CH712192A1 - Method for generating a magnetic field and rotating magnetic field generator - Google Patents

Abstract

The invention relates to a method for generating a magnetic field and a rotary magnetic field generator (10) comprising a fixed stator and a rotor coaxially mounted inside said fixed stator. It is in the form of a compact block (11) of generally cylindrical shape, clamped between two end plates (12 and 13) of substantially circular shape. The generator (10) is provided at its periphery with longitudinal grooves or air gaps, for example at the number of four air gaps which cut the peripheral surface of both the block (11) and the two end plates (12 and 13) in order to to form surface dwellings whose function is to contain bars of magnetocaloric material. Said stator comprises magnets arranged to produce a magnetic induction of constant value and said rotor comprising magnets arranged to produce a magnetic induction of value. The magnetic field generated by said rotor alternately has a polarity determined on half of said cycle and a reverse polarity on the other half of said cycle.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for generating a magnetic field by means of a rotating magnetic field generator comprising a fixed stator and a rotor mounted coaxially inside said fixed stator, said stator comprising magnets arranged for producing a constant-value magnetic induction (B0) and said rotor having magnets arranged to produce a magnetic value induction (Bi).

It also relates to a rotary magnetic field generator, said magnetic field generator comprising a fixed stator and a rotor mounted coaxially inside said fixed stator, said stator comprising magnets arranged to produce a magnetic induction of constant value ( B0) and said rotor having magnets arranged to produce a magnetic value induction (B ·,).

PRIOR ART [0003] Many magnetic permanent magnet systems make it possible to produce a constant magnetic induction field in a given air gap. To vary the amplitude of the magnetic field, electromagnets are generally made, which make it possible to adjust the amplitude of the field by the current. For the high values of the magnetic induction field, especially for values greater than 1 Tesla and / or for large air gaps, the electromagnet with its power supply system is bulky, energy-consuming and expensive.

[0004] It is well known to produce a magnetic field having a certain magnetic induction, for example greater than 1 tesla. Nevertheless, its instantaneous cancellation of the magnetic field in an air gap by means of permanent magnets is non-existent.

It is well known to produce cold by means of a refrigeration device magnetocaloric type. In this application, it is necessary to generate a large magnetic field variation between 0 and 1 Tesla, or even 2 Tesla, for example. The useful heat output and thermal efficiency of existing devices are limited due to some key components, such as the magnetic field generator, the characteristics of magnesium-to-calcium elements and the thermal capacity of the heat exchangers.

It is known that one can increase the power of magnetocaloric devices by increasing the amplitude of the magnetic field. Indeed, the greater the variation of the magnetic field, the greater the magneto-caloric effect is important, so that one can substantially increase the thermal power and therefore the output of a magnetocaloric thermal device, by increasing the magnetocaloric effect. intensity of the magnetic field.

For practical reasons, this increase in the magnetic field must be done by means of a magnetic field generator having a small footprint, easy to achieve and whose industrial production is economical.

DISCLOSURE OF THE INVENTION [0008] The present invention proposes to meet these requirements by producing a permanent magnet magnetic field generator generating a magnetic field of high value and variable in a gap, simple and economical construction and can be used in various fields, such as in a magnetorororic type cold generating device.

For this purpose, the method according to the invention is characterized in that said rotor is rotated relative to said stator, each complete revolution of said rotor around said stator defining a cycle of said magnetic field generator, and in the course of each of said cycles, the magnetic field generated by said rotor having alternately a polarity determined on half of said cycle and an inverse polarity on the other half of said cycle, such that on each cycle of said generator, said generated magnetic field varies substantially between a first value (B0 - B ·,) and a second value (B0 + B ·,).

According to an advantageous embodiment, said rotor is driven by a drive member independent of said magnetic field generator.

Preferably, said value (B-ι) produced by the magnets of the rotor is equal to the value (B0) produced by the magnets of the stator, so that said first value (B0-B ·,) is zero and said second value (B0 + Bi) is equal to 2 B0.

