Part made of smc (soft magnetic composite) or ferrite material fitted around the teeth of an electric machine

Abstract

The invention relates to a magnetic flux-generating component comprising a magnetic circuit (1) produced in the form of a toothed ring (2), the ring (2) and the teeth (3) forming a one-piece part made from electrical steel sheet, each tooth (3) having a constant cross section from a base (9) to a free end (10), each tooth (3) receiving a support (15) wound with electrically conductive wire (16). The support (15) comprises a sheath (17) which surrounds the tooth (3) and which extends from the base (9) to the free end (10) of the tooth (3), the support (15) comprising a free peripheral edge (18) rigidly attached to the sleeve (17) at the free end (10) of the tooth (3), the free peripheral edge (18) being flush with the free end (10) of the tooth (3) and extending so as to face the wire (16), the support (15) being made of a ferromagnetic material.

Description

Description Title of the invention: part made of SMC (Soft Magnetic Composite) or ferrite material, installed around the teeth of an electrical machine. Technical field

[0001] The invention relates to the field of rotating electrical machines equipped with a magnetic flux generating component, the component comprising a magnetic circuit produced in the form of a toothed crown, the teeth respectively receiving a support wound with electrically conductive wire. The component is structured to, depending on the requirements, generate an axial magnetic flux or a radial magnetic flux. The invention is used in vehicles such as electric or hybrid type automobiles, buses, or even agricultural machinery, boats, airplanes, industrial machines, or other. Previous techniques

[0002] There are different types of rotating electrical machines equipped with a magnetic flux generating component. Generally, a machine comprises at least one stator and at least one rotor.

[0003] In the non-limiting case of axial magnetic flux operation, a machine may comprise a rotor arranged between two stators, or a stator arranged between two rotors. The production of the stator is a complex process that requires technical choices in order to be simplified. This includes reducing manufacturing time and costs. There are different ways to make a stator.

[0004] An example is to make separate elements that will then be secured to a plate. An element is obtained by making a tooth from laminated iron, then partially covering the tooth with an electrically insulating layer such as a synthetic material, and then winding the insulating layer with a length of electrically conductive wire.

[0005] The plate fitted with the elements is a segmented stator, the advantage of which is the ease of winding the teeth. A difficulty, however, arises when assembling the elements with the plate. The circularity of the stator must be regular, with the teeth in contact with each other at their base, generally called the yoke. But the teeth are not perfect in the geometric sense of the term. In particular, the faces of each base are not strictly flat; the faces have a certain roughness, a consequence of the manufacturing processes. Once the teeth are placed on the plate, so that the bases are in contact to form a magnetic circuit, air gaps can appear in the form of spaces between the bases. This creates faults in the circulation of magnetic fluxes and reduces the overall performance of the machine, or can be a source of magnetic vibrations. In particular, there is a reduction in available torque and energy losses.

[0006] In order to improve the circulation of magnetic fluxes, a single-piece circuit structure has been proposed, obtained by winding a magnetic iron strip. The strip, of constant width in its original state, is first unwound and guided flat in a cutting device, for example by stamping. The strip emerges from the device, with notches, which delimit the gaps between the stator teeth, to be wound and form a toothed crown.

[0007] In the case of an axial magnetic flux stator, each tooth extends from its base to its free end in a direction parallel to the axial direction of the stator. It is possible to give the teeth different shapes, which affect the construction of the stator as a whole as well as its operation.

[0008] In some embodiments, each tooth has a variable section, widening towards the free end. In practice, the section of the tooth is initially constant over almost its entire length, more precisely from its base to a limit slightly set back from the free end. Between the limit and the free end, the tooth has two widenings, one facing one of the neighboring teeth, the other facing the other of the neighboring teeth. These widenings are generally called notch beaks or isthmuses, a notch being a space between two teeth.

[0009] Slotted jaws offer several advantages. They reduce mechanical torque surges in the machine running at no-load, without electrical current in the coils. The jaws also reduce eddy currents in the windings, currents that cause electrical losses. The jaws further reduce no-load losses in the magnetic circuit or in the magnets when used with a magnetized rotor.

