FR3069723A1 - ROTOR OF ROTATING ELECTRIC MACHINE WITH RESIN LAYER IN PERMANENT MAGNET CAVITIES - Google Patents

Abstract

The invention relates mainly to a rotating electrical machine (10), in particular for a motor vehicle, comprising: - a stator (11), - a rotor (12) comprising: - a body (28) comprising at least one cavity (30) at least one permanent magnet (29) arranged in the cavity, characterized in that a polymer resin layer (38) covers at least one face of the permanent magnet (29) so as to be interposed between said face of the permanent magnet (29) and an inner face of the cavity (30).

Description

ROTOR OF ROTATING ELECTRIC MACHINE PROVIDED WITH A

RESIN LAYER IN PERMANENT MAGNET CAVITIES

The present invention relates to a rotor of a rotary electrical machine provided with a layer of resin in the cavities of permanent magnets.

In a manner known per se, rotary electrical machines comprise a stator and a rotor secured to a shaft. The rotor may be integral with a driving and / or driven shaft and may belong to a rotating electrical machine in the form of an alternator, an electric motor, or a reversible machine capable of operating in both modes.

The stator is mounted in a casing configured to rotate the shaft on bearings by means of bearings. The stator comprises a body constituted by a stack of thin sheets forming a crown, the inner face of which is provided with notches open towards the inside to receive phase windings. The phase windings are obtained for example from a continuous wire covered with enamel or from conductive elements in the form of pins connected together by welding. These windings are polyphase windings connected in star or triangle whose outputs are connected to an inverter also operating as a rectifier bridge.

Furthermore, the rotor may include a body formed by a pack of sheets made of a magnetic material, in particular steel, as well as poles formed by a plurality of permanent magnets housed in cavities of the body.

Taking into account the manufacturing tolerances of the different parts, it is possible that the magnets are badly plated inside the cavities, which is likely to cause the deterioration of the magnets due to impacts between the magnets and the internal faces of the cavities. or between the magnets during the acceleration or deceleration phases of the rotor.

As illustrated in FIG. 1, in order to compensate for assembly play, it is known to insert in each cavity 2 provided to receive the magnets 3, a spring 4 exerting a holding force on the corresponding magnets 3. A flange 5 ensuring the closing of the cavities can also be used for balancing the rotor. Reference may be made to document WO13175117 for more details on this device.

The invention aims to propose an alternative solution to the use of springs. To this end, the subject of the invention is a rotary electric machine, in particular for a motor vehicle, comprising:

- a stator,

- a rotor comprising:

- a body comprising at least one cavity,

- At least one permanent magnet disposed in the cavity, characterized in that a layer of polymer resin covers at least one face of the permanent magnet so as to be interposed between said face of the permanent magnet and an internal face of the cavity.

The invention thus makes it possible, thanks to the presence of the layer of polymer resin, to ensure effective mechanical retention of the permanent magnets in the cavities so as to avoid breakage of the magnets during the operation of the electric machine at high speed. In addition, the resin may cover the faces of the permanent magnets located opposite one another in the cavity in order to reduce the losses by eddy currents. This improves the electromagnetic performance of the rotating electric machine.

According to one embodiment, the layer of polymer resin covers at least two faces of the permanent magnet, in particular two faces opposite one with respect to the other.

According to one embodiment, the layer of polymer resin covers all the faces of the permanent magnet.

According to one embodiment, a strip of paper is coated at least partially with the layer of polymer resin.

According to another aspect, the subject of the invention is a method of manufacturing a rotary electric machine, in particular for a motor vehicle, characterized in that it comprises:

a step of covering at least one face of a permanent magnet with a layer of polymer resin,

a step of inserting the permanent magnet into a cavity of a rotor, so that the resin layer is interposed between said face of the permanent magnet and an internal face of the cavity, and

a step of heating the rotor so as to polymerize the polymer resin.

According to one implementation, prior to the heating step, the method comprises a step of closing the cavity by placing at least one flange.

According to one implementation, the covering step is carried out by soaking the permanent magnet in a bath of polymer resin.

According to one implementation, the covering step is carried out by spraying polymer resin on the permanent magnet.

According to one implementation, the covering step consists in placing a strip of paper at least partially coated with polymer resin around the permanent magnet.