Advantageously, said magnetic field generated by said stator is produced by making a stack of annular ferromagnetic sheets, in that said stator is provided with a set of regularly distributed longitudinal cavities parallel to the axis of the stator. , and containing at least one permanent magnet separated by air gaps.

Advantageously, the rotor is constituted by means of a ferromagnetic carcass on which is formed several magnet rings juxtaposed, parallel to each other and each having a series of identical magnets arranged in an NS orientation on one half of the periphery of the corresponding ring and a series of magnets arranged in an opposite orientation, ie SN on the other half of the periphery of said ring.

Advantageously, permanent magnets in the form of curved tiles are used with a curvature equivalent to that of the peripheral curvature of said ferromagnetic carcass.

On each ring can be shifted magnets at a specific angle relative to adjacent magnets adjacent rings.

Advantageously, said rotor is driven by means of an electric drive motor coaxially mounted to said magnetic field generator, said electric drive motor comprising a rotor and a stator, said rotor being fixed to said rotor. said magnetic field generator and said stator being mounted on said stator of said generator.

In the context of an application in a magnetocaloric thermal apparatus, air gaps are provided at the periphery of said stator of the magnetic field generator, in said stack of annular ferromagnetic sheets, said air gaps being parallel to the axis of said stator and regularly distributed on the periphery of said stator.

For this purpose also the device according to the invention is characterized in that said rotor is rotated relative to said stator, each complete revolution of said rotor around said stator defining a cycle of said magnetic field generator (10), and during each of said cycles, the magnetic field generated by said rotor having alternately a determined polarity on the half of said cycle and an inverse polarity on the other half of said cycle, such that on each cycle of said generator, said magnetic field generated varies substantially between a first value (B0 -B-ι) and a second value (B0 + Bi).

According to a preferred embodiment, said stator comprises a stack of annular ferromagnetic sheets to form said annular-shaped stator and comprises a set of longitudinal cavities parallel to each other and to the axis of the stator, regularly distributed said cavities respectively housing at least one permanent magnet.

In this embodiment, said rotor advantageously comprises a ferromagnetic carcass on which are arranged several juxtaposed magnet rings each comprising a series of permanent magnets arranged in an NS orientation on one half of the periphery of each ring and a series identical permanent magnets disposed in an opposite orientation, SN on the other half of the periphery of said ring.

The permanent magnets of each of said rings are preferably in the form of curved tiles with a curvature equivalent to that of the peripheral curvature of said ferromagnetic carcass of said rotor.

On each ring the permanent magnets are preferably offset by a given angle relative to adjacent magnets adjacent rings.

The generator preferably comprises an electric drive motor which drives said rotor, said electric drive motor being coaxially mounted to said rotary magnetic field generator, said electric drive motor comprising a rotor and a stator, said rotor being attached to said rotor of said generator and said stator being mounted on said stator of said rotary generator.

For an application in an apparatus, an application in a magnetocaloric thermal apparatus, air gaps are provided at the periphery of said stator of the magnetic field generator, in said stack of annular ferromagnetic sheets, said air gaps being parallel to the axis of said stator and regularly distributed to the periphery of said stator.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention and its advantages will become more apparent in the following description of embodiments given by way of nonlimiting example, with reference to the appended drawings, in which: FIG. 1 represents a magnetic field generator according to the invention, viewed in perspective from one side of said generator, FIG. 2 represents the magnetic field generator of FIG. 1, seen in perspective on the opposite side, FIG. 3 represents the magnetic field generator of the preceding figures, seen in exploded perspective, FIG. 4 is a perspective view of the rotor of the magnetic field generator of FIGS. 1-3, and FIGS. 5A and 5B respectively represent front views and longitudinal section of the magnetic field generator according to the invention, equipped with a rotor drive motor.

