Magnet structure with unit magnets having a diamond-shaped section

Abstract

The invention relates to a unit magnet (4) in the form of an elongated pad in the shape of a polyhedron having a magnetization line extending along its length. The elongated pad forming each unit magnet (4) has a diamond-shaped section without a right angle at the apex, the section of each unit magnet (4) being less than 25 mm2 and a ratio of the largest diagonal of the diamond-shaped section of each unit magnet (4) to the length of the unit magnet (4) being less than 0.5. The invention also relates to a magnet structure (10) comprising a plurality of such unit magnets (4). Abstract Figure: FIGURE 4

Description

Title of the invention: Magnet structure with unit magnets having a diamond-shaped section

[0001] The present invention relates to a unitary magnet in the form of an elongated pad having a non-square diamond-shaped section, a magnet structure comprising such unitary magnets as well as a rotor for an axial flux electromagnetic motor or generator comprising at least one such magnet structure.

[0002] The present invention finds an advantageous but non-limiting application for an electromagnetic actuator delivering high power with a high rotor rotation speed, which is obtained by the use of one or more magnet structures according to the present invention. Such an electromagnetic actuator can be used for example in a fully electric or hybrid motor vehicle.

[0003] It has been proposed by the closest state of the art, in particular that described in WO2019 / 243996A1, to decompose a magnet structure which may be a whole magnet or a magnetic pole according to the state of the art into a plurality of small or micro-magnets.

[0004] Document WO2019 / 243996Al thus shows a three-dimensional magnet structure dimensions consisting of a plurality of unit magnets in the form of elongated pads. The magnet structure has a thickness, a front edge and a rear edge which are flat or rounded and joined by side faces, the unit magnets being arranged to have a first longitudinal end adjacent to the front edge of the magnet structure while the second longitudinal end is adjacent to the rear edge of the magnet structure.

[0005] The unit magnets are grouped in the magnet structure against each other forming a bundle by being individually coated in a layer of non-conductive resin.

[0006] Indeed, a large magnet is subject to greater eddy current losses than its equivalent in small or micro-magnets, as proposed in document WO2019 / 243996A1. The use of small magnets or micro-magnets as unit magnets therefore makes it possible to reduce magnetic losses which are detrimental to the operation of the electromagnetic actuator.

[0007] Document EP0 353 042 A1 describes a rotor of an electromagnetic motor or generator having a body comprising an internal hub concentric with a central axis of rotation of the rotor, branches extending radially with respect to the central axis of rotation from the internal hub towards a hoop forming a circular external periphery of the rotor, at least one magnet being housed in each delimited space between two adjacent branches, each magnet having an increasing width away from the inner hub to end against the hoop surrounding the rotor.

[0008] This document does not allow for a support for the multiple permanent magnets which can, on the one hand, hold the permanent magnets that the rotor supports effectively by preventing the magnets from detaching from the rotor while compensating for the centrifugal force effectively and, on the other hand, have a mechanical resistance such that the rotor can rotate at very high speeds.

[0009] Document FRI 475 501 A1 does not describe a rotor but only a magnet structure comprising several unit magnets without specifying an application for this magnet structure and suggesting that the disadvantages of the latter-mentioned document can be eliminated by the use of such a magnet structure with several unit magnets. Indeed, a use of such a magnet structure with several unit magnets for a rotor is not mentioned in this document.

[0010] A first problem addressed by the present invention is to further reduce magnetic losses in a magnet structure with multiple unit magnets grouped in a bundle and individually coated with resin by adopting a specific geometric shape that is as favorable as possible for each unit magnet.

[0011] This is all the more important since, in applications for a rotor rotating at high speed, it is necessary to reduce losses for optimal efficiency. In addition, particularly for automotive applications, miniaturization is increasingly sought after.

[0012] For this, it is important to have a compact system made possible by the reduction of the mass and size of the actuator, but also very good mechanical strength of the moving part, in order to improve the reliability of the system.

[0013] Particularly in a configuration of the magnet structure with multiple unit magnets electrically insulated from each other by individual embedding in a resin layer filling grooves between unit magnets, it is appropriate to reduce the stress concentrations in the resin layer at the grooves between the unit magnets, these concentrations being due to the centrifugal forces induced during high speed rotation, of the order of or greater than 10,000 rotations per minute, of the rotor comprising the magnet structure(s).

