Magnetic Refrigeration Apparatus

Abstract

A magnetic refrigeration apparatus is provided which is structured simply to implement synchronization between rotation of magnets and switching of flow paths and which is easy to adjust at the time of manufacture.The magnetic refrigeration apparatus includes a first magnet, a second magnet placed opposite to the first magnet, a rotation mechanism rotating the first and the second magnets, a magnetocaloric element filling unit interposed between the first and the second magnets and filled with a magnetic material having a magnetocaloric effect, flow paths letting a fluid pass through to exchange heat with the magnetocaloric element filling unit, and an electromagnetic valve switching the flow paths by approaching the magnetocaloric element filling unit when attracted by a leakage flux therefrom where the leakage flux is higher than a predetermined level and by being separated therefrom where the leakage flux is lower than the predetermined level.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese Patent Application No. 2024-117786 filed on Jul. 23, 2024, the entire contents of which are incorporated by reference herein.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The present invention relates to a magnetic refrigeration apparatus.2. Description of the Related Art

[0003] There is a need for cooling apparatuses that are highly efficient and have a low environmental impact with a view to realizing a sustainable society. Cooling apparatuses are used in diverse fields such as air conditioning, refrigeration facilities for foods and the like, and cooling of various machine tools and industrial facilities, and reduction in the environmental impacts of such apparatuses is important. Most cooling apparatuses currently in use employ the compression-expansion cycle of alternative fluorocarbon gas for cooling. With its high global warming potential, alternative fluorocarbon gas raises concern for a high environmental impact. Magnetic refrigeration apparatuses using the magnetocaloric effect of a magnetic material for cooling can achieve refrigeration with a low environmental impact compared with the colling apparatuses utilizing alternative fluorocarbon gas.

[0004] Patent Documents on magnetic refrigeration apparatuses include JP-2024-47959-A (Patent Document 1) and JP-2006-283987-A (Patent Document 2).

[0005] FIGS. 5 and 7 of Patent Document 1 depict a magnetic refrigeration apparatus (200) in which an upper magnetic field generating member (10) and a lower magnetic field generating member (20) are rotated by a rotation mechanism around a rotating shaft (60). A magnetic working material having the magnetocaloric effect and contained in a filling container (80) placed in a spatial gap (50) between the upper magnetic field generating member (10) and the lower magnetic field generating member (20) is subjected to a constant cycle of excitation and demagnetization in keeping with the rotational movement.

[0006] FIG. 7 of Patent Document 1 also depicts rotary valves (81 to 84) which, in linkage with the movement of the rotation mechanism, control the flow path of a heat exchange fluid exchanging heat with the magnetic working material.

[0007] The summary in Patent Document 2 describes a magnetic refrigerator including a housing, multiple heat exchangers secured inside the housing and filled with magnetic particles having the magnetocaloric effect, a rotation drive unit, a rotating shaft rotated by the rotation drive unit, magnetic field generating means attached to the rotating shaft and applying or removing a magnetic field to or from the magnetic particles in the multiple heat exchangers in keeping with the rotation of the rotating shaft, a refrigerant pump circulating a refrigerant in keeping with the rotation of the rotating shaft, a rotary refrigerant control valve controlling the supply and discharge of the refrigerant between the multiple heat exchangers in keeping with the rotation of the rotating shaft, and a refrigerant circuit configured by the refrigerant pump, the rotary refrigerant control valve, the multiple heat exchangers, a cooling unit, and a heat exhaust unit connected with one another. Application or removal of the magnetic field to or from the magnetic particles by the magnetic field generating means is arranged to synchronize with the supply and discharge of the refrigerant by the rotary refrigerant control valve between the multiple heat exchangers.

[0008] Also, FIG. 2 and paragraph in Patent Document 2 indicate a rotary refrigerant control valve (12) placed in a housing (1). It is explained that a quadrangular rotor (13) is attached to a rotating shaft (4) inside the rotary refrigerant control valve as depicted in FIGS. 2B and 2D, that each of the vertexes of the quadrangular rotor (13) has a sliding unit sliding in contact with the inner surface of a case of the rotary refrigerant control valve (12), and that introduction and discharge of the refrigerant are controlled by rotation of the rotor (13).