Illustrations of the invention and different ways of carrying it out With reference to the figures, the method according to the invention is based on the fact that said rotor is rotated with respect to said stator, each complete revolution of said rotor around said stator defining a cycle of said magnetic field generator, and that during each of said cycles, the magnetic field generated by said rotor having alternately a polarity determined on half of said cycle and a reverse polarity on the other half of said cycle, such so that on each cycle of said generator, said generated magnetic field varies substantially between a first value (BO - Bi) and a second value (B0 + Bi). The general case corresponds to the one where the values B0 and B-i are different. The particular preferred case is that in which the two values B0 and B-, magnetic inductions of the stator and the rotor are equal.

In the preferred case, a constant magnetic field of determined value B0 is produced by means of a fixed member and a field of the same intensity as that produced by means of a stationary or movable member is produced. of the field produced by the stator B0, but alternatively variable between said positive determined value + Bo (North-South or South-North) and negative -B0 (South-North or North-South), so that on a part of the cycle of operation said magnetic field varies between a zero value and a value: 2 B0.

By way of non-limiting example, if the value B0 is equal to 0.5 Tesla, the operational value of the magnetic field will be in one of the gaps of 1 Tesla and in the other of 0 Tesla. If the magnetic induction values of the rotor and the stator are equal to 1 Tesla, the extreme values will go from = to 2 Tesla and vice versa.

The implementation of this method makes it possible to construct a compact, relatively simple and inexpensive magnetic field generator with a high efficiency and whose application, especially in magnetronoretic effect cooling machines, is particularly advantageous because that it solves one of the critical problems of these machines namely the generation of an intense magnetic field with economic means and compact construction.

FIG. 1 is a perspective view showing a first embodiment of a compact magnetic field generator 10 according to the invention. This magnetic field generator 10 is in the form of a compact block 11 of generally cylindrical shape, clamped between two end plates 12 and 13 of substantially circular shape. The generator 10 is provided at its periphery with longitudinal grooves (gap) 14, for example at the number of four gaps that cut the peripheral surface of both the block 11 and the two end plates 12 and 13 to a certain depth radial designed to form surface housing whose function is to contain bars of magnetocaloric material by way of example.

FIG. 2 is an exploded perspective view of the magnetic field generator 10 of FIG. 1. It consists essentially of a stator 20 and a rotor 30 which is mounted coaxially inside the stator 20. The stator 20 consists of the compact block 11 formed of a stack of ferromagnetic sheets 21 stamped by stamping in flat sheet metal plates and pressed against each other to form said compact block 11. The ferromagnetic sheets 21 are cut so as to alternately provide one of the longitudinal grooves or air gap 14, regularly spaced at the periphery of the block 11, and two longitudinal cavities 22. The air gaps 14 and the longitudinal cavities 22 pass through the compact block 11, parallel to its central axis. In the example shown, the compact block 11 comprises four gaps 14 and eight longitudinal cavities 22, each air gap 14 is associated with two longitudinal cavities 22 respectively disposed on either side of one of each of the air gaps 14. In each of said longitudinal cavities 22 is housed at least one permanent magnet 23, that is to say eight in all, in the present embodiment. The longitudinal cavities 22 advantageously have a rectangular cross-section dimensioned so that the permanent magnets 23, which also have a rectangular cross section, can be housed inside and tightly fitted. During assembly, the two end plates 12 and 13, applied against the compact block 11, close the ends of the longitudinal cavities 22. These longitudinal cavities 22 are also closed on the top by an overflow of the ferromagnetic sheets 21 stacked . Due to the presence of the longitudinal cavities 22 and the longitudinal grooves 14, the block 11 stacked ferromagnetic sheets 21 is subdivided into pads 24 of substantially identical trapezoidal section. A portion of these studs 24, very precisely those which border respectively on either side of the gaps 14 are traversed from one side in the longitudinal direction by a cylindrical bore 25 intended to receive respectively a through rod 26 mounted on the two plates ends 12 and 13, by means of clamping bolts 27 housed in circular openings 28, of suitable dimensions, passing through said end plates 12 and 13. The means for machining and manufacturing these components and the means for The necessary assemblies make it possible to produce a compact block 11 that is inexpensive and requires virtually no maintenance.