[0010] However, the notch jaws have some drawbacks. The winding operation around each tooth must be done by passing the wires between the notch jaws. As a result, the winding operation is tedious and often impossible to carry out automatically. In addition, the installation of an insulating layer around the tooth is tricky.

[0011] In other embodiments, each tooth has a constant section over its entire length, more precisely from its base to its free end.

[0012] An advantage of the constant section tooth, that is to say without notch beaks, is that the winding operation can be carried out on a support made of insulating material away from the tooth. The material can be natural or synthetic, such as plastic or any equivalent. Once the winding is carried out, the support covered with electrically conductive wire is fitted directly onto the tooth. The winding of the support is easy to carry out, and its installation on a tooth can be obtained by a device of automated assembly.

[0013] However, disadvantages of the constant section tooth are those resulting from the absence of notch beaks. The functions provided by the beaks, mentioned above, are lost.

[0014] Manufacturers have sought to simultaneously achieve the advantages of a variable-section tooth and the advantages of a constant-section tooth. To achieve this, a constant-section tooth was proposed, equipped with notch tips after the installation of a wound support.

[0015] Concretely, tests were carried out to secure a thin flat plate to the free end of each tooth of a stator, each plate extending beyond two sides of the end to form two slotted beaks. It proved very difficult to manufacture laminated iron plates and position them to form the beaks, the difficulty being largely due to the thinness of the plates.

[0016] An alternative to laminated iron has been proposed for the plate, in the form of a composite material: fine, powdered iron grains agglomerated in a polymer binder. The composite material is often referred to by the acronym SMC, which comes from the English expression Soft Magnetic Composite. This material can be molded and has good magnetic properties, particularly permeability and high electrical resistivity.

[0017] Another alternative for the plate is to use a ferrite-type material: a binary magnetic ceramic. Ceramic is obtained from metal powders, mainly iron but also, in addition, nickel, manganese, zinc, magnesium, copper, or other. Ceramic can also be molded.

[0018] Whether made of composite or ferrite material, a plate is fairly easy to make. However, the plate is a small, thin part that must be handled and glued to a tooth. At the stator scale, it is a set of plates that must be secured to the teeth. Securing the plates is difficult, particularly because it requires a lot of time and precision. In addition, complex and expensive tooling is required to install them.

[0019] Generally speaking, the manufacture of a flux generating component, such as a stator or a rotor, has the disadvantage of comprising one or more difficult and / or complicated steps, at least for the production of the notch tips. Statement of the invention

[0020] The invention seeks to overcome the aforementioned drawbacks for the manufacture of a magnetic flux generating component, such as a stator or a rotor, in a rotating electrical machine. More specifically, the invention seeks to facilitate the rea- lization of notch beaks, or isthmuses, at the level of the teeth of a stator or a rotor.

[0021] As a corollary, the invention aims to maintain the ease of installing a wound support on a tooth.

[0022] The invention also aims to reduce manufacturing and maintenance costs, as well as the time the machine is not in use.

[0023] To this end, the invention provides a magnetic flux generating component comprising a magnetic circuit made in the form of a toothed crown, the crown and the teeth forming a single piece made from magnetic sheet metal, each tooth having a constant cross-section from a base to a free end, each tooth receiving a support wound with electrically conductive wire. The support comprises a sheath which surrounds the tooth and which extends from the base to the free end of the tooth, the support comprising a free peripheral edge secured to the sheath at the free end of the tooth, the free peripheral edge being flush with the free end of the tooth and extending opposite the wire, the support being made of a ferromagnetic material.

[0024] By its shape and by the material of which it is made, the peripheral edge delimits two notch beaks. A portion of the edge facing one of the neighboring teeth forms a first beak, and another portion of the edge facing the other of the neighboring teeth forms a second beak. It follows that the support fulfills two functions. One of them is the simplification of the winding operation, carried out away from the tooth before the latter receives the support. The other function is the production of the notch beaks. Compared to the prior art, the invention has changed the location of the beaks by subjecting them to the support and not to the tooth.

[0025] With the invention the effects obtained and the advantages which result from it are multiple.

