Method and device for machining an element with magnetic poles

Abstract

The invention relates to a method for machining a magnetic pole element (200) comprising a magnet block (210) made of magnetic material and a casing (220), the magnet block having a main face, the casing covering the main face (211, 212), the manufacturing method comprising the following steps: - installing the magnetic pole element on a machining device (100); - measuring a distance between a reference point of the machining device and the main face; - positioning, on the basis of the distance, a material removal member (141, 142) of the machining device; - removing a part of the casing covering the main face by means of the material removal member. Figure for abstract: Fig. 1.

Description

Title of the invention: Method and device for machining an element with magnetic poles Technical field of the invention

[0001] The present invention relates generally to the field of electrical machines.

[0002] It relates more particularly to a method of machining an element with magnetic poles.

[0003] It also relates to a device for machining an element with magnetic poles.

[0004] The invention finds a particularly advantageous application in the production of electric motors for electric or hybrid motor vehicles (car, truck, bus, etc.). It also applies more generally to other motorized devices, such as, for example, elevators, cranes, etc. State of the art

[0005] An axial flux electric machine generally comprises at least a stator and a rotor, a magnetic air gap separating the latter. The rotor carries a series of large permanent magnets, while a series of coils is carried by the stator. When the coils are supplied with an electric current, the rotor, which is secured to the output shaft of the electric machine, is subjected to a torque resulting from the magnetic field (the magnetic flux created being an axial flux for an axial flux electric machine).

[0006] To reduce eddy current energy losses in the rotor, and thus increase the performance of the electrical machine, the large permanent magnets can be replaced by “magnetic pole elements” each comprising a plurality of small unit magnets. Indeed, a large permanent magnet is subject to greater eddy current losses than its equivalent in small unit magnets.

[0007] The unit magnets are arranged tightly together and thus form a magnet block made of magnetic material. This magnet block is covered with an envelope, which is for example made of resin, in order to keep the unit magnets integral with each other. A connecting material, for example formed of the same resin as the envelope, can also be interposed between the unit magnets.

[0008] The envelope is conventionally overmolded around the magnet block. For this, the envelope is injected in the liquid state into a mold, the magnet block being centered in the mold so that the envelope coats it. A minimum gap is necessarily provided between the magnet block and the mold to allow a homogeneous flow of the envelope in liquid form. Below this minimum gap, the filling of the mold during pressure injection could be incomplete.

[0009] This minimum gap thus results in a minimum thickness of the envelope around the magnet block.

[0010] However, it is generally appropriate to limit the magnetic air gap between the coils and the magnetic material of the magnetic pole elements, i.e. between the teeth around which the coils are wound and the magnet blocks. Reducing the magnetic air gap in fact makes it possible to increase the performance of the electrical machine.

[0011] The thickness of the envelope around the magnet block therefore limits the performance of the electrical machine by imposing a minimum magnetic air gap. Presentation of the invention

[0012] In this context, the present invention provides a method of machining a magnetic pole element comprising a magnet block made of magnetic material and an envelope, the magnet block having a main face, the envelope covering the main face, the manufacturing method comprising the following steps: - installation of the magnetic pole element on a machining device; - measurement of a distance between a reference point of the machining device and the main face; - positioning, based on the distance, of a material removal member of the machining device; - removal of part of the envelope covering the main face using the material removal device.

[0013] Thus, thanks to the invention, the thickness of the envelope on the main face can be reduced precisely. Indeed, the measurement of the distance between the main face of the magnet block and the machining device makes it possible to position the material removal member so that the remaining envelope (not removed by the member) has a predetermined target thickness. The target thickness is typically less than the minimum distance necessary for injecting the envelope between the magnet block and the mold.

[0014] In the context of the invention, the main face is a face of the magnet block which is intended to extend opposite the stator. Reducing the thickness of the envelope on the main face therefore makes it possible to reduce the magnetic air gap and increase the performance of the electrical machine.

[0015] It will be noted that the invention proposes to measure the distance between a reference point of the machining device and the main face of the magnet block, and not between the reference point and the resin casing, so that the result is not affected by the thickness of the envelope (which may vary due to machining variations).

