WO2012006752A2

WO2012006752A2 - Magnetic field generator, and magnetocaloric device comprising said magnetic field generator

Info

Publication number: WO2012006752A2
Application number: PCT/CH2011/000163
Authority: WO
Inventors: Osmann Sari; Nathanaël ALBER
Original assignee: Haute Ecole D'ingenierie Et De Gestion Du Canton De Vaud (Heig-Vd)
Priority date: 2010-07-15
Filing date: 2011-07-13
Publication date: 2012-01-19
Also published as: CH703452A1; EP2593944A2; WO2012006752A3

Abstract

The invention relates to a magnetic field generator (10) comprising an assembly of anisotropic permanent magnets (30) that define air gaps (40) within which the magnetic flux is concentrated. The permanent magnet assembly consists of two assembly elements (21, 22) mounted on a carrier (50) symmetrically relative to a central axis of symmetry (A-A) and perpendicular to a middle plane (B-B) of the air gaps (40). The carrier (50) includes two substantially identical portions, i.e. an upper portion (50a) and a lower portion (50b). The upper portion (50a) consists of two identical arms (51a, 51b) arranged symmetrically relative to the central axis of symmetry (A-A). The lower portion (50b) consists of two identical arms (52a, 52b) arranged symmetrically relative to the central axis of symmetry (A-A). The ends of the identical arms (51a, 51b) have two anisotropic permanent magnets (30), respectively, wherein said permanent magnets are provided in the form of parallelepiped or cubical blocks. The magnetic circuit generated in each of the arms is closed by an arcuate block (61, 62) that is made of a ferromagnetic material and mounted on the end faces of the corresponding permanent magnets (30).

Description

MAGNETIC FIELD GENERATOR AND MAGNETOCALORIC DEVICE COMPRISING SAID MAGNETIC FIELD GENERATOR Technical Field

The present invention relates to a magnetic field generator comprising an assembly of anisotropic permanent magnets arranged to create a magnetic flux and defining air gaps within which said magnetic flux is concentrated, said permanent magnet assembly comprising a first element of assembly and a second connecting element arranged symmetrically with respect to a central axis of symmetry, each of said first and second assembly members having at least two permanent magnets, wherein said permanent magnet assembly comprises a central support, symmetrically symmetrical, with respect to said central axis of symmetry, said central support consisting of an upper part and a lower part symmetrical with respect to the other, the upper part comprising two branches, symmetrical with respect to said central axis of symmetry and carrying the magnets of said first and second assembly members the lower part having two branches symmetrical with respect to said central axis of symmetry and carrying the magnets of said first and second connecting elements, wherein the permanent magnets of each of said first and second connecting elements are arranged symmetrically two by two by relative to a median plane of said gaps. It also relates to a magnetocaloric thermal device comprising at least one magnetocaloric element traversed by a heat transfer fluid, said magnetocaloric element being mounted on a rotary element alternately through said air gaps of a magnetic field generator. Prior art

In order to economically obtain a large magnetic field in a defined space, it is known to produce a permanent magnet assembly. The literature describes such assemblies in particular for an application in the field of medical magnetic resonance imaging. In this field, one makes permanent magnet crowns that are arranged side by side. The permanent magnets used, however, have a complex geometric structure difficult to achieve, which increases the cost of the assembly of magnets.

The transposition of such magnet structures is therefore not possible in the context of smaller volume applications, and in particular in the field of magnetocaloric thermal generators. Indeed, in these devices, it is essential to generate a uniform, intense magnetic field in an air gap corresponding to the volume of a magnetocaloric material or element so that the magnetic field created can successively activate and deactivate magnetically one or more magnetocaloric materials alternately introduced then removed from the air gap. In order to obtain a large magnetic field in a defined space, it is known to make an assembly of permanent magnets and to arrange them in such a way that the magnetic flux is concentrated in an air gap of reduced section. A magnetocaloric device is known comprising a support on which magnetocaloric elements are mounted and which moves alternately along a linear path in this gap.