[0009] Further, FIGS. 1 and 2 and paragraph in Patent Document 2 indicate that application and removal of a magnetic field to and from magnetic particles (6) by a permanent magnet (8) are synchronized with supply and discharge of the refrigerant between heat exchangers (5a to 5d) by the rotary refrigerant control valve (12) as well as with discharge thereby of the refrigerant to the heat exhaust unit or to the cooling unit by use of a single motor (2) in keeping with rotation of the same rotating shaft (4). This arrangement makes it possible to lower the consumption of electric power by the motor (2).SUMMARY OF THE INVENTION

[0010] The technology described in Patent Document 1 has a problem of difficulty in synchronizing the rotation mechanism with the rotary valves (81 to 84) that are installed separately from one another.

[0011] In contrast, according to Patent Document 2, the same rotating shaft (4) is used to rotate the permanent magnet (8) and the rotor (13) in synchronism with each other. However, the technology described in Patent Document 2 has a problem of difficulty in adjusting the positional relation (angle) between the rotor (13) and the permanent magnet (8), and the position of the flow path of the refrigerant (20) at the time of manufacture, since it is necessary to precisely adjust the positional relation (angle) between the rotor (13) and the permanent magnet (8), and the position of the flow path of the refrigerant (20), as can be seen in FIG. 2 of Patent Document 2.

[0012] It is therefore an object of the present invention to provide a magnetic refrigeration apparatus which is simply structured to realize synchronization between rotation of magnets and switching of flow paths for a heat exchange fluid and which is easy to adjust at the time of manufacture.

[0013] In achieving the foregoing and other objects of the present invention, there is provided a magnetic refrigeration apparatus including a first magnet, a second magnet placed opposite to the first magnet, a rotation mechanism configured to rotate the first magnet and the second magnet, a magnetocaloric element filling unit interposed between the first magnet and the second magnet and filled with a magnetic material having a magnetocaloric effect, a plurality of flow paths configured to let a fluid pass through to exchange heat with the magnetocaloric element filling unit, and an electromagnetic valve configured to switch the flow paths by approaching the magnetocaloric element filling unit when attracted by a leakage flux therefrom where the leakage flux is higher than a predetermined level and by being separated therefrom where the leakage flux is lower than the predetermined level.

[0014] The present invention thus provides a magnetic refrigeration apparatus which is simply structured to realize synchronization between rotation of the magnets and switching of the flow paths for the heat exchange fluid and which is easy to adjust at the time of manufacture.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a cross-sectional view depicting an electromagnetic valve in a state of approach in a magnetic refrigeration apparatus according to an embodiment of this invention;

[0016] FIG. 2 is a cross-sectional view depicting the electromagnetic valve in a state of separation in the magnetic refrigeration apparatus according to the embodiment;

[0017] FIG. 3 is a top view of a magnetocaloric element container in the magnetic refrigeration apparatus according to the embodiment; and

[0018] FIG. 4 is a top view depicting the positional relation between main units of the magnetic refrigeration apparatus according to the embodiment.DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] A preferred embodiment of the present invention is described below with reference to the accompanying drawings. Throughout the ensuing description and the appended drawings, like reference signs designate like or corresponding constituent elements, and the explanations of such elements will be omitted where they are redundant.

[0020] FIG. 1 is a cross-sectional view depicting an electromagnetic valve in a state of approach in a magnetic refrigeration apparatus embodying the present invention.

[0021] A magnetic refrigeration apparatus 1 of this embodiment includes magnets 10, magnetic yokes 11, a rotation mechanism 12, and a magnetocaloric element container 13.

[0022] The magnets 10 include a first magnet 10A and a second magnet 10B placed opposite to the first magnet 10A. The magnets 10 are configured by permanent magnets, for example. A magnetic field is generated in a space between the first magnet 10A and the second magnet 10B. In this embodiment, there are two pairs of the first magnets 10A and the second magnets 10B. In this embodiment, as an example, the two first magnets 10A are connected by one magnetic yoke 11 and the two second magnets 10B are connected by another magnetic yoke 11 to constitute a magnetic circuit. Alternatively, at least one pair of the first magnet 10A and the second magnet 10B may be provided.

[0023] The rotation mechanism 12 rotates the first magnet 10A and the second magnet 10B. In this embodiment, as an example, the rotation mechanism 12 includes a drive unit 12A and a rotating shaft 12B, with the rotating shaft 12B connected to the magnetic yokes 11. In the rotation mechanism 12 of this embodiment, the drive unit 12A including a motor, for example, rotates the rotating shaft 12B. This allows the first magnets 10A and the second magnets 10B to be rotated by means of the magnetic yokes 11 around the rotating shaft 12B.

[0024] The magnetocaloric element container 13 includes a magnetocaloric element filling unit 14, flow paths 15, and an electromagnetic valve 16.