[0016] Other advantageous and non-limiting characteristics of the method according to the invention, taken individually or in all technically possible combinations, are the following: - the removal comprises a rectilinear movement, along a main axis, of the main face relative to the material removal member; - the positioning of the material removal member is carried out by a movement in a direction orthogonal or inclined relative to the main axis; - during the measuring step, provision is made for measuring a plurality of distances between a plurality of reference points of the machining device and the main face, then, between the measuring step and the removal step, determining an orientation of the main face relative to a reference direction of the machining device, aligning the main face with the reference direction; - the material removal member is a rotating grinding wheel and the main face is aligned so as to be parallel with an axis of rotation of the rotating grinding wheel; - the magnet block has another main face, the envelope also covering the other main face, the method comprising the following steps: measuring another distance between another reference point of the machining device and the other main face, positioning, on the basis of the other distance, another material removal member of the machining device, removing another part of the envelope covering the other main face by means of the other material removal member, the removal of the part of the envelope and the other part of the envelope being carried out simultaneously; - the distance measurement is carried out by means of an inductive sensor; - the installation includes gripping the element with magnetic poles at a peripheral edge bordering the main face; - the casing covers the peripheral edge and has hollow reliefs designed to receive gripping means suitable for installing the magnetic pole element on the machining device.

[0017] The invention also proposes a device for machining an element with magnetic poles comprising a magnet block made of magnetic material and an envelope, the magnet block having a main face, the envelope covering the main face, the device comprising: - a measuring unit comprising a sensor arranged to measure a distance between a reference point of the machining device and the main face; - a machining unit comprising a material removal member adapted to remove a part of the envelope covering the main face; - a means of gripping the element with magnetic poles adapted to be conveyed the magnetic pole element of the measuring unit to the machining unit; - a computer programmed to determine, on the basis of the distance measured by the measuring unit, a position of the material removal member of the machining device.

[0018] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0019] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0020] In the attached drawings:

[0021] [Fig-1] is a schematic side view of a device for machining an element to magnetic poles according to the invention, the magnetic pole element being represented in two successive positions within the device;

[0022] [Fig.2] is a schematic perspective view of a magnetic pole element intended to be machined by the device of [Fig.l];

[0023] [Fig.3] is a schematic perspective view of the pole element of [Fig.l] further having hollow reliefs for its retention by a gripping means.

[0024] [Fig.4] is a block diagram of a sequence of steps for machining the magnetic pole element of [Fig.3] by the machining device of [Fig.l].

[0025] A machining device 100 of a magnetic pole element 200 according to the invention is shown in [Fig.l]. Before describing this device, the magnetic pole element 200 can be defined.

[0026] The magnetic pole element 200 is here designed to be mounted within a rotor of an electrical machine, and more particularly of an axial flux electrical machine. As shown in [Fig.2], the magnetic pole element 200 has a generally trapezoidal shape.

[0027] The rotor (not shown) conventionally comprises a body which may conventionally have a star shape with branches extending radially, around an axis of rotation of the rotor, from a central hub. The branches then delimit between them notches radially open towards the outside, a magnetic pole element being inserted in each notch. The magnetic pole elements may then be surrounded by a hoop to be blocked.

[0028] The rotor thus has the overall shape of a disc centered around the axis of rotation.

[0029] The axial flux electric machine further comprises a stator, or preferably two stators located on either side of the rotor. The stators (not shown) have the shape of flattened rings and are equipped, on their faces located on the rotor side, with teeth around which are wound windings of electrically conductive wires. When these windings are supplied with electric current, they generate a rotating magnetic field driving the elements with magnetic poles, which sets the rotor in motion around the axis of rotation.

[0030] Within the electric machine, the distance between the magnetic pole element 200 and the tooth facing it is called the magnetic air gap. The magnetic air gap is preferably short so that the attraction force of the winding on the magnetic pole element 200 is high.

[0031] As shown in [Fig. 2], the magnetic pole element 200 comprises a magnet block 210 and a casing 220. The magnet block 210 is made of a magnetic material, for example a ferromagnetic material such as neodymium-iron-boron or samarium-cobalt alloys or ferrites, so that it can be attracted by the windings. The casing 220, shown transparently in [Fig. 2], is made of a non-magnetic material. The casing is for example made of resin, such as an epoxy resin, plastic material or bakelite resin.

[0032] The magnet block 220 here comprises a plurality of unit magnets 240 arranged tightly together, as shown in [Fig.2]. The unit magnets 240 here mainly have the shape of rectangular parallelepipeds, certain unit magnets 240 at the periphery of the magnet block 220 have different shapes.

