A magnet structure with unit magnets having a diamond-shaped cross-section

Abstract

The invention relates to a unit magnet (4) in the form of an elongated, polyhedral block having a magnetization line extending along its length. The elongated block forming each unit magnet (4) has a rhombus-shaped cross-section without a right angle at its apex, the cross-section of each unit magnet (4) being less than 25 mm², and the ratio of the longest diagonal of the rhombus-shaped cross-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 several such unit magnets (4). Abstract figure: FIGURE 4

Description

Title of the invention: Structure of a magnet with unit magnets having a diamond-shaped cross-section

[0001] The present invention relates to a unit magnet in the form of an elongated stud having a non-square rhombus-shaped cross-section, a magnet structure comprising such unit magnets and 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 not limiting, application in an electromagnetic actuator delivering high power with a high rotor speed, which is achieved by using 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 prior art, in particular that described in WO2019 / 243996A1, to decompose a magnet structure which can be a whole magnet or a magnetic pole according to the prior art into a plurality of small or micro-magnets.

[0004] Document WO2019 / 243996Al thus shows a three-part 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 lateral faces, the unit magnets being arranged so that a first longitudinal end is 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 together 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 the magnetic losses that are detrimental to the operation of the electromagnetic actuator.

[0007] Document EP0 353 042 Al 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, arms extending radially with respect to the central axis of rotation from the internal hub to a ring forming a circular outer circumference of the rotor, at least one magnet being housed in each delimited space between two adjacent branches, each magnet having an increasing width as it moves away from the inner hub to end against the ring surrounding the rotor.

[0008] This document does not permit a support for the multiple permanent magnets which can, on the one hand, maintain the permanent magnets which the rotor supports effectively by preventing the magnets from detaching from the rotor while effectively compensating the centrifugal force and, on the other hand, exhibit such mechanical resistance 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 or suggesting that the disadvantages of the aforementioned document could be eliminated by using such a magnet structure with several unit magnets. Indeed, the 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 because, in applications involving a high-speed rotating rotor, it is necessary to reduce losses for optimal efficiency. Furthermore, particularly for automotive applications, miniaturization is increasingly sought after.

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

[0013] In particular in a magnet structure configuration with multiple unit magnets electrically isolated from each other by individual encapsulation in a layer of resin filling grooves between unit magnets, it is necessary to reduce the stress concentrations in the resin layer at the level of the grooves between the unit magnets, these concentrations being due to the centrifugal forces induced during the high-speed rotation, on 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 in a situation of centrifugal stress, which occurs when the assembly carrying the magnet structure(s), for example a rotor, is set in rotation.

[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 rhombus-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 rhombus-shaped section of each unit magnet to the length of the unit magnet being less than 0.5.

[0016] In the case of a rhombus-shaped section, two diagonals connect two opposite vertices of the section, one of the two diagonals being longer than the other. A ratio less than 0.5 can correspond to a maximum longest 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 the rotation of the magnet structure around the axis of symmetry, makes it possible to reduce the concentrations of stresses suffered by the magnet structure, these stresses being due to the centrifugal force applied to the magnet structure.

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

[0020] The invention also relates to a three-dimensional magnet structure made up 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 that are flat or rounded and joined by lateral faces, the unit magnets being arranged so that a first longitudinal end is 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 together in the magnet structure, one against the other, forming a bundle, and 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 of less than 90 degrees with respect to a tangential force extending parallel to a tangent of the front 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 rhombus shape geometry of the cross-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 rectangular, square or even circular cross-section pads, the magnet structures with multiple unit magnets of the invention have been designed to reduce the mechanical stresses experienced by the magnet structure when subjected to centrifugal forces.

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

[0024] Furthermore, it has been shown that a structure with such a plurality of unit magnets has a high degree of insensitivity to spatial or current harmonics generated by the stator windings. Consequently, the losses generated in the magnet structures are very low, and the efficiencies, particularly at high speeds, are very high. Such a magnet structure can form a magnet pole or be a complete magnet.

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

[0026] Advantageously, two opposite vertex angles of the rhombus-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 fiber-reinforced.

[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 exhibit higher compressive strength than tensile strength. The compressive strength can, for example, be twice as high as the tensile strength, this difference between compression and tension varying according to the speed, temperature, and desired performance.

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

[0031] For a high-power motor, the rotor rotates at high speeds. The main disadvantage of a high-speed motor lies in the high probability of the individual stud-shaped magnets detaching from the magnet structure, leading to a risk of breakage of both the structure and the rotor. This can be avoided by using stud-shaped individual magnets with a non-square, rhombic cross-section to reduce the stresses experienced by the magnet structures under centrifugal loading.