[0014] A second problem addressed by the present invention is to reduce the stresses experienced by a magnet structure comprising multiple unit magnets grouped in a bundle and individually coated in resin under centrifugal stress, which occurs when the assembly carrying the magnet structure(s), for example a rotor, is rotated.

[0015] To this end, the present invention relates to a unit magnet in the form of an elongated pad in the shape of a polyhedron having a magnetization line extending along its length, characterized in that the elongated pad forming each unit magnet has a diamond-shaped section without a right angle at the apex, the section of each unit magnet being less than 25 mm2 and a ratio of the largest diagonal of the diamond-shaped section of each unit magnet to the length of the unit magnet being less than 0.5.

[0016] In the case of a diamond-shaped section, two diagonals respectively connect two opposite vertices of the section, one of the two diagonals being larger than the other. A ratio of less than 0.5 may correspond to a maximum largest diagonal length of 5 mm for a minimum unit magnet length of 10 mm.

[0017] Such a non-square diamond-shaped section for each unit magnet makes it possible to reduce the passage of eddy currents inside it, this passage being more restricted than that provided by a unit magnet having a rectangular or square section.

[0018] Furthermore, such a non-square diamond-shaped section of each unit magnet makes it possible to provide unit magnets which, when inserted into a magnet structure by being individually coated with resin with a specific orientation of a face of the structure likely to be stressed by a centrifugal force during rotation of the magnet structure along the axis of symmetry, makes it possible to reduce the stress concentrations experienced by the magnet structure, these stresses being due to the centrifugal force applied to the magnet structure.

[0019] The cross-section of each unit magnet less than 25 mm2 specifies that each unit magnet is in the form of an elongated pad or pin of small cross-section and not in the form of a bar or strip. The same applies to a ratio of the largest diagonal of the diamond-shaped cross-section of each unit magnet to the length of the unit magnet less than 0.5. These values ​​have proven optimal for designing unit magnets that reduce eddy currents.

[0020] The invention also relates to a three-dimensional magnet structure consisting of a plurality of unit magnets, each unit magnet being as previously described, the magnet structure having a thickness, a front edge and a rear edge which are flat or rounded and joined by side faces, the unit magnets being arranged to have a first longitudinal end adjacent to the front edge of the magnet structure while the second longitudinal end is adjacent to the rear edge of the magnet structure, the unit magnets being grouped in the magnet structure against each other forming a bundle by being individually coated in a layer of non-conductive resin, characterized in that the unit magnets are arranged in the magnet structure so that their sides form an angle less than 90 degrees with respect to a tangential force extending parallel to a tangent of the leading edge, the tangential force being applied to the magnet structure during a rotational movement of the magnet structure.

[0021] The magnet structure described in this invention is distinguished by the non-square diamond-shaped geometry of the section of each unit magnet composing the magnet structure.

[0022] Unlike conventional magnet structures with a multitude of unit magnets, generally in the form of pads of rectangular, square or even circular section, the magnet structures with multiple unit magnets of the invention have been designed to reduce the mechanical stresses experienced by the magnet structure when it is subjected to centrifugal forces.

[0023] The benefits related to the reduction of eddy currents cited above for a unit magnet of non-square diamond-shaped section can also be extrapolated to the magnet structure comprising such unit magnets.

[0024] Furthermore, it has been found that a structure with such a plurality of unit magnets has a great power of not being sensitive to space or current harmonics generated by the stator windings. Therefore, the losses generated in the magnet structures are very low, and the efficiencies, particularly at high speed, are very high. Such a magnet structure can form a magnet pole or be a complete magnet.

[0025] Advantageously, the diamond-shaped section is constant over the entire length of each unit magnet forming a stud. Stud is to be taken in the broad sense of an elongated body and not specifically conical.

[0026] Advantageously, two opposite apex angles of the diamond-shaped section between two sides on which the tangential force is applied are between 100 and 200 degrees.

[0027] Advantageously, the non-conductive resin layer is reinforced with fibers.

[0028] Advantageously, the non-conductive resin layer comprises fibers of reinforcement such as glass fibers or plastic fibers.