The rotor 30, shown in the exploded view of FIG. 3 and only in the perspective view of FIG. 4, comprises a central shaft 31 surrounded by a coaxial ferromagnetic yoke 32 carrying two identical sets 33a and 33b of permanent magnets 34a and 34b bonded to the surface of said ferromagnetic yoke 32, the permanent magnets 34a and 34b of each of the two sets 33a and 33b having opposite polarities. The individual permanent magnets 34a and 34b are identical in shape, which is that of a substantially rectangular tile, curved lengthwise to be plated on the surface of said cylindrical ferromagnetic yoke 32. The permanent magnets 34a and 34b are positioned to form rings 35 juxtaposed in the direction of the length of the peripheral surface of the ferromagnetic yoke 32. On each ring the permanent magnets 34a and 34b are substantially butt-fitted in the direction of the length, but with a small space to facilitate their assembly. Each ring 35 which consists of a row of permanent magnets 34a and 34b, comprises a half of magnets oriented North-South, which represent a half-length of the ring 35 and a half of magnets oriented South-North , which represent the other half-length of the ring 35. The rings 35 are all juxtaposed and cover the entire peripheral surface of the ferromagnetic yoke 32. The permanent magnets of each ring 35 are offset relative to the magnets of the ring next, advantageously of the order of 5 ° and the total offset magnets of the first ring

Claims (16)