This construction has several disadvantages, especially as regards the cost of operation. The reciprocal displacement of a part is caused by a linear motor, which represents a costly solution, both from a construction point of view and from the side of the use. In order to obtain a large magnetic field in a defined space, it is known to produce an assembly of permanent magnets according to a Halbarch structure. The literature, and particularly the publications, J. Lee, JM Kenkel and DC Jiles, Design of Permanent-Magnetic Field Source for Rotary Magnetic Refrigeration Systems, IEEE Trans Magn 38 5 (2002), pp. 2991-293, "K .Halbach, Nucl.Instr.Methods, vol.169, p.1, 1980 "," K.Halbach, Nucl.Instr.Methods, vol.187, p.109, 1981 "," F.BIoch, O.Gugat , JC.Toussaint and G. Meunier, IEEE Trans.Magn., Vol.34, p.2465, 1998 "," CERN Courier, vol.43, No.3, p.7, 2002 "and" SJLee and DCJiles, IEEE Trans Magn., Vol.36, No.5, p.3105, 2000 ", describes such assemblies especially for an application in the field of medical magnetic resonance imaging.

The judicious use of Halbach's structure makes it possible to obtain high magnetic fields in the air gap of magnetic sources based on permanent magnets. This configuration is used in particular in linear magnetic refrigeration systems (reciprocating) and difficult to exploit when it comes to rotating systems.

In order to obtain a large magnetic field, the current magnetic circuits, with regard to rotating circuits, are constructed from magnets assembled on a U-shaped structure. However, the latter form does not make it possible to reach levels of magnetic inductions in the gap with dimensions, shapes, size and reasonable cost.

The patent application US 2005/0242912 A1 describes a magnetic assembly which comprises two superimposed blocks which delimit an open slot in which the magnetic field generated by said magnetic assembly is concentrated. Various geometries are described, but none has a symmetry with respect to a central axis with two closed air gaps symmetrical about this axis and arranged in the same plane perpendicular to this axis. The patent application US 2005/0242912 A1 also describes a magnetic assembly similar to that of the patent application cited above. As before, the air gaps are open towards the outside of the permanent magnet block, so that there is leakage of magnetic flux and that the concentration of the magnetic field generated is not optimal in the gaps.

In order to cope with this problem, the present invention, adapted to the rotary system, makes it possible to approach the Halbach structure and thus to close the magnetic circuit (magnetic flux) on itself and thus to guarantee magnetic inductions. higher for simpler geometric configurations, more compact and inexpensive.

Presentation of the invention

The present invention aims at overcoming the disadvantages of the prior art by proposing a generator arranged to generate an intense and uniform magnetic field, easy to produce and having a low cost price in order to equip a compact and economical magnetocaloric device for the cold generation.

For this purpose, the invention relates to a magnetic field generator as defined in the preamble and characterized in that each of said assembly elements of the permanent magnet assembly comprises at least two permanent magnets, of opposite magnetic polarity, and one closing element of the magnetic circuits generated in the form of a block of ferromagnetic material and in that the air gaps of said first and second connecting elements, diametrically opposed with respect to said central axis of symmetry, are closed relative to the outside of said assembling magnets by said block of ferromagnetic material. According to a preferred embodiment of the invention, the support of the magnetic field generator comprises an upper part and a lower part, each of these parts comprising four identical branches arranged symmetrically with respect to the central axis of symmetry, these identical branches. each being composed of upper arms and identical lower arms, the axial planes of which form acute angles between them.

In this embodiment, each of the parts of the support further comprises two intermediate arms disposed respectively between the upper arms and the lower arms of the support.

Advantageously, the acute angles that form between them said axial planes of said upper arms and said lower arms are substantially between 10 and 120 degrees, and preferably between 10 and 45 degrees.

The upper arms and the lower arms of the symmetrical portions of the support each carry two permanent magnets of opposite magnetic polarity, the intermediate arms each carry a permanent magnet, and the magnetic circuit generated in each of said arms is closed by an arched block made of a material ferromagnetic and mounted on the end faces of the corresponding permanent magnets.

The magnetocaloric thermal device as defined in the preamble is characterized in that said magnetic field generator comprises an assembly of anisotropic permanent magnets arranged to create a magnetic flux and defining air gaps inside which said magnetic flux is concentrated, said assembly permanent magnet assembly comprising a first connecting element and a second connecting element mounted symmetrically with respect to a central axis of symmetry and each of said first and second connecting elements comprising at least two permanent magnets of opposite magnetic polarity, in which said assembly of permanent magnets comprises a central support, symmetrical with respect to said central axis of symmetry, said central support consisting of an upper part and a lower part, each of these parts comprising four identical branches arranged symmetrically with respect to the central axis of symmetry, said identical branches being each composed of identical upper arms and lower arms, carrying the magnets of said first and second assembly elements, and whose axial planes form acute angles between them, in that each of the parts the support further comprises two intermediate arms respectively arranged between the upper arms and the lower arms of said support, in that the air gaps of said first and second connecting elements are diametrically opposite with respect to said central axis of symmetry, in that the magnets of each of said first and second connecting members are arranged symmetrically rally two to two with respect to a median plane of said air gaps, and in that the magnetic circuit generated in each of said arms is closed by an arcuate block made of a ferromagnetic material and mounted on the end faces of the corresponding permanent magnets.

