Displacer device and refrigerator

Abstract

When adding a magnetic refrigeration function to achieve high-efficiency refrigerator performance, a displacer device and a refrigerator are provided that can ensure a reciprocating motion with a certain amplitude by a displacer and exhibit high-efficiency refrigeration capacity as designed. 【Solution means】A magnetic refrigeration material 15 is arranged on the low-temperature end side of the displacer 11, and a magnetic circuit 40 for changing the magnetic state of the magnetic refrigeration material 15 is provided outside the storage container 50 corresponding to the magnetic refrigeration material 15. The magnetic circuit 40 magnetizes and demagnetizes the magnetic refrigeration material 15 according to the position of the displacer 11. A magnetic material 115 having a shape through which a working fluid can pass is arranged on the high-temperature end side of the displacer 11, and another magnetic circuit 140 for changing the magnetic state of the magnetic material 115 is provided outside the storage container 50 corresponding to the magnetic material 115. The electromagnetic force F1 acting on the magnetic refrigeration material 15 and the electromagnetic force F2 acting on the magnetic material 115 have different directions.

Description

Technical Field

[0001] The present invention relates to a displacer device and a refrigerator that can ensure a reciprocating motion with a certain amplitude by a displacer when adding a magnetic refrigeration function to achieve high-efficiency refrigerator performance, and can exhibit a high-efficiency refrigeration capacity as designed.

Background Art

[0002] Generally, as a refrigerator, a Stirling refrigerator equipped with an expander that generates extremely low-temperature cold by the reciprocating motion of a displacer and a compressor that generates a vibration flow is well known. This Stirling refrigerator is configured such that a displacer operating in the cylinder of the expander and a piston operating in the cylinder of the compressor reciprocate in their respective cylinders.

[0003] On the other hand, Patent Document 1 describes a cooling device (3) that is a magnetic refrigeration device. That is, an active magnetic heat recovery device (18) is provided between the cold storage means (17) and the outlet of the storage conduit (14). The active magnetic heat recovery device (18) includes a superconducting magnet (19) disposed outside the cooling device (3) and generating a magnetic field inside the cooling device (3), and a magnetic substance (20) disposed inside the cooling device (3). This magnetic substance preferably has the shape of a piston, and this piston is axially supported inside the cooling device (3) so as to be slidable parallel to the longitudinal direction of the cooling device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, Patent Document 1 describes a cooling device (3) which is a magnetic refrigeration device. For precooling of this cooling device (3), since it has valves (4) at the high-pressure inlet (5) and valves (6) at the low-pressure discharge port (7), a GM refrigerator is used and cooled down to 77K. And when cooling down to 20K by the active magnetic heat recovery device (18), the entire cooling device (magnetic refrigeration device) (3) is in the temperature range from 77K to 20K. Also, the gas (usually helium gas) inside the device is at the same temperature.

[0007] As a result, in the cooling device (3) of Patent Document 1, the volume of the gas at low temperature becomes quite large, which all becomes the load of the GM refrigerator on the precooling side, and the performance of the GM refrigerator deteriorates.

[0008] Also, the discharge piston (11) and the push-pull rod (21) need to be reciprocated by a drive mechanism installed outside, and another power is required.

[0009] Furthermore, power is required to excite the superconducting magnet. That is, the performance of the base GM refrigerator deteriorates, and separate power and electricity are also required for the cooling device (3) which is a magnetic refrigeration device. Therefore, it is not always possible to supply high performance as the total efficiency of the refrigerator.

[0010] Therefore, it can be said that the cooling device described in Patent Document 1 cannot be expected to have high efficiency as the total refrigerator performance despite its large device configuration.

[0011] Therefore, when realizing a compact and highly efficient refrigerator, it is conceivable to add a magnetic refrigeration function to a Stirling refrigerator. However, due to the static magnetic field generated to demagnetize and magnetize the magnetic refrigerant, an electromagnetic force is generated on the magnetic refrigerant. Since this electromagnetic force acts only in one direction of the reciprocating motion direction of the displacer, it hinders the reciprocating motion with a certain amplitude by the displacer, and the refrigeration capacity as designed cannot be exhibited.

[0012] The present invention has been made in view of the above, and an object thereof is to provide a displacer device and a refrigerator that can ensure a reciprocating motion with a certain amplitude by a displacer and exhibit a highly efficient refrigeration capacity as designed when realizing a highly efficient refrigerator performance by adding a magnetic refrigeration function.

Means for Solving the Problems

[0013] In order to solve the above-described problems and achieve the object, a displacer device according to the present invention is a displacer device in which a displacer having a cold storage material inside is disposed, and the displacer reciprocates in a storage container to expand a working fluid compressed in the storage container to generate cold. A magnetic refrigerant is disposed on the low-temperature end side of the displacer, a magnetic circuit for changing the magnetic state of the magnetic refrigerant is provided outside the storage container corresponding to the magnetic refrigerant, the magnetic circuit magnetizes and demagnetizes the magnetic refrigerant according to the position of the displacer, and a magnetic material having a shape through which the working fluid can pass is disposed on the high-temperature end side of the displacer, and another magnetic circuit for changing the magnetic state of the magnetic material is provided outside the storage container corresponding to the magnetic material, and the electromagnetic force acting on the magnetic refrigerant and the electromagnetic force acting on the magnetic material are different in direction.

[0014] Further, in the present invention, in the above invention, a spring that gives a restoring force to the reciprocating motion in the axial direction of the displacer is provided, and the restoring force is assisted by a difference between the electromagnetic force acting on the magnetic refrigerant and the electromagnetic force acting on the magnetic material.

[0015] Further, in the present invention, in the above invention, the difference between the electromagnetic force acting on the magnetic refrigerant and the electromagnetic force acting on the magnetic material serves as a restoring force for the reciprocating motion in the axial direction of the displacer.

[0016] Further, in the present invention, in the above invention, a plurality of the magnetic refrigerants are arranged with a cold storage material interposed therebetween from the low-temperature end side in the displacer.

[0017] Further, in the present invention, in the above invention, a plurality of the magnetic materials are arranged with a cold storage material interposed therebetween on the high-temperature end side of the displacer.

[0018] Further, in the present invention, in the above invention, the magnetic material is a magnetic refrigerant.

[0019] Further, in the present invention, in the above invention, a plurality of different magnetic refrigerants are arranged from the low-temperature end side in the displacer.

[0020] Further, in the present invention, in the above invention, a drive device for controlling the position of the displacer is provided, and the position of the displacer is adjusted.

[0021] Further, in the present invention, in the above invention, the magnetic circuit and the other magnetic circuit each generate a magnetic field having directivity with respect to the magnetization regions of the magnetic refrigerant and the magnetic material.

[0022] Further, in the present invention, in the above invention, the magnetic refrigerant is arranged with the low-temperature end face of the magnetic circuit as a neutral position, and is demagnetized when the magnetic refrigerant moves from the neutral position to the low-temperature end side, and is magnetized when it moves from the neutral position to the high-temperature end side.

[0023] Further, the refrigerator according to the present invention includes a compressor that generates a pressure amplitude in a working fluid by the reciprocating motion of a compression piston, and a working fluid space that is connected to the compressor and filled with a working fluid having the pressure amplitude generated by the compressor. A displacer that reciprocates with a phase difference with respect to the reciprocating motion of the compression piston and has a regenerator inside is disposed in a storage container that forms the displacer. A displacer device having a mechanism for supporting the displacer in the storage container, and a magnetic refrigeration material is disposed on the low-temperature end side of the displacer, and a magnetic circuit for changing the magnetic state of the magnetic refrigeration material is provided outside the storage container corresponding to the magnetic refrigeration material. The magnetic circuit magnetizes and demagnetizes the magnetic refrigeration material according to the position of the displacer, and a magnetic material having a shape through which the working fluid can pass is disposed on the high-temperature end side of the displacer, and another magnetic circuit for changing the magnetic state of the magnetic material is provided outside the storage container corresponding to the magnetic material. The electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material are different in direction.

