EP2038988A1

EP2038988A1 - Active element for an electromagnetic machine, production method thereof and electromagnetic machine including one such active element

Info

Publication number: EP2038988A1
Application number: EP07803797A
Authority: EP
Inventors: Nicolas Ziegler; Daniel Matt
Original assignee: Messier Dowty SA
Current assignee: Safran Landing Systems SAS
Priority date: 2006-07-12
Filing date: 2007-06-28
Publication date: 2009-03-25
Also published as: JP2009543536A; CA2657451A1; ZA200900377B; RU2009104694A; FR2903823A1; BRPI0714245A2; US8981604B2; IL196412A0; US20110169350A1; CN101490935A; RU2444109C2; CN101490935B; FR2903823B1; WO2008006953A1

Abstract

The invention relates to an active element (20) for an electromagnetic machine, including, along a main axis (X), an alternating succession of segments (21) having a first magnetic property and segments (22) having a second magnetic property. The invention is characterised in that the active element includes a coating (25, 25) which is thin in relation to the thickness of the segments and which extends such as to cover a substantial part of an outer surface of the active element. The aforementioned coating is solidly connected to at least some of the segments and has a sufficient mechanical strength in order to form a member for the mechanical transmission of the magnetic forces experienced by the segments.

Description

An electromagnetic machine active element, a method of manufacturing such an active element, and an electromagnetic machine comprising such an element

The invention conc ^ u ^ ^x ^has rxîe active element in electromagnetic machine, a method of manufacturing such an active element, and a machine having such an active element.

BACKGROUND OF THE INVENTION

Linear electromagnetic machines having two moving parts relative to one another in a sliding direction are known. At least one of the parts comprises active elements comprising, arranged in the direction of sliding direction, a succession of portions having various magnetic properties.

In variable reluctance machines, the portions of each active element are alternately ferromagnetic and nonmagnetic. In machines with permanent magnets, the active elements of one of the parts comprise alternately ferromagnetic and non-magnetic portions, while the active elements of the other part comprise portions alternately magnetized in a first direction and magnetized in a second opposite direction. in the first sense.

The two parts are placed in electromagnetic interaction, one of the parts being associated with means for generating a magnetic field. The generation of magnetic fields causes the appearance of magnetic forces tending to relatively move the parts in the direction of sliding. Alternatively, the machine can operate as a generator by imposing a relative displacement on both parts.

In a first type of electromagnetic machine, the portions forming the active elements are in the form of plates or blades. The active elements of the two parts are parallel and form respectively nested combs one in the other so that a active element of one of the parts extends between two active elements of the other part (except of course for the external active elements).

In an embodiment illustrated by FIG. 5 of document FR 2 588 133, the portions forming the active elements of the mobile part are divided into two sub-portions which extend on either side of a support. central which maintains the sub-portions by one of their ends and takes again the magnetic efforts undergone by the parts. The portions forming the active elements of the fixed part are also divided into two sub-portions which are each held by one of their ends by an external support.

These supports are complex to manufacture and receive the sub-portions by one of their end, so that the latter are cantilevered and therefore undergo stresses tending to remove them from the support that receives them. In addition, the end of the sub-portions which is engaged in the supports is not in magnetic interaction with the sub-portions of the active element opposite, and therefore does not participate in the operation of the machine. In addition, the presence of the central supports and external supports increases the size of the machine. The supports do not participate either in the magnetic interaction between the active elements and therefore occupy a valuable place tending to limit the power density of the machine.

In a second type of electromagnetic machine shown in the article "Synchronous linear actuator with multi-rod permanent magnets", presented at the conference "Electrotechnics of the future, SUPELEC, 9-10 December 2003", the active elements of the moving part are rod-shaped and have cylindrical portions threaded on a central support. The central support maintains the portions and mechanically resumes magnets on the portions, and stiffens the stem.

In the same way as for the plates, the central support does not contribute to the magnetic interactions and occupies a precious place, tending to limit the power of the machine.

As suggested in document FR 2 588 133, it is possible to do without support and to glue or solder the portions of one and the same active element to each other. However, this method assumes that the portions are adjacent and can be brazed or glued. The magnetic forces are then mechanically transmitted by the links thus produced, which then work in tension, which is not ideal from a mechanical point of view.

OBJECT OF THE INVENTION The subject of the invention is a new active element offering greater efficiency.

BRIEF DESCRIPTION OF THE INVENTION

In order to achieve this goal, an active element for electromagnetic machine is proposed, comprising a succession in a main direction of portions having a first magnetic property alternated with portions having a second magnetic property. According to the invention, the active element comprises a thin amagnetic coating with respect to a thickness of the portions which extends to cover a substantial part of an external surface of the active element, the coating being secured to at least some of the portions and having sufficient mechanical strength to form a mechanical transmission member magnetic stresses experienced by the portions.