[0033] The unit magnets 240 are for example formed by cutting a large magnet. They are then held fixedly to each other by the envelope 220 which is molded around them. The envelope 220 is thus more specifically overmolded by injection around the magnet block 210. The envelope 220 can be molded in one or more times. The unit magnets 240 can also be cut in one or more times, different parts of the envelope being able to be molded between two cuts.

[0034] A connecting material, for example formed from the same material as the casing 220, may also be interposed between the unit magnets 240. The connecting material is for example injected at the same time as the casing 220. The space between the unit magnets 240 which is filled by the connecting material corresponds for example to the width of a wire used for cutting the unit magnets 240.

[0035] The magnet block 210 can also be a single-piece, as shown in [Fig. 1]. The casing 220 then, for example, provides a protective role for the magnet block 210.

[0036] In all cases, the envelope 220 coats the magnet block 210. Thus, the envelope 220 covers a first main face 211 and a second main face 212 of the magnet block 210. This means that the envelope 220 forms a layer extending in contact, ie on the first main face 211 and the second main face 212.

[0037] With reference to their orientation (detailed later) relative to the machining device 100, the first main face 211 is subsequently called the upper face 211 and the second main face 212 is subsequently called the lower face 212. More generally, the elements described as upper are here located above the elements described as lower relative to the vertical direction.

[0038] The upper face 211 and the lower face 212 are opposite each other. Preferably, the upper face 211 and the lower face 212 are each intended to be opposite a stator. The upper face 211 and the lower face 212 are here planar. The upper face 211 and the lower face 212 are here parallel to each other.

[0039] As shown in [Fig. 2], when the magnet block 220 comprises a plurality of unit magnets 240, the upper face 211 is defined by a set of first faces 241 of the unit magnets 240. Similarly, the lower face 212 is then defined by a set of second faces 242 of the unit magnets 240. The first faces 241 are here planar and aligned with each other. Likewise, the second faces 242 are here planar and are aligned with each other.

[0040] As shown in [Fig.l], the envelope 220 here has an upper thickness 221 at the upper face 211 and a lower thickness 222 at the lower face 212. The upper thickness 221 and the lower thickness 222 are here defined in an axial direction DI orthogonal to the upper face 211 and the lower face 212 ([Fig.l]). Thus, the upper thickness 221 corresponds to the dimension in the axial direction DI of the part of the envelope 220 extending on the upper face 211 and the lower thickness 221 corresponds to the dimension in the axial direction DI of the part of the envelope 220 extending on the lower face 211.

[0041] Before being machined by the machining device, the upper thickness 221 is here greater than a target upper thickness EC1. Before machining, the upper thickness 221 may however vary along the upper face 211. Similarly, before being machined by the machining device 100, the lower thickness 222 is here greater than a target lower thickness EC2. Before machining, the lower thickness 222 may however vary along the lower face 211.

[0042] The target upper thickness EC1 and the target lower thickness EC2 are predetermined according to the desired magnetic air gap. As detailed below, the target upper thickness EC1 and the target lower thickness EC2 correspond here to the upper thickness 221 and the lower thickness 222 of the envelope after its machining by the machining device 100.

[0043] For example, the target upper thickness EC1 and the target lower thickness EC2 are between 50 μm and 100 μm. Before machining, the upper thickness 221 and the lower thickness 222 are for example between 0.2 mm and 1.2 mm. In other words, before machining, the envelope 220 has excess thicknesses at the level of the upper face 211 and the lower face 212. As explained in the introduction, these excess thicknesses are necessary for the injection of the envelope 220 in liquid form.

[0044] The envelope 220 also covers a peripheral surface 213 of the magnet block 210. The peripheral surface 213 connects the upper face 211 and the lower face 212. The peripheral surface 213 here extends perpendicularly to the upper face 211 and the lower face 212.

[0045] As shown in Figures 2 and 3, the casing 220 forms a rib 223 at the level, i.e. opposite, the peripheral surface 213. The rib 223 is designed to fit into a groove of complementary shape provided on the branches of the rotor body.

[0046] As shown in [Fig.l], the machining device 100 provided for machining the magnetic pole element 200 comprises: - a structure 110; - a means 120 for gripping the magnetic pole element 200; - a unit of measurement 130; - a 140 machining unit; and - a 150 calculator.

[0047] The structure 110 provides a support role for the other parts of the machining device 100. As shown in [Fig.l], the structure 110 here is elongate. This means that the structure 110 extends along a main axis X, in particular in the direction where the measuring unit 130 and the machining unit 140 are aligned along the main axis X. The structure 110 comprises in particular an upper crosspiece 111 and a lower crosspiece 112, extending parallel to the main axis X.