[0024] Further, the present invention provides, in the above invention, a spring that applies a restoring force to the reciprocating motion in the axial direction of the displacer, and the restoring force is assisted by the difference between the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material.

[0025] Further, the present invention provides, in the above invention, that the difference between the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material serves as a restoring force for the reciprocating motion in the axial direction of the displacer.

[0026] Further, the present invention provides, in the above invention, that a plurality of magnetic refrigeration materials are arranged with a regenerator interposed therebetween from the low-temperature end side of the displacer.

[0027] Further, the present invention provides, in the above invention, that a plurality of magnetic materials are arranged with a regenerator interposed therebetween on the high-temperature end side of the displacer.

[0028] Further, in the present invention, the magnetic material is a magnetic refrigeration material.

[0029] Further, in the present invention, a plurality of different magnetic refrigeration materials are arranged on the low-temperature end side of the displacer in the magnetic refrigeration material.

[0030] Further, in the present invention, a drive device for controlling the position of the displacer is provided, and the position of the displacer is adjusted.

[0031] Further, in the present invention, the magnetic circuit and the other magnetic circuit each generate a magnetic field having directivity with respect to the magnetization regions of the magnetic refrigeration material and the magnetic material.

[0032] Further, in the present invention, the magnetic refrigeration material is arranged with the low-temperature end face of the magnetic circuit as a neutral position, and the magnetic refrigeration material is demagnetized when it moves from the neutral position to the low-temperature end side, and magnetized when it moves from the neutral position to the high-temperature end side.

Effect of the Invention

[0033] According to the present invention, when adding a magnetic refrigeration function to realize high-efficiency refrigerator performance, it is possible to ensure a reciprocating operation with a certain amplitude by the displacer and exhibit the designed high-efficiency refrigeration capacity.

Brief Description of the Drawings

[0034]

Figure 1

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Figure 15

[0035] Hereinafter, embodiments for carrying out this invention will be described with reference to the accompanying drawings.

[0036] <Overall Structure of the Underlying Refrigerator> FIG. 1 is a schematic diagram showing the overall structure of a refrigerator 100 that is the basis of an embodiment of the present invention. The refrigerator 100 has a displacer device 10 that is an expander, a compressor 20, and a pipe 30 that connects them, and a magnetic refrigeration material is incorporated into a Stirling refrigerator in which a working fluid G is filled at a constant pressure inside, and it is a composite refrigerator having both a Stirling refrigeration function (gas refrigeration function) and a magnetic refrigeration function with high refrigeration performance. Further, the refrigerator 100 is a refrigerator for generating liquefied hydrogen (20K). In FIG. 1, it is a type in which the displacer device 10 and the compressor 20 are connected by a pipe 30, but it may be an integrated configuration in which the displacer device 10 is directly attached to the connection portion of the pipe 30 on the compressor 20 side.

[0037] The compressor 20 generates a pressure amplitude in the working fluid G by the reciprocating motion of the compression pistons 23, 24. As the working fluid G, helium gas is usually used. The compression pistons 23, 24 are operated in the X direction in the same phase with one piston in the + direction and the other in the - direction with the neutral position as the initial position. In FIG. 1, this operation is performed by the movable magnet type linear motors 21, 22. The compression pistons 23, 24 are opposed to each other in order to absorb the primary vibration and reduce the vibration. The compression pistons 23, 24 operate at a high operating frequency of, for example, several tens to 100 Hz. Due to the reciprocating motion of the compression pistons 23, 24, compression and expansion are repeated for the working fluid G, and the pressure amplitude is transmitted to the displacer device 10 side through the pipe 30. Of course, the compressor 20 may generate a pressure amplitude by a single piston.

[0038] The displacer device 10 has a storage container 50 that forms a working fluid space filled with a working fluid G having a pressure amplitude generated by the compressor 20. The storage container 50 is configured such that a normal temperature container 51, a first-stage container 16, and a second-stage container 17 are connected in sequence. In the displacer device 10, a displacer 11 is disposed within the storage container 50. The displacer 11 has a first-stage regenerator 13 and a second-stage regenerator 14 incorporating a regenerative material that exchanges heat with the working fluid G. The regenerative material of the first-stage regenerator 13 is typically a fine mesh such as stainless steel, and the regenerative material of the second-stage regenerator 14 is typically lead balls having a high specific heat at low temperatures. Note that, as part of the magnetic refrigerator described above, a magnetic refrigerant 15 is disposed on the tip side of the cold head (the low-temperature end of the second-stage regenerator 14) in the displacer 11.

[0039] The magnetic refrigerant 15 can be a material having a conventional magnetocaloric effect that undergoes a ferromagnetic transition from a paramagnetic state to a ferromagnetic state upon application of a magnetic field, such as La(Fe X Si 1-X ) 13 or HoB2. Further, the magnetic refrigerant 15 can be a generalized antiferromagnet. Here, a generalized antiferromagnet is a substance that is in a magnetic order state although not all of the spins in the substance are aligned in a specific direction. In addition to a narrow sense antiferromagnet in which the absolute values of adjacent spins are the same and the angle between them is 180°, it may be a ferrimagnet in which the absolute values of adjacent spins are not the same, a helical magnet, or an antiferromagnet having parasitic ferromagnetism in which the angle between them is other than 180°. For example, Ho is a typical substance of a helical magnet.

[0040] The magnetic refrigerant 15 can be configured as an aggregate of polycrystalline spherical grains. In this configuration, when a generalized diamagnet is used for the magnetic refrigerant 15, a material with the smallest possible (substantially no) anisotropy in the metamagnetic transition magnetic field is selected as the generalized diamagnet.

[0041] The displacer 11 reciprocates in the X direction according to the pressure amplitude of the working fluid G. The driving force of the displacer 11 is the pressure difference between the normal temperature space E1 and the 77K space E21 and the 20K space E22. Since the phase of this pressure difference is in phase with the phase of the flow rate, the displacer 11 operates with an advanced phase difference with respect to the operation of the compression pistons 23, 24. In this case, since the displacer 11 does not move by its own power but moves passively, it is also called a free piston. The displacer 11 moves due to the pressure difference caused by the viscous resistance of the working fluid G, and the optimum value with respect to the compression pistons 23, 24 is a phase difference of π / 4.

[0042] The normal temperature container 51 is a normal temperature container that connects the working fluid G with the compressor 20 via the pipe 30, and has a flexure bearing structure that supports the shaft 12 of the displacer 11. The flexure bearing 53 is a leaf spring that operates only in one axial direction, and basically does not operate in the radial direction (Y-Z plane) perpendicular to the shaft 12, and also serves as a support member that reciprocates with a certain gap between the piston (displacer 11) and the cylinder (the first-stage container 16 and the second-stage container 17).

[0043] An aftercooler 52 is arranged between the normal temperature container 51 and the first-stage container 16, and heat is dissipated to a water-cooled jacket provided outside the normal temperature container 51. Also, a fixing portion for attaching the flexure bearing 53 is arranged inside the normal temperature container 51.

