Method and apparatus for making a stator for axial flux electric motors

Abstract

A method and an apparatus for making a stator for axial flux and distributed winding electric motors are described, as well as a stator and a motor obtained with the method described. The method provides for making coils with linear lengths of conducting wire. First linear lengths of coil are inserted into open stator slots of a stator body, so that to occupy all the stator slots. Second linear lengths of coil are gripped by a tool and roto-translated, with respect to the corresponding first linear lengths, up to also being inserted into the stator slots, above the first linear length of a different coil. For this, the apparatus comprises a lower tool having the task of holding the stator body with the open slots facing upward, and an upper tool provided with teeth which jut out towards the lower tool, to grip the coils and impart roto-translation. The linear lengths of the coils are preferably subjected to a pressing and / or carburizing treatment before being inserted into the stator slots.

Description

[0001] Method and apparatus for making a stator for axial flux electric motors

[0002] ***

[0003] DESCRIPTION

[0004] Field of the invention

[0005] The present invention concerns a method and an apparatus for making a stator for axial flux electric motors, in particular an axial flux and distributed winding stator, as well as a stator made with such method.

[0006] Known art

[0007] As is known, in the axial flux electric motors, the magnetic field induced by the current flowing through the stator windings is parallel to the rotation axis of the rotor, unlike the most common radial flux motors in which the magnetic field is oriented radially with respect to the rotation axis of the rotor. In the axial flux electric motors, the magnetic field has flux lines oriented axially between the stator and the rotor, i.e. flux lines extending parallel to the rotation axis of the rotor. This implies a different construction of the electric motor.

[0008] In particular, in the axial flux electric motors:

[0009] - the rotor is a disk-shaped component onto which permanent magnets are positioned, with a circumferential arrangement, arranged on a lying plane orthogonal to the rotation axis of the rotor, and

[0010] - the stator is a substantially toroidal component provided with stator teeth. One or more windings of one or more conducting wires, also named coils, are placed in the sectors constituted by the space between the stator teeth, more commonly named stator slots.

[0011] In the axial flux electric motors, the winding of the stator is obtained by arranging the coils circumferentially, so that the coils engage the stator slots and lie on a plane substantially orthogonal to the rotation axis of the rotor. This planar arrangement of the coils in the stator makes the coils be wedge-shaped on the lying plane, i.e. they have a smaller circumferential extent near the rotation axis of the rotor and a larger circumferential extent near the outer perimeter of the stator, away from the rotation axis of the rotor. This different construction of the axial flux electric motor, compared to a radial flux electric motor, implies a different form factor: the radial flux electric motors are generally cylinder-shaped, whereas the axial flux electric motors are generally disk-shaped, or anyhow have a larger radial extent than the axial extent (with respect to the rotation axis of the rotor) and this makes them more compact than the radial flux electric motors. Moreover, axial flux electric motors generally have the following further advantages, compared to radial flux motors of the same size: they are lighter, have a higher power density, have a higher torque / weight ratio, have higher efficiency and use fewer raw materials, anyhow providing greater design flexibility.

[0012] Axial flux electric motors are widely used in wind turbines; they are recently finding increasing applications in the automotive sector, such as in the motors of electric road vehicles.

[0013] Some examples of axial flux electric motors are described in EP4170869A (Honeywell Int Inc.), EP4289048A (Magelec Propulsion Ltd), EP4226477A (Schaeffler Technologies AG), EP3796525A (Whirlpool Co), EP3595138A (S & H S.r.L), EP3807977A (Indigo Tech Inc.).

[0014] Axial flux electric motors, as well as radial flux electric motors, can also be constructed with stator windings of the distributed type or the concentrated type. As is known:

[0015] - a winding of the concentrated type provides that each stator pole is wound from a single coil of conducting wire, i.e. conducting wires are wound on a single stator tooth;

[0016] - a winding of the distributed type provides that each coil of conducting wire intercepts several stator teeth, i.e. conducting wires are wound on two or more teeth.

[0017] As mentioned above, the present invention concerns axial flux and distributed winding electric motors.

[0018] Currently, the making of stators of axial flux and distributed winding electric motors provides that the conducting wire is wound directly on the stator teeth, i.e. provides that the formation of the coils occurs directly on the stator teeth, for example with a needle winding machine, or provides that the coils are fit onto the stator teeth when the coils are preformed on a winding tool, by inserting them axially into the stator slots.

[0019] Neither of the two techniques allows to reach a high filling factor defined as the ratio between the surface of the cross section occupied by conducting wires inside a stator slot and the total area available (always considered in cross section) in the stator slot. It is instead desirable to be able to insert a greater number of conducting wires, or the same number of wires of greater diameter, into the same stator slot, other factors being equal, since this would result in improved performance of the electric motor.

[0020] The Applicant has found that the current solutions adopted to make the stators of axial flux and distributed winding electric motors can be improved in order to obtain electric motors with improved performance.

[0021] US 9,287,757 discloses a method for making a stator for a radial flux alternator. The method includes deforming the coils by using jigs for obtaining the displacement of the linear lengths of the coils, according to the desired electrical scheme. The jigs are linear jigs and consists of two halves that are slidable one with respect to the other; therefore, the coils are initially set on a plane. Sliding one half of the jig with respect to the other half of the jig causes the deformation of the coils, so as to shift the linear lengths of the coils. The already deformed coils are then removed from the jigs and inserted into the statoric slots for assembling the stator.

[0022] US 7,550,892 discloses a filling method for filling the slots of a stator with preformed coils.

[0023] Summary of the invention

[0024] Aim of the present invention consists in providing a method and an apparatus for making a stator of an axial flux and distributed winding electric motor, which allow to overcome the limits of the currently available solutions, in order to maximize the filling factor and, generally, the performance of the completed electric motor.

[0025] A first aspect of the present invention therefore concerns the method according to claim 1 .

[0026] It is assumed that a stator has a stator body with a ring-shaped extent about an axis Z-X and radial stator slots accessible in axial direction, and closing elements which can be fastened to the stator body for closing the stator slots when the windings have been performed.

[0027] The method comprises the step A of making coils of conducting wire and the step C of assembling the stator.

[0028] Step A provides for making the coils by winding one or more conducting wires on a winding tool, so that to form at least one coil comprising at least one first linear length and at least one second linear length, which in turn comprise a plurality of individual linear lengths of conducting wire and which are adapted for being inserted into the stator slots.

[0029] The step C of assembling the stator provides for steps C1 -C4.

[0030] During step C1 , the coils are collected from the winding tool with a manipulator and the second linear lengths of the coils are inserted into corresponding first stator slots, so that a second linear length of coil is present in all the stator slots and so that the first linear lengths of the coils stay outside the stator slots. In practice, each stator slot is occupied by second linear lengths of the coils, while the first linear lengths stay free.

[0031] During step C2, all the first linear lengths of the coils are simultaneously engaged by a first tool named upper tool, in the sense that the upper tool engages the first linear lengths so that to be able to move them all together.

[0032] During step C3, all the coils are simultaneously deformed, by imparting, with the upper tool, a roto-translation to the first linear lengths until each first linear length is inserted into a second stator slot different from the first stator slot in which the second linear length of the same coil is located. In practice, the insertion of the first linear lengths into the stator slots of the stator body occurs with an angular offset with respect to the second linear lengths of the coils. During step C4, when both the first linear lengths of the coils and the second linear lengths of the coils are housed in the stator slots, the stator slots are closed with first linear lengths and second linear lengths of a coil therein. The closing of the stator slots is performed with the closing elements.

[0033] The method just described allows to achieve different advantages.

[0034] An improved filling factor of the stator slots is one of the advantages that can be achieved. The Applicant has calculated that the method allows to achieve, other conditions being equal, a filling factor greater than at least 20% than a stator made according to the known arts, i.e. made with the standard insertion of the windings into the stator slots.

[0035] The method according to the present invention also allows to make stators characterized by reduced losses in the windings, compared to a stator assembled with standard insertion of the coils into the stator slots.

[0036] As far as efficiency is concerned, comparing the solution according to the present invention with stators achieved with the standard technique of stator slot insertion, other conditions being equal (same size / power, same number of poles, same size of the slots between the teeth, same rotor and same size), a stator obtained with the method just described allows to achieve greater efficiency of about 5% at low rotation speeds than a motor assembled with a standard stator.

[0037] A further advantage is constituted by the fact that the angular offset between the linear lengths of the same coil can be changed by adapting the coil making step A, anyhow always automatically.

[0038] The method according to the present invention further allows to make stators of electric motors completed with the respective winding, in a quick, economical and simple way, since the completion of all stator windings is achieved with a single roto-translation.

[0039] A further advantage is constituted by the fact that the linear lengths of the coils and the stator slots have a perfectly complementary shape, because the linear lengths can be produced with a cross section complementary to the section of the linear slot.

[0040] More in detail, in step C3, the rotation imparted by the upper tool to the first linear lengths of coil corresponds to the angle between the electrical phases of the completed stator.

[0041] During the coil deforming step C3, the first linear lengths of the coils are held by the upper tool without possibility of being subjected to twisting. In turn, the second linear lengths of the coils are housed in the stator slots without possibility of being subjected to twisting. Consequently, the coil deformation obtained with the roto-translation described above occurs in the headers of the coils, i.e. in the coil portions connecting the linear lengths.

[0042] As will be seen hereunder, the headers of the coils are the portions which are not subjected to pressing and / or carburizing and which are therefore easily deformable. Deformation of the headers comprises twisting and / or pressing of the headers.

[0043] More in detail, in step C1 , the second linear lengths of the coils are inserted into the slot bottom of the first stator slots, and, in step C3, the first linear lengths of the coils are inserted into the stator slots above a second linear length of another coil (with respect to the coil of the first linear length).

[0044] During step C4, the coils are preferably held inside the stator slots by exerting a pressure on all the headers of the same coils simultaneously, or by anyhow providing an abutment surface which prevents the coils from coming out of the stator slots.

[0045] During step C4, the stator slots are preferably closed by inserting the closing elements radially between the stator teeth delimiting the stator slots on the stator body.

[0046] In the preferred embodiment, the method also comprises a pressing or carburizing step B, otherwise optional. It is a step during which the linear lengths of the coil are subjected to a pressing step, or are subjected to a thermal carburizing treatment, or to both the pressing step and the thermal carburizing treatment, in the desired order or simultaneously, such as to compact the individual linear lengths of wire according to the orderly arrangement achieved during the coil forming step A.

[0047] Advantageously, the wires of the linear lengths of the coils which were subjected to pressing and carburizing remain aggregated, do not separate and are not displaced one relative to the other. This detail allows to make and keep the winding in the best geometric configuration possible for maximizing the filling factor, for each stator slot size of the stator to be filled, and to avoid fraying while the coils are moving. Moreover, the linear wire lengths can be made of a shape perfectly complementary to the stator slot into which they must be inserted. In practice, thanks to the pressing and / or carburizing step B, the ideal position assumed by the conducting wires during winding on the winding tool is “frozen,” i.e. makes such position permanent.

[0048] Step B preferably lasts between 15 seconds and 2 minutes.

[0049] During the pressing and / or carburizing step B, the linear lengths of the coils are preferably pressed with one or more presser elements and are heated by means of one or more heating devices integrated in, or coupled to, the presser elements, while the coil is wound on a winding tool, i.e. before the coil is taken from the winding tool.

[0050] In a possible method, in the pressing and / or carburizing step B, the thermal carburizing treatment is performed by inserting one or more heating elements between the linear lengths of the coils, so that to heat them up to a predetermined carburizing temperature, generally in the range of 170°C - 210°C.

[0051] In a possible method, in the carburizing and pressing step B, the linear lengths are pressed by means of a pressing device which is inserted between said linear lengths of the coil after having removed the heating elements, by keeping the coil accommodated on the winding tool.

[0052] In a possible method, during the coil making step A, complementary and thinner conducting wires having a smaller section than the section of the main conducting wires, are added to the conducting wires named main wires; the complementary conducting wires occupy the free spaces between the main side-by-side conducting wires.

[0053] The method preferably also comprises a step of insulating the conducting wires. An electrically insulating element, for example a slot liner.

[0054] - is applied at least on the linear lengths of the coil, after the pressing and / or carburizing step B, when provided, or

[0055] - is applied between the teeth of the stator body before the coil inserting step.

[0056] The coil making step A is preferably implemented by making a series of several coils on the same winding tool, by making sure to keep a linear length of a coil spaced from the linear length of the successive coil. During the displacement of the coils from the winding tool to the stator body, an appropriate manipulator adjusts the pitch between the coils or between the portions of coil, correspondingly to the pitch between the stator slots of the stator.

[0057] A second aspect of the present invention concerns a stator of an axial flux and distributed winding motor, directly obtained with the method according to any one of the preceding claims.

[0058] The so-obtained stator preferably comprises a single level of coils or two levels of coils, which levels are arranged at different heights on the axis Z-Z.

[0059] A third aspect of the present invention concerns an axial flux and distributed winding electric motor comprising a stator directly obtained with the method described herein, and a rotor functionally coupled to the stator.

[0060] The electric motor can be made with the stator comprising a single level of coils, or two levels of coils, as explained above, and comprising one or two rotors arranged on opposite parts with respect to the stator.

[0061] A fourth aspect of the present invention concerns an apparatus for making a stator for axial flux and distributed winding electric motors according to claim 17. It is assumed that the stator comprises a stator body having ring-shaped extent about an axis 7-7 and radial stator slots.

[0062] The apparatus comprises a first tool, named upper tool, and a second tool, named lower tool. Both the lower tool and the upper tool extend about the axis 7-7 and are coaxial.