[0025] The magnetocaloric element filling unit 14 is interposed between the first magnet 10A and the second magnet 10B and filled with a magnetocaloric element as a magnetic material having the magnetocaloric effect. As an exemplary magnetic material having the magnetocaloric effect, a ferromagnetic material formed of gadolinium or a metal compound including gadolinium may be used. Preferably, the magnetocaloric element filling unit 14 may be filled with a granular magnetic material. Also, the magnetocaloric element filling unit 14 may preferably include a recessed and projected structure 14A positioned opposite to the electromagnetic valve 16, to be discussed later. The reasons for and the effects of these arrangements will be discussed later.

[0026] The flow paths 15 allow a fluid that exchanges heat with the magnetocaloric element filling unit 14 to flow through. The flow paths 15 include a first flow path 15A and a second flow path 15B, the two paths being switched by the electromagnetic valve 16.

[0027] In this embodiment, the electromagnetic valve 16 is operated by use of a leakage flux from the magnetocaloric element filling unit 14. Specifically, when the leakage flux from the magnetocaloric element filling unit 14 is higher than a predetermined level, the electromagnetic valve 16 is attracted by the leakage flux to approach the magnetocaloric element filling unit 14; when the leakage flux from the magnetocaloric element filling unit 14 is lower than the predetermined level, the electromagnetic valve 16 is separated from the magnetocaloric element filling unit 14. This is how the flow paths 15 are switched.

[0028] More specifically, the electromagnetic valve 16 of this embodiment includes valve units 16A that block the flow paths 15, a valve unit magnetic material 16B attracted by the leakage flux to let the valve units 16A approach the magnetocaloric element filling unit 14, and springs 16C that separate the valve units 16A from the magnetocaloric element filling unit 14. The valve unit magnetic material 16B is configured by a magnetic material. The valve units 16A are configured by a material chemically insensitive to the heat exchange fluid.

[0029] As depicted in FIG. 1, with magnetic fields applied to the magnetocaloric element filling unit 14 by the first magnet 10A and by the second magnet 10B, the magnetocaloric element filling unit 14 generates a leakage flux. The leakage flux attracts the valve unit magnetic material 16B, causing the valve units 16A to approach the magnetocaloric element filling unit 14. The valve units 16A deblocks the first flow path 15A and blocks the second flow path 15B. The flow paths 15 can be switched in this manner.

[0030] When the magnetic fields are applied to the magnetocaloric element filling unit 14, all magnetic field lines emanating from the magnets 10 toward the magnetocaloric element filling unit 14 will pass therethrough in an ideal case. In this case, there is fear that the valve unit magnetic material 16B may be prevented from generating magnetic force strong enough to move the electromagnetic valve 16. In order to avert such an eventuality, the recessed and projected structure 14A may be configured in the magnetocaloric element filling unit 14 to deliberately generate the leakage flux. This makes it possible to provide magnetic force strong enough to operate the electromagnetic valve 16.

[0031] In a case where the magnetocaloric element filling unit 14 is filled with a granular magnetic material, an irregular surface of the material helps generate the leakage flux. Thus, in a case where the magnetocaloric element filling unit 14 is filled with a granular magnetic material, the recessed and projected structure 14A may not be necessary. Also, in a case where the magnetocaloric element filling unit 14 is filled with a magnetic material that is not granular, the recessed and projected structure 14A may be provided as described above to generate the leakage flux. Moreover, in a case where the magnetocaloric element filling unit 14 is filled with a granular magnetic material but the leakage flux is still low, the recessed and projected structure 14A may be additionally provided to increase the leakage flux.

[0032] FIG. 2 is a cross-sectional view depicting the electromagnetic valve 16 in a state of separation in the magnetic refrigeration apparatus 1 according to the embodiment.

[0033] As illustrated in FIG. 2, in a state where the first magnet 10A and the second magnet 10B are rotated by the rotation mechanism 12 in such a manner that magnetic fields are not applied to the magnetocaloric element filling unit 14, no leakage flux is generated from the magnetocaloric element filling unit 14. As a result, the springs 16C separate the valve units 16A from the magnetocaloric element filling unit 14. In turn, the valve units 16A block the first flow path 15A and deblock the second flow path 15B. The flow paths 15 can be switched in this manner.