Brief description of the drawings

The present invention and its advantages will appear better in the following description of an embodiment given by way of non-limiting example, with reference to the appended drawings, in which: FIG. 1 is a schematic view of a first embodiment 2 is a side elevational view of a second embodiment of a magnetic field generator according to the invention; FIGS. 3A and 3B are views of a magnetic field generator according to the invention; plan respectively from above and from below of the embodiment represented by FIG. FIG. 4 shows the magnetic flux lines generated by the embodiment illustrated in FIGS. 2 and 3, FIG. 5 is a perspective view of a magnetocaloric device using the magnetic field generator of FIGS. 2 to 4, and FIG. Figure 6 is a side elevational view of the device of Figure 5.

Best ways to achieve the invention

FIG. 1 represents an elementary embodiment of a magnetic field generator 10 according to the invention. In this case, this magnetic field generator 10 is composed of an assembly of anisotropic permanent magnets arranged to create a magnetic flux and to define air gaps 40 inside which the magnetic flux is concentrated. The permanent magnet assembly consists of two connecting elements 21 and 22 mounted on a support 50, symmetrically with respect to a central axis of symmetry AA, perpendicular to a median plane BB of the gaps 40. In this embodiment, the support 50 comprises two substantially identical parts, a part 50a, said upper part, and a part 50b, said lower part. The upper part 50a consists of two identical branches 51a and 51b, symmetrical with respect to the axis of symmetry AA. Similarly, the lower part 50b consists of two identical branches 52a and 52b, symmetrical with respect to the axis of symmetry AA. The ends of the identical branches 51a and 51b respectively carry two anisotropic permanent magnets 30 having the shape of parallelepiped or cubic blocks and, symmetrically, the ends of the identical branches 52a and 52b respectively bear two anisotropic permanent magnets 30 also having the shape of blocks. parallelepipedic or cubic. To close the magnetic circuits of the connecting elements 21 and 22, a block of a ferromagnetic material 61, respectively 62, is mounted on the end faces two permanent magnets 30. The two blocks of ferromagnetic material 61 and 62 are called closure blocks of the magnetic circuits and have the function of channeling the magnetic flux. The embodiment of the generator according to the invention illustrated by FIGS. 2, 3A and 3B is more elaborate than that of FIG. 1, but substantially implements the same principles. As before, the magnetic field generator 100 comprises an assembly of anisotropic permanent magnets arranged to create a magnetic flux and to define air gaps 40 inside which the magnetic flux generated is concentrated. The assembly of permanent magnets consists of two assembly elements 21 and 22, mounted on a support 50 and arranged symmetrically with respect to an axis of symmetry AA, perpendicular to the median plane BB of the gaps 40.

The support 50 comprises, as before, an upper part 50a and a lower part 50b, which are identical and symmetrically arranged with respect to the median plane BB of the air gaps 40, each of these parts comprising four identical branches 51a, 51 ', 51b , 51'b, for the upper part 50a, and 52a, 52'a, 52b, 52'b, for the lower part 50b, arranged symmetrically with respect to the axis of symmetry AA. The four identical branches 51a, 51a and 51b, 51b of the upper part 50a and of the lower part 50b are arranged symmetrically with respect to the axis of symmetry AA and are angularly separated, said acute angles forming between them said axial planes being substantially between 10 and 120 degrees, and preferably between 10 and 45 degrees. These identical branches 51 a, 51 'a and 51 b, 51' b respectively 52a, 52'a and 52b, 52'b are each terminated by an arm, 510a, 51a and 510b, 51b respectively 520a, 521a and 520b, 521b, arranged to carry the permanent magnets 30. Each part of the support 50 is further provided with two intermediate arms 512a, 512b, respectively 522a, 522b, placed and secured by magnetic attraction of a support 20a, respectively 20b, in the shape of a circular arc of trapezoidal section. These arms intermediates are angularly arranged equidistantly, that is to say, centered longitudinally on the axis BB, between the arms 510a and 51a, respectively 510b and 51b and between the arms 520a and 521a. The arms 510a, 510b, 51a, 51b, respectively 520a, 521a and 520b, 521b, each carry two permanent magnets 30 in the form of parallelepipedal or cubic blocks which are placed so that the magnetic fields are opposite polarity, the intermediate arms 512a and 512b, respectively 522b and 522b, carrying only one permanent magnet. The magnetic circuits generated in each of the arms are closed by blocks of ferromagnetic materials to best prevent magnetic flux losses. The arms 510a, 51a have branches 51a and 51a and the intermediate arm 512a of the upper part 50a are respectively connected to the corresponding arms 520a, 521a and 522a of the lower part 50b by arcuate blocks 610, 61 and 612 of ferromagnetic material, and the arms 510b, 51 1b of the branches 51b and 51'b as well as the intermediate arm 512b are respectively connected to the corresponding arms 520b, 521b and 522b of the lower part 50b by arcuate blocks 620 , 621 and 622 of ferromagnetic material.