[0063] The upper tool is provided with a plurality of teeth facing the lower tool and adapted for the simultaneous comb insertion of first linear lengths of a number of coils corresponding to the number of stator slots of the stator.

[0064] The lower tool has a first seat inside which the stator body can be housed with the second linear lengths of the coils inserted into all the stator slots, i.e. with the coils protruding from the stator slots towards the upper tool.

[0065] The upper tool and the lower tool can be roto-translated one with respect to the other to cause the insertion of the first linear lengths of the coils into the stator slots, where the second linear lengths are already present. The roto- translation can be achieved by moving only one between the lower and upper tools, or both.

[0066] In the preferred embodiment, the lower tool is provided with a plurality of teeth distributed circumferentially at the inner perimeter of the lower tool and at the outer perimeter of the lower tool, jutting out towards the upper tool. The teeth are arranged with a pitch corresponding to the pitch between the stator slots of the stator. The distance (in circumferential direction) between adjacent teeth is sufficient to allow the insertion of the linear lengths of coil between them. This configuration allows the upper tool to comb-like insert the coils and impart the roto-translation, thus preventing the linear lengths of the coils from twisting, throughout their length. The teeth actually comb insert the ends of the linear lengths, making it impossible to transmit twisting in the individual linear length of coil.

[0067] The lower tool is preferably provided with a first ejector device equipped with a plurality of cylinders that can be inserted axially into the first seat, so as to cause the ejection of the stator body from the first seat on command, when the assembly C has been completed.

[0068] The teeth of the upper tool are also preferably distributed circumferentially at the inner perimeter of the upper tool and at the outer perimeter of the upper tool, jutting out towards the lower tool with a pitch corresponding to the pitch between the stator slots of the stator. The distance between adjacent teeth is sufficient to allow the linear lengths of coil to be inserted between them.

[0069] In the preferred embodiment, a second seat, intended for temporarily accommodating the first linear lengths of coil, is defined in the upper tool. The upper tool comprises a second ejector device provided with pins that can be axially inserted into the second seat in order to eject the coils from the second seat, upon completion of the assembly of the stator.

[0070] More in detail, the upper tool is susceptible to roto-translations with respect to the lower tool, between

[0071] - a distal position, at which the first linear lengths of the coils are comblike inserted by the teeth of the upper tool and the second linear lengths of the coils are inserted into the slot bottom of the stator slots of the stator body housed in the lower tool, and

[0072] - a proximal position, at which the teeth of the upper tool are at the height of the stator slots of the stator body housed in the lower tool, and the second linear lengths of the coils are inserted into the stator slots above the first linear lengths of the coils.

[0073] The apparatus preferably also comprises an outer presser element and an inner presser element having the task of facilitating the opening of the apparatus, i.e. the moving away of the upper tool from the lower tool. The outer presser element is ring-shaped and movable to an operating position at which it surrounds the upper tool coaxially and is in abutment against the headers of the deformed coils which protrude radially towards the outside of the upper tool, when roto-translation is completed. The inner presser element is disk-shaped and movable to an operating position at which it is inside and coaxial to the upper tool and in abutment against the headers of the deformed coils which protrude radially towards the inside of the upper tool, when roto-translation is completed. The presser elements exert a pressure, or anyhow define an abutment surface for the coils, which prevent the coils from coming out of the stator slots and anyhow prevent any undesired displacement before the stator slots are closed by respective closing elements.

[0074] The stator preferably comprises closing elements which can be fastened to the stator body for closing the stator slots. The outer presser element comprises radial seats for the closing elements. The closing elements are radially removable from the radial seats for engaging the stator. The displacement which brings the closing elements to engage the stator is imparted by an outer manipulator which radially pushes each closing element towards the axis Z-Z.

[0075] The apparatus preferably also comprises a winding tool on which the conducting wire is wound to form a series of coils or a coil with several portions of coil. The apparatus also comprises a pressing and / or carburizing device for pressing and / or carburizing the linear lengths of coil, and which can be operated on the coils still wound on the winding tool to make the reciprocal position of the linear lengths of conducting wire, which compose the linear lengths of coil, permanent.

[0076] The pressing and / or carburizing device preferably comprises one or more presser elements and one or more heating devices integrated in, or coupled to, said presser elements, which presser elements can be inserted between the linear lengths of the coils still wound on the winding tool.

[0077] Brief list of the figures

[0078] Further characteristics and advantages of the invention will become clearer from the description of some preferred, but not exclusive, embodiments of a method for making a stator, which are depicted by way of example and without limitations with the aid of the accompanying drawings, in which:

[0079] - figure 1 is a perspective and elevation view of a coil of conducting wire usable in the method and the stator according to the present invention;

[0080] - figure 2 is a front and elevation view of a first winding machine and its respective winding tool, which are configured for making coils usable in the method and the stator according to the present invention;

[0081] - figure 3 is a detail of the winding machine of figure 2;

[0082] - figures 4, 5 and 6 are sectional details of the first winding machine of figure 2, which are considered on different section planes;

[0083] - figures 7 and 8 are exploded views of a first embodiment of a winding tool combined with the first winding machine of figure 2;

[0084] - figures 9 and 10 are perspective views of the winding tool of figure 7, in successive steps;

[0085] - figure 11 is a side and elevation view of the winding tool shown in figure 7, in the condition of figure 9;

[0086] - figures 12, 13 and 14 are sectional views, along different planes, of the winding tool of figure 7;

[0087] - figure 15 is a perspective view of an apparatus for pressing and carburizing coils;

[0088] - figures 16 and 17 are sectional views of the apparatus of figure 15 at successive coil pressing and carburizing times;

[0089] - figures 18 and 19 are perspective views of a second embodiment of a winding machine and the corresponding winding tool;

[0090] - figures 20A, 20b and 20c are sectional views of the loops of different possible winding types;

[0091] - figures 21 A, 21 b and 21c are sectional views of the loops of different types of winding according to an optional solution;

[0092] - figure 22 is a perspective view of a detail of the second embodiment of the winding tool;

[0093] - figure 23 is a front view of the winding tool of figure 22;

[0094] - figure 24 is a side view of the winding tool of figure 22;

[0095] - figure 25 is a top view of the winding tool of figure 22; - figures 26A, 26B are perspective views which illustrate two successive steps of the thermal treatment process performed on a coil accommodated on the winding tool of figure 22;

[0096] - figures 27A, 27B are perspective views which illustrate two successive steps of the pressing process performed on a coil accommodated on the winding tool of figure 22;

[0097] - figure 27C is a cross sectional view which shows the step of the pressing process of figure 27B performed on a coil accommodated on the winding tool of figure 22;

[0098] - figure 28 is an isometric view of a second winding machine adapted for making coils usable in the method and the stator according to the present invention, in which the second winding machine is shown in a first configuration;

[0099] - figure 29 is a perspective view of the second winding machine shown in figure 28, in a second configuration;

[0100] - figure 30 is a perspective view of the second winding machine shown in figure 28, in a third configuration corresponding to the start of the coil making step;

[0101] - figure 31 is a perspective view of the second winding machine shown in figure 28, at a second time during the coil making step;

[0102] - figure 32 is a perspective view of the second winding machine shown in figure 28, at a third time during the coil making step;

[0103] - figure 33 is a perspective view of the second winding machine shown in figure 28, at a fourth time during the coil making step;

[0104] - figure 34 is a perspective side view of a detail of figure 32, in particular of the winding tool;

[0105] - figure 35 is a top plan view of the detail of figure 34;

[0106] - figure 36 is a perspective front view of a detail of figure 32, in particular of the winding tool;

[0107] - figure 37 is a top plan view of a detail of figure 33, in particular of the winding tool; - figure 38 is a perspective view of the second winding machine shown in figure 28, at a fifth time during the coil making step;

[0108] - figures 39-51 are perspective views of the second winding machine shown in figure 28, at corresponding times during the coil making step;

[0109] - figure 52 is perspective view of a portion of the second winding machine shown in figure 28, at a time corresponding to a completed coil;

[0110] - figure 53 is a perspective view of a coil still wound on the winding tool;

[0111] - figure 54 is a perspective view of the coil shown in figure 53 and of a pressing and / or carburizing apparatus;

[0112] - figure 55 is a perspective view of the coil shown in figure 53 and of the pressing and / or carburizing apparatus, at a first time corresponding to the start of the pressing and / or carburizing step of the linear lengths of the coil;

[0113] - figure 56 is a sectional view of figure 55, considered on a horizontal plane;

[0114] - figure 57 is a perspective view of the coil shown in figure 53 and of the pressing and / or carburizing apparatus shown in figure 54, at a second time corresponding to the start of the pressing and / or carburizing step of the linear lengths of the coil;

[0115] - figure 58 is a sectional view of figure 57, considered on a horizontal plane;

[0116] - figure 59 is a perspective view of the coil shown in figure 53 and of the pressing and / or carburizing apparatus shown in figure 54, at a third time corresponding to the start of the pressing and / or carburizing step of the linear lengths of the coil;

[0117] - figure 60 is a sectional view of figure 59, considered on a horizontal plane;

[0118] - figure 61 is a perspective view of the coil shown in figure 53 and of the pressing and / or carburizing apparatus shown in figure 54, at a fourth time corresponding to the start of the pressing and / or carburizing step of the linear lengths of the coil; - figure 62 is a sectional view of figure 61 , considered on a horizontal plane;

[0119] - figure 63 is a perspective view of the coil shown in figure 53 and of insulating elements ready to be wound on the linear lengths of the coil;

[0120] - figure 64 is a perspective view of the coil shown in figure 53 with insulating elements wound on the linear lengths of the coil;

[0121] - figure 65 is a perspective view of the coil shown in figure 53 and of the winding tool disassembled for releasing the coil;

[0122] - figure 66 is an exploded and axial sectional view of an apparatus according to the present invention for making a stator for axial flux electric motors;

[0123] - figure 67 is a perspective view of two components shown in figure 66, in particular of a lower component of the apparatus and of a stator body positioned therein;

[0124] - figure 68 is a sectional axial view of figure 67;

[0125] - figure 69 is a perspective view of two components shown in figure 66, in particular of a lower component of the apparatus and of a stator body positioned therein, and of coils which are housed in the stator body;

[0126] - figure 70 is a perspective view of two components shown in figure 66, in particular of a lower component of the apparatus and of a stator body positioned therein, and of two coils housed in the stator body;

[0127] - figure 71 is a perspective view of the apparatus shown in figure 66, closed in a first configuration;

[0128] - figure 72 is a sectional axial view of figure 71 ;

[0129] - figure 73 is a perspective view of the apparatus shown in figure 66, at a first time during the roto-translation;

[0130] - figure 74 is a perspective view of the apparatus shown in figure 66, at a second time during the roto-translation;

[0131] - figure 75 is a perspective view of the apparatus shown in figure 66, at a third time during the roto-translation; - figure 76 is a sectional axial view of figure 75;

[0132] - figure 77 is a perspective view of the apparatus shown in figure 66, at a fourth time during the roto-translation;

[0133] - figure 78 is a sectional axial view of figure 77;

[0134] - figure 79 is a perspective view of the apparatus shown in figure 66, when the roto-translation has been completed, at a later time than that shown in figure 78;

[0135] - figure 80 is a sectional axial view of figure 79;

[0136] - figure 81 is a perspective view of the apparatus shown in figure 66, at a time corresponding to the coils being held in the stator slots by means of a component of the apparatus;

[0137] - figure 82 is a sectional axial view of figure 81 ;

[0138] - figure 83 is a perspective view of the apparatus shown in figure 66, at a time corresponding to the opening of the apparatus;

[0139] - figure 84 is a perspective view of the apparatus shown in figure 66, at a time corresponding to the raising of an upper component of the apparatus;

[0140] - figure 85 is a perspective view of the apparatus shown in figure 66, at a time corresponding to the closing of the stator;

[0141] - figure 86 is a sectional axial view of figure 86;

[0142] - figure 87 is a perspective view of the completed stator, still positioned in a lower component of the apparatus shown in figure 66;

[0143] - figure 88 is a sectional axial view of figure 87;

[0144] - figure 89 is a perspective view of the completed stator, during the ejection from the lower component of the apparatus shown in figure 66;

[0145] - figure 90 is a sectional axial view of figure 89;

[0146] - figure 91 is a perspective and partial schematic view of a first embodiment of the stator according to the present invention, before its completion;

[0147] - figure 92 is a perspective view and partial schematic view of the stator shown in figure 91 , but completed; - figure 93 is a perspective and partial schematic view of a first embodiment of an electric motor incorporating the stator according to the present invention;

[0148] - figure 94 is a perspective and partial schematic view of a second embodiment of an electric motor incorporating the stator according to the present invention;

[0149] - figure 95 is a perspective and partial schematic view of a third embodiment of an electric motor incorporating the stator according to the present invention;

[0150] - figure 96 is a perspective and partial schematic view of a fourth embodiment of an electric motor incorporating two stators according to the present invention;

[0151] - figure 97 is a perspective and partial schematic view of a fifth embodiment of an electric motor incorporating two stators according to the present invention;

[0152] - figure 98 is a flow diagram illustrating the method according to the present invention;

[0153] - figure 99 is a comparison showing, in vertical section, a stator slot with a traditional winding compared to the same stator slot with winding obtained with the method according to the present invention;

[0154] - figure 100 is a torque-speed diagram which helps to understand the higher efficiency of the electric motors obtained by incorporating the stator according to the present invention, compared to conventional solutions, all conditions being equal.