35 relative to the magnets of the last ring 35 is of the order of 30 °. This offset has the advantage of reducing the driving torque of the rotor 30, with respect to the stator 20. The rotor 30 is mounted in the central cylindrical opening 29 formed in the block 11 of the stator 20. The space between the inner wall of the central cylindrical opening 29 and the peripheral wall of the rotor 30 is as narrow as possible. The rotational guidance of the rotor 30 is carried out thanks to the very precise positioning of the central shaft 31 on its two end pieces 36a and 36b which are held by respective bearings 37a and 37b mounted on rings 38 on the two plates ends 12 and 13 by means of bolts or the like. Figs. 5A and 5B show the magnetic field generator 10 according to the invention equipped with an electric motor 40 for rotating the rotor 30. The electric motor 40 is mounted coaxially on the generator 10 and comprises a stator 41 which is mounted on the stator 20 of the generator 10 and a central rotor 42 which is integral with the rotor 30 of said generator 10. The central rotor 42 of the drive motor 40 is fixed by means of bolts to the ferromagnetic yoke 32 of the rotor 30. The body of the stator 41 of the drive motor 40 is fixed by means of bolts 44 to the end plate 12 of the stator 20 of said magnetic field generator 10. This relatively simple construction allows for an extremely compact and efficient assembly, easy to assemble and economical to manufacture. The present invention is not limited to the embodiments described but extends to any modification and variation obvious to a person skilled in the art while remaining within the scope of protection defined in the appended claims. claims A method for generating a magnetic field by means of a rotating magnetic field generator having a fixed stator and a rotor coaxially mounted within said fixed stator, said stator including magnets arranged to produce a constant-value magnetic induction ( B0) and said rotor comprising magnets arranged to produce a magnetic value induction (B-ι), characterized in that said rotor is rotated with respect to said stator, each complete revolution of said rotor around said stator defining a cycle of said generator magnetic field, and during each of said cycles, the magnetic field generated by said rotor having alternately a determined polarity on the half of said cycle and an inverse polarity on the other half of said cycle, such that on each cycle of said generator , said generated magnetic field varies substantially between a first value (B0 - B ·,) and a second value (B0 + B ·,). 2. Method according to claim 1, characterized in that said rotor is driven by a drive member independent of said magnetic field generator. 3. Method according to claim 1, characterized in that said value (B-ι) produced by the magnets of the rotor is equal to the value (B0) produced by the magnets of the stator, so that said first value (B0 - B ·,) Is zero and said second value (B0 + B ·,) is equal to 2 B0. 4. Method according to claim 1, characterized in that said magnetic field generated by said stator is produced by performing a stack of annular ferromagnetic plates, in that a statically distributed longitudinal cavity is housed in said stator, parallel to the axis of the stator, and containing at least one permanent magnet separated by air gaps. 5. Method according to claim 1, characterized in that said rotor is constituted by means of a ferromagnetic carcass on which is formed several magnet rings juxtaposed, parallel to each other and each having a series of identical magnets arranged in an NS orientation on one half of the periphery of the corresponding ring and a series of magnets disposed in opposite orientation, SN on the other half of the periphery of said ring. 6. Method according to claim 5, characterized in that permanent magnets are used in the form of curved tiles with a curvature equivalent to that of the peripheral curvature of said ferromagnetic carcass. 7. Method according to claim 5, characterized in that on each ring the magnets are shifted by a given angle relative to adjacent magnets adjacent rings. 8. The method as claimed in claim 2, characterized in that said rotor is driven by means of an electric drive motor coaxially mounted to said magnetic field generator, said electric drive motor comprising a rotor and a rotor. stator, said rotor being fixed to said rotor of said magnetic field generator and said stator being mounted on said stator of said generator. 9. Method according to claim 4, characterized in that, for an application in a magneto-caloric thermal apparatus, air gaps (14) are housed at the periphery of said stator of the magnetic field generator, in said stack of ferromagnetic sheets. annular, said air gaps being parallel to the axis of said stator and regularly distributed at the periphery of said stator. 10. Rotating magnetic field generator (10), said magnetic field generator (10) comprising a fixed stator and a rotor coaxially mounted inside said fixed stator, said stator comprising magnets arranged to produce a magnetic induction of constant value (B0) and said rotor comprising magnets arranged to produce a magnetic value induction (B-ι), characterized in that said rotor is rotated with respect to said stator, each complete revolution of said rotor around said stator defining a cycle of said magnetic field generator (10), and during each of said cycles, the magnetic field generated by said rotor having alternately a determined polarity on half of said cycle and a reverse polarity on the other half of said cycle, so that on each cycle of said generator, said generated magnetic field varies substantially between a first value (B0-Bi) and a second value (B0 + B ·,). 11. rotary magnetic field generator (10) according to claim 10, characterized in that said stator comprises a stack of annular ferromagnetic sheets to form said annular-shaped stator and comprises a set of longitudinal cavities parallel to the axis of the stator , regularly distributed said cavities respectively housing at least one permanent magnet. Rotational magnetic field generator (10), according to claim 10, characterized in that said rotor comprises a ferromagnetic carcass on which are arranged a plurality of juxtaposed magnet rings each comprising a series of identical permanent magnets arranged in a NS orientation on one half of the periphery of each ring and a series of identical permanent magnets arranged in an opposite direction, SN on the other half of the periphery of said ring. Rotational magnetic field generator (10), according to claim 10, characterized in that the permanent magnets of each of said rings are shaped curved tiles with a curvature equivalent to that of the peripheral curvature of said ferromagnetic carcass of said rotor. Rotational magnetic field generator (10), according to claim 10, characterized in that on each ring the permanent magnets are offset by a given angle with respect to adjacent magnets of the adjacent rings. Rotational magnetic field generator (10), according to claim 11, characterized in that it comprises an electric drive motor which drives said rotor, said electric drive motor being mounted coaxially with said field generator rotary magnetic motor, said electric drive motor having a rotor and a stator, said rotor being fixed to said rotor of said generator and said stator being mounted on said stator of said rotary magnetic generator (10). Rotational magnetic field generator (10), according to claim 11, characterized in that for an application in a magnetocaloric thermal apparatus, said magnetic field generator comprises air gaps (14) at the periphery of said stator, said air gaps (14). ) being parallel to the axis of said stator and regularly distributed at the periphery of said stator.