[0048] Here, as shown in [Fig.l], the machining device 100 also has a height Y orthogonal to the main axis X and a depth Z orthogonal to the main axis X and to the height Y. The height Y corresponds for example to the vertical direction while the main axis X and the depth Z extend horizontally.

[0049] The gripping means 120 is adapted to grip the magnetic pole element 200.

[0050] The gripping means 120 (part of which is shown only in [Fig.3]) is mounted on the structure 110. The gripping means 120 is secured and movable relative to the structure 110 in order to move the magnetic pole element 200 relative to the structure 110, in particular along the main axis X.

[0051] The gripping means 120 is more specifically adapted to convey the magnetic pole element 200 from the measuring unit 130 to the machining unit 140.

[0052] Preferably, the gripping means 120 is adapted to orient the upper face 211, and therefore the lower face 212, relative to the main axis X. This means that the gripping means 120 is adapted to modify an angle between the upper face 211 and the main axis X.

[0053] Here, the gripping means 120 is also adapted to orient the upper face 211, and therefore the lower face 212, relative to the depth Z. This means that the gripping means 120 is also adapted to modify an angle between the upper face 211 and the depth Z. In other words, the gripping means 120 is then adapted to orient the upper face 211, and therefore the lower face 212, in a three-dimensional reference frame linked to the machining device 100, for example in the XYZ reference frame defined by the main axis X, the height Y and the depth Z.

[0054] For this, the magnetic pole element 200 is gripped at the peripheral surface 213 of the magnet block 210, more specifically at the envelope 220 covering the peripheral surface 213. Advantageously, the upper face 211 and the lower face 212 are also free, i.e. clear of the gripping means, which allows the machining of the envelope 220 covering them.

[0055] As shown in [Fig. 3], the gripping means 120 more particularly comprises rods 121, here four in number, coming into contact with the rib 223. The rib 223 has hollow reliefs 224, here four in number, designed to each receive one end 122 of a rod 121. The ends 122 of the rods 121 and the hollow reliefs 224 are here designed to fit together, with a clearance, so as to form ball joints. The fitting together therefore means here an insertion leaving several degrees of freedom in rotation. The hollow reliefs 224 and the ends 122 of the rods 121 extend for example along hemispherical surfaces.

[0056] Since the ribs 223 are formed by the casing 220, it is advantageous to locate the hollow reliefs 224 there since the quantity of casing material is significant. The hollow reliefs 224 are located on rectilinear lateral edges 201 of the magnetic pole element 200. These lateral edges 201 are intended to be opposite the branches of the rotor body. Once the magnetic pole element 200 is inserted into the notch of the body, the stresses on the rib 223 are lower on the lateral edges 201 than on a central edge 202 and a peripheral edge 203. Thus, remarkably, locating the hollow reliefs 224 on lateral edges 201 limits the risks of breakage of the rib 223.

[0057] The rods 121 are movable in several directions. Each rod 121 is movable in the direction of the magnetic pole element 200, which makes it possible to fit or disfit the ends 122 into the hollow reliefs 224. This direction corresponds here to the depth Z.

[0058] Each rod 121 is also movable, independently of the others, along the height Y to allow the orientation of the magnetic pole element 200. Finally, the rods 121 are also movable, for example in a coordinated manner, along the main axis X to allow the routing of the magnetic pole element 200 from the measuring unit 130 to the machining unit 140. The rods 121 are for example mounted on rails.

[0059] As shown in [Fig.l], the measuring unit 130 is also mounted on the structure 110, here in a fixed manner.

[0060] The measuring unit 130 preferably comprises a plurality of sensors 131. Each sensor 131 is adapted to measure a distance between said sensor 131 and a magnetic material, here the magnet block 210. The distance between said sensor 131 and the magnet block 210 is here measured along a measuring axis M of said sensor 131 which is parallel to the height Y.

[0061] The position of each sensor 131 is predetermined relative to the structure 110. In other words, the position of each sensor 131 in the XYZ reference frame is known. The sensors 131 thus make it possible to determine the position of the upper face 211 and the lower face 212. They therefore make it possible in particular to determine the orientation of the upper face 211 and the lower face 212 relative to the main axis X.