[0032] Advantageously, when single, 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 to a fret forming a circular outer perimeter 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 cover disc being disposed 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 for 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 magnetized tile, with at least two types of cut presenting an angle other than right between them,

[0038] - positioning and maintaining the individual 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] The positioning of the unit magnets can be done 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 joining together all the unit magnets of the same magnet structure, the heel being able to belong or not to belong to the final coated magnet structure.

[0043] Other features, objectives and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings, which are given by way of non-limiting examples and on which:

[0044] [Fig.1] is an enlarged schematic representation of a side section of a unit magnet in the form of an elongated block according to the prior art with a square cross-section, a tangential force being applied perpendicularly on a longitudinal side of each unit magnet forming part of a magnet structure during the rotation of a rotor comprising it,

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

[0046] [Fig.3] is a schematic representation of a perspective front view of a magnet structure with unit magnets in the form of elongated square-section studs in accordance with the prior 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 with a non-square, rhombus-shaped cross-section, according to 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 with a non-square rhombus-shaped cross-section according to a second embodiment of the present invention, the angles at the apex of the rhombus being different from the first embodiment,

[0049] [Fig.6] is a schematic representation of a front view of a rotor comprising several magnet structures with unitary magnets in the form of elongated pads with a non-square rhombus cross-section according to an embodiment of the present invention, the rotor comprising branches separating the magnet structures.

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

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

[0052] In figures 4 to 6, a single unit magnet 4 in the form of a stud 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] Everything stated for one of these referenced elements applies to all similar unreferenced elements.

[0054] Figures 2, 4 to 6 show respectively 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 unit magnet 4' with a square cross-section and a magnet structure 10' according to the prior art comprising this type of unit magnet. The reference numerals for elements common to all these figures remain the same except for a unit magnet with a square cross-section of 4' instead of 4, and a magnet structure 10' with unit magnets of square cross-section instead of 10, according to the prior art.

[0056] With particular reference 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 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.1], the section of the unit magnet 4' in the form of an elongated stud, advantageously parallelepiped, is square in accordance with the prior art.

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

[0059] In relation to the first problem underlying the present invention, the arrows inside 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 dot appearing when the unit magnet 4', 4 is subjected to a variable magnetic field.

[0060] In [Fig.1], 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, rhombus-shaped section SL of the unit magnet 4, although this section SL occupies the same area as the square section of [Fig.1], this section SL is flatter along a first axis and more elongated on the other axis perpendicular to the first axis. This results in the eddy currents, whose path P is symbolized by the arrows inside the section SL, circulating over a smaller surface.

[0062] Since the resistance is inversely proportional to the circulation area, the eddy currents are less important in the case of unit magnets 4 with a non-square, rhombus-shaped cross-section SL, thus resulting in a reduction of 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 stud when the magnet structure comprising the unit magnets 4', 4 in the form of a stud is rotated, for example as 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 encapsulating a unit magnet 4' in the form of a square cross-section block 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 encasing a unit magnet 4 in the form of a block with a non-square rhombus-shaped cross-section 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 rhombus on which the tangential force Ft is applied with respect 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 area S of the unit magnet 4 with a non-square, rhombus-shaped cross-section SL:

[0069] o = Ftcosa / S

[0070] Given that the surface area S of a side of a rhombus is related by the following equation to the surface area S' of a side of a square, we obtain:

[0071] S = S' / cosa

[0072] o = Ftcos2a / S'

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

[0074] The elongated stud forming each unit magnet 4 has a rhombus-shaped cross-section SL without a right angle at the apex, therefore not square. The rhombus-shaped cross-section SL of each unit magnet 4 is less than 25 mm2. In addition, the ratio of the longest diagonal of the rhombus-shaped section SL of each unit magnet 4 to the length of the unit magnet is less than 0.5.

[0075] These dimensional characteristics allow the individual magnet 4 to be classified as a micro-magnet and clearly distinguished from bar or strip-shaped magnets. Furthermore, these characteristics significantly reduce the eddy currents circulating in each individual magnet 4.

[0076] With reference mainly to figures 2, 4 to 6, the present invention relates to a three-dimensional magnet structure 10 made up 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 lateral 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 into the thickness of the magnet structure and not tangentially to the front edge 5 or the rear edge 6 as would be the case with magnet bars.

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

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

[0080] The unit magnets 4 are grouped together 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 in a manner that is approximately parallel to each other and are separated only by grooves of dimensions just necessary to receive the non-conductive resin layer 23 coating them.

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

[0083] With reference 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 front 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 studs with a non-square, diamond-shaped cross-section SL.

[0085] Such unit magnets 4 in a blank magnet structure 10 can be previously held together by a portion of heel present on the rear face of the magnet structure 10, this not being shown in the figures.

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

[0087] The resin thus penetrates grooves arranged between the individual magnets 4, each shaped like a stud. This arrangement fills the empty spaces between the individual magnets 4, thereby strengthening the mechanical resistance of the magnet structure 10.

