Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/22—Rotating parts of the magnetic circuit
  • H02K1/27—Rotor cores with permanent magnets
  • H02K1/2793—Rotors axially facing stators
  • H02K1/2795—Rotors axially facing stators the rotor consisting of two or more circumferentially positioned magnets
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/02—Details of the magnetic circuit characterised by the magnetic material
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/22—Rotating parts of the magnetic circuit
  • H02K1/28—Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures
  • H02K1/30—Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures using intermediate parts, e.g. spiders
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
  • H02K15/02—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
  • H02K15/03—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies having permanent magnets
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K16/00—Machines with more than one rotor or stator
  • H02K16/04—Machines with one rotor and two stators
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
  • H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
  • H02K21/24—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets axially facing the armatures, e.g. hub-type cycle dynamos
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K2213/00—Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
  • H02K2213/12—Machines characterised by the modularity of some components

Definitions

• the present invention relates to a rotor for an electromagnetic axial flow motor or generator having an advantageously enlarged hub from which tapering branches leave with at least one magnet structure between two adjacent branches.
• the invention also relates to an electromagnetic motor or generator equipped with such a rotor.
• the present invention finds an advantageous but nonlimiting application for an electromagnetic motor delivering a high power with a high rotational speed of the rotor, which is obtained by the specific characteristics of the rotor according to the present invention.
• a motor can be used, for example, as an electromagnetic motor in a fully electric or hybrid motor vehicle.
• the electromagnetic motor or generator can comprise at least one rotor framed by two stators, these elements being able to be superimposed relative to each other by being separated by at least one air gap on the same shaft.
• the rotor comprises a body in the form of a discoidal support for magnets having two circular faces connected by a thickness, the disc being delimited between an external crown formed by a hoop and an internal periphery delimiting a recess for a rotation shaft.
• the magnets are each held in the disc support by holding means, a gap being left between the magnets.
• Axial flux motors are often used as an engine having higher torque than radial flux motors. They can therefore be used in low speed applications.
• the design of the rotor in an axial flow motor is more delicate because the forces due to centrifugal effects cause fairly high mechanical stresses in the rotor.
• the eddy current losses become preponderant both in the magnets and also in the rotor part when this is made with electrically conductive materials.
• the main disadvantage of a motor at high rotational speed lies in the high probability of detachment of the magnet or magnets from the rotor as well as at least partial breakage of the rotor. .
• the rotor of such an engine must therefore be able to withstand high rotational speeds.
• One solution may be to make meshes of elongated unit magnets in fibrous and resinous structures, so as to reduce the eddy currents and to use a body of composite material for the rotor which does not conduct electricity, ideally a fiberglass rotor, with a hoop placed at the periphery of the rotor so as to maintain the forces due to centrifugal effects.
• the document EP-A-0 353 042 representing the closest prior art, 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 relative to the central axis of rotation from the internal hub to a hoop forming a circular external periphery of the rotor, at least one magnet being housed in each space delimited between two adjacent branches, each branch having a decreasing width away from the internal hub to end with a tapered tip against the hoop, each magnet having an increasing width away from the internal hub to end against the hoop surrounding the rotor.
• an arrangement of unitary magnets independent of each other has the great disadvantage of being sensitive to space harmonics or currents generated by the stator windings. Consequently, the losses generated in the magnet structures are very high and the yields, particularly at high speed, are reduced.
• the document FR-A-1 475 501 does not describe a rotor but only a magnet structure comprising several unitary magnets without specifying an application for this magnet structure and suggesting that the disadvantages of the two above-mentioned documents can be eliminated by the use of such a magnet structure with several unit magnets, since use of such a magnet structure for a rotor is not mentioned in this document.
• the problem underlying the present invention is to design a rotor for the support of several permanent magnets provided with a hoop for an electromagnetic machine with axial flux which can, on the one hand, hold the permanent magnets that the rotor supports from effectively by preventing the magnets from detaching from the rotor while effectively compensating for the centrifugal force and, on the other hand, having a mechanical resistance such that the rotor can rotate at very high speeds.
• the present invention relates to 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 to a hoop forming a circular external periphery of the rotor, at least a magnet being housed in each space delimited between two adjacent branches, each branch having a decreasing width moving away from the internal hub to end with a tapered point against the hoop, each magnet having an increasing width moving away from the internal hub for finish against the hoop surrounding the rotor, characterized in that each magnet is in the form of a magnet structure consisting of a plurality of unit magnets secured by an insulating material reinforced with fibers, each unit magnet being of elongated shape extending in the axial direction of the rotor.