Thus, the coating is disposed outside the active element, i.e. in a zone of maximum inertia so that the coating contributes to strongly stiffen the active element, despite its thinness. The electromagnetic interactions then take place through the coating .

The magnetic forces exerted on the portions are mechanically transmitted by shear in the coating, which is very favorable from a mechanical point of view. The coating thus forms an effective transmitter of effort, very compact.

Thus, in the context of an active element in the form of a plate or a blade, it is advantageous to provide a coating comprising two thin walls substantially covering the two large faces of the active element through which the electromagnetic interactions take place. In the context of a rod-shaped active element, it is advantageous to provide a coating comprising a tubular thin wall covering the cylindrical portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood in the light of the description which follows with reference to the figures of the accompanying drawings, in which: FIG. 1 is a perspective view of an electromagnetic machine comprising plate-shaped active elements according to the invention; ;

FIG. 2 is a broken detail view of an active element of the machine illustrated in FIG. 1; FIG. 3 is a broken detail view of another active element of the machine illustrated in FIG. 2;

FIG. 4 is a view of the active element of FIG. 3 illustrated during manufacture;

- Figure 5 is a view of the active element of Figure 3 illustrated during manufacture according to an alternative embodiment;

FIG. 6 is a perspective view of an electromagnetic machine comprising rod-shaped active elements according to the invention; FIG. 7 is a detail view partially cut away from a section of active element of the machine illustrated in FIG.

DETAILED DESCRIPTION OF THE INVENTION The invention is firstly described with reference to a linear electromagnetic machine with polycarriers such as that illustrated in FIG. 1. In a manner known per se, such a machine comprises a cage 1 made of ferromagnetic material receiving here three coils 2 electrically powered so as to be successively phase shifted by 120 degrees. The magnetic field generated by the coils 2 is transmitted in an active zone of the cage 1 in which:

- Active elements in the form of fixed plates 10 parallel to each other and immobile relative to the cage 1 (only one fixed plate is referenced). Each of the fixed plates 10 comprises a succession of permanent magnets, as will be detailed below in relation to FIG. 2;

- Active elements in the form of movable plates 20 parallel to each other and each extending between two fixed plates 10 to present with them a plurality of air gaps (a single movable plate 20 is referenced). Each of the movable plates 20 comprises a succession of ferromagnetic portions and non-magnetic portions, as will be detailed below in relation to FIGS. 3 to 5. The movable plates 20 are secured together by means of pins 30 extending to cross all the movable plates 20. These slide in a direction of sliding X opposite the fixed plates 10.

As illustrated in FIG. 2, each fixed plate 10 comprises permanent magnets 11 oriented in a first direction alternately arranged with permanent magnets 12 oriented in a second direction opposite to the first direction, as indicated by the arrows drawn on the tremities permanent magnets. Permanent magnets 11, 12 are adjoined bars and form successive portions having alternating magnetic properties. According to an essential aspect of the invention, each fixed plate 10 comprises nonmagnetic thin walls 15 which extend on either side of the fixed plate 10 on the large faces thereof, being secured to the permanent magnets 11, 12, for example by gluing. The large areas are formed by the adjacent side walls of the bars.

By way of example, the permanent magnets 11, 12 have a thickness of the order of 1 mm, while the thin walls 15 have a thickness of 0.1 mm. Here, the tubular thin wall 75 is made of bronze. The thin walls 15 form support means for the permanent magnets 11, 12 which are very compact. The entire height of the permanent magnets 11, 12 is thus able to interact electromagnetically with the moving plates 20 opposite through the thin walls 15 so that all the magnets are used to produce mechanical forces on the movable plates 20.

In addition, the thin walls 15 form the outer layers of a sandwich whose core is constituted by the permanent magnets 11,12, which gives the fixed plate 10 a high flexural rigidity.

As illustrated in Figure 3, each movable plate 20 has ferromagnetic portions 21 arranged alternately with non-magnetic portions 22. The portions 21,22 form contiguous bars. Each movable plate 20 further comprises nonmagnetic ends 23 extending in the extension of the portions 21,22 and intended to receive the pins 30 which secure the movable plates 20 together to form the mobile element of the machine. According to an essential aspect of the vention, each movable plate 20 has thin walls 25 which extend on either side of the movable plate 20 on the large faces thereof, being secured to the portions 21, 22 and the ends 23, by example by gluing.

In addition to their already mentioned role of stiffening, the thin walls also ensure the mechanical transmission at the ends 23 of the magnetic stresses sustained by the portions 21, 22. The mechanical transmission of forces between the thin walls 25 and the portions 21, 22 is by shear, which is an efficient mode of transmission in bonded assemblies. Here too, the thin walls 25 are made of bronze.