[0062] As illustrated in [Fig.l], the measuring unit 130 comprises an upper series 132 of sensors 131 which are here mounted on the upper crosspiece 111 and which are arranged opposite the upper face 211 when the magnetic pole element 200 is held within the measuring unit 130. The upper series 132 comprises for example three non-aligned sensors 131, i.e. defining a triangle in a horizontal plane (the three sensors 131 are however shown in line in [Fig.l]). The upper series 132 thus makes it possible, thanks to a measurement from each of its sensors 131, to determine the position and orientation of the upper face 211 in the XYZ reference frame.

[0063] Correspondingly, the measuring unit 130 comprises a lower series 133 of sensors 131 which are here mounted on the lower crosspiece 112 and which are arranged opposite the lower face 212 when the magnetic pole element 200 is held within the measuring unit 130. The lower series 133 comprises for example three non-aligned sensors 131, i.e. defining a triangle (the three sensors 131 are however shown in line in [Fig.l]). The lower series 133 thus makes it possible, thanks to a measurement from each of its sensors 131, to determine the position of the lower face 212 in the XYZ reference frame.

[0064] Each sensor 131 is here an inductive sensor. Each sensor 131 comprises for example a coil in which a current circulates whose impedance depends on the distance from the magnet block 210. Alternatively, the sensors may be magnetic sensors comprising for example a Hall cell or a magnetoresistance.

[0065] The machining unit 140 is also mounted on the structure 110, as shown in [Fig. 1]. The magnetic pole element 200 is held within the unit machining 140 by the gripping means 120, which is recalled to leave the upper and lower faces free so that they can be machined.

[0066] As shown in [Fig.l], the machining unit 140 here comprises a first material removal member 141, hereinafter called the upper member 141, adapted to remove a portion of the envelope 220 covering the upper face 211. The machining unit 140 also comprises a second material removal member 142, hereinafter called the lower member 142, adapted to remove a portion of the envelope 220 covering the lower face 212.

[0067] The upper member 141 is mounted on the upper cross member 111 and the lower member 142 is mounted on the lower cross member 112. The upper member 141 and the lower member 142 are each movable relative to the structure 110, in particular along the height Y, in the sense that their positions relative to the structure 110 can be modified (here independently). The upper member 141 and the lower member 142 are for example mounted in translation on rails.

[0068] The upper member 141 and the lower member 142 each comprise a rotating grinding wheel. A circular section of each rotating grinding wheel is shown in [Fig.l]. The axis of rotation R of each rotating grinding wheel is here parallel to the depth Z. Each rotating grinding wheel here has a cylindrical abrasive working surface whose generatrices are parallel to the depth Z. Each rotating grinding wheel here comprises abrasive particles distributed in a binder. The size of the abrasive particles is determined according to the material of the casing 220 to ensure efficient removal.

[0069] As shown diagrammatically in [Fig.l], the upper member 141 and the lower member 142 are thus adapted to remove a part of the envelope 220 when the magnetic pole element 200 is moved along the main axis X by the gripping means 120.

[0070] The fact that the upper member 141 is movable along the height Y therefore means here that the distance between the upper crosspiece 111 and the axis of rotation R of its rotary grinding wheel is adjustable. Similarly, the fact that the lower member 142 is movable along the height Y therefore means here that the distance between the lower crosspiece 112 and the axis of rotation R of its rotary grinding wheel is adjustable.

[0071] Preferably, each rotary grinding wheel has a width greater than the width of the magnetic pole element 200. The width is here defined as the dimension along the depth Z. Thus, the rotary grinding wheels are wide enough to machine the entire envelope 200 covering the main faces 211, 212 in a single pass. For example, the magnetic pole element 200 has a width of between 20 mm and 100 mm, and the rotary grinding wheels have a width of between 40 mm and 120 mm.

[0072] The computer 150 is here programmed to control the machining device 100 in the sense that it allows you to order: - the gripping means 120, in particular the movement of the rods 121; - the measuring unit 130, in particular the distance measurements by the sensors 131; - the machining unit 140, in particular the position of the upper member 141 and the lower member 142 as well as their activation (i.e. here their rotation).

[0073] The computer 150 comprises, for example, a processor and a memory. The memory is a computer-readable data carrier which comprises instructions which, when executed by the processor, make it possible to control the machining device. The computer 150 is therefore connected to the gripping means 120, to the measuring unit 130 and to the machining unit 140.