[0155] Detailed description of the invention

[0156] In order to achieve a high filling factor, in the stator according to the present invention, the windings are formed by making, in an appropriate tool outside of the stator, coils characterized by an extremely orderly distribution of the conducting wire, or conducting wires, and by then inserting the coils into the stator slots. Figure 1 is a perspective and elevation view of a coil 1 adapted for implementing the method according to the present invention. The coil 1 can be made by using a single conducting wire or several conducting wires having different characteristics, for example having different diameters. For simplicity, in figure 1 , the single conducting wire cannot be distinguished and the lengths of the coil 1 are schematized. Since the stator intended to be assembled is of the distributed winding type, the coil 1 is made in portions 2, 3, each of which is intended to be inserted into a corresponding stator slot. The portions 2 and 3 of the coil 1 can also be named coils 2-3 in series. In the example shown in figure 1 , the coil 1 is made with two portions 2 and 3 but, in general, can also be made with three or more portions; therefore, the coil 1 shown in figure 1 has two terminals 4 and 5.

[0157] Each portion 2, 3 of the coil 1 comprises two linear lengths 6 and 7, i.e. straight lengths, an outer header 8 and an inner header 9. The headers 8 and 9 are substantially curved, anyhow also being able to be made with linear lengths. The inner header 9 is intended to be positioned in the stator so that to be more radially inward than the outer header 8 which comprises the terminals 4 and 5 and which will radially protrude outward from the stator. Each linear length 6 and 7 is made by stratifying at least one conducting wire.

[0158] The method according to the present invention initially comprises a step A of making the coils 1 , which can be implemented in several ways, as will now be made clearer.

[0159] Figures 2-27C illustrate a first winding method, i.e. a first method of making the coils 1 , and a first winding tool 100 for making the carrying out A, both the winding machine and the winding method being particularly adapted for making coils 1 having linear lengths 6 and 7 of a length equal to 3 cm or longer.

[0160] The winding machine 100 comprises a supporting structure 101 which supports:

[0161] - a plurality of wire tensioning devices 103 (of the known type) for tensioning the conducting wires 10 to be wound, henceforth only wires 10 for simplicity;

[0162] - a wire guiding device 106 provided with a wire guiding tube 104 and movable along a wire guiding guide 105 (preferably consisting of a bar),

[0163] - a winding spindle 144 rotated by a motor 114 and adapted to rotate the winding tool 20 which will be described hereunder, in practice being coupled to the sleeve for hooking to the spindle 144.

[0164] Such winding machine 100 can therefore be configured in an operative winding configuration, wherein the wires 10 to be wound are tensioned and come out of the wire tensioning devices 103 towards the wire guiding device 106, which in turn guides the wires 10 towards the winding tool 20 kept rotating.

[0165] Optionally, the winding machine 100 also comprises a tailstock 115 positioned coaxially to the spindle 144 and adapted for being coupled to the removable wall 24’ (figure 7) of the winding tool 20.

[0166] Figure 3 shows, in detail, the wire guiding device 106 which comprises a base 117 on which wire directing elements 116 (preferably pairs of wheels) for directing the wire 10 are fastened and direct the wires 10 into the wire guiding tube 104 which is placed at the lower end of the base 117 facing the winding tool 20.

[0167] A reeling member 118, which is preferably present in the winding machine 100 and positioned coaxially to the spindle 144, in which the wires 10 coming out of the wire guiding tube 104 are aligned in loops before being wound on the winding tool 20, is illustrated in figure 4.

[0168] Figure 5 is a magnification of figure 4.

[0169] Figure 6 shows a section of the wire guiding tube 104, considered on the sectional plane P1 -P1 of figure 3, which consists of a plurality of sectors defining a plurality of separate ducts 151 in which the wires 10 run, so that the wires 10 intended to form a level, or layer, of a loop are kept in position in each duct 151. There are three ducts 151 in the example illustrated and the wires 10 are arranged on three levels with a 5-4-5 sequence (five wires on the first level, four on the second level and five on the third level) for a total of fourteen parallel wires 10 per loop, each wire 10 being managed by one of the fourteen wire tensioning devices 103 visible in figure 2.

[0170] Obviously, the number of wires 10 wound in parallel per loop (and therefore the number of wire tensioning devices 103), the number of levels (and therefore of ducts 151 in the wire guiding tube 104) and the number of wires 10 per level can be varied and selected depending on the design requirements.

[0171] Figures 7-14 show a first embodiment of the winding tool 20; a second embodiment is shown in figures 18-19 and in figures 22-27C.

[0172] With reference to figures 7-14, the winding tool 20 preferably comprises a plurality of movable walls 22 comprised between an anchor wall 23’ and a removable disassembly wall 24’.

[0173] The anchor wall 23’ is configured for being operatively coupled to a winding spindle 144 so that to drive the rotation of the movable walls 22 and optionally comprises, for this purpose, a sleeve for hooking to the spindle 25.

[0174] The removable disassembly wall 24’ can be decoupled from the anchor wall 23’ to release the movable walls 22 and allow the displacement of the coils 1 already wound.

[0175] The movable walls 22 form one or more winding chambers 24 in which the wires 10 are wound to form the coils 1 .

[0176] More in detail, the anchor wall 23’ also comprises a wire clamp element

[0177] 26 configured for clamping the wires 10 (which are already arranged in the proper configuration) coming into the winding.

[0178] Conveniently, the anchor wall 23’ is further provided with a centering pin

[0179] 27 to center the movable walls 22, which centering pin juts out towards the removable wall 24’ and engages a tunnel formed by central holes 28 which are obtained at the center of each movable wall 22.

[0180] A hooking end 71 , for hooking the anchor wall 23’ to the removable wall 24’, is present at the end of the centering pin 27.

[0181] The anchor wall 23’ is further provided with a plurality (four in the example illustrated) of axial positioning pins 31 which also jut out towards the removable wall 24’ and which have the task of keeping the proper axial position of the movable walls 22 while winding, by occupying respective positioning holes 29 obtained in the movable walls 22, so that to ensure the proper size of the winding chambers 24.

[0182] As can be noted in the figures, the axial positioning pins 31 are formed by a plurality of longitudinal portions of different diameters and decreasing towards the removable wall 24’, and the positioning holes 29 are of a different diameter in each movable wall 22, decreasing towards the removable wall 24’, so that each movable wall 22 is locked on a respective longitudinal portion of the axial positioning pins 31.

[0183] The movable walls 22 therefore ensure the axial size (determined by the thickness of the walls 22 and by the distance between the walls 22 themselves) during the step of winding the conducting wire 10 (for making the coils 4), but can move closer to each other under the thrust of a press during the pressing step (if provided), which will be described hereunder. Such axial dimension is conveniently ensured by mechanical reference elements 291 which ensure the repeatability of the process and the consistency of the final dimensions of the pressed coil 4. In practice, the winding tool 20 is configured so that the movable walls 22 can move closer to each other, under the action of a pressure, up to a distance defined by the mechanical reference elements 291 which act as a limit abutment.

[0184] The number of movable walls 22 in the winding tool 20 is determined by the number of portions of coil 1 to be made series.

[0185] The movable walls 22 are substantially rectangular in plan, both in vertical section and in horizontal section. The movable walls 22 are preferably provided, on the sides jutting out outside the winding tool 20, with manipulation seats 249.

[0186] In the preferred embodiment, each movable wall 22 is formed by a central support 221 , two winding cheeks 222 fixed to the two sides of the central support 221 , in this case the manipulation seats 249 are obtained in the winding cheeks 222. In practice, in these embodiments, the winding chambers 24 are defined between the winding cheeks 222.

[0187] Preferably, a thermal insulator is interposed between the central support 221 and the winding cheeks 222 to limit thermal loss during the thermal carburizing treatment which will be described hereunder.

[0188] The removable disassembly wall 24’ is removable in the sense that it can be decoupled from the fixed wall to allow to pull out the movable walls 22.

[0189] In the preferred embodiments, the removable wall 24 is also provided with a respective wire clamp element 261 configured for clamping the wires 10 coming out of the winding, thus keeping them arranged in the proper configuration.

[0190] The removable wall 24’ then comprises a coupling device 241 for the direct or indirect coupling to the anchor wall 23’ in which, for example, the hooking end 271 of the centering pin 27 of the anchor wall 23’ is hooked.

[0191] Preferably, the removable wall 24’ further comprises a gripping element 242 adapted to be grasped or hooked to allow its movement.

[0192] In the preferred embodiments, the winding tool 20 comprises a plurality of angle elements 245 coupled to the removable wall 24’, which slide on respective appropriately inclined guides 246. Such guides 246 extend from the removable wall towards, and preferably up to, the anchor wall 23’. The angle elements act as an abutment for the wires 10 while winding and, in particular, provide support to the wire portion 10 which will not be part of the rectilinear lengths 6, 7, i.e. the wire portion 10 forming the headers 8 and 9 of the coil 1 .

[0193] In the example shown, the angle elements 245 are at least four, one for each angle.

[0194] Thanks to the sliding along the guides 246, the angle elements 245 slide towards the center of the winding tool 20 (as shown in figures 9 and 10) during the detachment of the removable wall 24’ from the hooking wall, so that to cancel stress from the wires 10 forming the coils 1 and thus to allow the removal of the coils 1 without scrapes, so that to prevent the wire 10 from being damaged. In particular, in figure 10, the angle elements 245 are more backward with respect to their position in figure 9.

[0195] Figure 11 is a side and elevation view of the winding tool 20 shown in figure 7, in the condition of figure 9, i.e. with the coil 1 completely wound and with the winding tool 20 ready for the displacement of the angle elements 245. Three section planes are depicted in figure 11 : the horizontal plane P2-P2 parallel to the rotation axis of the winding tool 20 passing through the axial positioning pins 31 , the plane P3-P3 parallel to the plane P2-P2 and intermediate between the plane P2-P2 and the gripping element 242, and finally the vertical plane P4-P4 passing through the rotation axis 242.

[0196] Figures 12, 13 and 14 are sectional views of the winding tool 20 in the condition shown in figures 9 and 11 , considered respectively on the planes P2- P2, P3-P3 and P4-P4.

[0197] Successively to the coil forming step A, the method provides an optional, although preferential, pressing and / or carburizing step B, in which the at least one linear length 6, 7 of the at least one coil 1 is pressed and / or subjected to a thermal carburizing treatment so that to compact the individual linear lengths 6, 7 of wire 10 together, thus “freezing” the orderly arrangement achieved on the winding tool 20. In order to obtain the freezing of the respective position of the wires 10 composing the linear lengths 6, 7 of the coil 1 , step B is carried out with the coil 1 still aboard the winding tool 20. In other words, the coil 1 is not collected from the winding tool 20 but step B is carried out on the linear lengths 6, 7 still tensioned between the angle elements 245.

[0198] In practice, the coil 1 already formed on the winding tool 20 is displaced and positioned, together with the winding tool 20, in a pressing and / or carburizing apparatus 300.

[0199] Figure 15 shows an example of an apparatus 300 in perspective.

[0200] Figure 16 is a vertical sectional view of the apparatus 300 shown in figure 15, at the start of step B.

[0201] Figure 17 is a vertical sectional view of the apparatus 300 shown in figure 15 during step B, i.e. during pressing and / or carburizing of the linear lengths 6, 7 of the coil 1 .

[0202] In the preferred embodiment, the apparatus 300 performs both the pressing and the carburizing of the linear lengths 6, 7 of the coil 1 and comprises a housing seat 301 configured for housing the winding tool 20 with the coil 1 aboard, and one or more presser elements 30 configured for exerting a pressure on the at least one linear length 6, 7 of the coil 1 wound on the winding tool 20.

[0203] Preferably, there are two presser elements 30 positioned coaxially on opposite sides of the housing seat 301 and which, once operated, exert pressure one in direction of the other, preferably in the horizontal direction, so that to press each of the two linear lengths 6, 7 opposite each coil 1 .

[0204] The presser elements 30 are provided with at least one heating device 41 (preferably comprising one or more inductors) configured for heating the linear lengths 6, 7 before, after or during the application of the pressure by the pressers 30, so that to perform the thermal carburizing treatment while the coil 1 is wound on the winding tool 20 and, thus, while the arrangement of the conducting wire 10 is perfectly orderly.

[0205] The presser elements are activated by means of a pressure kinematic 304 which, in the embodiment illustrated, comprises a piston and a spring coaxial thereto.

[0206] In some embodiments, the heating devices 41 are comprised in, or coupled to, the presser elements 30 and more precisely in their heads 32, which constitute the ends of the presser elements 30 themselves and which come into contact with the linear lengths 6, 7 during the pressing.

[0207] Conveniently, there is a number of heating devices 41 equal to the number of movable walls 22.

[0208] Optionally, the pressing and / or carburizing apparatus 300 comprises thermal probes 34 and / or pyrometers 35, which are preferably coupled to the presser elements 30, for allowing the feedback control of the carburizing treatment by a control system which controls the heating elements 41 .

[0209] More in detail, the pressing and / or carburizing apparatus 300 comprises, at the housing seat 301 , fixed abutments 311 on which the winding tool 20 rests. Such fixed abutments 311 have bearing planes made of a thermally insulating material, on which the winding tool 20 rests to limit heat dispersion.

[0210] Preferably, the pressing and / or carburizing apparatus 300 further comprises a pressing head 302 which moves orthogonally with respect to the presser elements 30, vertically in the example depicted, so that to compress the winding tool (and therefore the coil 1 ) in orthogonal direction with respect to the presser elements 30, thus causing the movable walls 22 to move closer, so that to further compact the linear lengths 6, 7 of the coil 1 and to determine its thickness, using the mechanical reference elements 291 acting as limit abutments as reference. In practice, the pressing head 302 compresses the winding tool 20 (and thus the coil 1 ) against the fixed abutments 311 .