[0034] In the magnetic refrigeration apparatus 1 of this embodiment, as explained above, the rotation by the rotation mechanism 12 of the first magnet 10A and the second magnet 10B is synchronized with the varying intensity of the leakage flux from the magnetocaloric element filling unit 14. The electromagnetic valve 16 is operated in synchronism with the intensity variation of the leakage flux to switch the flow paths 15. The embodiment thus can implement synchronization between rotation of the magnets 10 and switching of the flow paths 15 for the heat exchange fluid in a simple structure, which constitutes the magnetic refrigeration apparatus 1 that is easy to adjust at the time of manufacture.

[0035] FIG. 3 is a top view of the magnetocaloric element container 13 in the magnetic refrigeration apparatus 1 of the embodiment.

[0036] Explained below with reference to FIG. 3 is an exemplary positional relation between the magnetocaloric element filling unit 14 and the flow paths 15 for the heat exchange fluid in the magnetocaloric element container 13. This embodiment has, inside the magnetocaloric element container 13, the magnetocaloric element filling unit 14 shaped to be divided into four equal parts of a circle. Each of the four magnetocaloric element filling units 14 is connected with two first flow paths 15A and two second flow paths 15B. Each of the first flow paths 15A and the second flow paths 15B is provided with the electromagnetic valve 16, indicated in FIG. 1, halfway through a passage to the magnetocaloric element filling unit 14. Whereas the magnetocaloric element filling unit 14 of this embodiment is divided into four equal parts of a circle, the magnetocaloric element filling unit 14 may alternatively be divided into eight or 16 equal parts of a circle.

[0037] FIG. 4 is a top view depicting the positional relation between the main units of the magnetic refrigeration apparatus 1 of this embodiment.

[0038] Explained below with reference to FIG. 4 is the positional relation between the first magnets 10A and the magnetocaloric element filling unit 14. The magnetic yokes 11 connected to the rotating shaft 12B and the first magnets 10A are rotated at the top of the magnetocaloric element container 13. The magnetocaloric element filling unit 14 is provided in a region where the first magnets 10A connected to the magnetic yokes 11 pass while being rotated.

[0039] Explained next in detail is the heat exchange cycle for cooling by use of the magnetocaloric effect of the magnetic refrigeration apparatus 1 of this embodiment.

[0040] The magnetocaloric element filling unit 14 is filled with the magnetic material having the magnetocaloric effect. Preferably, this magnetic material may be a ferromagnetic material capable of providing a large magnetocaloric effect. Also, the Curie temperature may preferably be close to the temperature range primarily targeted by the magnetic refrigeration apparatus 1. For example, for use at or near the room temperature, gadolinium with a Curie temperature of approximately 19° C. may be adopted as the magnetic material capable of producing the temperature variation through a relatively large magnetocaloric effect. Alternatively, the magnetocaloric element filling unit 14 may be filled with a compound of gadolinium and some other metal attaining a suitable Curie temperature, a lanthanum-silicon-iron compound, a metal or a metal compound providing a large magnetocaloric effect near the room temperature, or a mixture of any of these materials.

[0041] The magnetic refrigeration apparatus 1 implements the cooling cycle by letting the heat exchange fluid flow in keeping with the temperature variation upon application and removal of magnetic fields to and from the magnetocaloric element filling unit 14 for heat exchange purposes. The magnetic fields are generated by the magnetic circuit configured by the magnetic yokes 11 connected to the rotating shaft 12B and by the magnets 10 connected to the magnetic yokes 11. Application and removal of the magnetic fields thus generated are carried out by rotation of the magnets 10. The magnetic yokes 11 are fabricated by an iron with few impurities or low-carbon steel, for example. In order to achieve high cooling performance, the magnets 10 are required to generate the strongest possible magnetic fields. For this reason, the use of neodymium-based magnets is preferred. Also, a magnetic flux may be arranged to be concentrated on the magnetocaloric element filling unit 14 as much as possible so as to apply much stronger magnetic fields. This arrangement may be implemented by configuring a magnetic circuit that uses Halbach array magnets, for example.

[0042] The heat exchange procedure in the magnetic refrigeration cycle is explained below. The above-mentioned magnetic circuit is used to apply the magnetic fields to the magnetocaloric element filling unit 14. This generates heat through the magnetocaloric effect. A first heat exchange fluid is then introduced into the magnetocaloric element filling unit 14 via the first flow path 15A to exchange the generated heat with the first heat exchange fluid. Next, the rotating shaft 12B rotates the magnetic circuit formed by the magnetic yokes 11 and magnets 10 in such a manner as to remove the magnetic fields applied to the magnetocaloric element filling unit 14. This absorbs the heat through the magnetocaloric effect. At this point, a second heat exchange fluid is introduced into the magnetocaloric element filling unit 14 via the second flow path 15B for heat exchange. Application and removal of the magnetic fields are synchronized with switching of the flow paths 15 to repeat heat exchange with the first and the second heat exchange fluids. This causes the temperature to rise in the first heat exchange fluid and to drop in the second heat exchange fluid. That is, the magnetic refrigeration cycle is realized in which the heat is transferred from the second heat exchange fluid to the first heat exchange fluid. The flow paths 15 are formed in such a manner that the first heat exchange fluid is introduced into an exhaust heat exchanger, not depicted, and that the second heat exchange fluid is led into a cold head, not depicted.