According to one implementation, the paper strip has a U-shape.

According to one implementation, the paper strip is an individual strip arranged around the permanent magnet.

According to one implementation, the paper strip is arranged around a plurality of permanent magnets intended to be inserted inside the same cavity.

According to one implementation, the permanent magnet is wrapped in the paper strip) so that the paper strip covers all the faces of the permanent magnet.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1, already described, is an exploded perspective view of a rotor provided with retaining springs according to the prior art;

Figure 2 is a sectional view of the rotary electrical machine according to the present invention;

FIG. 3 is a perspective view of a rotor of a rotary electrical machine according to the present invention without the closing flanges of the cavities receiving the permanent magnets;

FIGS. 4a to 4d are perspective and schematic views of the steps of a first implementation of the method according to the invention;

Figures 5a to 5d are perspective and schematic views of the steps of a second implementation of the method according to the invention;

Figures 6a to 6d are perspective and schematic views of the steps of a third implementation of the method according to the invention.

Identical, similar, or analogous items retain the same reference from one figure to another.

FIG. 2 shows a rotary electric machine 10 comprising a stator 11 surrounding a rotor 12 mounted on a shaft 13 with the presence of an air gap between the external periphery of the rotor 12 and the internal periphery of the stator 11. The stator 11 is mounted fixed to the inside of a casing 16 carrying the shaft 13 of the rotor 12 in rotation. For this purpose, the casing 16 comprises a front bearing 17 and a rear bearing 18 each provided with a housing for receiving a bearing 21, in particular a ball bearing, inserted radially between the shaft 13 and the bearing of the corresponding electric machine.

The stator 11 comprises a body 24 constituted by a stack of thin sheets forming a crown, the inner face of which is provided with notches open towards the inside to receive a coil 25. The coil 25 is obtained for example from a continuous wire covered with enamel or from conductive elements in the form of pins connected together by welding. The winding comprises polyphase windings connected in star or triangle, the outputs of which are connected to a rectifier bridge.

Furthermore, as can be seen in FIG. 3, the rotor 12 comprises a body 28 formed by a pack of sheets made of a magnetic material, in particular steel, as well as a plurality of permanent magnets 29 intended to be housed in cavities 30 of the rotor body 28.

The sheets of the body 28 may be held by means of rivets 33 passing axially through the rotor 12 through and through via holes provided for this purpose. As a variant, the sheets are held together by gluing, welding, or buttoning.

The rotor body 28 has a central opening 35 for the passage of the shaft 13 extending along the axis X. The shaft 13 can be force-fitted inside the opening 35 to link in rotation the rotor body 28 with the shaft 13. In its central part, the rotor body 28 has recesses 36 to lighten the rotor 12.

More precisely, in a section plane P orthogonal to the axis X, the cavities 30 extend longitudinally in a direction D1. The cavities 30 may be axially through or of a blind configuration, that is to say that they open on one axial side of the body. The magnetic poles of the rotor 12 are each formed by the magnets 29 housed in two adjacent cavities 30 forming a V in the orthogonal plane P. As a variant, the cavities 30 extend in a radial or orthoradial direction relative to the axis X .

Each cavity 30 receives a plurality of magnets 29 stacked axially on each other. In this case, each cavity 30 receives six magnets 29 of parallelepiped shape. As a variant, the number of magnets 29 could of course be different. A single magnet 29 can also be inserted inside each cavity 30. The permanent magnets 29 can be made of rare earth or ferrite depending on the applications and the desired power of the machine.

In addition, a layer of polymer resin 38 covers at least one face of the permanent magnet 29 so as to be interposed between said face of the magnet 29 and an internal face of the cavity 30. Advantageously, the layer of resin 38 covers at least two faces of the magnet 29, in particular two faces opposite one with respect to the other. According to a preferred embodiment, the resin layer 38 covers all the faces of each permanent magnet 29.

A first implementation of the method according to the invention enabling the rotor 12 with permanent magnets according to the invention to be described below, with reference to FIGS. 4a to 4d, is described below.

During a first step shown in FIG. 4a, the magnets 29 are soaked in a bath of very little or no polymerized polymer resin 40. This makes it possible to cover all of the faces of the magnets 29 with a layer of resin 38. Alternatively, the magnets 29 are covered with a layer of resin 38 by spraying with polymer resin.