[0074] The computer 150 is more specifically programmed to implement a machining process represented in [Fig.4] and comprising the following main steps: - installation of the magnetic pole element 200 on the machining device 100; - measuring a distance between a reference point of the machining device 100 and the upper face 211; - positioning, on the basis of said distance, of the upper member 141; - removal of a part of the envelope 220 covering the upper face 211 by means of the upper member 141.

[0075] The machining method is here implemented by the machining device 100.

[0076] As shown in [Fig.4], the method begins with a step E1 of providing the magnetic pole element 200. Step E1 comprises, for example, cutting the unit magnets 240 and injecting the envelope 220 in liquid form into a mold containing the unit magnets 240.

[0077] At the end of step E1, the magnetic pole element 200 has the above-mentioned extra thicknesses at the level of the upper face 211 and at the level of the lower face 212. The magnetic pole element 200 also comprises the hollow reliefs 224 which are directly molded or machined on the rib 223 after molding.

[0078] The method then continues with a step E2 of installing the magnetic pole element 200 within the machining device 100. Step E2 here comprises gripping the magnetic pole element 200 by the gripping means 120. During step E2, the ends 122 of the rods 121 are fitted into the hollow reliefs 224.

[0079] Then, during a step E3 of the method, the computer 150 determines the position of the upper face 211 and, respectively, of the lower face 212, in the XYZ reference frame linked to the structure 110.

[0080] Step E3 firstly comprises the positioning of the magnetic pole element 200 within the measuring unit 130 using the gripping means 120. Such positioning is illustrated on the left of [Fig.l].

[0081] Step E3 more specifically comprises the measurement, by the sensors 131, of a plurality of distances between a plurality of reference points of the machining device 100 and the upper face 211 and, respectively, the lower face 212. Each reference point is for example a point of the structure 110. Each reference point can also be a point of the sensor 131, for example its center, which measures the distance between said reference point and the machining device 100.

[0082] The distances are here measured according to the height Y (to which the measurement axes M of the sensors 131 are parallel). Thus, the distance between a reference point of the machining device 100 and the upper face 211 is for example equal to the distance, referenced H1 in [Fig. 1], between the upper crosspiece 111 and the upper face 211 according to the height Y.

[0083] In all cases, the reference points each have a determined position in the XYZ reference frame linked to the structure 110.

[0084] Here, during step E3, the upper series 132 acquires three distances according to the height Y (one for each sensor 131), which allows the computer 150 to determine the position of the upper face 211 in the XYZ reference frame. Similarly, the lower series 132 acquires three distances (one for each sensor 131) according to the height Y, which allows the computer 150 to determine the position of the upper face 211 in the XYZ reference frame.

[0085] By determining the position of the upper face 211 and the position of the lower face 212 in the XYZ reference frame, the computer 150 therefore also determines the orientation of the upper face 211 and the lower face 212 relative to the main axis X and relative to the depth Z.

[0086] After step E3, all the movements of the magnetic pole element 200 being controlled by the computer 150, the computer 150 updates the position of the upper face 211 and the lower face 212 in the XYZ reference frame throughout the method.

[0087] The method then comprises a step E4 of aligning the magnetic pole element 200 with a reference direction D2 of the machining device 100, here parallel to the main axis X.

[0088] Step E4 is implemented only when the upper face 211 and the lower face 212 are inclined relative to the main axis X and to the depth Z, that is to say when they are not orthogonal to the height Y. Here, this corresponds to the case where the upper face 211 and the lower face 212 are not oriented horizontally.

[0089] In this case, step E4 comprises the alignment of the upper face 211 and the lower face 212 with the main axis X and with the depth Z. For this, the rods 121 are moved according to the height Y so that the upper face 211 and the lower face 212 are aligned with the main axis X and with the depth Z. lower 212 are parallel to the main axis X and to the depth Z.

[0090] Remarkably, step E4 makes it possible to align the upper face 211 and the lower face 212 with respect to the machining device 100 even when the magnet block 210 is not correctly centered in the casing 220. In fact, it is possible for the magnet block 210 to be inclined with respect to an external surface 225 of the casing 220. Thanks to the sensors 13, this reorientation can be carried out even if the inclination of the magnet block 210 is not visible through the casing 220.

[0091] This alignment makes it possible, as appears below, to machine a constant upper thickness 221 over the entire upper surface 211 and a constant lower thickness 222 over the entire lower surface 212.

[0092] The method then continues with a step E5 of positioning the upper member 141 and the lower member 142.