[0044] The interior of the displacer 11 is composed of a first-stage regenerator 13 and a second-stage regenerator 14. The cylinder that houses the displacer 11 is also composed of a first-stage container 16 and a second-stage container 17. The low-temperature part of the first-stage container 16 has a first-stage cold head 18, and this stage is cooled to about 77K. The low-temperature part of the second-stage container 17 has a second-stage cold head 19 and is cooled to 20K or lower. As described above, a stainless-steel mesh is used as the material for the first-stage regenerator 13, and lead balls are used as the material for the second-stage regenerator 14. This is because the volumetric specific heat of helium gas increases at low temperatures, so a regenerator material with a high volumetric specific heat is required even at low temperatures. Therefore, there are cases where a stainless-steel mesh with a thinner wire diameter and a higher mesh count is used as the material for the second-stage regenerator 14, or passive magnetic materials such as lead balls, Er3Ni, and their composites, which have a high volumetric specific heat even at low temperatures, are used.

[0045] There is a minute gap between the cylinder (the first-stage container 16 and the second-stage container 17) and the displacer 11, which forms a sealing function (so-called clearance seal). This is achieved by the flexure bearing 53 that moves only in the uniaxial direction described above. As a result, the performance of the refrigerator can be maintained for a long time, and a highly reliable refrigerator can be supplied. Of course, a sliding material for preventing wear may be installed between the cylinder and the displacer 11 for sliding. As the sliding material, a Teflon (registered trademark)-based low-friction-resistance material is generally used, but there is also a method of forming a DLC (Diamond-Like Carbon) film on both sides of the sealing surface. In this case, the amount of wear on the sealing surface can be suppressed, contributing to an extended service life. Also, in this case, the structure can be simplified by using a general coil spring instead of the flexure bearing.

[0046] On the low-temperature side of the second-stage regenerator 14, a magnetic refrigerant 15 is disposed. And FIG. 1 shows the state when the displacer 11 is in the neutral position. At this time, the magnetic circuit 40 is disposed outside the second-stage container 17 as shown in FIG. 1. When the displacer 11 is in the neutral position, a magnetic field of medium magnitude is applied to the magnetic refrigerant 15 by the magnetic circuit 40. When the displacer 11 moves to the low-temperature end side (the left side in FIG. 1), the magnetic field applied to the magnetic refrigerant 15 decreases, and it can be in a demagnetized state and cooled. When the displacer 11 moves to the high-temperature end side (the right side in FIG. 1), conversely, the magnetic field increases, and it can be in a magnetized state and heated. The explanation of the heating and cooling by this magnetocaloric effect matching the timing of heating and cooling by the gas refrigerator will be described later.

[0047] FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. As shown in FIGS. 2 and 1, the magnetic circuit 40 is preferably configured to be able to efficiently control the magnetic state of the magnetic refrigerant 15. In other words, the displacer 11 is magnetized and heated when it comes to a position where the magnetic field created by the magnetic circuit 40 in a direction perpendicular to the operating direction X of the displacer 11 (YZ plane) is relatively large, and demagnetized and cooled when it comes to a position where the magnetic field created by the magnetic circuit 40 is relatively small. Thereby, magnetization (heating) and demagnetization (cooling) of the magnetic refrigerant 15 are repeated in synchronization with the reciprocating motion of the displacer 11. For this reason, the width of the magnetic refrigerant 15 in the axial direction (X direction) is preferably the same as or substantially the same as the stroke width of the displacer 11. This is because the magnetic refrigerant 15 can be effectively used over the entire area. Note that the displacer 11 reciprocates at high speed, but there is no time delay in heating and cooling due to magnetization and demagnetization of the magnetic refrigerant 15 because the speed of magnetic phase transition in the magnetic refrigerant 15 is equivalent. However, a time delay occurs in heat transfer from the magnetic refrigerant 15 to the gas. This will be described later.

[0048] The magnetic circuit 40 is configured to be able to form a highly directional spatial magnetic field so as to effectively control the magnetic state of the magnetic refrigerant 15. Here, effective control of the magnetic state means applying a magnetic field change that can sufficiently obtain the magnetocaloric effect by ferromagnetic transition from a paramagnetic substance to a ferromagnetic substance, or applying a magnetic field change that can sufficiently obtain the magnetocaloric effect by metamagnetic transition from a generalized antiferromagnetic substance to a ferromagnetic substance. Generally, metamagnetic transition is often a sharper phase transition than ferromagnetic transition, and a large magnetocaloric effect can be obtained with a small magnetic field change.

[0049] However, the metamagnetic transition magnetic field of a generalized antiferromagnetic substance may have anisotropy, and there are cases where the metamagnetic transition does not become sharp when a magnetic field is applied to the non-oriented magnetic refrigerant 15. To prevent this, although some use an oriented single crystal, it is preferable to select a material with less anisotropy of the metamagnetic transition magnetic field from the viewpoint of mass productivity.

[0050] In addition, when using a substance that causes a metamagnetic transition in the magnetic refrigerant 15, the magnetic field received by the magnetic refrigerant 15 due to the reciprocating motion of the displacer 11 only needs to go back and forth before and after the static magnetic field created by the external magnetic circuit 40, and it is not necessarily required to create a state where the magnetic refrigerant 15 hardly receives a magnetic field during the reciprocating motion of the displacer 11.

[0051] Also, when the magnetic circuit 40 uses a substance that causes a metamagnetic transition in the magnetic refrigerant 15, the magnetic field received when the magnetic refrigerant 15 is located at the position farthest from the magnetic circuit 40 during the reciprocating motion of the displacer 11 is less than the magnetic field that causes the metamagnetic transition, and the magnetic field received when the magnetic refrigerant 15 is located at the position closest to the magnetic circuit 40 during the reciprocating motion of the displacer 11 is equal to or greater than the magnetic field that causes the metamagnetic transition.

[0052] The first-stage container 16 and the second-stage container 17 are housed in the vacuum container 41. Also, the magnetic circuit 40 is supported by a separate structure, for example, from the high-temperature side of the first-stage cold head 18 or the second-stage container 17. The magnetic circuit 40 may basically be at room temperature, but in this embodiment, since the portion of the magnetic circuit 40 facing the second-stage container 17 is at a low temperature of about 20K, in order to reduce the radiative heat transfer to the second-stage container 17, it is desirable to cool the magnetic circuit 40 to a temperature equivalent to that of the first-stage container 16 by anchoring. Further, multilayer heat insulation materials are applied to the first-stage container 16, the first-stage cold head 18, the second-stage container 17, and the second-stage cold head 19 as a whole to block the heat due to radiation.

[0053] When generating liquefied hydrogen (20K) by this refrigerator 100, heat exchangers (the first-stage heat exchanger and the second-stage heat exchanger) through which hydrogen gas can pass are attached to the outer peripheries of the first-stage cold head 18 and the second-stage cold head 19, and the two heat exchangers are connected by a low-temperature pipe. First, hydrogen gas from room temperature is passed through the first-stage heat exchanger to take away the sensible heat of the hydrogen gas and cool it to near 77K. Then, the gas is led to the second-stage heat exchanger, and it is liquefied by taking away the sensible heat, latent heat, and conversion heat specific to hydrogen of this gas. The liquefied hydrogen is taken out separately, but the details are omitted here. Note that the temperature of the second-stage cold head 19 needs to be maintained at a temperature below the liquefied hydrogen temperature.

[0054] Note that when it is used as a zero boil-off (ZBO) that is attached to the upper part of the heat insulation container filled with liquefied hydrogen (20K) to re-condense the evaporated hydrogen gas, the second-stage cold head 19 is directly attached to the upper part of the heat insulation container. Also, it becomes more efficient if a heat exchanger with a large heat transfer area is attached to the cold head part.