Note that the intermediate arms 512a, 512b and the corresponding arms 522a and 522b of the lower part 50b are not essential, intermediate magnets can be maintained under the effect of magnetic attraction in the space delimited by the side arms and magnet blocks supported by these arms. These intermediate magnets, whether or not carried by intermediate arms, have the effect of reinforcing the power of the magnetic field in the air gaps, which improves the efficiency of the magnetocaloric device. Moreover the number of arms of each branch is limited only by dimensional and constructive reasons. Their number could be increased to reach higher powers. FIG. 4 represents the magnetic flux lines generated by this embodiment as illustrated by FIG. 3 along line EE. The arrangement and orientation of the magnets are of great importance. They make it possible to close the magnetic field on itself and thus to concentrate the magnetic flux in the air gaps 40. It can thus be seen that these flux lines are concentrated at the air gaps 40. The upper portions 50a and 50b that serve to closing the magnetic field and the arcuate blocks 61 1 and 621 made of a ferromagnetic material make it possible to produce regular magnetic flux loops, concentrated only in the volume of the magnetic field generator, which are predominant and uniformly distributed in the gaps 40 This gives a generator capable of generating an intense field in its air gaps 40 despite the use of a reduced number of permanent magnets which have the advantage of having an easy and economical manufacturing structure.

The magnetic field generators 10 and 100 described above are in particular usable in a magnetocaloric thermal device comprising at least one magnetocaloric element. This magnetocaloric element may be constituted by one or more magnetocaloric materials and is traversed by a circulating heat transfer fluid whose particular function is to evacuate the calories generated during the passage of the magnetocaloric elements in the air gaps 40.

The magnetocaloric device 200 illustrated in FIGS. 5 and 6 and using the magnetic field generator 100 according to the invention comprises a central shaft 70 corresponding to the axis of symmetry AA, on which is mounted a wheel 80 which serves as support for elements 81 in one or more magnetocaloric materials. The elements 81 in magnetocaloric materials are located in the peripheral zone of the wheel 80, that is to say the one which passes through the air gaps 40 of the magnetic field generator 100 as described with reference to FIGS. 2 to 4. The construction of this device is symmetrical. The movement of the wheel 80 carrying the magnetocaloric elements 81 is a continuous rotation whose speed is determined in such a way that the heat exchange at a circulating heat transfer fluid, in a manner known per se in contact with said magnetocaloric elements 81, be optimal. Depending on whether the device 200 is used in a heating system or a cold generator, the calories produced during the passage of the magnetocaloric elements 81 are either used or eliminated. Possibilities of industrial application

It is clear from this description that the invention achieves the goals set, namely to propose a generator for generating a magnetic field whose realization is structurally simple and economical and which allows to obtain a large magnetic field with relatively few magnetic matter. Such a generator can in particular find an industrial as well as domestic application when it is integrated in a magnetocaloric heat generator intended to be used in the field of heating, air conditioning, tempering, cooling or other, at competitive costs and with a small footprint.