[0093] For this, the calculator 150 determines, i.e. calculates, the position of the upper member 141 and the position of the lower member 142, here according to the height Y, on the basis of the positions of the upper face 211 and the lower face 212 in the XYZ reference frame, and therefore on the basis of the plurality of distances measured in step E3.

[0094] Here, the positions of the upper member 141 and the lower member 142 are also respectively determined on the basis of the target upper thickness EC1 and the target lower thickness EC2.

[0095] Here, the calculator 150 calculates the positions of the upper member 141 and the lower member 142 so that after machining, the upper thickness 221 is equal to the target upper thickness EC1 and the lower thickness 222 is equal to the target lower thickness EC2.

[0096] By way of example, when the upper face 211 is orthogonal to the height Y and located at the distance H1 from the upper crosspiece 111, the upper member 141 is positioned at a distance referenced H2 in [Fig.l] calculated as the difference between i) the distance H1 between the upper face 211 and the upper crosspiece 111, and ii) the target upper thickness EC1. In the example of [Fig.l], it is more particularly an end 143 of the upper member 141 in a direction parallel to the height Y which is positioned at the distance H2. The lower member 142 can be positioned according to a similar calculation.

[0097] Once the positions of the upper member 141 and the lower member 142 have been determined, the computer 150 controls the movement of the upper member 141 and the lower member 142 so that they are located at said positions.

[0098] The positioning of the upper member 141 and the lower member 142 is carried out by a movement of the latter according to the height Y or according to a direction inclined relative to the main axis X, that is to say here both according to the height Y and according to the main axis X.

[0099] After positioning the upper member 141 and the lower member 142, the method finally comprises a step E6 of removing a part of the envelope 220.

[0100] Step E6 begins with the movement, by the gripping means 120, of the magnetic pole element 200 from the measuring unit 130 to the machining unit 140.

[0101] Step E6 then comprises a rectilinear movement, along the main axis X, of the magnetic pole element 200 relative to the upper member 141 and the lower member 142. During this movement, the upper member 141 and the lower member 142 are active in the sense that they remove the parts of the casing 220 coming into contact with them. Here, this means that the rotating grinding wheels are rotating.

[0102] This rectilinear movement is illustrated on the right of [Fig. 1], in which the upper member 141 and the lower member 142 are located approximately in the middle of the upper face 211 and the lower face 212. As [Fig.l] clearly illustrates, before passing the upper member 141, the upper thickness 221 of the envelope 220 is greater than the target upper thickness EC1, while afterwards, the upper thickness 221 of the envelope 220 is equal to the target upper thickness EC1. Similarly, before passing the lower member 142, the lower thickness 222 of the envelope 220 is greater than the target lower thickness EC2, while afterwards, the lower thickness 222 of the envelope 220 is equal to the target lower thickness EC2.

[0103] Here, thanks to the alignment step E4, the axes of rotation R of the rotating grinding wheels are parallel to the upper face 211 and to the lower face 212. In addition, the rotating grinding wheels are wider than the magnetic pole element 220. A single passage of the magnetic pole element 220 between the material removal members 141, 142, that is to say in a single translation along the main axis X, therefore makes it possible to obtain the target upper thickness EC1 and the target lower thickness EC2.

[0104] Remarkably, the removal of a portion of the envelope 220 covering the upper face 211 is carried out at the same time as the removal of a portion of the envelope 220 covering the lower face 212, that is to say simultaneously during the same passage.

[0105] The removal step E6 therefore makes it possible to flatten the envelope 220 in the sense that it removes any irregularities from the envelope 220 and that it adjusts the upper thickness 221 and the lower thickness 222.

[0106] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variant in accordance with the invention.

[0107] For example, the gripping means may comprise only three rods. Three support points in fact make it possible to orient the magnetic pole elements. The rods may also have suction cups or electromagnets to hold the element with magnetic poles. Other gripping means can also be implemented, such as a conveyor belt allowing the main faces to be machined one by one.

[0108] The measuring unit may have more or less than six sensors, for example a single sensor per series to measure the distance between a main face and the structure. The measurement of a single distance, depending on the height, may in fact be sufficient to position a material removal member relative to a main face. It can in fact be considered that the magnet block is correctly oriented and that only the position of one of its faces needs to be determined.

[0109] With a single sensor, it is also possible to determine the orientation of a main face by moving the latter relative to the sensor and acquiring several distances with this same sensor.