[0055] <Refrigeration function of Stirling refrigerator> Figure 3 shows the time-series data of the compression piston position, the displacer position, and the low-temperature end flow rate, with the time when the compression piston is at the neutral position taken as the reference point (point 0). For ease of understanding, the horizontal axis is shown as the angle (ωt) obtained by multiplying the time t by the angular frequency ω. The unit is rad. The waveforms L1, L2, and L3 represent the positions of the compression pistons 23 and 24, the position of the displacer 11, and the gas flow rate at the low-temperature end, respectively. First, the operating principle of the Stirling refrigerator will be explained using thermoacoustic theory. The Stirling refrigerator is basically a traveling-wave refrigerator, and there is a phase difference between the pressure and the gas position. Also, there is a phase difference between the compression piston and the displacer. In the case of a free-piston type displacer, the theoretical refrigeration output is maximized when the displacer position is phase-advanced by π / 4 compared to the compression piston position. Thus, it is represented in this Figure 3. The pressure within the system is almost determined by the compression piston position. First, when the compression pistons 23 and 24 are on the top dead center (the point where both pistons are closest) side (between time points A and B in Figure 3), heating due to compression occurs. This means that the acoustic power (compression work) is converted into heat. The gas with the increased temperature is moved to the high-temperature end side because the flow direction is toward the high-temperature end side, and heat is transferred to the nearby wall (regenerator). Here, if ωτ (the product of the angular frequency and the heat relaxation time, which means the factor that dominates the heat transfer between the wall and the gas in the oscillating flow) is much smaller than 1, heat exchange occurs without a time delay. Usually, the ωτ in the regenerator is configured to be much smaller than 1.

[0056] Then, in the next step, as the compression piston moves toward the bottom dead center (the point where the two pistons are farthest apart) (between time point C and time point D in FIG. 3), cooling due to the expansion of the gas occurs. The gas at the lowered temperature is transported to the low-temperature end side. At the low-temperature end, heat is absorbed from outside the system and maintained at a constant temperature. This is the generation of cold. The gas also returns to its original position and repeats this vibration. By repeating this, in the first-stage regenerator 13 and the second-stage regenerator 14, the heat exchange between the gas that has moved to the high-temperature end side and the wall, and between the wall and the gas is sequentially repeated, and the heat of the gas with increased temperature is moved to the high-temperature end side in a forward direction. In terms of entropy, it means that it moves unidirectionally from the low-temperature end side to the high-temperature end side within the first-stage regenerator 13 and the second-stage regenerator 14, and the entropy is increasing. That is, it satisfies the second law of thermodynamics. The acoustic power (work) entering from the high-temperature end side is gradually converted into heat within the regenerator and is all converted into heat at the second-stage cold head 19. There is a part that is not completely converted, and this remains as enthalpy. This means that the first law of thermodynamics is satisfied at any cross-section within the displacer device 10. This is the cooling principle of the Stirling refrigerator from the thermoacoustic perspective.

[0057] The refrigeration capacity Qsc of the Stirling refrigerator can be calculated by solving its basic equation from the thermoacoustic perspective shown above. For example, it can be calculated using software such as DeltaEC provided by the Los Alamos National Laboratory in the United States. Also, as a simple calculation method, it can be calculated as the value obtained by subtracting the heat loss Qsls from the refrigeration output Qpv at the low-temperature end. Since this is easy to understand the physical meaning of the refrigeration capacity, it has been a commonly used method. That is, the refrigeration capacity Qsc is expressed by the following equation (1). Qsc = Qpv - Qsls …(1)

[0058] Here, the refrigeration output Qpv can be calculated from the pressure change and volume change at the low-temperature end. That is, it is obtained by solving the equations of motion for the compression piston and the displacer, and is expressed as the following equation (2). Qpv = πf·ΔPc·ΔV·sinφ …(2) Here, f is the operating frequency, ΔPc is the pressure amplitude value at the low-temperature end, ΔV is the volume change width at the low-temperature end (the value obtained by multiplying the displacer amplitude by the cross-sectional area), and φ is the phase difference between the pressure and the displacer position. Equation (2) is obtained by solving the equations of motion for the compressor and the displacer.

[0059] On the other hand, the heat loss Qsls mainly consists of heat due to heat conduction from the displacer tube and the cylinder tube, heat (entropy loss) brought in from the high-temperature side because the regenerator and the gas cannot achieve complete heat exchange, and heat (shuttle loss) transferred to the cylinder due to the reciprocating motion of the displacer.

[0060] The normal operating frequency of a Stirling refrigerator is as high as about 10 - 100 Hz. It can be seen from Equation (2) that the refrigeration output Qpv is proportional to the operating frequency f. Therefore, as a design of the refrigerator, by increasing the operating frequency f and decreasing other parameters such as ΔPc and ΔV, it is possible to miniaturize the size of the refrigerator. For other refrigerators, such as GM refrigerators, which are usually about 1 - 2 Hz, it is necessary to increase ΔPc and ΔV. One of the features of a Stirling refrigerator is that it can have a smaller refrigerator size compared to other refrigerators.

[0061] <Refrigeration Function of a Magnetic Refrigerator> Next, it is explained that the part incorporating the magnetic refrigerant 15 operates as a magnetic refrigerator. In magnetic refrigeration, it has already been described that heating occurs during magnetization and heat absorption (cooling) occurs during demagnetization. The problem is the time delay when this generated heat is transferred to the gas. Assuming the magnetic entropy change is ΔS, the heat quantity is Q, and the temperature is T, the following Equation (3) holds. T·ΔS = ΔQ …(3) Also, in the case of an adiabatic condition where the specific heat C is constant, the following Equation (4) holds. ΔQ = C·ΔT …(4) Then, differentiating Equation (4) with respect to time and considering the oscillatory flow operation (sinusoidal waveform) to transform the equation, the following Equation (5) is obtained. T = ΔS / C·T C· sin(ωt - π / 2) …(5) Here, TC where \(T_{L}\) is the temperature at the low-temperature end, \(\omega\) is the angular frequency, and \(t\) is time. From Equation (3), it can be seen that the temperature change lags behind the phase of the magnetic entropy change by \(\pi / 2\). In this calculation, it is assumed that the specific heat is a constant value independent of temperature, but in reality, it has a temperature dependence. Also, in an actual refrigerator, the adiabatic condition is not satisfied, and during magnetization, gas flows from the low-temperature end side to the high-temperature end side. Therefore, it is considered that the phase between the temperature change and the magnetic entropy change also changes from \(\pi / 2\). Since it becomes forced convection heat transfer due to the gas flow, the phase lag is in the direction of decreasing.

[0062] As shown in FIG. 3, in the case of a Stirling refrigerator, as described above, when the compression pistons 23 and 24 come to the top dead center side, that is, between points A and B in time, the entire gas is compressed and heated. Conversely, when it comes to the bottom dead center side, that is, between points C and D in time, the entire gas is expanded and cooled. Note that the positions of the compression pistons 23 and 24 shown in FIG. 1 are at the neutral position when time \(t = 0\), and then move toward the top dead center side. The position of the displacer 11 has a phase advanced by \(\pi / 4\) compared to the compression piston when time \(t = 0\). The displacer 11 then once moves to the low-temperature end side (+) and gets closest to the low-temperature end side, and then returns to the neutral position side.