[0211] Therefore, the linear lengths 6, 7 of each coil 1 are preferably subjected to two pressures in orthogonal directions to each other, as is possible to verify in the comparison between figures 16 and 17.

[0212] Conveniently, only the linear lengths 6, 7 of the coil 1 are appropriately pressed and subjected to the thermal treatment, while the non-linear lengths 8, 9, i.e. the headers connecting the linear lengths 6, 7 and which are mainly curved, are left untreated, so that to be able to shape them easily during the assembly of the stator.

[0213] Once the predetermined carburizing temperature has been reached, which depends on the characteristics of the wire 10 used, the pressure elements 30, and possibly the vertical press 302, keep the pressure for the time needed for cooling, which is assisted by cooling devices (for example with air, not depicted), so that to stabilize the linear lengths 6, 7 at their permanent size and structure.

[0214] In the example shown in the figures, the pressure exerted is within the range of 140-300 bars and the temperature reached by the heating elements 31 is within the range of 170°-210°C. The duration of step B is between 15 seconds and 2 minutes.

[0215] Optionally, the pressing and / or carburizing apparatus 300 comprises a loading slide 330 visible in figure 15 and configured for bringing the winding tool 20 with the coil 1 into the housing seat 301 and depositing it on the fixed abutments 311. The loading slide 330 can slide along horizontal tracks 331 and is provided with a platform movable vertically and adapted for raising the winding tool 20.

[0216] Advantageously, the pressing and / or carburizing step B conforms and makes the size of the linear lengths 6, 7 of the coil 1 repeatable and compacts them, thus maximizing the filling factor. Moreover, the linear lengths 6, 7 as treated are solidified so that the arrangement of the wires 10 stays unchanged throughout the process. The wires 10 are arranged and kept in an orderly and repeatable matrix configuration and are not grouped randomly but keep the orderly arrangement given during winding on the winding machine 100.

[0217] In the example described, the linear lengths 6, 7 of the coil 1 are first subjected to pressing and then to carburizing, but the method can generally be implemented by performing either only the pressing or the carburizing, or both, in the order described and also backwards, or even by performing the pressing and carburizing simultaneously.

[0218] After the pressing and / or carburizing step B, when the coil 1 has cooled and the linear lengths 6, 7 are therefore solidified, the coil 1 is disassembled from the winding tool 20. By supporting the winding tool 20 by means of the sleeve for hooking to the spindle 25 and / or the gripping element 242, the coupling device 241 is unlocked (pneumatically).

[0219] The wire clamp elements 26, 261 are therefore opened, for example by means of two outer controls, for releasing the wires 10 coming in and out of the portions 2, 3 of the coil 1. At this point, a manipulator (not depicted), which guides the removable wall 24’ of the winding tool 20, starts to move away axially from the anchor wall 23’. During the first step of this movement, the angle elements 245, sliding on the respective guides 246, start to move towards the center of the winding tool 20, so that to cancel stress the wire 10 and allow to pull out the coil 1 .

[0220] The manipulator guiding the removable wall 24’ therefore continues to axially move away from the anchor wall 23’ and a second manipulator takes the movable walls 22 by means of the manipulation seats 249 and moves them until pulling them out from the anchor wall 23’ (by pulling them out of the pins 27, 231 ).

[0221] At this point, the coil 1 , or coils 1 , is / are removed from the winding tool 20 by means of a manipulator, to be inserted into the stator slots of a stator, as will be made clearer hereunder.

[0222] Figures 18-19 illustrate a second winding method, i.e. a second way of making coils 1 , and a second winding machine 100’ for carrying out step A. More in detail, figures 18 and 19 are perspective views of a winding machine 100’ and the corresponding winding tool 20’. A wire directing device 150, which automatically allows to manage the distance between the various levels of wires 10 coming in by means of a controlled axis, is used instead of the wire guiding device 206 with a single wire guiding tube 104 of figures 2-3.

[0223] This device 150 for directing the wire 10 comprises an axial guide 151 along which a plurality of wire guiding tubes 152 can slide in a controlled way and independently of one another.

[0224] The axial guide 151 in turn slides along a perpendicular guide 153, such as the wire guiding tubes 152 are movable along at least two axes.

[0225] Each wire guiding tube 152 is crossed by, and in practice directs, a layer of wires 10.

[0226] During the various winding steps, the wire guiding tubes 152 can move closer to each other up to bringing the various levels of wire 10 into contact, or can move away from one another so that each layer enters the winding independently and at different times than the others.

[0227] This makes it possible to deposit each layer on the winding tool 20' independently of the others so that to prevent them from getting in each other's way.

[0228] When required, the wire guiding tubes 152 move closer to each other again to facilitate the operations which require all wires 10 to be close together.

[0229] Optionally, in this embodiment, the winding tool 20’ is rotated by a winding spindle 244’ which is integral with a motor assembly 157 fastened to a carriage 158 movable along a track 159 (guide or rail or the like).

[0230] Figures 20A, 20B and 20C show three different examples of loops which can be obtained with the winding tool 20 or 20’, in which:

[0231] - in figure 20A, each loop S1 , S2 is formed by two layers: a first layer of five wires 10 and a second layer of four wires 10;

[0232] - in figure 20B, each loop ST, S2’ is formed by two layers, both of five wires 10;

[0233] - in figure 20C, each loop S1 ”, S2” is formed by three layers: a first layer of five wires 10, a second layer of four wires 10 and a third layer of five wires 10.

[0234] As can be noted, the wires with circular section tend to leave free spaces; in order to overcome this problem, it is possible to resort to an optional solution depicted in figures 21 A, 21 B, 21 C.

[0235] According to this optional and advantageous solution for the filling factor, during the coil making step and, more precisely, while winding, complementary conducting wires of a smaller section 10’, which occupy the space left free from the tangency of the wires 10 of a greater section (i.e. the free spaces between the aforesaid wires 10 of a greater section), are added to each loop ST, S2’ or S1 ”, S2”. This way, during the winding step, each loop ST, S1 ”, S2’, S2” will be formed by layers of wires of a different section, alternated with each other and which, once wound, allow to achieve an even greater filling factor.

[0236] Figures 22-25 show the second embodiment of the winding tool 20’ in detail. In particular, figure 22 is an isometric view, figure 23 is a front and elevation view, figure 24 is a side and elevation view, figure 25 is a top plan view.

[0237] The winding tool 20’ comprises a supporting frame 21 supporting a series of angle elements 23; each series is substantially arranged along an edge of an ideal parallelepiped. The angle elements 23 of each series are spaced from one another so that to define a corresponding series of winding chambers 24 for accommodating the wire 10 forming the coil 1.

[0238] Reference 26’ denotes a wire clamp element used to hold the ends of the wires 10. The numbers of reference equal to those used for the first embodiment of the winding tool 20 denote identical or equivalent elements.

[0239] Successively to the coil forming step A, the method according to the present invention preferably provides a pressing and / or carburizing step B, as previously described and as will now be illustrated with reference to figures 26A to 27C.

[0240] The heating device 30’ shown in figures 26A-27C comprises one or more heating elements 41 , preferably by induction.

[0241] These heating elements 41 are shaped and arranged so that to be inserted between the linear lengths 6, 7 of the coils 1 , in contact therewith or adjacent thereto. It is possible to perform this operation while the coil 1 is still accommodated on the winding tool 20, 20’, thanks to the fact that the linear lengths 6, 7 are left free.

[0242] These heating elements 41 therefore have a longitudinal extent substantially equivalent to that of the linear lengths 6, 7 to be heated.

[0243] It should be noted that in the embodiment depicted, the heating elements 41 substantially form a comb of elements parallel to one another.

[0244] In practice, the heating elements 41 are inserted between the linear lengths 6, 7 of the coils 1 , so that to heat them up to the carburizing temperature, as depicted in figure 26B.

[0245] By exploiting the thermal inertia of the material, there is therefore time to remove the heating elements 41 and to insert, in their place, the pressing device 300 which presses the winding and heats it when needed, if it is itself provided with heating elements 41 .

[0246] In the embodiment illustrated in figures 27A-27C, concerning to the winding tool 20’ mounted on the winding machine 200, the pressing device 300 comprises a plate 301 to which a series of inclined planes 303 adapted for coming into contact with the linear lengths 6, 7 to be pressed is coupled. The plate 301 is inserted into, or is anyhow mechanically coupled to, a complementary counterplate 302’ positioned on the opposite part of the linear lengths 6, 7 and which acts as an abutment element.

[0247] The plate 301 is pushed, by means of a thrust device (not shown) against the counterplate 302. The inclined planes 303 are configured so that the moving of the plate 301 towards the counterplate 302 causes, by direct mechanical interaction, the compacting of the linear lengths 6, 7 of the coil.

[0248] The linear lengths 6, 7 of the winding are therefore compacted to the desired dimensions by exploiting the force of the thrust device and the appropriately made inclined planes 303.

[0249] These carburizing and pressing operations can be implemented alternately or simultaneously on the two sides of the winding tool 20, 20’, depending on the cycle time required by the plant during production.

[0250] Conveniently, only the linear lengths 6, 7 of the coil 1 are pressed and / or subjected to the thermal treatment, while the non-linear lengths 8, 9 (i.e. the headers which are mainly curved) are left untreated so that to be able to easily shape them in the successive steps.

[0251] After the pressing and / or carburizing step B, when the coil 1 has cooled and therefore solidified in the linear lengths 6, 7, the coil 1 , or coils 1 , can be removed from the winding tool 20, 20’ (any one of those described herein).

[0252] Optionally, when a series of several coils 1 , or a coil 1 , with several portions is made on the same winding tool 20, 20’ in the coil making step A so that a linear length 6, 7 of a coil 1 is spaced by a given pitch distance from the linear length 6, 7 of the successive coil or portion of coil 1 , a process of pitch correction between the coils 1 is performed before housing the coils 1 in the stator slots. The pitch correction is achieved by:

[0253] - taking the series of coils 1 from the winding tool 20, 20’ and bringing them on a pitch-correcting device (not shown) configured for correcting the pitch distance between the linear lengths 6, 7 of the different coils 1 ,

[0254] - taking the coils 1 from the pitch-correcting device by means of the grippers configured for keeping the pitch distance unchanged between the linear lengths 6, 7 of the coils 1 , after having completed the pitch correction. These grippers will insert the coils 1 into the stator slots.

[0255] Thanks to the above-described step A of forming the coils 1 , coils 1 with rectilinear lengths 6, 7 and whose cross sections have a shape complementary to that of the stator slot into which they must be inserted, are made. It is therefore possible to exploit the whole area of the stator slot while simultaneously keeping the conducting wires 10, 10’ orderly and maximizing the filling factor.

[0256] With reference to figures 28-52, a second method of winding and a second winding machine usable for making coils 1 will now be described, the winding method and the winding machine being particularly adapted for making coils 1 having linear lengths 6 and 7 of a length of less than 3 cm.

[0257] The second method and the second winding machine are apparently similar to methods and winding machines conventionally used for making coils with alpha windings (a-winding coils), but the winding is actually formed differently.

[0258] In particular, figure 28 shows, in perspective, the second winding machine 400 which comprises:

[0259] - a wire guiding device 401 having the task of guiding the wires 10 coming from corresponding wire spools,

[0260] - a first spindle 402 having the task of rotating a winding tool 20” (third embodiment);

[0261] - one or more satellites 404 for storing the wire 10;

[0262] - a second spindle 403 having the task of rotating the satellites 404 and the respective motors about the respective rotation axis X-X (horizontal).

[0263] As can be noted, the wire guiding device 401 is provided with a plurality of holes 405 into which corresponding wires 10 are slidably inserted. After having crossed the holes 405, the bundle of wires 10 is inserted into the wire guiding tube 406 which, similarly to what is described for the wire guiding tube 104 of figure 3, ensures perfect stratification, i.e. perfect orderly arrangement, of the wires 10. The wire guiding tube 406 is oriented towards the winding tool 20” mounted on the first spindle 402.

[0264] The first spindle 402 is mounted on a frame 407 and the second spindle 403 is mounted on a frame 408. The first frame 407 is rotatable on the axis (vertical) Y-Y defined by a pin 409. The axis Y-Y is orthogonal and incident to the axis X-X of the second spindle 403. For simplicity, the actuator which controls the rotation of the frame 407 and of the first spindle 402 on the axis Y-Y is not shown. Reference 410 denotes the motors of the satellites 404 for storing the wire 10.

[0265] Thanks to this configuration, the winding machine 400 is configurable:

[0266] - with the spindles 402 and 403 aligned on the rotation axis X-X of the second spindle 403 and the rotation axis X-X is thus also the rotation axis of the winding tool 20”, or

[0267] - with the first spindle 402 misaligned with respect to the rotation axis X-X of the second spindle 403, by making the frame 407 and the first spindle 402 rotate on the (vertical) axis Y-Y.

[0268] Similarly to what has been described for the other versions of the winding tool 20, 20’, the winding tool 20” is also provided with two or more winding chambers generally denoted by 24 and arranged in succession. This allows to make coils 1 with several portions for actually obtaining distributed winding on the stator. In the example shown in the figures, the winding tool 20” has two winding chambers 24’ and 24”.

[0269] The start of the coil making step A is shown in figure 29: the frame 407 of the first spindle 402 is rotated on the axis Y-Y so that an acute angle is defined between the vertical plane containing the rotation axis X-X of the winding tool 20” and the median vertical plane passing through the wire guiding tube 406. The storage satellites 404 are raised. As will be made clearer hereunder, directing the bundle of wires 10 (appropriately stratified) at an angle to the rotation axis X-X of the winding tool 20” is a characteristic feature of the present solution with respect to conventional systems for obtaining alpha windings in which the conducting wire is always fed in the direction orthogonal to the rotation axis of the winding tool.