[0029] Advantageously, the resin of the non-conductive layer is selected to have a higher compressive stress resistance than a tensile stress resistance. The compressive strength may be, for example, twice as high as the tensile strength, this difference between compression and traction varying according to the speed, the temperature and the desired performance.

[0030] The invention also relates to a rotor rotating around its center, characterized in that it comprises a single magnet structure or several magnet structures as previously mentioned, the magnet structure(s) being arranged concentrically in the center of the rotor.

[0031] For a high power motor, the rotor rotates at high rotational speeds. The main disadvantage of a high rotational speed motor is the high probability of detachment of the unitary stud-shaped magnets from the magnet structure, causing a risk of breakage of the structure as well as the rotor. This can be avoided by using unitary stud-shaped magnets having a non-square diamond-shaped cross-section to reduce the stresses experienced by the magnet structures under centrifugal loading.

[0032] Advantageously, when unique, the magnet structure forms a single magnet extending around the center of the rotor or, when multiple, the magnet structures are successive blocks forming successive magnet poles.

[0033] Advantageously, the rotor has a body comprising an internal hub concentric with a central axis of rotation of the rotor, branches extending radially with respect to the central axis of rotation from the internal hub towards a hoop forming a circular external periphery of the rotor, a magnet structure forming a magnet pole being housed in each space delimited between two adjacent branches associated with the magnet structure.

[0034] Advantageously, the rotor has circular faces delimiting it axially, a covering disc being arranged on at least one circular face of the rotor.

[0035] The invention finally relates to an axial flux electromagnetic motor or generator characterized in that it comprises at least one rotor as previously mentioned.

[0036] The invention also relates to a method of manufacturing such a magnet structure, characterized in that it comprises the following steps:

[0037] - cutting in a magnetic tile having a length, a width and a thickness forming three dimensions of the tile of several unit magnets according to the three dimensions of the magnetic tile, with at least two types of cut having an angle other than right between them,

[0038] - positioning and maintaining the unit magnets at a distance from each other,

[0039] - injection of a layer of resin around the unit magnets for their coating.

[0040] By cutting in three dimensions and in particular in width and length of the tile, it turned out that the unit magnets had improved magnetic properties compared to the properties of a comparable portion of the magnetic tile.

[0041] Positioning of the unit magnets may be accomplished by receiving the magnets in a mesh, in which case the mesh becomes part of the magnet structure by being embedded in the resin layer.

[0042] Alternatively, the positioning can be done outside or inside a blank of the magnet structure, for example by a heel securing together all the unit magnets of the same magnet structure, the heel being able to belong or not belong to the final coated magnet structure.

[0043] Other characteristics, aims and advantages of the present invention will appear on reading the detailed description which follows and with regard to the appended drawings given as non-limiting examples and in which:

[0044] [Fig.l] is an enlarged schematic representation of a side section of a unit magnet in the form of an elongated stud according to the state of the art with a square section, a tangential force being applied perpendicularly on a longitudinal side of each unit magnet forming part of a magnet structure during a rotation of a rotor comprising it,

[0045] [Fig.2] is an enlarged schematic representation of a side section of a unit magnet in the form of an elongated stud according to an embodiment of the present invention, the section of the unit magnet being in the form of a non-square diamond, a tangential force being applied at a non-right angle with a longitudinal side of each unit magnet forming part of a magnet structure during rotation of a rotor comprising it,

[0046] [Fig.3] is a schematic representation of a front perspective view of a magnet structure with unit magnets in the form of elongated pads of square section in accordance with the state of the art,

[0047] [Fig.4] is a schematic representation of a front view of a structure of a magnet with unit magnets in the form of elongated studs of non-square diamond-shaped section in accordance with a first embodiment of the present invention,

[0048] [Fig.5] is a schematic representation of a front view of a structure of a magnet with unit magnets in the form of elongated studs of non-square diamond-shaped section in accordance with a second embodiment of the present invention, the angles at the apex of the diamond being different from the first embodiment,

[0049] [Fig.6] is a schematic representation of a front view of a rotor comprising a plurality of magnet structures with unit magnets in the form of elongated pads of non-square diamond-shaped cross-section in accordance with one embodiment of the present invention, the rotor comprising branches separating the magnet structures.

[0050] The figures are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of the practical applications. In particular, the dimensions of the various parts are not representative of reality.