In a second step shown in FIG. 4b, a series of magnets 29 stacked axially on each other and covered with resin are inserted into a cavity 30 in the rotor body 28.

In a third step shown in FIG. 4c, the closing flanges 42 are put in place on the axial end faces of the rotor body 28 in order to close the ends of the cavities 30. For this purpose, fixing members 43, such as clamping screws, are inserted inside fixing holes made in the flanges 42 and the rotor body 28. The clamping screws 43 thus pass right through the assembly formed by the rotor body 28 and the flanges 42. Clamping nuts 44 allow the assembly to be locked.

Advantageously, the closing flanges 42 are made of a non-magnetic material having great mechanical rigidity, for example non-magnetic steel or aluminum. These flanges 42 can also ensure balancing of the rotor 12 while allowing good maintenance of the magnets 29 inside their cavity 30. Balancing can be carried out by adding or removing material. The removal of material can be carried out by machining projecting studs referenced 46, while the addition of material can be carried out by implanting elements in openings provided for this purpose and distributed along the circumference of the flange 42.

In a fourth step shown in FIG. 4d, a step of heating the rotor 12 is carried out so as to polymerize the resin 38 located inside the cavities 30. For this purpose, the rotor 12 is placed inside an oven. The temperature is chosen so as to be lower than the temperature capable of altering the magnetization of the permanent magnets 29.

At the end of the process, a layer of polymerized resin 38 is interposed between the faces of the magnets 29 and the internal faces of the cavity 30, which makes it possible to ensure effective mechanical retention of the magnets 29 inside the cavities 30. In addition, the fact that a layer of resin 38 is disposed between the facing faces of two magnets 29 located in the same cavity 30 makes it possible to reduce the losses by eddy currents.

FIGS. 5a to 5d illustrate an alternative implementation of the method for manufacturing the rotor 12 with permanent magnets according to the invention.

During a first step shown in FIG. 5a, a paper strip 50 at least partially coated with polymer resin is placed around an axial stack of permanent magnets 29. More precisely, the paper strip 50 is folded in U-shaped so as to have two walls 51, 52 covering the longest sides of the stack of magnets 29 opposite one another, as well as a connecting wall 53 covering an end face of the stack of magnets 29.

In a second step shown in FIG. 5b, the assembly formed by the impregnated paper strip 50 and the series of stacked magnets 29 covered by the strip 50 is inserted into a corresponding cavity 30 in the rotor 12.

In a third step shown in FIG. 5c, the closing flanges 42 are put in place on the axial end faces of the rotor body 28 in order to close the ends of the cavities 30. For this purpose, fixing members 43, such as clamping screws, are inserted inside fixing holes made in the flanges 42 and the rotor body 28. The clamping screws 43 thus pass right through the assembly formed by the rotor body 28 and the flanges 42. Clamping nuts 44 allow the assembly to be locked.

In a fourth step shown in FIG. 5d, a step of heating the rotor 12 is carried out so as to polymerize the resin impregnating the paper strips 50. For this purpose, the rotor 12 is placed inside an oven. The temperature is chosen so as to be lower than the temperature capable of altering the magnetization of the permanent magnets 29.

At the end of the process, a layer of polymerized resin 38 corresponding to the resin impregnating the paper strips 50 is interposed between the largest faces of the permanent magnets 29 and the internal faces of the cavity 30, which makes it possible to maintain effective magnets inside the cavities 30.

FIGS. 6a to 6d illustrate an alternative implementation of the method for manufacturing the rotor 12 with permanent magnets according to the invention.

During a first step shown in FIG. 6a, a strip of paper 50 'at least partially coated with polymer resin is placed around each magnet 29 located in the axial stack of magnets 29.

More specifically, the individual paper strip 50 ′ is folded in a U shape so as to present two walls 51 ′, 52 ′ covering the longest sides of each magnet 29 opposite one another, as well as a connecting wall 53 ′ covering an end face of the magnet 29. As a variant, each magnet 29 can be wrapped in a paper strip 50 ′, so that the paper strip 50 ′ covers by folding all the faces of magnet 29.