[0110] When the dimensions of the magnet block are known, for example transmitted to the computer, determining the position of one of the main faces by means of the sensors allows the computer to determine the position of the other main face. Only one series of sensors is then necessary.

[0111] It is also possible to machine the main faces one after the other. The machining device can then comprise a single series of sensors and a single material removal member, for example mounted on the same crosspiece.

[0112] The material removal member may also comprise means other than rotating grinding wheels for removing material. The material removal may for example be carried out by laser, by high-pressure water jet, or by a milling cutter whose axis of rotation is parallel to the height.

[0113] The positioning of the material removal members can also be modified during the movement of the magnetic pole element so as to obtain variable upper and lower thicknesses on the main faces, for example to form specific patterns.

[0114] It is also conceivable that the main faces are not planar. A plurality of distance measurements between the main faces and the machining device can then make it possible to obtain a three-dimensional representation of the main faces in the reference frame linked to the machining device, which then makes it possible to position the material removal members accordingly.

[0115] It is also possible for the main faces not to be parallel. They are then, for example, machined one after the other or with a displacement of the material removal members during machining.

[0116] Finally, if the electrical machine only has one stator and one rotor, it is possible to machine only one face of the element with magnetic poles.

Claims

Claims

1. A method of machining a magnetic pole element (200) comprising a magnet block (210) made of magnetic material and a casing (220), the magnet block (210) having a main face, the casing (220) covering the main face (211, 212), the manufacturing method comprising the following steps: - installing the magnetic pole element (200) on a machining device (100); - measuring a distance between a reference point of the machining device (100) and the main face (211, 212); - positioning, on the basis of the distance, a material removal member (141, 142) of the machining device (100); - removal of a part of the envelope (220) covering the main face (211, 212) by means of the material removal member (141, 142).

2. Method according to claim 1, in which the removal comprises a rectilinear movement, along a main axis (X), of the main face (211, 212) relative to the material removal member (141, 142).

3. Method according to claim 2, in which the positioning of the material removal member (141, 142) is carried out by a movement in a direction orthogonal (Y) or inclined relative to the main axis (X).

4. Method according to one of claims 1 to 3, in which it is provided: - during the measuring step, the measurement of a plurality of distances between a plurality of reference points of the machining device (100) and the main face (211, 212); then, between the measuring step and the removal step, - the determination of an orientation of the main face (211, 212) relative to a reference direction of the machining device (100); - the alignment of the main face (211, 212) with the reference direction (X).

5. A method according to claim 4, wherein the material removal member (141, 142) is a rotating grinding wheel and wherein the main face (211, 212) is aligned so as to be parallel with an axis of rotation (R) of the rotating grinding wheel.

6. Method according to one of claims 1 to 5, in which the magnet block (210) has another main face, the envelope (220) covering also the other main face (211, 212), the method comprising the following steps: - measuring another distance between another reference point of the machining device (100) and the other main face (211, 212); - positioning, on the basis of the other distance, another material removal member (141, 142) of the machining device (100); - removing another part of the casing (220) covering the other main face (211, 212) by means of the other material removal member (141, 142); the removal of the part of the casing (220) and the other part of the casing (220) being carried out simultaneously.

7. Method according to one of claims 1 to 6, in which the measurement of the distance is carried out by means of an inductive sensor (131).

8. Method according to one of claims 1 to 7, in which the installation comprises gripping the magnetic pole element (200) at a peripheral edge (213) bordering the main face (211, 212).

9. Method according to claim 8, in which, the envelope (220) covering the peripheral edge (213) and having hollow reliefs (224), said gripping is carried out by gripping means (120) which cooperate with said hollow reliefs for the installation of the magnetic pole element (200) on the machining device (100).

10. Machining device (100) of a magnetic pole element (200) comprising a magnet block (210) made of magnetic material and an envelope (220), the magnet block (210) having a main face, the envelope (220) covering the main face (211, 212), the device comprising: - a measuring unit (130) comprising a sensor (131) arranged to measure a distance between a reference point of the machining device (100) and the main face (211, 212); - a machining unit (140) comprising a material removal member (141, 142) adapted to remove a portion of the envelope (220) covering the main face (211, 212); - a gripping means (120) for the magnetic pole element (200) adapted to convey the magnetic pole element (200) from the measuring unit (130) to the machining unit (140); - a computer (150) programmed to determine, on the basis of the distance measured by the measuring unit, a position of the member material removal device (141, 142) of the machining device (100).

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