[0270] At this initial time, in the upper part, the winding tool 20” is devoid of the supports 421 defining the winding chambers 24’, 24”, with the exception of the central support 42T provided with a chase 422 for the passage of the wires 10. The chase 422 is a niche, or anyhow a seat into which the wires 10 are inserted, so that to bring them to the height of the winding surface of the winding tool 20”. The supports 421 are installed successively on opposite parts with respect to the central support 42T. In the lower part, the winding tool 20” is instead already provided with the supports 421 .

[0271] Figure 30 shows a successive time during Step A of making the coils 1. Two distinct bundles 11 and 12 of wires 10 extend from the wire guiding tube 406 towards a corresponding storage satellite 404. In particular, the upper bundle 11 of wires 10 extends between the wire guiding tube 406 and the most radially outward storage satellite 404, and the lower bundle 12 of wires 10 extends between the wire guiding tube 406 and the most radially inward storage satellite 404.

[0272] Each bundle 11 , 12 of wires 10 will generally be wound on a corresponding storage satellite 404; therefore, if step A provides for making coils 1 with several layers of wire 10, the winding machine 400 will be provided with a number of storage satellites 404 corresponding to the number of layers of wire 10 to be managed.

[0273] A length of the corresponding bundle 11 , 12 of wires 10, corresponding to the length required for making a portion 2, 3 of coil 1 , is wound on each storage satellite 404. In short, each storage satellite 404 therefore stores a bundle 11 , 12 of wires 10 for a length sufficient for making the corresponding portion 2, 3 of coil 1 .

[0274] Figure 31 shows a successive time during Step A of making the coils 1. The storage satellites 404 are rotated on the axis X-X, staying radially aligned and resulting in overlapping the bundles 11 and 12 of wire 10 which are then inserted through the chase 422 present in the central support 42T of the winding tool 20”.

[0275] The insertion of the bundles 11 and 12 of wire 10 into the chase 422 of the central support 42T allows to locally deform the bundles 11 and 12 of wire 10 precisely at the support 42T, as will now be explained, by performing a rotation of the frame 407 and realigning the two spindles 402 and 203. In practice, the central support 42T of the winding tool is therefore used as a tool for locally deforming the wires 10 and allows, on the one hand, to align the bundles 11 and 12 of wire 10 present on the storage satellite 404 with a winding chamber 24” and to align the bundles 11 and 12 coming out of the wire guiding tube 406 with the other winding chamber 24’, on the other hand.

[0276] Figure 32 shows a successive time during which the winding tool 20” is completed, in its upper part, with the mounting of two supports 421 on opposite parts with respect to the central support 42T. Two winding chambers 24’ and 24” are configured this way. The side supports 421 have a lower chase to allow the passage of the bundles 11 and 12 of wire 10.

[0277] At this point, the bundles 1 1 and 12 of wire 10 therefore extend on a lying plane orthogonal to the axis X-X and oblique to the rotation axis of the spindle 402, which was rotated on the (vertical) axis Y-Y. The bundles 11 and 12 of wire 10 therefore extend obliquely to the winding tool 20”, i.e. an acute angle is defined between the lying plane of the bundles 11 , 12 of wire 10 and the vertical plane passing through the axis of the spindle 402.

[0278] Figure 33 shows a successive time at which the frame 407 is rotated to the initial position shown in figure 28, i.e. with both spindles 402, 403 aligned on the rotation axis X-X. At this point, it is possible to operate the storage satellites 404 for performing the winding of the bundles 11 , 12 of wire 10 in the winding chambers 24 of the winding tool 20”.

[0279] Figure 34 is a magnification, in perspective, of the winding tool 20” in the configuration shown in figure 32. The central support 42T with the chase 422 open upward, which chase allowed to insert the bundles 11 and 12 of wire 10 from the top, are well visible, and the side supports 421 define the winding chambers 24’ and 24” together with the central support 42T. The same configuration of supports 421 and winding chambers 24’ is also present in the lower part of the winding tool 20”.

[0280] Figure 35 is a top plan view of the winding tool 20” in the configuration shown in figure 34, i.e. with the two bundles 11 and 12 of wire 10 extending, overlapping, through the chase 422 present in the central support 42T and through the two side supports 421 between the wire guiding tube 406 and storage satellites 404. As can be clearly seen, the rotation axis of the first spindle 402 is inclined with respect to the feed plane of the bundles 11 and 12 of wire 10.

[0281] Figure 36 is a magnification, in perspective, of the winding tool 20” in the configuration shown in figure 33, i.e. after the first spindle 402 and the second spindle 403 were once again aligned on the rotation axis X-X of the second spindle 403. The realignment of the spindles 402 and 403 caused the deformation of the bundles 11 and 12 of wire 10 inside the chase 422 of the central support 42T of the winding tool 20”, as mentioned above. The deformation obtained is well visible in figure 37.

[0282] Figure 37 is a top plan view of the winding tool 20” in the configuration shown in figure 36, i.e. with the two spindles 402, 403 aligned on the axis X-X. As can be noted, the described above realignment of the spindles 402, 403 has allowed to obtain the localized deformation of the bundles 11 and 12 of wire 10 at the chase 422. The localized deformation of the wires 10, observed in plan, is almost S-shaped. The localized deformation of the wires 10 at the locked portion 10x allows to achieve this result:

[0283] - a first length 10.1 of the bundles 11 and 12 of wire 10 extends between the wire guiding tube 406 and the central support 42T, staying aligned with the first winding chamber 24’ found to the left of the central support 42T, and

[0284] - a second length 10.2 of the bundles 11 and 12 of wire 10 extends between the central support 42T and the storage satellites 404, staying aligned with the second winding chamber 24” found to the right of the central support 421’.

[0285] In practice, the localized deformation of the wires 10 at 10x allowed to align the two winding chambers 24’ and 24” with the corresponding lengths 10.1 and 10.2 of wire 10 which - worth recalling - are grouped in two bundles 11 and 12 appropriately stratified thanks to the wire guiding device 401 and the wire guiding tube 406.

[0286] At this point, it is possible to start winding the wires 10 simultaneously in both the winding chambers 24’ and 24”, without having to make the storage satellites 404 move forward or else the wire guiding tube 406 along the axis X- X. The coil 1 which will therefore be made, corresponding to the coil 1 shown in figure 1 , will have a first portion 2 made in the first winding chamber 24’ and a second portion 3 made in the second winding chamber 24”.

[0287] The detail just described therefore allows to obtain coils 1 with two portions 2 and 3 without having to translate one of the spindles 402, 403, or the wire guiding tube 406 or the storage satellites 404, along the axis X-X.

[0288] Figure 38 is a perspective view of the winding machine 400 at a later time than the one shown in figures 33 and 36-37. The two spindles 402 and 403 are coaxial on the axis X-X. The first spindle 402 starts to rotate the winding tool 20” on the axis X-X and this results in the dragging of the bundles 11 and 12 from the wire guiding tube 406 and the consequent winding of the first length 10.1 of wires 10 in the first winding chamber 24’. The second spindle 403 simultaneously starts to rotate the storage satellites 404 about the axis X-X and about the winding tool 20”, in the same direction as that of the first spindle 402, and this results in the winding of the second length 10.2 of wires 10 in the second winding chamber 24”. The arrows on the spindles 402 and 403 denote the direction of the rotation imparted.

[0289] Figures 39 to 51 show, in sequence, successive steps of the making of a coil 1. They are perspective views. As can be understood, the winding tool 20” and the storage satellites 404 each perform the number of revolutions required on the rotation axis X-X for completing the corresponding portion 2, 3 of coil 1 . In other words, the number of revolutions of the two spindles 402 and 403 is selected to obtain the desired stratification of the bundles 11 and 12 of wire 10 on the winding tool 20”, respectively in the winding chamber 24’ as far as the wires 10 coming from the wire guiding device 401 are concerned and in the winding chamber 24” as far as the wires 10 coming from the satellite spindles 404 are concerned. In other words, the coil 2 in the winding chamber 24’ is made by collecting the wires 10 only from the wire guiding tube 406 and the coil 3 in the winding chamber 24” is made by collecting the wires 10 only from the storage satellites 404.

[0290] Figure 51 shows one of the final steps of forming the coil 1 : the first length 10.1 of the bundles 11 and 12 of wire 10 was completely wound on the winding tool 20”, in the first winding chamber 24’. The wire guiding tube 406 is actually shown empty, free of wires 10. The storage satellites 404 are completing the last revolution about the rotation axis X-X.

[0291] Figure 52 shows the final step of making the coil 1 : The first spindle 402 is stopped and kept stationary for locking the winding tool 20”. The second spindle 403 (not shown) is also stopped and, when needed, backed up or moved away to give access to the winding tool 20”.

[0292] At this point, the winding tool 20” with the coil 1 wound thereon is ready to be collected. It should be noted that the wires 10 composing the coil 1 still wound on the winding tool 20” have retained the orderly arrangement and stratification imposed by the wire guiding device 401 and by the wire guiding tube 406, for example the arrangement and stratification shown in figures 20A to 21 C.

[0293] The step A of forming the coil 1 is now completed and it is possible to assemble the stator. Clearly, step A of forming the coils 1 will be repeated as many times as the number of coils 1 needed to assemble the stator.

[0294] As mentioned above, before assembling the stator, the coil 1 is preferably subjected to a pressing and / or carburizing step B, in order to freeze the orderly arrangement and stratification of the wires 10.

[0295] When step B should not be provided, the winding tool 20” would be collected from the first spindle 402 to release the winding machine 400 and allow a new coil 1 to be formed, and the winding tool 20” would therefore be disassembled to release the coil 1 which would be collected by an appropriate manipulator (not shown) provided with grippers which, by gripping onto the coil 1 , would move the coil 1 without altering the orderly arrangement and stratification of the wires 10 to therefore insert the linear lengths 6 and 7 of the coil 1 into the stator slots.

[0296] The pressing and / or carburizing step B will now be described with reference to figures 53-62, in case the winding machine 400 and the winding tool 20” are used to make the coil 1 , i.e. to implement step A.

[0297] Figure 53 shows an isometric view of the winding tool 20” of the winding machine 400. The winding tool 20” can have been collected from the winding machine 400 or can still be anchored to the first spindle 402: figure 53 omits this difference for simplicity. As can be observed, the coil 1 is completely formed with the two portions 2 and 3 and the terminals 4 and 5. The wire 10 or wires 10, 10’ defining the linear lengths 6 and 7 are perfectly orderly and keep the arrangement and stratification shown, for example, in figures 20A to 21 C.

[0298] Figure 54 shows the start of the optional pressing and / or carburizing step by an appropriate apparatus 500 comprising, in the example shown, presser elements 501 , 502 and a countering element 503. The presser elements 501 , 502 are intended for being inserted, radially from the outside, between the linear lengths 6, 7 of the coil 1 and for this reason are comb-shaped; the countering element 503 is intended for being inserted axially into the winding tool 20” through the coil 1 , to provide countering surfaces to the presser elements 501 , 502. In practice, the presser elements 501 , 502 and the countering element 503 therefore cooperate for surrounding the linear lengths 6, 7 of the coil 1 throughout their extent.

[0299] Both the presser elements 501 , 502 and the countering element 503 are provided with heating elements 504, for example of inductive or resistive type.

[0300] The presser elements 501 , 502 are advantageously provided with wedge-shaped inserts 505 defining grooves 506 of a shape corresponding to the shape to be imparted to the linear lengths 6, 7 of the coil 1 , which corresponds to the shape of the stator slots, so that to have a perfect shape coupling between the coils 1 and the stator. In other words, the presser elements 501 , 502, together with the countering element 503, impart the shape complementary to the inner volume of the stator slots to the linear lengths 6, 7 of the coil 1 .

[0301] The countering element 503 moves axially along the axis X-X; the presser elements 501 , 502 move both axially, for being aligned with the linear lengths 6, 7 of the coil 1 , and radially, for pressing the linear lengths 6 and 7.

[0302] Figures 55 and 56 show the pressing and / or carburizing apparatus 500 moving further toward the winding tool 20”. In particular, figure 56 is a sectional and perspective view of figure 55, with the section considered on a horizontal plane containing the rotation axis X-X. The presser elements 501 , 502 are aligned with the linear lengths 6 and 7 of the coil 1 , with the presser element 501 positioned on the opposite part of the presser element 502 with respect to the winding tool 20”. The countering element 503 is inserted into the winding tool in the axial direction. As can well be observed in figure 56, the presser elements 501 , 502 are substantially comb-shaped for actually being slipped between the linear lengths 6 and 7 of the coil 1 and allowing it to be heated on its three sides, encompassing all the layers 11 and 12 defining each linear length 6 or 7. The countering element 503 comprises a body 503’ and wedge-shaped elements 503” which can be inserted into corresponding seats formed in the body 503’. The wedge-shaped elements 503” are partially extracted from the body 503’ of the countering element 503 in figure 56.

[0303] Figures 57 and 58 show the pressing and / or carburizing apparatus 500 with the countering element 503 completely inserted through the winding tool 20” and through the coil 1 wound on the winding tool 20”. In particular, figure 58 is a sectional and perspective view of figure 57, with the section considered on a horizontal plane containing the rotation axis X-X. The countering element 503 defines an abutment surface inside the winding tool 20” so that, when the presser elements exert a radial thrust directed towards the countering element 503, an undesired deformation neither occurs in the linear lengths 6, 7 nor in the winding tool 20”. The wedge-shaped elements 503” are partially extracted from the body 503’ of the countering element 503 in figure 58.