[0063] As shown in Fig. 3, the Stirling refrigeration function and the magnetic refrigeration function have heating and heat absorption processes within one cycle. In order to add the magnetic refrigeration function to the Stirling refrigeration function and enable each of them to exert its refrigeration function, it is necessary to set the timing such that one heating process and the other heat absorption process do not overlap in time. If they overlap, the refrigeration functions will cancel each other out, and thus the high refrigeration performance resulting from the synergistic action of the Stirling refrigeration function and the magnetic refrigeration function cannot be expected. First, in the Stirling refrigeration function, heating is generated by gas compression. In Fig. 3, the period between time point A and time point B is the heating period. This heat is transferred to the regenerator. Since ωτ (the product of the angular frequency and the relaxation time, which determines the heat transfer between the gas and the substance in the oscillatory flow from a thermoacoustic perspective) is configured to be much smaller than 1, the heat transfer from the gas to the regenerator occurs without time delay. Similarly, the heat transfer from the regenerator to the gas also has no time delay. Although it may seem unexpected, heat is transferred without delay even at high frequencies on the order of several tens to 100 Hz. To put it simply, usually, the regenerator uses metal wires with a diameter on the order of several tens of microns, and the amount of helium gas (the heat capacity of the gas) around it is small and exists within the thermal boundary layer, so heat is transferred between the two without time delay. The heating generated by the Stirling refrigeration function is transported to the high-temperature end side through the regenerator. This is achieved by the gas flow flowing to the high-temperature end side between time point B and time point C. On the other hand, between time point C and time point D, the gas expands, resulting in heat absorption (cooling). Since the gas flow flows to the low-temperature end side from time point D to near time point D', low-temperature gas moves to the low-temperature end and the cooling progresses.

[0064] Next, it will be explained that the magnetic refrigeration function can generate cold without impairing the Stirling refrigeration function. In order for the magnetic refrigeration function to exhibit refrigeration capacity, magnetization and demagnetization are performed in consideration of the phase of the temperature change and the magnetic entropy change according to Equation (5) as described above. In FIG. 3, magnetization occurs from time point tz to time point A'. As shown in Equation (5), the phase is delayed by π / 2, and heating occurs from time point A' to time point B'. However, between time point C and time point B', part of the heat absorption of the Stirling refrigeration function overlaps with the heating of the magnetic refrigeration function, and the heat absorption of the Stirling refrigeration function during this period will be canceled out. Also, from time point B' to time point C', the magnetic refrigerant undergoes demagnetization, and heat absorption occurs between time point C' and time point D' with a phase delay of π / 2 from Equation (5) as well. However, between time point E and time point D', part of the heating of the Stirling function overlaps with the heat absorption of the magnetic refrigeration function, and the heat absorption of the magnetic refrigeration function during this period will be canceled out. In this way, the magnetic refrigeration function and the Stirling refrigeration function cannot act synergistically, and sufficiently high refrigeration performance cannot be obtained.

[0065] Theoretically, it is as described above. To verify this, a proof-of-concept machine was fabricated and experimental confirmation was carried out. The proof-of-concept machine is equivalent to the one shown in FIG. 4. As shown in FIG. 4, the performance of a Stirling refrigerator + magnetic refrigerator (referred to as a "magnetic Stirling refrigerator" hereafter) with a magnetic circuit attached and a pure Stirling refrigerator without a magnetic circuit attached was compared. As a result of this experimental verification, the performance of the magnetic Stirling refrigerator showed significantly higher refrigeration performance compared to the performance of the pure Stirling refrigerator. This suggests that the phase delay of the heating after magnetization does not delay up to π / 2, and as described above, the phase delay is small. That is, it is considered that the section where the heat between time point C and time point B' is canceled out is smaller or has disappeared. In other words, it is considered that time point A' and time point B' have advanced (move to the left in FIG. 3). The same applies to the phase delay of the heat absorption after demagnetization. It is considered that the section where the heat between time point E and time point D' is canceled out is smaller or has disappeared.

[0066] Here, the magnetic refrigeration function will be described in association with a specific example of the positional relationship between the magnetic circuit 40 and the displacer 11. First, FIG. 4 is a diagram showing the positional relationship between the magnetic circuit 40 with the permanent magnet pieces 43 arranged in a Halbach array and the displacer 11. In this magnetic circuit 40, permanent magnet pieces 43 of segments (arc-shaped) with different magnetization directions AR are arranged in a Halbach array as shown in FIG. 4 within a cylindrical fixed frame 42. In FIG. 4, the number of permanent magnet pieces 43 is 12, but this may be a little more or less as long as it is an even number (preferably a multiple of 4). In this Halbach array magnet of the permanent magnet pieces 43, a high magnetic field can be formed in the +Z direction (upward from the top and bottom in FIG. 4) with respect to the center space into which the magnetic refrigerant 15 enters. Of course, the magnetization direction of the permanent magnet pieces is not limited to this.

[0067] In FIG. 4(b), the magnetic circuit 40 composed of Halbach array magnets is housed and arranged within the fixed frame 42. In the displacer device 10a shown in FIG. 4(b), the tip of the low-temperature end of the displacer 11 within the expansion cylinder 50a is filled with spherical or linear magnetic refrigerants 15, and the other parts of the displacer 11 are inserted with heat storage materials 14a. Note that FIG. 4(b) is a single-stage displacer device for convenience of explanation, and only a part of the displacer 11 and the expansion cylinder 50a are shown, and springs, position control devices, etc. that are normally connected to the displacer 11 are not shown. Also, the same explanation applies to the two-stage displacer shown in FIG. 1 as the displacer 11.

[0068] In FIG. 4(b), the displacer 11 is exactly at the neutral position and vibrates in the ±X direction around the reference position XP of the magnetic circuit 40. The neutral position of the displacer 11 shown in FIG. 4(b) is where the position of the displacer 11 in FIG. 3 is at the 0 point. This neutral position may be where the displacer 11 moves from the reference position XP to the low-temperature end side (+ side) or the high-temperature end side (- side).

[0069] FIG. 5 is a diagram showing an example of the magnitude of the magnetic field applied from the magnetic circuit 40 corresponding to the position of the displacer 11. FIG. 5 is an example of the calculation result of the magnetic field by the magnetic circuit 40 in which neodymium magnet pieces are arranged in a Halbach array as shown in FIG. 4. In FIG. 5, when the displacer 11 moves from -5 mm to +5 mm with the reference position XP as the neutral position, the magnetic field changes from +1.09 T to 0.36 T, and the change width is 0.73 T. In FIG. 3, the time on the horizontal axis is expressed in terms of the angle (ωt), and since one cycle is 2π, from the time point tz to the time point A', the displacer 11 moves 71% of the entire movable range, and magnetization is increased in this range. In this calculation example, the magnetic field increase width is 0.57 T. As already described, the heat transfer to the gas is delayed by π / 2 from Equation (3), so heating occurs between the time points A' and B'. When the displacer 11 moves from the time point A' to the time point B', the magnetization increase width and the demagnetization width are the same, and the magnetic entropy change is canceled out, that is, no thermal movement occurs. Next, when the displacer 11 moves from the time point B' to the time point C', this time the magnetic field to the magnetic refrigerant 15 is demagnetized, and the demagnetization width is 0.57 T. Since heat absorption (cooling) occurs with a delay of π / 2 as in the case of magnetization, heat absorption (cooling) occurs between the time points C' and D'. As suggested by the verification results in the experiment as described above, the phase delay of heat is smaller than π / 2.