• the rotor configuration according to the present invention is based on the observation that the maximum stresses applying at very high speed on a rotor are made at the level of the hub surrounding the median axis of rotation of the rotor. It is therefore necessary to solidify this internal portion of the rotor. This is done at the expense of the magnets placed in this area which must be replaced by an enlarged hub. It is also advisable to equip the rotor with relatively thick branches at least at their connection with the hub. The more we thicken the shape of the branches, the less magnets we put.
• the main idea underlying the present invention is that the arms need not be thickened essentially only at their connection with the hub, the stresses exerted on the rotor decreasing the further one moves away from the center of the rotor.
• the Applicant has become aware that, in the case of an axial flow machine, the torque is proportional to the cube of the radius of the rotor. Therefore, it is more clever to add surface magnets to the periphery of the rotor than in more internal portions of the rotor. Hence an absence of magnet near the axis of rotation can be easily compensated for by an addition of magnet on the periphery of the rotor, which can be obtained by configurations of branches decreasing in width the further one moves away from the center of the rotor until they are only tapered points with a width close to zero.
• the rotor can have, between each branch, unitary magnets grouped together in a magnet structure.
• Each three-dimensional magnet structure consists of a plurality of unit magnets.
• Such a magnet structure can form a magnet pole or be a complete magnet.
• One of the measures of the present invention is to decompose a magnet structure which can be an entire magnet or a magnetic pole according to the state of the art into a plurality of small or micro-magnets.
• a large magnet is subject to greater eddy current losses than its equivalent in small or micro-magnets.
• the use of small magnets or micro-magnets therefore makes it possible to reduce these losses which are detrimental to the operation of the electromagnetic actuator.
• the length of a unitary magnet is appreciably increased compared to the diameter or to a diagonal of its planar longitudinal face compared to what the widespread practice, this essentially to answer needs of mechanical resistance of the structure, which is the main object of the present invention.
• the Applicant has discovered that a plurality of unit magnets in a magnet structure gives a magnet structure having a much greater mechanical resistance while retaining magnetic properties almost similar to those of a single magnet having an equal surface. to n times the elementary surface of the n unit magnets when n unit magnets are present.
• the tapered tip of each branch is at least half the width of a base of the branch connected to the internal hub.
• the bases of two adjacent branches are separated by an intermediate portion of the internal hub, the intermediate portion being of concave shape rounded in the direction of the axis of the rotor, the internal hub having a radius equal to at least a quarter of a rotor radius.
• the inward curvatures of the intermediate portions between branches make it possible to reduce the mechanical stresses at the level of the thickest section of the branches bearing on the external periphery of the hub.
• the hub and the branches are made of glass fibers cast in resin. These reinforcing fibers help to increase the resistance of the magnet structure and in particular the rigidity to bending and buckling.
• each unit magnet of the plurality of unit magnets is of polygonal shape or each unit magnet has an at least partially ovoid outline by comprising a first portion forming the body of the unit magnet having a larger section and extending over a greater length of the unitary magnet than at least a second longitudinal end portion pointing towards an associated longitudinal end of the magnet by decreasing in section as it approaches the longitudinal end.
• Ovoid magnets can have facets.
• the contact between two adjacent unitary magnets is more reduced by being able to be only punctual and corresponds substantially to a reduced arc of circle between the two magnets unit.
• a groove can be dug to the dimension of the arc of contact circle between two adjacent unit magnets to receive glue, advantageously in the form of resin.
• each magnet structure incorporates at least one mesh having meshes each delimiting a housing for a respective unitary magnet, each housing having sufficient internal dimensions sufficient to allow a unitary magnet to be introduced into its interior while leaving a space between the housing and the unitary magnet filled with a fiber reinforced resin, the meshes being made of fiber reinforced insulating material.
• the mesh remains in place, being able to also be coated in a layer of composite.
• Such a mesh makes it possible to maintain unitary magnets during the manufacture of the magnet structure and has the advantage of representing an additional solidification element of the magnet structure, the mesh possibly also containing reinforcing fibers.
• a honeycomb mesh is known to reinforce the resistance of an element, in this case a magnet structure.