As illustrated in FIG. 4, and according to a preferred embodiment, each movable plate 20 is obtained by using a sheet of non-magnetic material 26 in which parallel windows 27 are cut to receive the ferromagnetic portions 21. movable plate 20, is glued on a large face of the cut sheet 26 a thin wall 25, here on the large lower face. Then the ferromagnetic portions 21 are placed in the windows 27. One of the ferromagnetic portions 21 is illustrated during placement in one of the windows 27. Then the other thin wall 25 is glued to the large face The lateral edges of the cut sheet 26 are then outlined by the dashed lines so that the portions of the cut sheet 26 which remain between the ferromagnetic portions 21 form the non-magnetic portions 22. piercing the ends 23 to make the receiving holes of the pins 30.

In a variant illustrated in FIG. 5, the cut sheet 26 is made of ferromagnetic material, while the windows are filled with liquid resin 28 intended to form the non-magnetic portions. After curing the resin, bonding the upper thin wall, and flattening the side edges according to the dotted lines, the portions of the cut sheet extending between the windows form the ferromagnetic portions 21 while the resin 28 forms the non-magnetic portions 22 .

The manufacturing method illustrated here in FIGS. 4 and 5 can of course be applied to a fixed plate, or even to a plate without an end. In the same way, we can leave the windows empty, the air which is there forming the nonmagnetic portions.

In known machines, it is sought to keep gaps between the facing plates to prevent them from touching because the facing portions are not covered and may slide against each other and cling to the makes multiple edges at the boundary between the portions. Maintaining these voids requires external guidance of the moving plates relative to the fixed plates and give rise to magnetic instabilities tending to bring the plates closer to each other, and thus to stress them in flexion, which leads to variable air gaps. . These voids considerably increase the air gaps between the plates, and therefore reduce the efficiency of the machine. On the contrary here, and according to a particularly interesting aspect of the invention, the machine of Figure 1 is designed so that in operation, the fixed plates 10 and the movable plates 20 slide with a very low clearance allowing contact between the plates. The precise guidance thus produced makes it possible to maintain the air gap between the magnetic parts of two plates facing approximately constant and equal to the maximum thickness of the thin walls rubbing between them increased sliding clearance. The plates are here in contact via their thin walls 15,25 which are continuous and without edges, which facilitates their sliding.

In addition, the precise guidance thus produced increases the rigidity and therefore the buckling resistance of the movable plates 20, which can be long. The movable plates 20 can thus be mounted floating on the pins 30.

The material used for the thin walls 15,25 (here bronze) allows a relative sliding of the plates with a low coefficient of friction. As a variant, the thin walls 15, 25 may be made of another non-magnetic material and, if this material does not have a favorable coefficient of friction, the thin walls 15, 25 will advantageously be coated with a surface layer with a low coefficient of friction. , for example polytetrafluoroethylene (PTFE), compatible with the operating conditions of the machine, and in particular the internal temperature.

The invention is now illustrated with reference to a linear rod electromagnetic machine illustrated in FIG.

This type of machine also comprises a cage 51 receiving three coils 52 out of phase at 120 degrees. The magnetic field generated by the coils 52 is transmitted in an active zone of the cage 51 in which:

a fixed core 60 composed of permanent magnets in the form of disks having alternating magnetizations;

- Movable rods 70 parallel to each other and extending into orifices of the fixed core 60 to present with the latter annular air gaps (a single movable rod 70 is referenced). Each of the movable rods 70 comprises a succession of ferromagnetic portions and non-magnetic portions, as will be detailed later in connection with FIG. The movable rods 70 are interconnected by means of a flange 80 to which are fixed the ends of the movable rods 70. These slide in a direction of sliding X. The fixed core 60 here plays the same role as the fixed plates 10 , while the movable rods 70 play the same role as the movable plates 20.

As can be seen in FIG. 7, each movable rod 70 comprises ferromagnetic portions 71 alternately arranged with non-magnetic portions 72. Each movable rod 70 further comprises threaded non-magnetic ends 73 extending in the extension of the portions 71. , 72 and intended to be received on one of the flanges 80 which secure the movable rods 70 between them to form the mobile element of the machine. According to an essential aspect of the invention, each movable rod 70 comprises a tubular thin wall 75 (shown partially cut away for the sake of clarity of the figure) which extends around the movable rod 70 being secured to the portions 71, 72 and at the ends 73, for example by gluing. The electromagnetic interaction between the portions of the movable rods and the fixed core is through the tubular thin wall 75.

In the same way as for the plates, the tubular thin wall 75 holds the portions 71, 72, rigidly stiffens the movable rod 70, and mechanically transmits the magnetic stresses experienced by the portions 71, 72 at the ends 73 (by shear, like before) . In addition, the absence of central support allows for portions 71.72 full, without central orifice, which increases the efficiency of the machine.