[0304] Figures 59 and 60 show the pressing and / or carburizing apparatus 500 at a later time than the one shown in figures 57-58: the wedge-shaped elements 503” were completely inserted into the body 503’ of the countering element 503 to cause an elastic deformation of the body 503’ such that the body 503’ exerts an outward thrust in the radial direction both on the linear lengths 6 of the coil 1 and on the linear lengths 7 of the coil 1 , i.e. towards the presser elements 501 , 502. In practice, wedging the wedge-shaped elements 503” into the body 503’ results in the widening of the body 503’ and, therefore, in the application of a thrust directed radially from the inside to the outside of the winding tool 20” on the linear lengths 6 and 7 of the coil 1 .

[0305] The same technical solution is adopted on the presser elements 501 , 502: the wedge-shaped inserts 505 are actually slidingly movable at the body of the respective presser element to exert an axial thrust on the linear lengths 6 and 7 of the coil 1 , as will become clearer in the following paragraph.

[0306] Figure 61 and 62 show the pressing and / or carburizing apparatus 500 at a later time than the one shown in figures 59-60 and precisely show the final step of the pressing and / or carburizing process. As mentioned above, pressing and carburizing can be alternately or simultaneously carried out, at the same time or in succession, in the desired order.

[0307] Step B is preferably carried out by providing for both the pressing of the linear lengths 6 and 7 of the coil 1 and their carburizing.

[0308] In the position shown in figure 61 , the presser elements 501 and 502 are applying a force on the linear lengths 6 and 7 of the coil 1 , on opposite parts of the winding tool 20”, as denoted by the arrows, i.e. radially towards the axis X- X. The countering element 503 simultaneously applies a force directed radially towards the presser elements 501 , 502 on the linear lengths 6 and 7 of the coil 1. Figure 62 is a sectional and perspective view of figure 61 , with the section considered on a first horizontal plane containing the rotation axis X-X. In figure 62, by way of example, four arrows denote the direction of the force applied on each side on the linear length 6. The wedge-shaped inserts 505 and the wedge- shaped elements 503” are forcefully inserted into the respective seats to generate thrusts and, therefore, pressures, as described above.

[0309] Step B preferably lasts between 15 seconds and 2 minutes and the heating elements 504 bring the temperature of the presser elements 501 , 502 and of the countering element 503 to a value within the range of 170°C - 210°C.

[0310] During the pressing and / or carburizing step B, the linear lengths 6, 7 of the coil 1 are preferably pressed while the coil 1 is wound on a winding tool 20”, i.e. before the coil 1 is collected from the winding tool 20”.

[0311] At this point, the pressing and / or carburizing step B being completed, the presser elements 501 and 502 and the countering element 503 are moved away from the winding tool 20” to allow the coil 1 to be extracted and the stator to be assembled.

[0312] Figures 63 and 64 are isometric views of the winding tool 20” with the coil 1 still wound, although preferably already subjected to the pressing and / or carburizing step B which substantially made the linear lengths 6 and 7 non- deformable, having shaped them complementary to the stator slots. At this time, an insulating slot liner P, which will then stay interposed between the wires 10 and the stator slot, is applied on the linear lengths 6 and 7. The insulating slot liner P is applied with an appropriate manipulator (not shown).

[0313] Figure 64 shows the coil 1 completed and insulated with the slot liners P at the linear lengths 6 and 7.

[0314] At this point, the winding tool 20” can be opened, i.e. disassembled, to release the completed and insulated coil 1 ready for being inserted into the stator slots.

[0315] Figure 65 is an isometric and exploded view of the winding tool 20” and the released coil 1 .

[0316] Figure 66 is an exploded and axisymmetric sectional view of an apparatus 600 according to the present invention, intended for making a stator for axial flux electric motors. Observing figure 66, the apparatus 600 comprises an upper tool 602 also named first tool, and a lower tool 601 also named second tool, and presser elements 603, 604, in particular an outer presser element 603 and an inner presser element 604. The Z-Z reference denotes the (vertical) axis around which the apparatus 600 extends.

[0317] The lower tool 601 defines a toroidal seat 605 in which a stator body 701 is housed, in practice a lamination stack. The seat 605 is delimited by an inner wall 607 and an outer wall 608; both the walls 607 and 608 are crenelated, or comb-shaped, with the merlons or teeth of the comb 609, 610 extending upward cantileverly, i.e. towards the upper tool 602, and are arranged circumferentially with regular pitch. For simplicity, the merlons or teeth will henceforth only be named teeth 609, 610. The teeth 609 extend cantileverly from the inner wall 607 of the seat 605 and the teeth 610 extend cantileverly from the outer wall 608 of the seat 605. As will be explained hereunder, the teeth 609, 610 have the task of being inserted between the linear lengths 7 of the coils 1 , those facing downward. For this reason, the pitch between the teeth 609, 610 corresponds to the pitch of the stator slots and, therefore, to the pitch which must be maintained between the coils 1 . The lower tool 601 is provided with an ejector device 611 , defined first ejector device 611 , having the task of causing the extraction of the lamination stack 701 from the seat 605. The first ejector device 611 comprises a plurality of cylinders 612 parallel to the axis Z-Z and which can be inserted slidingly by command into the seat 605, from the bottom; for this reason, the first ejector device 611 is provided with its own actuator (not shown). The cylinders 612 are therefore translatable axially, i.e. parallel to the axis Z-Z, between a retracted or lowered position shown in figure 66, at which the cylinders 612 do not occupy the seat 605, and an extended or raised position, at which the cylinders 612 are at least partly inserted into the seat 605 and cause the extraction of the lamination stack 701 from the seat 605.

[0318] The stator body 701 is a substantially toroidal lamination stack in which the stator slots 703 separated by stator teeth 704 are defined. The stator body 701 is open on top, in the sense that the stator slots 703 are devoid of pole shoes and are accessible from the top. As will be made clearer, the stator slots 703 will be closed once the assembly has been completed.

[0319] A plurality of coils 1 , obtained with a step A of forming the coils 1 , for example one of the steps A described herein, is also shown in figure 66. The coils 1 are shown one side-by-side the successive one to form a donut, in the reciprocal position they will assume once they are inserted into the stator body 701. The coils 1 are arranged with regular pitch, corresponding to the pitch between the stator slots 703, which in turn corresponds to the pitch between the teeth 609, 610 of the lower tool 601. The angular pitch between the coils 1 and the portions 2, 3 of coil 1 is adjusted and adapted by means of a manipulator (not shown), before the insertion into the stator body 701. The coils 1 are oriented radially with respect to the axis Z-Z, with the lower header 9 facing inward and the upper header 8 facing outward, where the terminals 4 and 5 are also located.

[0320] The upper tool 602 is a component which, similarly to the lower tool 601 , is toroidal and extends around the axis Z-Z. The upper tool 602 comprises a seat 614 intended for accommodating the linear lengths 6 of the coils 1 , those facing upward. The seat 614 is delimited by teeth 615, 616 extending downward cantileverly, i.e. towards the lower tool 601. First teeth 615, which can also be named inner teeth, extend at the inner perimeter of the upper tool 602, and second teeth 616, which can also be named outer teeth, extend at the outer perimeter of the upper tool 602, so that the outer teeth 616 are radially more outward than the inner teeth 615.

[0321] The upper tool 602 is also provided with an ejector device 617, named second ejector device 617, having the task of ejecting the coils 1 from the seat 614. For this purpose, the second ejector device 617 comprises a plurality of pins 618 extending cantileverly from a ring 619, parallel to the axis Z-Z, and being slidingly inserted into corresponding holes 620 formed in the upper tool 602. The pins 618 are therefore translatable axially, i.e. parallel to the axis Z-Z, between a retracted position shown in figure 66, at which the pins 618 do not occupy the seat 614, and an extended position, at which the pins 618 are at least partly inserted into the seat 614 and cause the extraction of the coils 1 from the seat 614.

[0322] The inner presser element 604 is a disk coaxial to the axis Z-Z and intended to go into abutment against the lower headers 9 of the coils 1 and hold them during the operation of the second ejector device 617, as will be explained hereunder. For this reason, the diameter of the presser element 604 corresponds to the diameter of the circle inscribed between the headers 9 of the coils 1. The presser element 604 is translatable on the axis Z-Z between a raised position, at which it does not exert pressure on the headers 9 of the coils 1 , and a lowered position, at which it exerts pressure on the headers 9 of the coils 1 .

[0323] The outer presser element 603 is a ring-shaped element whose inner diameter corresponds to the diameter of the circumference intercepted by the upper headers 8 of the coils. In practice, the radial distance between the inner presser element 604 and the outer presser element 603 is equal to the length of the linear lengths 6 of the coils 1 . Seats 622, oriented radially with respect to the axis Z-Z and inside each of which a closing element 702 is housed for closing a stator slot 703, are formed on the presser element 603. The closing elements 702 are movable between a retracted position, at which they are substantially accommodated in the respective seats 622, and an extended position, at which they are pushed outside of the seats 622 towards the axis Z-Z, to engage the lamination stack 701 and close the stator slots 703 on top, therefore making a shape coupling. An actuator (not shown) applies the thrust necessary for moving the closing elements 702 radially between the two positions just described.

[0324] The stator assembling step C, using the apparatus 600, will now be described with reference to figures 67-91 .

[0325] Initially, the stator body 701 is inserted into the seat 605 of the lower tool, as shown in the perspective view of figure 67. As can be appreciated, the pitch between the stator teeth 704 (which are radial) and, therefore, the pitch between the stator slots 703, is equal to the pitch between the teeth 609, 610 of the lower tool 601 .

[0326] Figure 68 is an axisymmetric sectional view of the lower tool 601 with the stator body 701 housed therein, as shown in figure 67. It can be noted that the cylinders 612 of the first ejector device 611 stay flush with the floor of the seat 605 and, therefore, in abutment against the lower surface of the stator body 701.

[0327] The stator teeth 704 rest against the outer teeth 610 of the lower tool 601 , at its outer perimeter, and against the teeth 609 of the lower tool 601 , at the inner perimeter.

[0328] Figure 69 is a perspective view substantially identical to figure 67 but shows a later time of the assembling step C during which the coils 1 are inserted into the stator slots 703, in particular, each portion 2, 3 of the coils 1 is inserted into a corresponding stator slot 703 by means of a manipulator (not shown), for example provided with grippers, which prearranges the coils 1 as shown in figure 69 with the proper angle between the portion 2 and the portion 3 of the coil 1 , so that the two linear lengths 7 (one of the portion 2, the other of the portion 3 of the coil 1 ) are easily inserted into the corresponding stator slots 703, which are actually arranged radially and define an angle among one another at the center on the axis 7-7.

[0329] Figure 70 is similar to figure 69, except that it shows a greater number of coils 1 inserted into the stator body 701 in turn housed in the lower tool 601. The assembling step C continues until all the coils 1 have been properly housed in the slots 703, so that all the slots have a linear length 7 of coil 1 therein.

[0330] Figure 71 shows the apparatus 600 at a time at which all the coils 1 were inserted into the lower tool 601 and the upper tool 602 was lowered on the lower tool 601 with a translational movement on the axis 7-7, so that to comb insert the linear lengths 6 of the coils 1 , which are free at this time, with the teeth 615, 616. In practice, in the configuration shown, the portions 2, 3 of coil 1 are therefore each lying on a plane containing the axis 7-7 and arranged radially; the linear lengths 7 are inserted into the stator slots 703 between the teeth 609, 610 of the lower tool 601 and the linear lengths 6 are inserted between the teeth 615, 616 of the upper tool 602. The upper tool 602 is in the distal position, i.e. at the maximal distance from the lower tool 601 : in this position, the coils 1 extend non-deformed on radial planes with respect to the axis 7-7 and the teeth 615, 616 of the upper tool 602 comb insert the first linear lengths 6.

[0331] Figure 72 is an axisymmetric sectional view of figure 71. As can be noted, there is no component of the apparatus 600 between the linear lengths 7 and the linear lengths 6 of the coils 1 and the coils 1 delimit a substantially toroidal volume.

[0332] It is clear that the extent of the coils, parallel to the axis 7-7, is not compatible with the height of the stator slots 703 and, therefore, the assembly of the stator must provide for the deformation of the coils 1 , as will now be described. With reference to figures 73-78, the step of deforming the coils 1 , obtained by means of a roto-translation movement of the upper tool 602 with respect to the lower tool 601 about the axis 7-7, will now be described. It is made clear herein that the roto-translation movement can be obtained in different ways, for example by keeping the lower tool 601 stationary and only moving the upper tool 602, or by keeping the upper tool 602 stationary and only moving the lower tool 601 , or by moving both the lower tool 601 and the upper tool 602.

[0333] Moreover, the roto-translation can be obtained by a single movement, i.e. by simultaneously carrying out the rotation and the translation, or alternating the rotation and the translation over time.

[0334] Figure 73 shows the apparatus 600 in perspective during the roto- translation, which in the example shown is obtained by keeping the lower tool 601 stationary. The upper tool 602 is rotated on the axis 7-7 (clockwise when observing the figure), so that to drag the linear lengths 6 of the coils 1 , while the linear lengths 7 stay stationary and housed in the stator slots 703 in the stator body 701 housed in the lower tool 601. The dragging of the linear lengths 6 of the coils 1 is possible thanks to the teeth 615, 616 of the upper tool 602, which actually comb insert the linear lengths 6. In practice, the rotation of the upper tool 602 causes the setting down of the coils 1 , thus forming a sort of domino effect. The translation of the upper tool 602 along the axis 7-7 can be carried out simultaneously to the rotation or at a later time.