In a second step shown in FIG. 6b, the assembly formed by the series of magnets 29 each covered by a strip 50 ′ and stacked axially on each other is inserted into a corresponding cavity 30 in the rotor 12.

In a third step shown in FIG. 6c, the closing flanges 42 are placed on the axial end faces of the rotor body 28 in order to close the ends of the cavities 30. For this purpose, fixing members 43, such as clamping screws, are inserted inside fixing holes made in the flanges 42 and the rotor body 28. The clamping screws 43 thus pass right through the assembly formed by the rotor body 28 and the flanges 42. Clamping nuts 44 allow the assembly to be locked.

In a fourth step shown in FIG. 6d, a step of heating the rotor 12 is carried out so as to polymerize the resin impregnating the paper. For this purpose, the rotor 12 is placed inside an oven. The temperature is chosen so as to be lower than the temperature capable of altering the magnetization of the permanent magnets 29.

At the end of the process, a layer of polymerized resin 38 corresponding to the resin impregnating the paper strips 50 ′ is interposed between the largest faces of the permanent magnets 29 and the internal faces of the cavity 30, which ensures a effective holding of the magnets inside the cavities 30. In addition, there is a layer of resin 38 disposed between the facing faces of two magnets 29 located in the same cavity 30, which makes it possible to reduce losses by eddy currents.

In the case where the cavities 30 are blind, a single flange 42 is sufficient to close the cavities 30 before carrying out the heating step.

As a variant, the paper strip 50, 50 ′ is perforated in order to optimize the effect of impregnating the resin.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention from which one would not depart by replacing the various elements with any other equivalent.

Furthermore, the different features, variants, and / or embodiments of the present invention can be combined with one another in various combinations, insofar as they are not incompatible or mutually exclusive of one another.

Claims (13)

1. Rotating electric machine (10), in particular for a motor vehicle, comprising: - a stator (11), - a rotor (12) comprising: - a body (28) comprising at least one cavity (30), - at least one permanent magnet (29) disposed in the cavity (30), characterized in that a layer of polymer resin (38) covers at least one face of the permanent magnet (29) so as to be interposed between said face of the permanent magnet (29) and an internal face of the cavity (30). 2. Rotating electric machine according to claim 1, characterized in that the layer of polymer resin (38) covers at least two faces of the permanent magnet (29), in particular two opposite faces with respect to each other. 3. Rotating electric machine according to claim 1 or 2, characterized in that the layer of polymer resin (38) covers all the faces of the permanent magnet (29). 4. Rotating electric machine according to any one of claims 1 to 3, characterized in that a strip of paper (50) is coated at least partially with the layer of polymer resin (38). 5. Method for manufacturing a rotary electrical machine (10), in particular for a motor vehicle, characterized in that it comprises: a step of covering at least one face of a permanent magnet (29) with a layer of polymer resin (38), - a step of inserting the permanent magnet (29) into a cavity (30) of a rotor (12), so that the resin layer (38) is interposed between said face of the permanent magnet (29 ) and an internal face of the cavity (30), and - A step of heating the rotor (12) so as to polymerize the polymer resin. 6. Method according to claim 5, characterized in that, prior to the heating step, the method comprises a step of closing the cavity (30) by placing at least one flange (42). 7. Method according to claim 5 or 6, characterized in that the covering step is carried out by soaking the permanent magnet (29) in a polymer resin bath (40). 8. Method according to claim 5 or 6, characterized in that the covering step is carried out by spraying polymer resin on the permanent magnet (29). 9. Method according to claim 5 or 6, characterized in that the covering step consists in placing a strip of paper (50, 50 ') coated at least partially with polymer resin around the permanent magnet (29). 10. Method according to claim 9, characterized in that the paper strip (50, 50 ') has a U-shape. 11. Method according to claim 10, characterized in that the paper strip (50 ') is an individual strip arranged around the permanent magnet (29). 12. Method according to claim 10, characterized in that the paper strip (50) is arranged around a plurality of permanent magnets (29) intended to be inserted inside the same cavity (30). 13. Method according to claim 10, characterized in that the permanent magnet (29) is wrapped in the paper strip (50 ') so that the paper strip (50') covers all the faces of the permanent magnet (29).