[0051] In what follows, a single branch 3 is referenced for all the branches in [Fig.6]. The same applies to a single magnet structure referenced 10.

[0052] In Figures 4 to 6, a single unit magnet 4 in the form of a pad is referenced for all the unit magnets as well as a single layer of resin 23 between unit magnets 4 in Figures 4 and 5.

[0053] Anything stated for one of these referenced elements applies to all similar unreferenced elements.

[0054] Figures 2, 4 to 6 respectively show embodiments of a unit magnet 4, a magnet structure 10 or a rotor 1 with magnet structures 10 according to the present invention.

[0055] Figures 1 and 3 respectively illustrate a unitary magnet 4' with a square section and a magnet structure 10' according to the state of the art comprising this type of unitary magnet. The references for elements common to all these figures remain the same except for a unitary magnet with a square section 4' instead of 4, and a magnet structure 10' with unitary magnets with a square section instead of 10, of the state of the art.

[0056] Referring more particularly to Figures 1 and 2, these figures show a section of a unit magnet 4', 4 in the form of an elongated body, for example a pin or a stud, intended to be incorporated into a magnet structure 10', 10, not shown in Figures 1 and 2 but shown in Figures 3 to 6 of the present patent application.

[0057] In [Fig.l], the section of the unit magnet 4' in the form of an elongated, advantageously parallelepipedal, stud is square in accordance with the state of the art.

[0058] In [Fig.2], the section of the unit magnet 4 is a non-square diamond-shaped section SL, a square section being a particular form of a diamond-shaped section SL not forming part of the scope of the invention.

[0059] In relation to the first problem underlying the present invention, the arrows inside the sections SL of figures 1 and 2 symbolize the path P', P of eddy currents respectively through the unit magnet 4', 4 in the form of a plot appearing when the unit magnet 4', 4 is subjected to a variable magnetic field.

[0060] In [Fig.l], as shown by the arrows in the section of the unit magnet 4', these currents tend to flow along a path P' up to the boundary formed by the sides of the parallelepiped formed by the unit magnet 4'.

[0061] In [Fig.2], as shown by the arrows in the non-square diamond-shaped section SL of the unit magnet 4, although this section SL occupies the same area as the square section of [Fig.l], this section SL is more flattened on a first axis and more elongated on the other axis perpendicular to the first axis. This means that the eddy currents, whose path P is symbolized by the internal arrows in the SL section, circulate over a smaller surface.

[0062] Since the resistance is inversely proportional to the circulation area, the eddy currents are less significant in the case of unit magnets 4 with a non-square diamond-shaped SL section, thus leading to a reduction in losses.

[0063] It may also be of interest to note that the non-square diamond shape is closer to that of the sheets used for magnetic circuits, a shape which is optimal for minimizing eddy current losses.

[0064] In relation to the second problem underlying the present invention, the arrow Ft represents the tangential force which is applied to each unit magnet 4', 4 in the form of a pad when the magnet structure comprising the unit magnets 4', 4 in the form of a pad is rotated, for example by forming part of a rotor 1 of an electric motor, as shown in [Fig.6].

[0065] In relation to [Fig. 1], the tensile stress in the resin coating a unit magnet 4' in the form of a square-section pad is symbolized by the parameter o' and can be expressed according to the following equation by dividing the tangential force Ft by the transverse surface S' facing the tangential force Ft of the unit magnet 4':

[0066] o' = Ft / S'

[0067] In relation to [Fig.2], the tensile stress in the resin coating a unit magnet 4 in the form of a non-square diamond-shaped cross-section pad SL is symbolized by the parameter o, the angle a being the angle of inclination of the transverse surface S of one side of the non-square diamond on which the tangential force Ft is applied relative to the tangential force Ft.

[0068] The tensile stress can be expressed according to the following equation by dividing the tangential force Ft by the transverse surface S of the unit magnet 4 with a non-square diamond-shaped section SL:

[0069] o = Ftcosa / S

[0070] Knowing that the surface S of one side of a rhombus is linked by the following equation with the surface S' of one side of a square we obtain:

[0071] S = S' / cosa

[0072] o = Ftcos2a / S'

[0073] Referring primarily to [Fig.2], the present invention relates to a unit magnet 4 in the form of an elongated pad in the shape of a polyhedron having a line of magnetization extending along its length.

