bottom surface is a first cylinder inner bottom surface;the heater block is a first heater block, andthe urging member is a first urging member, the heating device further comprising:a second heater block configured to be accommodated in the cylinder and located at a side of the first heater block opposite the first urging member; anda second urging member located between the first heater block and the second heater block and configured to press the second heater block against a second cylinder inner bottom surface of the cylinder.

5. The heating device according to claim 2, whereinthe cylinder inner bottom surface is a first cylinder inner bottom surface,the heater block is a first heater block,the urging member is a first urging member, andthe tube configured to be accommodated in the cylinder is a first tube, the heating device further comprising:a second heater block configured to be accommodated in the cylinder and located at a side of the first heater block opposite the first urging member;a second urging member located between the first heater block and the second heater block and configured to press the second heater block against a second cylinder inner bottom surface of the cylinder; anda second tube configured to be accommodated in the cylinder and including an open part to which the second heater block is coupled,wherein the second tube has a thermal conductivity that is lower than that of the second heater block.

6. The heating device according to claim 5, whereinthe first heater block and the first tube are included in a first tubular body,the second heater block and the second tube are included in a second tubular body, andthe first tubular body and the second tubular body are configured such that the second tubular body is adjustable in position relative to the first tubular body in an axial direction of the first tubular body.

7. The heating device according to claim 5, whereinthe second heater block is formed from copper or aluminum, andthe second tube is formed from stainless steel.

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