[0335] Figure 74 shows a later time of the assembling step C during which the upper tool 602 is further rotated on the axis 7-7 and simultaneously translated on the same axis 7-7 to move it closer to the lower tool and, therefore, the stator body 701 . The rotation of the upper tool 602 is used to align the linear lengths 6 of the coils 1 with a stator slot 703 different from the stator slot 703 in which the linear length 7 of the same coil 1 is housed, so that to obtain an angular offset between the lengths 6 and 7 corresponding to the electrical winding pattern of the completed stator. Clearly, the linear lengths 6 will be inserted into stator slots 703 in which a linear length 7 of another coil 1 is already present.

[0336] The translation of the upper tool 602 along the axis 7-7 is used to press the coils 1 , i.e. deform them in axial direction, so that to move the linear lengths 6 closer to the stator slots 703 for which they are intended. The axial extent of the coils 1 is therefore reduced.

[0337] As mentioned with reference to the step A of deforming the coils 1 , the deformation referred to during the assembling step C only concerns the headers 8 and 9 of the coils 1 , since the linear lengths 6 and 7 stay non-deformed, are not affected by movements of the wires 10, precisely because intending to achieve the maximal filling factor. The linear lengths 6 and 7 stay confined in the lower tool 601 , the stator body 701 and the upper tool 602, without possibility of being subjected to deformations, while the headers 8 and 9 stay free, in the air, and can therefore be deformed.

[0338] Figures 75 and 76 are similar to figures 73 and 74 but show a later time of the assembling step C during which the coils 1 are further deformed by the roto-translational movement of the upper tool 602. The headers 8 and 9 of the coils 1 are pushed away from the axis 7-7 and towards the axis 7-7, respectively.

[0339] In particular, figure 76 is an axial sectional view of the apparatus 600 at the time shown in figure 75. From this section, when comparing it with the section of figure 72, it can be noted that the linear lengths 6 of the coils 1 were moved closer to the linear lengths 7 and are about to be inserted into the stator slots 703.

[0340] Figures 77 and 78 are similar to figures 75 and 76 but show the final time of the roto-translation of the upper tool 602, which has reached the limit stop, in the completely lowered and completely rotated position. In this position, the teeth 615, 616 of the upper tool 602 are in abutment against, or at a minimal distance from, the teeth 609, 610 of the lower tool 601 aligned therewith. The coils 1 were subjected to the maximum deformation and the linear lengths 6 of a coil 1 are resting on the linear lengths 7 of another coil 1 in the same stator slot 703. In other words, the upper tool 602 pushes the linear lengths 6 of the coils 1 against the linear lengths 7 until they are completely pushed in the slot bottom of the stator slots 703. At this point, the coils 1 have been completely inserted into the stator slots 703 and the apparatus 600 is ready to complete the assembly of the stator.

[0341] It is recalled that the method according to the present invention allows to obtain the correct insertion of the linear lengths 6 and 7 of the coils 1 into the stator slots 703 without subjecting the linear lengths 6, 7 to twisting: thanks to the fact that the linear lengths 7 actually stay inserted into the stator slots 703 from the start and thanks to the fact that the linear lengths 6 stay comb inserted by the teeth 615, 616 of the upper tool 602, the roto-translation described above occurs by always keeping the linear lengths 6, 7 of the coils 1 arranged radially with respect to the axis 7-7 and without subjecting the linear lengths 6, 7 to twisting throughout their extent, so that they can be perfectly shape coupled to the stator slots 703. The headers 8 and 9 are the only parts of the coils 1 which are free to be deformed, for example radially, but also by being subjected to twisting, and they are not even optionally subjected to the pressing and / or carburizing step B.

[0342] Figures 77 and 78 also show the operation of the first ejector device 611 and its cylinders 612, which are pushed upward, so that to cause the raising of the stator body 701 , i.e. of the lamination stack, and the further deformation of the coils 1 , with the consequent complete insertion of the linear lengths 6 and 7 into the stator slots 703, until they occupy them throughout their height in axial direction, from the slot bottom to the top.

[0343] Figures 79-90 illustrate how the stator is completed and extracted from the apparatus 600.

[0344] The presser elements 603, 604, coaxial to the axis 7-7 and which are translated on the axis 7-7 towards the coils 1 held by the lower tool 601 and the upper tool 602, are shown in figure 79. Figure 80 is an axisymmetric sectional view of figure 79. The presser element 603, which is a substantially flat ring-shaped element, is intended for going into abutment against the upper headers 8 of the coils 1 , thus surrounding the upper tool 602. The presser element 604 is a substantially disk-shaped element intended for entering coaxially through the upper tool 602 and going into abutment against the lower headers 9 of the coils 1 .

[0345] The cylinders 612 stay raised and keep the stator body 701 partially extracted from the seat 605 of the lower tool 601 .

[0346] Figure 81 shows a later time at which the presser elements 603, 604 are actually lowered against the coils 1 .

[0347] Figure 82 is an axisymmetric sectional view of figure 81 .

[0348] The upper tool 602 is in the proximal position, i.e. at the minimal distance from the lower tool 601 : in this position, the teeth 615, 616 of the upper tool 602 are at the height of the stator slots 703 and the second linear lengths 7 of the coils 1 , previously housed in the slot bottom of the stator slots 703, are preferably between the teeth 615, 616.

[0349] As can be noted by observing figures 81 and 82, the inner diameter of the presser element 603 is slightly larger than the outer diameter of the upper tool 602 and the outer diameter of the presser element 604 is slightly smaller than the inner diameter of the upper tool 602. As mentioned above, the presser element 603 is in abutment against the headers 8 of the coils 1 and the presser element 604 is in abutment against the headers 9 of the coils 1. This configuration is used to prevent the coils 1 from coming out of the stator slots 703 when the apparatus 600 is opened, i.e. when the upper tool 602 is raised and moved away from the lower tool 601 .

[0350] At this point, the pins 618 of the upper tool 602 are operated and extended, i.e. they are made to protrude below the upper tool 602, to extract the teeth 615, 616 (of the upper tool 602) from the linear lengths 6 of the coils 1 which stay held in position by the presser elements 603, 604.

[0351] Figures 83 and 84 show a later time at which the pins 618 are operated and the upper tool 602 is moved away from the lower tool 601 , disengaging the coils 1 . As shown in figure 84, the first ejector device 611 stays operational, with the cylinders 612 raised.

[0352] Figure 84 is an axisymmetric sectional view of figure 83.

[0353] Figures 85 and 86 show a later time at which the closing elements 702 of the stator slots 703 are pushed outside of the respective seats 622 present on the pusher element 603; in particular, the closing elements 702 are pushed radially towards the axis 7-7 by a manipulator (not shown). Translating radially, the closing elements 702 leave the presser element 603 and engage the stator slots 703 and, in particular, make a shape coupling with the stator teeth 704, therefore staying in abutment against the linear lengths 6 of the coils which are therefore properly confined in the finally closed stator slots 703. The coupling of the closing elements 702 to the stator teeth 704 makes the position and shape of the coil 1 permanent and no longer changeable.

[0354] Figures 87 and 88 show a successive time at which the presser elements 603 and 604 are removed and the completed stator 700, i.e. the stator complete with windings and the stator slots 703 closed on top by the closing elements 702, stays accessible on the lower tool 601 , ready for being collected. As shown in figures 87 and 88, the completed stator 700 is simply resting on the lower tool 601 . In the section of figure 88, it is possible to see that the linear lengths 7 of a first coil 1 and, above them, the linear lengths 6 of a second coil 1 , are present in each stator slot 704: the linear lengths 6 of the first coil 1 are positioned in a successive stator slot 104 and the linear lengths 7 of the second coil are positioned in a previous stator slot 704. This configuration will be described in detail with reference to figures 91 -92.

[0355] Figures 89 and 90 show the final time of the assembling step C at which the completed stator 700 is disengaged from the lower tool 601 , by further raising the cylinders 612 of the first ejector device 611 so that to bring them to the limit stop (upper point) and completely pulling out the stator 700 from the teeth 607 and 608 of the lower tool 601 . Figure 91 shows the initial arrangement of the coils 1 , at the start of the assembling step C, and figure 92 shows the completed stator 700. The individual linear lengths 6 and 7 are labeled U1 , U2, V1 , V2, W1 , W2, etc. to explain the electrical layout in a simple way. The comparison between figures 91 and 92 allows to notice that the coils are initially arranged on a lying plane radial with respect to the axis 7-7 and, consequently, the linear lengths 6 and 7 are aligned according to the following electrical layout: from left to right U1 -U2, U1 -U2, W2-W1 , W2-W1 , V1 -V2, V1 -V2, U2-U1 , U2-U1 , W1 -W2, W1 -W2, V2- V1 , V2-V1 , U1 -U2, etc. Once the stator 700 has been completed as described above, with the roto-translation of the coils 1 , the electrical layout obtained provides to offset the linear lengths 6 and 7 of the same coil 1 : from left to right U1-U1 , W2-U1 , W2-W2, V1 -W2, V1 -V1 , U2-V1 , U2-U2, W1 -U2, W1 -W1 , V2- W1 , V2-V2, U1 -V2, U1 -U1 , etc. As highlighted in dark color in figure 92, the linear length 6 of a coil 1 is therefore offset by five stator slots 704 with respect to the linear length 7 of the same coil 1 .

[0356] Figures 93-97 show different embodiments of an electric motor 800 comprising one stator 700 that can be obtained with the method and apparatus 600 according to the present invention.

[0357] In particular, figure 93 shows an electric motor 800 which incorporates a stator 700 according to the present invention and a corresponding rotor 801 with permanent magnets 802. As can be noted, the coils 1 lie on planes inclined with respect to the axis 7-7 and the magnets 802 face the upper part of the stator 700, i.e. the feet of the stator slots 704 and the closing elements 702. The configuration shown can be named SSSR-SL (single stator, single rotor, single layer), i.e. motor with a single stator 700, single rotor 801 and coils 1 arranged on one level.

[0358] Figure 94 shows an electric motor 800 which incorporates a stator 700 according to the present invention and two corresponding rotors 801 with permanent magnets 802. As can be noted, the coils 1 are arranged on two levels and the magnets 802 of the upper rotor 801 face the upper part of the stator 700, i.e. the feet of the stator slots 704 and the closing elements 702, and the magnets 802 of the lower rotor 803 face the lower part of the stator 700. The configuration shown can be named SSDR-DL (single stator, double rotor, double layer), i.e. motor with a single stator 700, double rotor 801 , 803 and coils 1 arranged on two levels in the same stator 700.

[0359] Figure 95 shows an electric motor 800 which incorporates a stator 700 according to the present invention and two corresponding rotors 801 with permanent magnets 802, positioned on opposite parts with respect to the stator 700. The configuration can be named SSDR-SL (single stator, double rotor, single layer), i.e. motor with a single stator 700, double rotor 801 and coils 1 arranged on the same level in the same stator 700 for each rotor 801 .

[0360] Figure 96 shows an electric motor 800 which incorporates two stators 700’ and 700 according to the present invention, between which a single rotor

[0361] 801 with permanent magnets 802 is functionally arranged. The rotor 801 has two series of magnets 802, one facing upward, and therefore the upper stator 700’, the other facing downward, and therefore the lower stator 700”. The configuration shown can be named DSSR-DL (double stator, single rotor, double layer), i.e. motor with a double stator 700’, 700", single rotor 801 and coils 1 arranged on two levels.

[0362] Figure 97 shows an electric motor 800, similar to the electric motor 800 of figure 96, which incorporates two stators 700’ and 700” according to the present invention, between which a single rotor 801 with permanent magnets

[0363] 802 is functionally arranged. The rotor 801 has two series of magnets 802, one facing upward, and therefore the upper stator 700’, the other facing downward, and therefore the lower stator 700”. The configuration shown can be named DSSR-SL (double stator, single rotor, single layer), i.e. motor with a double stator 700’, 700", single rotor 801 and coils 1 arranged on one level.

[0364] “Pancake” configurations are also possible, by stacking the configurations of figures 93-97 one on another to obtain motors with multiple stators and multiple rotors. Figure 98 is a flow diagram which describes the method according to the present invention for making stators 700 of axial flux and distributed winding electric motors 800, which comprises:

[0365] - a step A of making the coils 1 , which can be carried out by means of the winding method and the winding machines 100, 100’, 400 described above;

[0366] - an optional pressing and / or carburizing step B, which can be carried out by means of the pressing and / or carburizing methods and the machines 300, 500 described above;

[0367] - a step C of assembling the stator, which can be carried out by means of the method and the machine 600 described above, where step C provides for

[0368] C1 , inserting first linear lengths 7 of the coils 1 into a stator body 701 , and in particular into the open stator slots 703, therefore leaving the second linear lengths 6 of the coils 1 outside of the stator slots 703 free;

[0369] C2, engaging the second free linear lengths 6 of the coils 1 with a tool 602, so that to prevent said second linear lengths 6 from twisting;

[0370] C3, deforming the coils 1 with a roto-translation movement, which can be obtained by roto-translating the tool 602 with respect to the stator body 701 , so that to insert all the linear lengths 6, 7 of the coils 1 into the respective stator slots 703, and

[0371] C4, completing the stator 700 by closing the stator slots 703 with appropriate closing elements 702, when the linear lengths 6, 7 of the coils 1 are inserted into the stator slots 703.

[0372] Concerning steps C1 and C2, it should be noted that the linear lengths 7 inserted into the stator slots cannot be subjected to twisting, as the linear lengths 6 comb inserted between the teeth 615, 616 of the upper tool 602. This detail allows to keep the arrangement of the wires 10 orderly also when the pressing and / or carburizing step B is not carried out. The optimal result is clearly obtained by also carrying out step B.