[0070] Summarizing the above explanation, it is as follows. As shown in FIG. 3, it is considered that the heating timing by the Stirling refrigeration function and the heating timing by the magnetic refrigeration function occur almost without overlapping as a result of experimental verification. Also, it is considered that the heat absorption timing by the Stirling refrigerator and the heat absorption timing by the magnetic refrigeration function occur almost without overlapping. Therefore, the Stirling refrigeration function and the magnetic refrigeration function can exhibit refrigeration performance synergistically without canceling each other's performance.

[0071] Here, an equation for simply calculating the refrigeration output Qmc by the magnetic refrigeration function in the same manner as the Stirling refrigerator is shown. The refrigeration output Qmc can be expressed by the following equation (6). Qmc = Qmt - Qmls …(6) Note that Qmt is the magnetic refrigeration capacity.

[0072] Also, the magnetic refrigeration capacity Qmt in Equation (6) can be calculated by the following Equation (7). Qmt = πf·Vm·ΔT·ΔS …(7) Here, f is the operating frequency, Vm is the volume of the magnetic refrigerant, ΔT is the value calculated by Equation (5), and ΔS is the magnetic entropy change. Qmls in Equation (6) is the heat loss generated in the magnetic refrigerant, and the main losses are the hysteresis loss and the eddy current loss.

[0073] <Magnetic Refrigerant> By the way, there are various candidate materials as the magnetic refrigerant 15. FIG. 6 is a diagram showing the material characteristics of the magnetic refrigerant described in Non-Patent Document 1. In FIG. 6, the horizontal axis represents temperature and the vertical axis represents the magnetic entropy change (ΔS). Here, in the region from around 20K to 80K, the materials that are candidates for application as the magnetic refrigerant 15 are listed below. Rare earth compounds having a Laves structure (cubic crystal) such as RAl2 and RNi2 (where R is Er, Ho, Dy) can be used as the magnetic refrigerant 15. These are basically second-order transition type magnetic materials and the peak value of the magnetic entropy change is not very large, but it is broad with respect to temperature. Also, ErCo2 has the same Laves structure but is a first-order transition material due to the itinerant electron metamagnetic transition. ErCo2 has a high peak value of the magnetic entropy change even at a low magnetic field of about 1T, but the peak width is small. For this reason, it is suitable for a low magnetic field application type configuration using a permanent magnet or the like as a magnetic circuit. As the magnetic refrigerant 15, either a second-order transition material or a first-order transition material can be used. In that case, the relationship between temperature and magnetic entropy change and the characteristics of the magnetization curve should be well understood, and appropriate arrangement and amount should be selected for the temperature range. Also, it is possible to obtain higher performance by using a hybrid of a second-order transition material and a first-order transition material.

[0074] <Magnetic Circuit> FIG. 7 is a diagram showing an example of a magnetic circuit. The magnetic circuit 40 shown in FIG. 4 was a Halbach array of permanent magnet pieces 43, but as shown in FIG. 7, the permanent magnet pieces 43 may be constituted by electromagnets. In the magnetic circuit 45 shown in FIG. 7, twelve electromagnets in which coils 45c are wound around cores 45b are arranged in a Halbach array within a support member 45a. This configuration has several features compared to the case of using a fixed magnet type. One is that regardless of the position of the displacer 11, the timing, application time, and magnitude of the magnetic field for magnetization and demagnetization can be freely changed. Also, this correspondence is possible regardless of the position of the magnetic refrigerant 15.

[0075] Note that, instead of the Halbach array shown in FIG. 4, a magnetic circuit may be constituted by a pair of permanent magnets and a magnetic body (yoke). FIG. 8 is a diagram showing the configuration of a magnetic circuit 46 using a pair of permanent magnets 46b. As shown in FIG. 8, the pair of permanent magnets 46b are adsorbed and fixed to a cylindrical yoke 46a and arranged so as to sandwich the magnetic refrigerant 15. Even with such a pair of permanent magnets 46b, a magnetic field can be applied across the displacer 11. Note that in FIGS. 7 and 8, a single-stage displacer 11 is used for explanation, but a two-stage displacer 11 can be similarly applied.

[0076] <Synergistic refrigeration function by a Stirling refrigerator and a magnetic refrigerator> The refrigeration capacity Qc by a Stirling refrigerator and a magnetic refrigerator can be expressed by the following equation (8) according to equations (1) and (6). Qc = Qsc + Qmc …(8) That is, the refrigeration capacity Qc is the sum of the refrigeration capacity Qsc by the Stirling refrigerator and the refrigeration capacity Qmc by the magnetic refrigerator. The refrigeration capacity at the low temperature end is refrigeration generated by completely different refrigeration principles of the Stirling refrigerator and the magnetic refrigerator. Therefore, the capacity of the entire refrigerator can be obtained by simply adding the two, and a high refrigeration capacity can be generated.

[0077] <Embodiment> FIG. 9 is a schematic diagram showing the configuration of the displacer device 110 according to the present embodiment. FIG. 10 is a diagram showing the relationship among the electromagnetic force F1 acting on the magnetic refrigerant 15, the electromagnetic force F2 acting on the magnetic material 115, and the electromagnetic force F10 acting on the displacer 11 as the displacer 11 shown in FIG. 9 moves. Since the magnetic refrigerant 15 at the low-temperature end of the displacer 11 is a magnetic material, an electromagnetic force F1 is generated by the static magnetic field generated by the magnetic circuit 40. The magnitude of the electromagnetic force F1 acting on the magnetic refrigerant 15 is determined by the positional relationship between the magnetic circuit 40 and the magnetic refrigerant 15 as shown in FIG. 10.

[0078] As shown in FIG. 9, when the vibration direction of the displacer 11 is defined as the x direction with the neutral position of the displacer 11 as the 0 point (reference position XP) and the low-temperature end side as the plus (+) direction, the high-temperature end of the magnetic refrigerant 15 and the left end of the magnetic circuit 40 (the minus-side end in the x direction) are at the position of x = 0. In this case, as shown in FIG. 10, the electromagnetic force F1 acting on the magnetic refrigerant 15 is a force in the minus (-) direction. The electromagnetic force shown in FIG. 10 is an example (normalized value) calculated under certain conditions, but in the operating range of the displacer 11, the electromagnetic force F1 is a unidirectional force that is applied only in the minus (-) direction with respect to the x direction.

[0079] By the way, a force generated by the pressure difference at both ends of the displacer 11 acts as a reciprocating power on the displacer 11, and there is a force to return it, that is, a restoring force by the flexure bearing 53, so that it can vibrate with a constant amplitude. Here, if a unidirectional electromagnetic force is generated, it will inhibit the movement of the original displacer 11 and the refrigerating capacity as designed cannot be achieved. Therefore, in the first modified example, in order to counteract the electromagnetic force F1 applied to the magnetic refrigerant 15, as shown in FIG. 9, a magnetic material 115 is arranged on the high-temperature end side of the displacer 11 so as to generate a symmetric electromagnetic force F2, and a magnetic circuit 140, which is another magnetic circuit, is arranged outside the expansion cylinder (storage container 50) corresponding to the magnetic material 115.

[0080] That is, assuming the distance between the magnetic circuit 40 and the magnetic circuit 140 is 2L, the magnetic circuits 40 and 140, and the magnetic refrigeration material 15 and the magnetic material 115 are respectively arranged symmetrically with respect to the x-direction with the axis of x = -L. The magnetic circuit 40 and the magnetic refrigeration material 15 are arranged in the +x direction, and the magnetic circuit 140 and the magnetic material 115 are arranged in the -x direction respectively.