[0026] The invention increases the iron surface available for the circulation of magnetic flux. The increase is provided by the ferromagnetic material of the support. This allows an increase in the torque provided by the component, and therefore by the machine.

[0027] Parts of a laminated iron stator can be brought as close as possible to a rotor. These parts are the free ends of the teeth, which are not covered with plates. This allows for better conduction of the magnetic flux, and therefore better efficiency of the machine equipped with the component.

[0028] The notch jaws are easily installed without being fixed to a tooth, since they are integral with the winding support. The jaws can therefore be dismantled: simply release the support. As a result, maintenance is simplified, and operating costs are lower.

[0029] A bracket is obtained using a molding technique. This means that each bracket has the same dimensions. This allows for quick and easy placement of the brackets on the teeth, while simplifying the manufacturing process. An advantage that The result is the geometric precision of the component: the position of the notch jaws is precise and regular at the periphery of the component.

[0030] Because it contains a lot of iron particles, the support conducts heat well. This advantageously improves the transmission of heat released by a winding to a tooth, due to the Joule effect. As a corollary, the cooling of the component is improved.

[0031] In one embodiment, the holder includes a base peripheral edge secured to the sleeve at the base of the tooth, the base peripheral edge extending opposite the wire. This causes the holder to accommodate three winding faces. As a result, the wire is better held, and the holder is easier to handle.

[0032] The sheath, the free peripheral edge and the supporting peripheral edge form a single piece. This part, generally obtained by molding, for example by injection, has dimensions that will be identical for all supports. As a result, the geometry of the component, which depends partly on the geometry of the elements that constitute it, is much more precise and more regular for mass production.

[0033] Ferromagnetic material is a composite material comprising iron grains in a synthetic material matrix, or the ferromagnetic material is of the ferrite type. This makes the support magnetically conductive. As a result, the volume of material useful for the circulation of the magnetic flux is greater. As a result, the useful magnetic torque is greater.

[0034] A bonding agent is placed between the tooth and the bracket, and / or an insulating layer is placed between the wire and the bracket. The bonding agent facilitates the placement of the bracket on the tooth, because in this phase it is liquid or viscous and acts as a lubricant. Then the bonding agent holds the bracket on the tooth, because it has hardened. The insulating layer reinforces the insulation already present on the electric wire.

[0035] The component is a stator. In this case the component is a fixed part of a machine.

[0036] Each cross-section of a tooth is parallel to the crown. In this case, the wire of each winding is wound along an axis parallel to the axis of the crown. It follows that the magnetic flux of the stator is axial.

[0037] The component is a rotor. In this case the component is a moving part of the machine, more precisely a rotating part.

[0038] The invention also relates to a rotating electrical machine comprising a magnetic flux generating component, in particular a stator, comprising a toothed crown made from magnetic sheet metal as presented above.

[0039] The invention also relates to a method for manufacturing a magnetic flux generating component for a rotating machine, the method comprising a step of rea- lisation of a magnetic circuit in the form of a toothed crown, the crown and the teeth forming a single piece of magnetic sheet metal, each tooth of a selection having a constant section from a base to a free end. The method comprises a step of producing a support wound with electrically conductive wire for each tooth of the selection, the support comprising at least one sheath and a free peripheral edge secured to the sheath, the support being made of a ferromagnetic material, the method comprising a step of placing the wound support so that the sheath surrounds the tooth and so that the free peripheral edge is flush with the free end of the tooth. Brief description of the drawings

[0040] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0041] - [Fig.l] is a perspective view of a magnetic circuit for a magnetic flux generating component, according to one embodiment of the invention,

[0042] - [Fig.2] is a perspective view of a support wound with electrically conductive wire, in place on a tooth of the magnetic circuit of [Fig.l],

[0043] - [Fig.3] is a section along III-III of [Fig.2],

[0044] - [Fig.4] is a diagram which describes the structure of a material used in the invention. Detailed description

[0045] In [Fig.l], for the embodiment described, we can see a magnetic circuit 1 intended for the manufacture of a component of a rotating electrical machine. The component as a whole is not shown. Neither is the machine.