According to a particularly interesting aspect of the invention, the movable rods 70 are received in the orifices of the stationary fixed core 60 with a slight clearance, allowing contact between the movable rods 70 and the fixed core 60. Thus, the movable rods 70, which can be long, are perfectly guided, which increases their rigidity and their resistance to buckling. In addition, the air gap is perfectly controlled and substantially equal at most to the thickness of the tubular thin wall 75 increased sliding clearance. Here, the tubular thin wall 75 is made of bronze, a material having a low coefficient of friction. The tubular thin wall 75 rubs directly into the orifice of the fixed core. However, the thin wall 75 is continuous and without edges, which promotes the sliding of the associated movable rod.

The invention is not limited to what has just been described, but on the contrary covers any variant within the scope defined by the claims.

In particular, although machines have been described here in which some of the active elements have magnetized portions, it will of course be possible to apply the invention to other types of machines, for example variable reluctance machines without permanent magnets. portions making up the active elements then being alternately ferromagnetic and non-magnetic.

Although the portions of an active element have been shown here adjacent, a void may be left between the portions. Moreover, a portion may consist entirely of emptiness.

Although the active elements illustrated here comprise an outer coating in the form of one or more continuous thin walls covering the entirety of an outer face of the active element, the coating may take other forms. In particular, the coating may comprise not continuous walls but strips which extend in the direction of sliding of the active element on the surface of the active element. Preferably then, the bands of an active element will be arranged to face the bands of the active element opposite. In any case, it is important that the coating be sufficiently solid to mechanically recover the magnetic stresses sustained by the portions of the active element.

Although it has been indicated that the coating is adhered to the portions, other modes of connection may be used. The coating may for example be obtained by coating the portions with a heated material which on cooling forms the coating. The coating can still be projected on the portions in the gas phase.

Although it has been indicated that all the portions are secured to the coating, only some of the portions, for example every other portion, may be secured. The magnetic forces will then be transmitted to the thin wall or walls only by the secured portions, always in shear.

Finally, although the invention has been described in relation to linear electromagnetic machines, the invention may be applied to rotary machines, comprising, for example, active elements in the form of disks. In this case, the portions extend along angular sectors and are alternated in a main direction which extends in a circle. The coating then comprises two thin walls which extend on the two large faces of the disk formed by the adjacent side faces of the portions.

Claims

1. Active element (10, -20, -70) for electromagnetic machine, comprising an alternating succession in a main direction (X) of portions (11; 21; 71) having a first magnetic property and portions (12; 22; 72) having a second magnetic property, characterized in that the active element comprises a thin non-magnetic coating (15, -25; 75) with respect to a thickness of the portions which extends to cover a substantial portion of an outer surface of the active element, the coating being secured to at least some of the portions and having sufficient mechanical strength to form a mechanical transmission member of the magnetic forces experienced by the portions.

2. The active element according to claim 1, wherein the portions are bars (11, 12; 21, 22) so that the active element is substantially plate-shaped having two large opposite faces formed by adjacent side faces of the bars, the coating (15, -25) extending to cover a substantial portion of the large faces.

3. Active element according to claim 2, wherein the coating comprises two thin walls (15; 25) attached to the large faces of the active element.

4. The active element according to claim 1, wherein the portions are in the form of cylindrical sections (71,72) so that the active element is substantially rod-shaped having a peripheral face, the coating (75) is extending to cover at least a substantial portion of the peripheral face.

The active element of claim 4, wherein the coating (75) has a tubular thin wall extending around the active element.

6. Active element according to claim 1, carrying at least one end which extends in the extension of the portions and which is secured to the coating so that the magnetic forces experienced by the portions are mechanically transmitted to the end by the coating.

An electromagnetic machine having at least one active element according to one of the preceding claims, wherein the active element is slidably received in a fixed part of the machine with a small clearance for contacts between the active element and the fixed part of the machine.

An electromagnetic machine comprising a plurality of active elements according to claim 2, nested so that a moving active element is between two fixed active elements, wherein the active elements slide with a small clearance allowing contacts between the active elements. opposite.

Electromagnetic machine according to claim 7 or claim 8, wherein the coating has at least one surface layer with a low coefficient of friction.

The linear electromagnetic machine of claim 9 wherein the entire coating is made of a low friction material.

11. A method of manufacturing an active element according to claim 2, comprising the steps of:

- Cut parallel windows in a sheet (26) having a first magnetic property; or leave the windows empty;

- report in the windows portions with a second magnetic property;

- Apply on both sides of the sheet a coating that substantially covers the sheet portions; - sharpen the side edges of the sheet so that the parts of the sheet which extend between two windows themselves form portions.