[0081] Here, for the magnetic material 115, a mesh or small spherical shape made of iron, nickel, etc. is suitable. Since this magnetic material 115 is arranged on the high-temperature side near the middle of the cold storage material, it is desirable that it is a material that functions as a cold storage material. Magnetic materials such as martensite-based materials made of stainless steel mesh or random fibers are also effective. When a material having the same BH characteristics as the magnetic refrigeration material 15 is arranged for the magnetic material 115, as shown in FIG. 10, the electromagnetic force F2 acting on the magnetic material 115 is rotationally symmetric about the origin 0 point with the electromagnetic force F1 acting on the magnetic refrigeration material 15.

[0082] Also, a magnetic refrigeration material can be used as the magnetic material 115. In this case, it is desirable to select the magnetic refrigeration material so that the phase transition temperature of the magnetic refrigeration material is the temperature at the location where the magnetic refrigeration material is placed or the temperature in its vicinity. As a result, cooling by the magnetocaloric effect is possible even on the high-temperature side. Since this acts separately from the cooling by the magnetic refrigeration material installed at the low-temperature end, the total refrigeration performance can be increased.

[0083] Therefore, as shown in FIG. 10, when the displacer 11 moves in the +x direction, the electromagnetic force F10 acting on the displacer 11 in total exerts a force in the - direction, and when it moves in the -x direction, a force in the + direction is exerted. That is, a restoring force is applied to the displacer 11.

[0084] This acts as a vibration force synchronized with the operating frequency of the compressor 20. The vibration force caused by this electromagnetic force F10 is determined by the BH characteristics and the respective positional relationships of the magnetic circuits 40, 140, the magnetic refrigeration material 15, and the magnetic material 115 in FIG. 9. What is important is that a vibration force synchronized with the operating frequency is applied to the displacer 11.

[0085] In the case where the displacer 11 has a free piston configuration, a restoring force is required to generate a constant vibration, and this role is played by a spring (flexure bearing 53). When adopting the configuration including the magnetic material 115 and the magnetic circuit 140 shown in FIG. 9, a restoring force due to an electromagnetic force F10 opposite to the propulsive force generated by the pressure difference at both ends of the displacer 11 is applied to the displacer 11. For this reason, since the restoring force becomes larger than that of a normal free piston type, it is possible to reduce the force of the spring, leading to a simplification of the structure. There is no problem at all with the performance of the refrigerator. That is, by adopting the configuration shown in FIG. 9, in addition to the high refrigeration function by the basic Stirling refrigerator, a refrigeration configuration having a magnetic refrigeration function can be achieved.

[0086] Further, by optimizing the magnitude of the electromagnetic force F10, it is also possible to adopt a configuration in which the flexure bearing 53 is unnecessary. That is, the restoring force of the spring is replaced with the restoring force due to the electromagnetic force. In this way, a configuration without a flexure bearing is achieved, leading to a simplification and a simplification of the structure.

[0087] <Configuration serving as the basis of Modification 1> FIG. 11 is a schematic diagram showing the configuration of a displacer device 10c in a refrigerator serving as the basis of Modification 1 of the present embodiment. As shown in FIG. 11, in the refrigerator serving as the basis of Modification 1, the material of the second-stage regenerator 14 is configured such that a magnetic refrigerant and a regenerative material are alternately arranged from the low-temperature side. That is, a plurality of magnetic refrigerants 15a, 15b, 15c corresponding to the magnetic refrigerant 15 are arranged with a regenerative material interposed therebetween from the low-temperature side (tip side) of the second-stage regenerator 14. And at positions corresponding to the respective magnetic refrigerants 15a, 15b, 15c, magnetic circuits 40a, 40b, 40c corresponding to the magnetic circuit 40 are arranged outside the second-stage container 17.

[0088] The length of each of these magnetic refrigerants 15a, 15b, and 15c in the X direction is arbitrary, and the length of the cold storage material between each of the magnetic refrigerants in the X direction is also arbitrary. In this case, the magnetic circuits 40a, 40b, and 40c are also arranged at positions corresponding to the magnetic refrigerants 15a, 15b, and 15c. In FIG. 11, three magnetic refrigerants are installed, but this number is also arbitrary. Usually, in order to achieve high refrigeration performance, the temperature profile of the displacer in the X direction is designed to be linear. Each magnetic refrigerant selects a magnetic refrigerant having a phase transition temperature at or near its temperature at the place where it is placed.

[0089] In the refrigerator that is the basis of Modification 1, the cold generated on the magnetic refrigerator (magnetic refrigerant) side can be further increased.

[0090] <Modification 1> FIG. 12 is a diagram showing a configuration in which a plurality of magnetic materials 115a, 115b, 115c and a plurality of magnetic circuits 140a, 140b, 140c are arranged corresponding to the embodiment with respect to the configuration that is the basis of Modification 1. In the displacer device 10c shown in FIG. 12, the sum of the electromagnetic forces F1a to F1c acting on the magnetic refrigerants 15a to 15c is substantially equal to the sum of the electromagnetic forces F2a to F2c acting on the magnetic materials 115a to 115c at the zero point (see FIG. 10) and is canceled out, and as the displacer 11 moves, the difference between the sum of the electromagnetic forces F1a to F1c and the sum of the electromagnetic forces F2a to F2c acts as a restoring force.

[0091] <Modification 2> FIG. 13 is a diagram showing a configuration in which one magnetic material 115d and one magnetic circuit 140d are arranged corresponding to the embodiment with respect to the configuration that is the basis of Modification 1. In the displacer device 10c shown in FIG. 13, the sum of the electromagnetic forces F1a to F1c acting on the magnetic refrigerants 15a to 15c is substantially equal to the electromagnetic force F2d acting on the magnetic material 115d at the zero point (see FIG. 10) and is canceled out, and as the displacer 11 moves, the difference between the sum of the electromagnetic forces F1a to F1c and the electromagnetic force F2d acts as a restoring force.

[0092] <Modification 3> FIG. 14 is a diagram showing the configuration of the displacer device 10d in the refrigerator according to Modification 3 of the present embodiment. In FIG. 14, the configurations of the magnetic material 115 and the magnetic circuit 140 are omitted. As shown in FIG. 14, in this Modification 3, a drive device 60 for controlling the position of the shaft 12 of the displacer 11 is further provided to adjust the phase difference of the reciprocating motion of the displacer 11 based on the positions of the compression pistons 23 and 24.

[0093] The drive device 60 in the normal temperature container 51a can perform axial position control on the shaft 12a extending the shaft 12 of the displacer 11 by a linear motor or the like. The control unit 61 acquires the compression piston position PD and performs feedback control via the drive device 60 to adjust the phase difference that causes the position of the displacer 11 to lead or lag with respect to the pressure phase.

[0094] In this Modification 3, since the timing of heating and cooling of the magnetic refrigerant 15 and the timing of heating and cooling of the Stirling refrigerator can be adjusted, the refrigeration efficiency of the entire refrigerator can be optimized.

[0095] <Modification 4> FIG. 15 is a schematic diagram showing the configuration of the displacer device 120 according to Modification 4 of the present embodiment. In FIG. 15, the configurations of the magnetic material 115 and the magnetic circuit 140 are omitted. FIG. 15(b) shows the cross-sectional structure of the displacer device 120, and FIG. 15(a) is a cross-sectional view taken along line B-B of FIG. 15(b). In this Modification 4, a plurality of magnetic refrigerants are stacked in the vibration direction of the displacer 11. As shown in FIG. 15, the magnetic refrigerant 15 is configured by stacking two magnetic refrigerants 15g and 15h in the vibration direction of the displacer 11. For example, the magnetic refrigerant 15g is a material with a large magnetic entropy change near 4K such as TmAl2. The magnetic refrigerant 15h is a material with a large entropy change at 20K such as HoAl2.