Claims

claims

1. Magnetic field generator (10) comprising an assembly of anisotropic permanent magnets arranged to create a magnetic flux and defining air gaps (40) within which said magnetic flux is concentrated, said permanent magnet assembly comprising a first an assembly member (21) and a second connecting member (22) arranged symmetrically about a central axis of symmetry (AA), each of said first (21) and second (22) connecting members having at least two permanent magnets (30), wherein said permanent magnet assembly comprises a central support (50), symmetrical about said central axis of symmetry (AA), said central support consisting of an upper portion (50a) and a lower portion (50b) symmetrical relative to each other, the upper portion (50a) having two legs (51a, 51b), symmetrical with respect to said central axis of symmetry (AA) and carrying them said first (21) and second (22) connecting members, the lower portion (50b) having two legs (52a, 52b), symmetrical about said central axis of symmetry (AA) and carrying the magnets of said first (21) ) and second (22) connecting elements, wherein the permanent magnets (30) of each of said first (21) and second (22) connecting elements are arranged symmetrically in pairs relative to a median plane of said air gaps ( 40), characterized in that each of said assembly members (21, 22) of the permanent magnet assembly comprises at least two permanent magnets (30) of opposite magnetic polarity and a closing element of the magnetic circuits generated under the shape of a block of ferromagnetic material (61, 62) and in that the air gaps (40) of said first (21) and second (22) connecting elements, diametrically opposed with respect to said central axis of symmetry (AA) are closed compared outside said magnet assembly by said block of ferromagnetic material.

Magnetic field generator (100) according to claim 1, characterized in that the support (50) comprises an upper part (50a) and a lower part (50b), each of these parts comprising four identical branches (51a, 51'a , 51b, 51 'b, 52a, 52'a, 52b, 52'b), arranged symmetrically with respect to the central axis of symmetry (AA), these identical branches being each composed of upper arms (510a, 510b, 511a). 511b) and lower arms (520a, 520b; 521a, 521b) whose axial planes form acute angles between them.

Magnetic field generator (100) according to claim 2, characterized in that each of the portions of the support (50) further comprises two intermediate arms (512a, 512b, 522a, 522b) respectively arranged between the upper arms (510a, 510b, 511a, 511b) and the lower arms (520a, 520b; 521a, 521b) of said support (50),

Magnetic field generator (100) according to claim 2, characterized in that said acute angles that form between them said axial planes of said upper arms (510a, 510b, 511a, 511b) and said lower arms (520a, 520b, 521a, 521b) are substantially between 10 and 120 degrees, and preferably between 10 and 45 degrees.

Magnetic field generator (100) according to claims 1 and 2, characterized in that said upper arms (510a, 510b, 511a, 511b) and said lower arms (520a, 520b, 521a, 521b) of the symmetrical portions (50a, 50b ) of the support (50), each carry two permanent magnets (30), of opposite magnetic polarity, in that the intermediate arms (512a, 512b, 522a, 522b) each carry a permanent magnet (30), and that the magnetic circuit generated in each of said arms is closed by an arcuate block (610, 611, 612, 620, 621, 622) made of a material ferromagnetic and mounted on the end faces of the corresponding permanent magnets (30).

6. A magnetocaloric heat device (200) comprising at least one magnetocaloric element (81) through which a heat transfer fluid passes through, said magnetocaloric element (81) being mounted on a rotary element (80) alternately passing through the air gaps of a magnetic field generator, characterized in that said magnetic field generator (100) comprises an assembly of anisotropic permanent magnets (30) arranged to create a magnetic flux and defining air gaps (40) within which said magnetic flux is concentrated, said assembly of permanent magnets having a first connecting member (21) and a second connecting member (22) mounted symmetrically with respect to a central axis of symmetry (AA) and each of said first (21) and second (22) elements assembly comprising at least two permanent magnets (30) of opposite magnetic polarity, wherein said permanent magnet assembly comprises a support c entral (50), symmetrical about said axis of symmetry (AA), said central support consisting of an upper part (50a) and a lower part (50b), each of these parts having four identical branches (51a, 51 'a, 51b, 51'b, 52a, 52'a, 52b, 52'b) arranged symmetrically with respect to the axis of symmetry (AA), said identical branches being each composed of upper arms (510a, 510b , 511a, 511b) and lower arms (520a, 520b; 521a, 521b), carrying the magnets of said first (21) and second (22) connecting elements, the axial planes of which form acute angles between them, and in that each of the parts of the support (50) further comprises two intermediate arms (512a, 512b, 522a, 522b) respectively arranged between the upper arms (510a, 510b, 511a, 511b) and the lower arms (520a, 520b; 521a, 521b) of said support (50), that the air gaps (40) of said first (21) and second (22) connecting elements are diametrically opposed with respect to said axis of symmetry (AA), in that the magnets of each of said first (21) and second (22) connecting elements are arranged symmetrically two by two with respect to a median plane of said air gaps (40), and in that the magnetic circuit generated in each of said arms is closed by an arcuate block (610, 611, 612, 620, 621,

622) made of a ferromagnetic material and mounted on the end faces of the corresponding permanent magnets (30).