[0043] Here, the first and the second heat exchange fluids are fluids that permit efficient heat exchange with the magnetocaloric element. Whereas various types of fluids are usable as refrigerants or the like in general, the use of water with its low environmental impact is preferred in the magnetic refrigeration apparatus 1 targeted for operation near the room temperature. Also, if there is a possibility that the magnetic refrigeration apparatus 1 may be used near or below 0° C., a mixture of water and ethylene glycol may be employed. Moreover, if there is fear that the heat exchange fluid may produce reaction products such as rust when coming into contact with the magnetic material having the magnetocaloric effect, a rust inhibitor or the like may be added to the fluid. The first and the second heat exchange fluids are each introduced into the magnetocaloric element filling unit 14 for circulation using a circulating pump, for example. Alternatively, the same heat exchange fluid may be circulated in such a manner that the fluid functions as the first heat exchange fluid in one region and functions as the second heat exchange fluid in another region.

[0044] As described above, application and removal of the magnetic fields need to be synchronized with switching of the flow paths for the first and the second heat exchange fluids that are introduced into the magnetocaloric element filling unit 14. The flow paths are switched at the time when the magnetic fields are sufficiently applied to or removed from the magnetocaloric element filling unit 14. This can implement the above-described magnetic refrigeration cycle efficiently. The magnetic refrigeration cycle is realized by use of the electromagnetic valve 16 described above with reference to FIGS. 1 and 2. The workings of the electromagnetic valve 16 have thus been explained already and will not be discussed further.

[0045] In embodying the present invention as described above, the magnetic refrigeration apparatus 1 is configured to have the magnetocaloric element container 13 incorporating the structure for switching the flow paths 15 by means of the electromagnetic valve 16. The heat exchange is carried out in keeping with application and removal of the magnetic fields in a manner approaching a more ideal magnetic refrigeration cycle. The switching of the flow paths 15, which tend to be complicatedly structured to supply two kinds of heat exchange fluids to multiple magnetocaloric element filling units 14, can be implemented in a relatively shortened and simplified forms of the flow paths 15. These features combine to provide the magnetic refrigeration apparatus 1 that is small-sized but offers high cooling performance.

[0046] It is to be understood that, while the preferred embodiment of the present invention has been explained above in specific terms, the structures of this embodiment are not limitative of this invention. Diverse variations and alternatives are possible within the technical scope of the present invention. Also, part or all of the structures discussed above in conjunction with the embodiment may be combined suitably to devise other embodiments.

Claims

1. A magnetic refrigeration apparatus comprising:a first magnet;a second magnet placed opposite to the first magnet;a rotation mechanism configured to rotate the first magnet and the second magnet;a magnetocaloric element filling unit interposed between the first magnet and the second magnet and filled with a magnetic material having a magnetocaloric effect;a plurality of flow paths configured to let a fluid pass through to exchange heat with the magnetocaloric element filling unit; andan electromagnetic valve configured to switch the flow paths by approaching the magnetocaloric element filling unit when attracted by a leakage flux therefrom where the leakage flux is higher than a predetermined level and by being separated therefrom where the leakage flux is lower than the predetermined level.

2. The magnetic refrigeration apparatus according to claim 1,wherein the magnetic valve includes a valve unit configured to block the flow paths, a valve unit magnetic material attracted by the leakage flux to let the valve unit approach the magnetocaloric element filling unit, and a spring configured to separate the valve unit from the magnetocaloric element filling unit.

3. The magnetic refrigeration apparatus according to claim 1,wherein the magnetocaloric element filling unit is filled with a granular magnetic material.

4. The magnetic refrigeration apparatus according to claim 1,wherein the magnetocaloric element filling unit is filled with a ferromagnetic material formed of gadolinium or a metal compound including gadolinium.

5. The magnetic refrigeration apparatus according to claim 1,wherein the magnetocaloric element filling unit has a recessed and projected structure positioned opposite to the electromagnetic valve.

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