[0096] In the fourth modification example, by providing a plurality of magnetic refrigerants having a large magnetic entropy change and different temperature ranges, it becomes possible to fabricate a cryogenic refrigerator at a lower temperature, which is difficult with only a gas refrigeration function, for example, a cryogenic refrigerator of 4.2 K.

[0097] Note that the width of the magnetic refrigerant 15 and the effective magnetic field width generated by the magnetic circuit 40 (the region where the change in the magnetic entropy of the magnetic refrigerant 15 is effectively generated by the magnetic field created by the magnetic circuit 40) are substantially the same. Substantially the same means that the absolute value of the difference between the width of the magnetic refrigerant 15 and the effective magnetic field width generated by the magnetic circuit 40 is within a minute range of ± a predetermined width.

[0098] Furthermore, if the stroke of the displacer 11 is increased and the frequency of the compressor 20 is further increased, further miniaturization is possible and the refrigeration efficiency can also be enhanced.

[0099] Also, each configuration illustrated in the above-described embodiments and modification examples is schematic in function, and it is not necessarily physically configured as illustrated. That is, the form of dispersion and integration of each device and component is not limited to that illustrated, and all or a part thereof can be functionally or physically dispersed and integrated in any unit according to various usage situations and the like.

Explanation of Reference Numerals

[0100] 10, 10a, 10c, 10d, 110, 120 Displacer device 11 Displacer 12, 12a Shaft 13, First-stage regenerator 14 Second-stage regenerator 14a Regenerative material 15, 15a, 15b, 15c, 15g, 15h Magnetic refrigerant 16 First-stage container 17 Second-stage container 18 First-stage cold head 19 Second-stage cold head 20 Compressor 21, 22 Linear motor 23, 24 Compression piston 30 Pipe 40, 40a, 40b, 40c, 45, 46, 140, 140a - 140d Magnetic circuit 41 Vacuum vessel 42 Fixed frame 43 Permanent magnet piece 45a Support member 45b Iron core 45c Coil 46a Yoke 46b Permanent magnet 50, 50a Storage container (expansion cylinder) 51, 51a Normal temperature container 52 After - cooler 53 Flexible bearing 60 Driving device 61 Control unit 100 Refrigerator 115, 115a - 115d Magnetic materials A, B, C, D, E, F, A’, B’, C’, D’, tz Time points AR Magnetization direction E1 Normal temperature space E21 77K space E22 20K space F1, F1a - F1c, F2, F2a - F2d, F10 Electromagnetic force G Working fluid L1, L2, L3 Waveforms PD Compression piston position XP Reference position

Claims

1. A displacer device having a cold storage material inside, wherein the displacer reciprocates within a storage container to expand a working fluid compressed within the storage container to generate cold, comprising: a magnetic refrigeration material is disposed on the low-temperature end side of the displacer; a magnetic circuit for changing the magnetic state of the magnetic refrigeration material is provided outside the storage container corresponding to the magnetic refrigeration material; the magnetic circuit magnetizes and demagnetizes the magnetic refrigeration material according to the position of the displacer; a magnetic material having a shape through which the working fluid can pass is disposed on the high-temperature end side of the displacer; another magnetic circuit for changing the magnetic state of the magnetic material is provided outside the storage container corresponding to the magnetic material; a displacer device, characterized in that the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material have different directions.

2. equipped with a spring that provides a restoring force against the reciprocating motion of the displacer in the axial direction; The displacer device according to claim 1, characterized in that the restoring force is assisted by the difference between the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material.

3. The displacer device according to claim 1, characterized in that the difference between the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material becomes a restoring force against the reciprocating motion of the displacer in the axial direction.

4. The displacer device according to claim 1, characterized in that a plurality of magnetic refrigeration materials are arranged with a cold storage material interposed therebetween from the low-temperature end side of the displacer.

5. The displacer device according to claim 1, characterized in that a plurality of magnetic materials are arranged with a cold storage material interposed therebetween on the high-temperature end side of the displacer.

6. The displacer device according to claim 1, characterized in that the magnetic material is a magnetic refrigeration material.

7. The displacer device according to claim 1, characterized in that a plurality of different magnetic refrigeration materials are arranged from the low-temperature end side of the displacer.

8. equipped with a driving device for controlling the position of the displacer, and adjusting the position of the displacer, the displacer device according to claim 1.

9. The displacer device according to claim 1, characterized in that the magnetic circuit and the other magnetic circuit each generate a magnetic field having directivity with respect to the magnetization region of the magnetic refrigeration material and the magnetic material.

10. The magnetic refrigeration material is arranged with the low-temperature end side end face of the magnetic circuit as the neutral position, and is demagnetized when the magnetic refrigeration material moves from the neutral position to the low-temperature end side, and is magnetized when it moves from the neutral position to the high-temperature end side. The display device according to claim 1, characterized in that.

11. A compressor that generates a pressure amplitude in the working fluid by the reciprocating motion of the compression piston, In a storage container that is connected to the compressor and forms a working fluid space filled with a working fluid having the pressure amplitude generated by the compressor, a displacer that reciprocates with a phase difference with respect to the reciprocating motion of the compression piston and has a cold storage material inside is arranged, and a displacer device having a mechanism for supporting the displacer in the storage container; A refrigerator comprising: A magnetic refrigeration material is arranged on the low-temperature end side of the displacer, A magnetic circuit for changing the magnetic state of the magnetic refrigeration material is provided outside the storage container corresponding to the magnetic refrigeration material, The magnetic circuit magnetizes and demagnetizes the magnetic refrigeration material according to the position of the displacer, A magnetic material having a shape through which the working fluid can pass is arranged on the high-temperature end side of the displacer, Another magnetic circuit for changing the magnetic state of the magnetic material is provided outside the storage container corresponding to the magnetic material, A refrigerator, characterized in that the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material have different directions.

12. Comprising a spring that applies a restoring force to the reciprocating motion in the axial direction of the displacer, The refrigerator according to claim 11, characterized in that the restoring force is assisted by the difference between the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material.

13. The refrigerator according to claim 11, characterized in that the difference between the electromagnetic force acting on the magnetic refrigeration material and the electromagnetic force acting on the magnetic material becomes a restoring force for the reciprocating motion in the axial direction of the displacer.

14. The refrigerator according to claim 11, characterized in that a plurality of the magnetic refrigeration materials are arranged with a cold storage material interposed therebetween from the low-temperature end side in the displacer.

15. The refrigerator according to claim 11, characterized in that a plurality of the magnetic materials are arranged with a cold storage material interposed therebetween on the high-temperature end side of the displacer.

16. The refrigerator according to claim 11, characterized in that the magnetic material is a magnetic refrigeration material.

17. The refrigerator according to claim 11, wherein a plurality of different magnetic refrigerants are arranged from the low-temperature end side in the displacer.

18. The refrigerator according to claim 11, further comprising a driving device for controlling the position of the displacer, and adjusting the position of the displacer.

19. The refrigerator according to claim 11, wherein the magnetic circuit and the other magnetic circuit each generate a magnetic field having directivity with respect to the magnetization regions of the magnetic refrigerant and the magnetic material.

20. The refrigerator according to claim 11, wherein the magnetic refrigerant is arranged with the low-temperature end side end face of the magnetic circuit as a neutral position, and is demagnetized when the magnetic refrigerant moves from the neutral position to the low-temperature end side, and magnetized when the magnetic refrigerant moves from the neutral position to the high-temperature end side.

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