• the unit magnets are inserted in hexagonal housings which ensure their maintenance.
• the walls of the housings serve as electrical insulation and the density of the housings in the magnet structure can be considerably increased.
• the honeycomb mesh can be made of an insulating composite material reinforced with fibers.
• the hoop is made of glass fibers or carbon fibers.
• the composite hoop circumferentially surrounds large magnets or magnet structures at an outer periphery of the rotor.
• the hoop contributes, if necessary, to the radial retention of the magnets in addition to that guaranteed by the external coating layer of composite.
• the tapered tips of the branches can be joined or not the hoop.
• the magnet structure between two adjacent branches is embedded in a layer of composite, the rotor also being coated in a layer of composite.
• cover discs are arranged on each circular face of the rotor.
• the present invention preferably uses a multitude of unit magnets replacing a compact magnet of the prior art, the heat dissipation is less and cover discs can be used as axial holding means, these discs advantageously replacing means of axial retention between magnets and rotor body, necessitating if necessary modifications of the magnets or of their coating to produce additional fixing means with fixing means carried by the rotor.
• the invention also relates to a method of manufacturing such a rotor, in which the width of each branch at a point of its length extending radially from the external periphery of the hub to the internal periphery of the hoop is determined from '' an evaluation of an admissible mechanical stress likely to be applied to the rotor, of a maximum admissible speed of rotation of the rotor and of a mechanical resistance of the material of the branch, a decrease in the width of each branch away from the hub being obtained by selecting for each branch a width for each point of its length making it possible to obtain an iso-stress inside the branch.
• the maximum stress exerted on a branch towards its end connected to the hub can be evaluated at 120 mega Pascals. Obtaining this iso-stress makes it possible to minimize the width of the branch and therefore to put more surface area of large magnets or magnet structures, therefore in the latter case more unit magnets, which allows to obtain more torque and more than compensate for the loss of magnet surface towards the hub.
• K being a constant varying according to a thickness of the hoop and representative of the mechanical resistance of the material of the branch
• p a density of the magnet structure
• am an admissible mechanical stress capable of being applied to the rotor and consequently on the branch
• Q an opening angle of each magnet structure
• W the maximum permissible speed of rotation of the rotor and r the distance from the point of the length taken with respect to the center of the rotor.
• the invention finally relates to an electromagnetic motor or generator with axial flow, characterized in that it comprises at least one such rotor, the electromagnetic motor or generator comprising at least one stator carrying at least one winding, the electromagnetic motor or generator. comprising one or more air gaps between said at least one rotor and said at least one stator.
• the electromagnetic motor or generator comprises at least one rotor associated with two stators.
• FIG. 1 is a schematic representation of a front view of a rotor for an electromagnetic machine with axial flow according to a first embodiment of the present invention, magnet structures composed of unitary magnets being each inserted between two adjacent branches of a disc-shaped support for the magnets, the branches having a width which decreases away from the hub of the rotor,
• FIG. 2 is an enlarged schematic representation of a portion of the rotor shown in FIG. 1,
• Figures 3a, 3b and 3c are schematic representations for Figures 3a and 3b of a respective embodiment of a unitary magnet of ovoid shape and for Figure 3c of a magnet structure comprising unitary ovoid magnets , four unitary ovoid magnets being shown spaced from the magnet structure,
• FIG. 4 shows a branch width curve of a rotor according to the present invention as a function of a point located at a distance r from the central axis of rotation of the rotor, the branch having a width decreasing away from the central axis of rotation of the rotor.
• a single branch 3 a single base 3a and a single tapered point 3b of the branch 3 are referenced for all the branches in FIGS. 1 and 2.
• a single unitary magnet 4 is referenced for all the unit magnets as well as a single layer of adhesive 6 between unit magnets and a single external layer 5 enveloping a structure of magnet 10.
• FIG. 1 shows a rotor 1 and an enlargement of a portion of a rotor 1 according to the present invention with two branches 3 interposing between them a structure of magnet 10 composed of several unitary magnets 4 polygonal.
• Such a rotor 1 is used in an electromagnetic motor or generator, advantageously with axial flow.
• the rotor 1, advantageously substantially circular, has a body comprising an internal hub 2 concentric with a central axis 7 of rotation of the rotor 1 or longitudinal median axis of the rotor 1.