[0074] The elongated pad forming each unit magnet 4 has a diamond-shaped section SL without a right angle at the top and therefore not square. The diamond-shaped section SL of each unit magnet 4 is less than 25 mm2. In addition, a ratio of the largest diagonal of the diamond-shaped section SL of each unit magnet 4 to the length of the unit magnet is less than 0.5.

[0075] These dimensional characteristics make it possible to classify the unit magnet 4 in micro-magnets and to clearly distinguish it from bar or strip-shaped magnets. In addition, these characteristics make it possible to significantly reduce the eddy currents circulating in each unit magnet 4.

[0076] Referring primarily to Figures 2, 4 to 6 the present invention relates to a three-dimensional magnet structure 10 consisting of a plurality of unit magnets 4, each unit magnet 4 being as previously mentioned.

[0077] The magnet structure 10 has a thickness, a front edge 5 and a rear edge 6 which are flat or rounded and joined by side faces 9, the unit magnets 4 being arranged to have a first longitudinal end adjacent to the front edge 5 of the magnet structure 10 while the second longitudinal end is adjacent to the rear edge 6 of the magnet structure 10. The unit magnets 4 therefore extend in the thickness of the magnet structure and not tangentially to the front edge 5 or to the rear edge 6 as magnet bars would do.

[0078] In Figures 3 to 5, the magnet structures 10', 10 have lateral lugs 11 for insertion into the rotor shown in [Fig.6].

[0079] In [Fig.6], it can therefore be observed that the unitary magnets 4 in the form of a stud according to the present invention extend in the thickness of the magnet structure 10 and therefore in the thickness of the rotor 1 and not on the circumference of the rotor 1.

[0080] The unit magnets 4 are grouped in the magnet structure 10 against each other forming a bundle by being individually coated in a layer of non-conductive resin 23.

[0081] Bundle, bouquet or cluster of unit magnets 4 means that the unit magnets 4 are grouped together being approximately parallel to each other and are separated only by grooves of dimensions just necessary to receive the layer of non-conductive resin 23 coating them.

[0082] Such a grouped collection of magnets cannot be likened to bars located at a distance from each other, each being, where appropriate, composed of a set of bars not extending into the thickness of a rotor 1, as shown in document FR3 014 255A1.

[0083] Referring to Figures 2 and 4 to 6, in the or each magnet structure 10, the unit magnets 4 are arranged so that their sides form an angle of less than 90 degrees with respect to a tangential force Ft extending parallel to a tangent of the leading edge 5, the tangential force Ft being applied to the magnet structure 10 as a centrifugal force during a rotational movement of the magnet structure 10.

[0084] The magnet structure 10 described in this invention is composed of unit magnets 4 in the form of elementary pads of non-square diamond-shaped section SL.

[0085] Such unitary magnets 4 in a blank of magnet structure 10 may be previously held integral with each other by a heel portion present on the rear face of the magnet structure 10, this not being shown in the figures.

[0086] Such a blank of magnet structure 10 is then coated with a layer of thermosetting resin 23, with the exception of the front face which is ground so as to reveal the unit magnets 4.

[0087] The resin thus penetrates into grooves arranged between the unit magnets 4, each in the form of a stud. This arrangement makes it possible to fill the empty spaces between the unit magnets 4, reinforcing the mechanical resistance of the magnet structure 10.

[0088] The resin used is specifically selected for its properties of mechanical resistance in traction and compression, so as to prevent potential damage caused by the conditions of use of the magnet structure 10, in particular when it is subjected to high rotation speeds, for example greater than 10,000 revolutions / minute, and therefore to significant centrifugal forces.

[0089] Referring more particularly to [Fig.6], such magnet structures 10 are intended to be integrated into a rotor 1. This rotor 1 may be that of a motor or an electromagnetic generator.

[0090] Without this being limiting, such a rotor 1 may have a body comprising an internal hub 2 concentric with a central axis 7 of rotation of the rotor 1.

[0091] Branches 3 may extend radially relative to the central axis 7 of rotation from the inner hub 2 towards a hoop 8 forming a circular outer periphery of the rotor 1. In [Fig.6], the branches 3 are shown to be of substantially rectangular polygonal shape but the branches 3 may also be tapered with a point facing the hoop 8.