[0373] Figure 99 is a comparative view which shows, in vertical section considered on a plane orthogonal to the radius of the stator, two geometrically identical stators 700, 700b, i.e. provided with identical stator slots 703 in particular having the same area and closed on top by closing elements 702. In the stator 700b on the left, the slot 703 delimits a winding defined by two rectilinear lengths ml , m2 of two coils made with the conventional manufacturing processes of random wire insertion, and the stator 700 on the right is a stator according to the present invention, in which the winding is obtained by using coils 1 , as described above, with linear lengths 6 and 7 and subjected to the pressing and / or carburizing step B.

[0374] As can be noted, the arrangement of the wires 10 in the stator 700b on the left is more disorderly than the arrangement of the wires 10 in the stator 700 on the right, resulting in a greater filling factor of the stator 700 than the filling factor of the stator 700b, all geometric conditions being equal. The filling factor for the stator 700b is equal to 45%; the filling factor for the solution 700 according to the present invention is equal to 67%, therefore significantly higher.

[0375] Figure 100 is a mechanical torque (N / m) - rotation speed (rounds / minute) diagram of the electric motor 800 which, in practice, corresponds to a differential efficiency map of the electric motor 800 made by integrating the stator 700 according to the present invention, shown in figure 99 on the right, compared to the same electric motor made by integrating the conventional stator 700b shown in figure 99, on the left. The greater the differential, the better the efficiency of the motor 800 according to the present invention compared to the solution obtained with the conventional stator 700b. It can actually be noted that, at low speeds, the solution 800 according to the present invention is more than 5 percent more efficient thanks to the increase in the filling factor highlighted above, from 45% to 67%. At high speeds, the differential decreases, although present, since both solutions 700, 700b use wires with circular section which minimize high frequency losses in an almost indistinguishable way for both solutions.

[0376] Ultimately, the apparatus 600 and method according to the present invention therefore allow to achieve:

[0377] - a perfect stratification of the conducting wire 10 in each winding and the control of the position of the individual conducting wire 10 inside the stator slots 703; - the effective insulation of the coils 1 in the stator slots 703;

[0378] - the formation of the coils 1 outside the stator 700 and the assembly of the stator 700 at a later time, with the insertion of the already formed coils 1 ;

[0379] - pressing and carburizing are preferably only carried out on the linear lengths 6, 7 of the coils 1 ; - stators 700 and, therefore, electric motors 800 which, substantially all dimensions and geometries being equal, have better performance than solutions obtained with the known winding techniques.

Claims

CLAIMS1. A method for making a stator (700) for axial flux and distributed winding electric motors (800), the stator (700) having a stator body (701 ) with a ring-shaped extent about an axis (Z-Z) and radial stator slots (703) accessible in axial direction and having closing elements (702) which can be fastened to the stator body (701 ) for closing said stator slots (703), the method comprising:- making (A) coils (1) of conducting wire (10, 10’), wherein one or more conducting wires (10, 10’) are wound on a winding tool (20, 20’, 20”) so that to form at least one coil (1 ) comprising at least one first linear length (6) and at least one second linear length (7) which in turn comprise a plurality of individual linear lengths of conducting wire (10, 10’) and which are adapted for being inserted into said stator slots (703);- assembling (C) the stator,- collecting (C1) the coils (1 ) from the winding tool (20, 20’, 20”) with a manipulator and inserting the second linear lengths (7) into corresponding first stator slots (703), so that a second linear length (7) of a coil (1) is present in all the stator slots (703) and so that the first linear lengths (6) of the coils (1) stay outside the stator slots (703);- engaging (C2) all the first linear lengths (6) of the coils (1 ) simultaneously with a first tool (602), named upper tool',- deforming (C3) all the coils (1) simultaneously by imparting, with the upper tool (602), a roto-translation to the first linear lengths (6) until each first linear length (6) is inserted into a second stator slot (703) different from the first stator slot (703) in which the second linear length (7) of the same coil (1 ) is located;- closing (C4) the stator slots (703), with first linear lengths (6) and second linear lengths (7) of a coil (1 ) therein, by said closing elements (702).

2. Method according to claim 1 , wherein, during step C3 of deforming the coils (1 ), the first linear lengths (6) of the coils (1 ) are held by the upper tool(602) without possibility of being subjected to twisting, the second linear lengths (7) of the coils (1) are held in the stator slots (703) without possibility of being subjected to twisting, and the deformation of the coils (1 ) occurs at the headers (8, 9), i.e. in the portions of coil (1 ) which connect the linear lengths (6, 7).

3. Method according to claim 2, wherein deforming the headers (8, 9) of the coils (1 ) comprises twisting and / or pressing the headers (8, 9).

4. Method according to any one of claims 1 -3, wherein in step C1 the second linear lengths (7) of the coils (1 ) are inserted into the slot bottom of the first stator slots (703) and in step C3 the first linear lengths (6) of the coils (1 ) are inserted into the stator slots (703) above a second linear length (7) of another coil (1).

5. Method according to any one of claims 1-4, wherein the coils (1 ) are held inside the stator slots (703) during step C4 by exerting a pressure on all the headers (8, 9) of the same coils (1 ) simultaneously or by providing an abutment surface which prevents the coils (1 ) from coming out of the stator slots (703).

6. Method according to any one of claims 1-5, wherein the stator slots (703) are closed during step C4 by inserting said closing elements (702) radially between the stator teeth (704) delimiting the stator slots (703).

7. Method according to any one of claims 1 -6, characterized by a pressing and / or carburizing step B before the assembling step C, wherein said first linear length (6) and second linear length (7) of each coil (1 ) are subjected to pressing or are subjected to a thermal carburizing treatment, or to both pressing and thermal carburizing treatment, in the desired order or simultaneously, so that to compact said individual linear lengths (6, 7) of conducting wire (10, 10’) and to make the reciprocal position assumed by the conducting wires (10, 10’) on the winding tool (20, 20’, 20”) permanent.

8. Method according to claim 7, wherein said pressing and / or carburizing step B comprises pressing the linear lengths (6, 7) of the coil (1 ) with one or more presser elements (30, 301 -302, 501-503) and heating said linear lengths(6, 7) by means of one or more heating devices (31 , 504) integrated in, or coupled to, said presser elements (30, 501 -503), while the coil (1 ) is wound on said winding tool (20, 20’, 20”).

9. Method according to claim 7 or claim 8, wherein, in the pressing and / or carburizing step B, said thermal carburizing treatment is made by inserting one or more heating elements (30’) between the linear lengths (6, 7) of the coils (1), so that to heat them up to a predetermined carburizing temperature, while said coil (1 ) is accommodated on the winding tool (20, 20’, 20”).

10. Method according to one or more of preceding claims 7-9, wherein, in said pressing and / or carburizing step B, the linear lengths (6, 7) of the coil (1 ) are pressed by means of a pressing device (300, 500) which is inserted between said linear lengths (6 7), while the coil (1 ) is accommodated on the winding tool (20, 20’, 20”).

11. Method according to one or more of the preceding claims, wherein, in said coil making step A, complementary wires (10’) having a smaller section than the section of said conducting wires (10) are added to said one or more conducting wires (10), so that said complementary wires (10’) occupy the free spaces between said conducting wires (10).

12. Method according to one or more of the preceding claims, wherein, in said coil making step A, a series of several coils (1 ), or a coil with several portions (2, 3) of coil, is made on the same winding tool (20, 20’, 20”), so that a linear length (6, 7) of a coil (1) is spaced from the linear length (6, 7) of the successive coil (1 ), or successive portion (2, 3) of the coil (1 ), and wherein the angular pitch of the coils (1 ) or portions (2, 3) of coil (1 ), before being inserted into the stator slots (703), is adapted to the pitch between the stator slots (703) of the stator body (701 ).

13. A stator (700) of axial flux and distributed winding motor (800), directly obtained with the method according to any one of the preceding claims.

14. Stator (700) according to claim 13, comprising a single level of coils (1 ) or two levels of coils (1 ), which levels are arranged at different heights onthe axis Z-Z.

15. An axial flux and distributed winding electric motor (800) comprising a stator (700) directly obtained by the method according to any one of the preceding claims and a rotor (801 ) functionally coupled to the stator (700).

16. Electric motor (800) according to claim 15, wherein the stator (700) comprises a single level of coils (1) or two levels of coils (1 ), and comprises one or more rotors (801) arranged on opposite sides with respect to the stator (700).

17. An apparatus (600) for making a stator (700) for axial flux and distributed winding electric motors (800), wherein the stator (700) comprises a stator body (701 ) having a ring-shaped extent about an axis (Z-Z) and radial stator slots (703), the apparatus (600) comprising a first tool (602), named upper tool, and a second tool (601 ), named lower tool, wherein the lower tool (601 ) and the upper tool (602) extend about said axis (Z-Z) and are coaxial, and wherein the upper tool (602) is provided with a plurality of teeth (615, 616) adapted for the simultaneous comb insertion of first linear lengths (6) of a number of coils (1) of conducting wire (10, 10’) corresponding to the number of stator slots (703) of the stator (700), and wherein the lower tool (601 ) has a first seat (605) inside which said stator body (701 ) can be housed with second linear lengths (7) of said coils (1) inserted into all the stator slots (703), and wherein the upper tool (602) and the lower tool (601 ) can be roto- translated one with respect to the other to cause the insertion of said first linear lengths (6) of the coils (1) into said stator slots (703).

18. Apparatus (600) according to claim 17, wherein the lower tool (601) is provided with a plurality of teeth (609, 610) distributed circumferentially at the inner perimeter of the lower tool (601 ) and at the outer perimeter of the lower tool (601 ), which jut out towards the lower tool (601 ) with a pitch corresponding to the pitch between the stator slots (703) of the stator (700), and wherein the distance between adjacent teeth (609, 610) is sufficient to allow the linearlengths (6, 7) of coil (1 ) to be inserted between them.

19. Apparatus (600) according to claim 17 or claim 18, wherein the lower tool (601 ) is provided with a first ejector device (611 ) provided with a plurality of cylinders (612) that can be axially inserted into said first seat (605) to cause the ejection of the stator body (701 ) from the first seat (605).

20. Apparatus (600) according to any one of preceding claims 17-19, wherein the teeth (615, 616) of the upper tool (602) are distributed circumferentially at the inner perimeter of the upper tool (602) and at the outer perimeter of the upper tool (602), with a pitch corresponding to the pitch between the stator slots (703) of the stator (700), and wherein the distance between adjacent teeth (615, 616) is sufficient to allow the first linear lengths (6) of coil (1 ) to be inserted between them.

21. Apparatus (600) according to any one of preceding claims 17-20, wherein a second seat (614) intended for temporarily accommodating said first linear lengths (6) of a coil (1) is defined in the upper tool (602), and wherein the upper tool (602) comprises a second ejector device (617) provided with pins (618) that can be axially inserted into said second seat (614) in order to eject the coils (1 ) from the second seat (614).

22. Apparatus (600) according to any one of preceding claims 17-21 , wherein the upper tool (602) is susceptible to roto-translations with respect to the lower tool (601 ), between- a distal position, at which the first linear lengths (6) of the coils (1 ) are comb-like inserted by the teeth (615, 616) of the upper tool (602) and the second linear lengths (7) of the coils (1 ) are inserted into the slot bottom of the stator slots (703) of the stator body (701 ) housed in the lower tool (601 ), and- a proximal position, at which the teeth (615, 616) of the upper tool (602) are at the height of the stator slots (703) of the stator body (701 ) housed in the lower tool (601), and the first linear lengths (6) of the coils (1) are inserted into the stator slots (703) above the second linear lengths (7) of the coils (1 ).

23. Apparatus (600) according to any one of preceding claims 17-22,comprising an outer presser element (603) and an inner presser element (604), wherein the outer presser element (603) is ring-shaped and movable to an operating position at which it surrounds the upper tool (602) coaxially and is in abutment against the headers (8) of the deformed coils (1 ) which protrude radially towards the outside of the upper tool (602) when roto-translation is completed, and wherein the inner presser element (604) is disk-shaped and movable to an operating position at which it is inside and coaxial to the upper tool (602) and in abutment against the headers (9) of the deformed coils (1 ) which protrude radially towards the inside of the upper tool (602) when roto-translation is completed.

24. Apparatus (600) according to claim 23, wherein the stator comprises closing elements (702) which can be fastened to the stator body (701 ) for closing said stator slots (703), and wherein the outer presser element (603) comprises radial seats (622) for the closing elements (702), and wherein the closing elements (702) are radially removable from said radial seats (622) for engaging the stator body (701 ).

25. Apparatus (600) according to any one of preceding claims 17-24, comprising a winding tool (20, 20’, 20”) on which conducting wire (10, 10’) is wound to form a series of coils (1) or a coil with several portions (2, 3) of coil (1 ), wherein the coils (1 ) comprise at least one first linear length (6) and at least one second linear length (7) which, in turn, comprise a plurality of individual linear lengths of conducting wire (10, 10’), and comprising a pressing and / or carburizing device (30’, 300, 500) for pressing and / or carburizing said linear lengths (6, 7) which is operable on the coils (1 ) still wound on the winding tool (20, 20’, 20”).

26. Apparatus (600) according to claim 25, wherein the pressing and / or carburizing device (30’, 300, 500) comprises one or more presser elements (30, 301-302, 501-503) and / or one or more heating devices (31 , 504) integrated in, or coupled to, said presser elements (30, 501 -503), which heating devices canbe inserted between the linear lengths (6, 7) of the coils (1) still wound on the winding tool (20, 20’, 20”).

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