[0046] The magnetic circuit 1 has the general shape of a toothed crown, of axis L1, with the crown 2 itself and teeth 3. The crown 2 and the teeth 3 form a single piece made from magnetic sheet metal, in this case a strip of constant width. The strip is kept intact on one side and notched on the other. The notches, obtained by any suitable means such as a stamping device, delimit notches 4 between two successive teeth 3. It is the winding of the notched strip which gives its shape to the magnetic circuit 1. In the embodiment described, the magnetic circuit 1 comprises twenty-four teeth, knowing that this number can be smaller or larger.

[0047] In a non-limiting manner, the teeth 3 are distributed regularly around the periphery of the crown 2. The teeth 3 and the notches 4 all have the same dimensions respectively. This allows the magnetic flux to circulate regularly.

[0048] Each tooth 3 extends in length between an external face 5 and an internal face 6. The external face 5 is located at an external diameter of the magnetic circuit 1, which is also the external diameter of the crown 2. Thus the external face 5 is convex, that is to say curved and protruding. The internal face 6 is located at an internal diameter of the magnetic circuit 1, which is also the internal diameter of the crown 2. Thus the internal face 6 is concave, that is to say curved and hollow.

[0049] Each tooth 3 extends in width between a first lateral face 7 and a second lateral face 8. The first lateral face 7 partly delimits a notch 4 and the second lateral face 8 partly delimits another notch 4. Each of the first and second lateral faces 7, 8 is flat and perpendicular to the crown 2.

[0050] Each tooth 3 extends in height from a base 9 to a free end 10, the base 9 being the part of the tooth 3 which is at the level of the crown 2. The bases 9 of each tooth 3 are located respectively in the same plane perpendicular to the axis L1 of the circuit 1. By corollary the free ends 10 of each tooth 3, which are flat, are located respectively in another plane also perpendicular to the axis L1 of the circuit 1.

[0051] It follows from the above that each cross-section of a tooth 3 is constant from its base 9 to its free end 10. Each cross-section is parallel to the crown 2. In other words, a plane which contains a cross-section of the tooth 3 is perpendicular to the axis L1 of the magnetic circuit 1. It can also be said that the tooth 3 projects in the axial direction L1 of the crown.

[0052] Figures 2 and 3 show how a tooth 3 accommodates a support 15 wound with electrically conductive wire 16.

[0053] According to the invention, the support 15 comprises a sheath 17 which surrounds the tooth 3 and which extends from the base 9 to the free end 10 of the tooth 3. The support 15 also comprises a free peripheral edge 18 secured to the sheath 17 at the free end 10 of the tooth 3. The peripheral edge 18 is perpendicular to the sheath 17. The peripheral edge 18 is flush with the free end 10 of the tooth 3, in the sense that it borders the end 10 without covering it, and extends opposite the wire 16, for example along the entire thickness of the winding. The peripheral edge 18 tapers from the sheath 17 to its contour 20. Thus, the peripheral edge 18 defines a notch beak projecting from the first lateral face 7 of the tooth 3, and a notch beak projecting from the second lateral face 8 of the tooth 3, the beaks being carried by the sheath 17.

[0054] In a non-limiting manner, the support 15 also comprises a base peripheral edge 19 secured to the sheath 17 at the base 9 of the tooth 3. The base peripheral edge 19 is perpendicular to the sheath 17 and extends opposite the electric wire 16, again for example along the entire thickness of the winding. The base peripheral edge 19 has a constant thickness from the sheath 17 to its contour 21.

[0055] The support 15 is made of a ferromagnetic material. As a corollary, the sheath 17, the free peripheral edge 18 and the base peripheral edge 19 are respectively made of a ferromagnetic material. In a non-limiting manner, as shown in [Fig. 4], the ferromagnetic material is a composite material comprising iron grains 22 in a matrix of synthetic material 23. The iron grains 22 are generally nanoparticles, or microparticles. Dimensions between 5 and 500 nm have given good results. The synthetic material 23 is a thermoformable material, such as a polyamide, a polyethylene, a polyvinyl chloride, or any equivalent.