[0092] At least one magnet structure 10 is housed in each space delimited between two adjacent branches 3, this magnet structure 10 comprising unit magnets 4 in the form of a pad and a non-square diamond-shaped section SL.

[0093] The magnet structures 10 with multiple unit magnets 4 can be glued to the hub 2 by means of an adhesive present on the contact faces between the magnet structure 10 and the hub 2 of the rotor 1.

[0094] When such a rotor 1 is subjected to high rotation speeds, each meshed magnet structure 10 generates centrifugal forces perpendicular to the longitudinal edge of the structure 10, i.e. in the radial direction. The glue and the hoop 8 of the rotor 1 recover part of these forces, however a significant percentage of these pass into the fret 8 because of its greater rigidity compared to the glue.

[0095] The sliding between each magnet structure 10 and the hoop 8, not directly glued together, this sliding being due to centrifugal forces, also generates a tangential component parallel to the longitudinal edge of the magnet structure 10 which then stresses in traction in this zone the grooves between unit magnets 4 contained in the magnet structure 10, these grooves being filled with the resin layer 23.

[0096] This tangential component is particularly significant at the outer radius of the magnet structure 10. This tangential component does not, however, exert a great influence at the inner radius of the magnet structure 10 due to the bonding of the magnet structure 10 to the glue, this area at the outer radius of the magnet structure 10 is therefore mainly subjected to tensile forces due to centrifugal forces in the radial direction.

[0097] It follows that, the greater the centrifugal forces, the greater the traction forces will be in the grooves between unit magnets 4.

[0098] In the case of a magnet structure 10 with unit magnets 4 of square or rectangular shape as suggested by the state of the art, the resin layer 23 located in the grooves is thus entirely stressed in traction.

[0099] In the case of a magnet structure 10 according to the present invention, the component of the stress in the direction of the groove is multiplied by a factor k=cos2a, where a represents the angle of inclination of the grooves relative to the axis of symmetry of the unit magnet.

[0100] The angle of inclination of the grooves therefore affects the influence of the tangential component of the centrifugal force at the outer radius and the influence of the centrifugal force at the inner radius, this angle of inclination being advantageously the angle between the tensile stress and the tangential force. The greater the angle of inclination of the grooves, the more the component of the tensile stress will be reduced, because it will be multiplied by cos2a, always less than 1.

[0101] Furthermore, the tensile stress decreases by promoting the compressive stress of the resin, the latter having a breaking limit in compression on average four times greater than in tension.

[0102] In summary, in the magnet structures 10', as shown in [Fig. 3], according to the state of the art subjected to centrifugal forces, the tensile stresses are high in the resin located in the grooves between unit magnets 4' of the magnet structure 10', unlike the magnet structures 10 according to the present invention, designed to promote compressive stress on the resin 23, and thus reduce the tensile stresses in the grooves between the unit magnets 4 when subjected to centrifugal forces.

[0103] This approach is made possible by the non-parallel and non-perpendicular orientation of the grooves relative to the longitudinal edge of the magnet structure 10 with multiple unit magnets 4, as well as the compressive strength of the resin, which is on average four times greater than its tensile strength. The absence of a right angle between two consecutive sides of an elementary pad forming a unit magnet 4 also makes it possible to avoid localized stress concentrations in the resin at these said angles.

[0104] As a result, the invention provides an innovative means of reducing the stresses experienced by the magnet structures 10 with multiple unit magnets 4 in a centrifugal loading situation, thus improving their durability and performance.

[0105] The contribution in terms of performance is particularly verified at the upper and lower ends, that is to say at the outer and inner radii of the magnet structure 10 where the resin layer 23 is particularly and respectively, in the case of a magnet structure 10 of the state of the art, stressed in traction in the radial and orthoradial directions.

[0106] Advantageously but not limitatively, the resin layer may be made of a thermosetting epoxy resin.

[0107] The diamond-shaped section SL of each unit magnet 4 may be constant over the entire length of each unit magnet 4 forming a pad.

[0108] As can be seen in Figures 4 and 5, two opposite apex angles of the diamond-shaped section SL between two sides on which the tangential force is applied can be between 100 and 200 degrees.