[0088] The resin used is specifically selected for its mechanical resistance properties in tension 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 rotational speeds, for example greater than 10,000 revolutions per minute, and therefore to significant centrifugal forces.

[0089] With particular reference to [Fig.6], such magnet structures 10 are intended to be integrated into a rotor 1. This rotor 1 can be that of a motor or an electromagnetic generator.

[0090] Without 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 can extend radially with respect to the central axis 7 of rotation from the internal hub 2 towards a fret 8 forming a circular outer perimeter of the rotor 1. In [Fig.6], the branches 3 are shown to be of substantially rectangular polygonal shape but the branches 3 can also be tapered with a point turned towards the fret 8.

[0092] At least one magnet structure 10 is housed in each delimited space between two adjacent branches 3, this magnet structure 10 comprising unit magnets 4 in the form of a stud and a non-square lozenge-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 rotational 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 adhesive and the ring 8 of the rotor 1 absorb some of these forces; however, a significant percentage of These pass through the 8th fret due to its greater rigidity compared to glue.

[0095] The slippage between each magnet structure 10 and the fret 8, not directly glued together, this slippage being due to centrifugal forces, also generates a tangential component parallel to the longitudinal edge of the magnet structure 10 which then stresses in tension in this area 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 important 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 tensile 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 prior art, the resin layer 23 located in the grooves is thus entirely stressed in tension.

[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 with respect 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 advantageously being the angle between the tensile stress and the tangential force. The greater the angle of inclination of the grooves, the more the tensile stress component will be reduced, since it will be multiplied by cos2a, which is always less than 1.

[0101] Moreover, the tensile stress decreases by favoring the compressive stress of the resin, the latter having a limit to rupture in compression on average four times greater than in tension.

[0102] In summary, in magnet structures 10', as shown in [Fig.3], according to the prior 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', contrary to the magnet structures 10 according to the present invention, designed to promote a 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 with respect to the longitudinal edge of the magnet structure 10 with multiple unit magnets 4, as well as by the compressive strength of the resin, which is on average four times greater than its tensile strength. The absence of right angles between two consecutive sides of an elementary pad forming a unit magnet 4 also prevents localized stress concentrations in the resin at these angles.

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

[0105] The contribution in terms of performance is particularly verified at the upper and lower ends, i.e. 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 prior art, stressed in tension in the radial and orthoradial directions.

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

[0107] The diamond-shaped section SL of each unit magnet 4 can 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 vertex angles of the rhombus-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 encapsulating the unit magnets 4 in the form of a stud and a non-square, diamond-shaped cross-section SL can be reinforced with fibers, for example reinforcing fibers such as glass fibers or plastic fibers.

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

[0111] A rotor 1 rotating about its center according to the present invention may comprise a single magnet structure 10 or several magnet structures 10 as previously mentioned. The magnet structure(s) 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 cuboids forming successive magnet poles.

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

[0114] Non-square diamond-shaped magnets, on the other hand, exhibit better performance and can rotate at speeds exceeding 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

Demands

1. A three-dimensional magnet structure (10) consisting of a plurality of unit magnets (4), each unit magnet (4) in the form of an elongated polyhedral stud having a magnetization line extending along its length, the elongated stud forming the unit magnet (4) having a rhombus-shaped cross-section (SL) without a right angle at the apex, the cross-section of the unit magnet (4) being less than 25 mm2 and a ratio of the longest diagonal of the rhombus-shaped cross-section (SL) of the unit magnet (4) to the length of the unit magnet (4) being less than 0.5, the magnet structure (10) having a thickness, a front edge (5) and a rear edge (6) that are flat or rounded and joined by lateral 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 together in the magnet structure (10) against each other in a bundle by being individually coated in a layer of non-conductive resin (23), the unit magnets (4) being 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 front edge (5), the tangential force (Ft) being applied to the magnet structure (10) during a rotational movement of the magnet structure (10),the magnet structure (10) being characterized in that the resin (23) of the non-conductive layer is selected to exhibit higher compressive strength than tensile strength.

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

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

4. Rotor (1) rotating about its center, characterized in that it comprises a single magnet structure (10) or several magnet structures (10) according to any one of claims 1 to 3, the magnet structure(s) (10) being arranged concentrically at the center of the rotor (1).

5. 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 pads forming successive magnet poles.

6. Rotor (1) according to any one 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), arms (3) extending radially with respect to the central axis (7) of rotation from the internal hub (9) to a ring (8) forming a circular outer perimeter of the rotor (1), a magnet structure (10) forming a magnet pole being housed in each space delimited between two adjacent arms (3) associated with the magnet structure (10).

7. Rotor (1) according to any one of the three preceding claims, wherein the rotor (1) has circular faces delimiting it axially, a cover disc being disposed on at least one circular face of the rotor (1).

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