[0056] In a non-limiting manner, the sheath 17, the free peripheral edge 18 and the base peripheral edge 19 form a single-piece part. This is obtained by any suitable technique such as injection molding. A molded single-piece part is easy to produce and has high dimensional accuracy. Consequently, the dimensional accuracy of the magnetic circuit 1 is also high. This advantageously results in a homogeneous circulation of the magnetic flux.

[0057] Referring again to [Fig. 3], it can be seen that a bonding agent 24 is disposed between the tooth 3 and the support 15. In practice this agent 24 is a glue, a resin, or any suitable material. In a non-limiting manner, the bonding agent extends along the sleeve 17 and along the base peripheral edge 19. This distribution provides the largest possible bonding surface, for better retention of the support 15 on the tooth 3.

[0058] We can also see an insulating layer 25 arranged between the wire 16 and the support 15. The insulating layer 25 reinforces the electrical insulation between the winding and the support 15.

[0059] When in place on tooth 3, the wound support 15 increases the quantity of material capable of carrying a magnetic flux. In fact, it is both tooth 3 and sheath 17 which are each conductors of magnetic flux, and not the tooth alone. This results in better energy efficiency of the magnetic circuit 1, and consequently better efficiency of the machine in which it is installed.

[0060] The invention is not limited to the embodiment described, and includes all equivalents which may fall within the scope of the claims which follow.

[0061] In particular, various shape variants can be provided for the components of the magnetic circuit 1. For example, each tooth could be oriented in a radial direction of the crown 2. In this case, a cross-section of the tooth would be parallel to the axis L1 of the magnetic circuit 1.

Claims

Claims

1. A magnetic flux generating component comprising a magnetic circuit (1) made in the form of a toothed crown (2), the crown (2) and the teeth (3) forming a single piece made from magnetic sheet metal, each tooth (3) having a constant cross-section from a base (9) to a free end (10), each tooth (3) receiving a support (15) wound with electrically conductive wire (16), characterized in that the support (15) comprises a sheath (17) which surrounds the tooth (3) and which extends from the base (9) to the free end of the tooth (3), the support (15) comprising a free peripheral edge (18) secured to the sheath (17) at the free end (10) of the tooth (3), the free peripheral edge (18) being flush with the free end (10) of the tooth (3) and extending opposite the wire (16), the support (15) being made of a ferromagnetic material.

2. A component according to claim 1, wherein the support (15) comprises a base peripheral edge (19) secured to the sheath (17) at the base (9) of the tooth (3), the base peripheral edge (19) extending opposite the wire (16).

3. Component according to claim 2, in which the sheath (17), the free peripheral edge (18) and the base peripheral edge (19) form a single piece.

4. Component according to one of claims 1 to 3, in which the ferromagnetic material is a composite material comprising iron grains (22) in a matrix of synthetic material (23), or in which the ferromagnetic material is of the ferrite type.

5. Component according to one of claims 1 to 4, wherein a bonding agent (24) is arranged between the tooth (3) and the support (15), and / or an insulating layer (25) is arranged between the wire (16) and the support (15).

6. Component according to one of claims 1 to 5, which is a stator.

7. A component according to claim 6, wherein each cross-section of a tooth (3) is parallel to the crown (2).

8. A component according to one of claims 1 to 5, which is a rotor.

9. Rotating electrical machine comprising a magnetic flux generating component according to one of claims 1 to 8.

10. Method of manufacturing a magnetic flux generating component for a rotating machine, the method comprising a step of producing a magnetic circuit (1) in the form of a toothed crown (2), the crown (2) and the teeth (3) forming a single piece of magnetic sheet metal, each tooth (3) having a constant section from a base (9) to a free end 10), the method being characterized in that it comprises a step of producing a support (15) wound with electrically conductive wire (16) for each tooth (3), the support (15) comprising at least one sheath (17) and a free peripheral edge (18) secured to the sheath (17), the support (15) being made of a ferromagnetic material, the method comprising a step of placing the support (15) wound so that the sheath (17) surrounds the tooth (3) and so that the free peripheral edge (18) is flush with the free end (10) of the tooth (3).

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