[0109] The non-conductive resin layer 23 individually coating the unit magnets 4 in the form of a pad and a non-square diamond-shaped section SL may be reinforced with fibers, for example reinforcing fibers such as glass fibers or plastic fibers.

[0110] The resin of the non-conductive layer may be selected to have a higher stress resistance in compression than in tension.

[0111] A rotor 1 rotating around its center according to the present invention may comprise a single magnet structure 10 or several magnet structures 10 as previously mentioned. The one or more magnet structures 10 are arranged concentrically at the center of the rotor 1.

[0112] When single, the magnet structure 10 forms a single magnet extending around the center of the rotor 1. When multiple, the magnet structures 10 are successive blocks forming successive magnet poles.

[0113] Simulations have shown that the speed of 17,500 revolutions per minute or rpm is a limiting rotation speed for unit magnets with parallelepiped studs of rectangular section, that is to say oriented at 0° and 45° relative to the axis of symmetry of the unit magnet due to the strength of the resin which is approximately 107 MPa.

[0114] Non-square diamond-shaped magnets, on the other hand, have better performance and can rotate at speeds above 17,500 revolutions per minute or rpm with stresses of 14 MPa at the outer radius and approximately 20 MPa at the inner radius of the resin.

Claims

Claims

1. Unit magnet (4) in the form of an elongated pad in the shape of a polyhedron having a magnetization line extending along its length, characterized in that the elongated pad forming the unit magnet (4) has a diamond-shaped section (SL) without a right angle at the apex, the section of the unit magnet (4) being less than 25 mm2 and a ratio of the largest diagonal of the diamond-shaped section (SL) of the unit magnet (4) to the length of the unit magnet (4) being less than 0.

5.

2. A three-dimensional magnet structure (10) consisting of a plurality of unit magnets (4), each unit magnet (4) being according to claim 1, the magnet structure (10) having a thickness, a front edge (5) and a rear edge (6) which are planar or rounded and joined by side faces (9), the unit magnets (4) being arranged to have a first longitudinal end adjacent to the front edge (5) of the magnet structure (10) while a second longitudinal end is adjacent to the rear edge (6) of the magnet structure (10), the unit magnets (4) being grouped in the magnet structure (10) against each other in a bundle by being individually coated in a non-conductive resin layer (23),characterized in that the unit magnets (4) are arranged in the magnet structure (10) so that their sides form an angle of less than 90 degrees with respect to a tangential force (Ft) extending parallel to a tangent of the leading edge (5), the tangential force (Ft) being applied to the magnet structure (10) during a rotational movement of the magnet structure (10).,

3. Magnet structure (10) according to the preceding claim, in which the diamond-shaped section (SL) is constant over the entire length of each unit magnet (4) forming a pad.

4. A magnet structure (10) according to any one of the preceding two claims, wherein two opposite apex angles of the diamond-shaped section (SL) between two sides on which the tangential force (Ft) is applied are between 100 and 200 degrees.

5. A magnet structure (10) according to any one of the three preceding claims, wherein the resin (23) of the layer non-conductive is selected to have a higher stress resistance in compression than in tension.

6. Rotor (1) rotating around its center, characterized in that it comprises a single magnet structure (10) or several magnet structures (10) according to any one of claims 2 to 5, the magnet structure(s) (10) being arranged concentrically in the center of the rotor (1).

7. Rotor (1) according to the preceding claim, wherein, when single, the magnet structure (10) forms a single magnet extending around the center of the rotor (1) or, when multiple, the magnet structures (10) are successive blocks forming successive magnet poles.

8. Rotor (1) according to either of the two preceding claims, which has a body comprising an internal hub (2) concentric with a central axis (7) of rotation of the rotor (1), branches (3) extending radially with respect to the central axis (7) of rotation from the internal hub (9) towards a hoop (8) forming a circular external periphery of the rotor (1), a magnet structure (10) forming a magnet pole being housed in each space delimited between two adjacent branches (3) associated with the magnet structure (10).

9. Rotor (1) according to any one of the three preceding claims, in which the rotor (1) has circular faces delimiting it axially, a covering disc being arranged on at least one circular face of the rotor (1).

10. Axial flux motor characterized in that it comprises at least one rotor (1) according to any one of the four preceding claims.

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