• Branches 3 extend radially in the rotor 1 relative to the central axis 7 of rotation from the internal hub 2 towards a hoop 8 forming a circular external periphery of the rotor 1.
• At least one magnet structure 10 comprising a plurality of small unit magnets 4 is housed in each space delimited between two adjacent branches 3.
• each branch 3 has a width I, visible in FIGS. 1 and 4, decreasing as it moves away from the internal hub 2, ending with a tapered tip 3b against the hoop 8.
• the width I is shown for the greatest width of a branch 3 in FIG. 1, that is to say at the base 3a of this branch 3a connected to the hub 2.
• Each magnet structure 10 has an increasing width away from the internal hub 2 to finish against the hoop 8 surrounding the rotor 1. It is the largest width of the magnet structure 10 which illustrates the width 1a to Figure 1.
• the tapered tip 3b of each branch 3 can be at least two to four times less wide than a base 3a of the branch 3 connected to the internal hub 2.
• the bases 3a of two adjacent branches 3 can be separated by an intermediate portion 9 of the internal hub 2.
• This intermediate portion 9 may be of concave shape rounded in the direction of the axis of the rotor 1.
• the internal hub 2 may have a radius ri equal to at minus a quarter of a radius of the rotor 1, making it a hub 2 larger than a hub 2 of the prior art.
• the radius of the rotor is equal to the radius re of a branch 3 to which radius re is added a hoop thickness 8.
• the hub 2 and the branches 3 may be made of glass fibers cast in resin. Resistant plastic fibers can also be used in order to increase the resistance of the rotor 1 and in particular the rigidity to bending and buckling.
• the rotor 1 and the branches 3 may be in one piece.
• the branches 3 can be joined or not to the hoop 8 by their tapered end 3b.
• each magnet structure 10 can consist of a plurality of unit magnets 4 secured by an insulating material reinforced with fibers, each unit magnet 4 being of elongated shape in s extending in the axial direction of the rotor 1.
• the unit magnets 4 of which only one is referenced by figure are not to be confused with the magnet structures 10 nor with large magnets not shown in the figures.
• each magnet structure 10 can be three-dimensional and made up of a plurality of unit magnets 4.
• each unit magnet 4 of the plurality of unit magnets 4 is of polygonal shape.
• each unitary magnet 4 can have an at least partially ovoid contour by comprising a first portion 4a forming the body of the unitary magnet 4 having a larger section and extending over a greater length of l unitary magnet 4 that at least a second portion 4b of longitudinal end pointing towards an associated longitudinal end of unitary magnet 4 by decreasing in section as it approaches the longitudinal end.
• the unit magnet 4 has an almost perfect ovoid shape with a first portion 4a and two second portions 4b of rounded end and of convex shape. As can be seen in FIG. 3c, the contact between two adjacent and ovoid unitary magnets 4 is substantially punctual or extends in a limited arc.
• the unitary magnet 4 can have an at least partially ovoid external contour with the first portion 4a forming the body of the unitary magnet 4 having a larger section and extending over a greater length of the unitary magnet. 4 that said at least a second portion 4b.
• the unitary magnet 4 can have at least a second portion 4b at at least one longitudinal end of the unitary magnet 4 as an extension of the first portion 4a. There may be two second portions 4b with a second portion 4b respectively at a longitudinal end of the unitary magnet 4.
• the second portion (s) 4b can point towards an associated longitudinal end of the magnet by decreasing in section by approaching the longitudinal end.
• the second portion (s) 4b of longitudinal end can be curved while being convex in shape.
• the second portion (s) 4b of longitudinal end may terminate at their associated longitudinal end by a median facet 11 forming the longitudinal end.
• this median facet 11 forming the longitudinal end is however curved and is only optional.
• the second portion (s) 4b of the longitudinal end may include lateral facets inclined towards an axis of the unit magnet 4 by approaching the associated longitudinal end of the unit magnet 4.
• the unit magnets 4 are directly adjacent to each other by being partially in contact.
• the unit magnets 4 are glued by depositing glue.
• the plurality of unit magnets 4 provides a mesh of magnets without interposing holding elements between them other than glue, the unit magnets 4 being in direct contact between adjacent magnets.
• the first portion 4a and the second portion 4b for a unitary magnet are also shown in this figure 3c.
• the unit magnets 4 are glued against each other without mesh between them.
• the reference 5 designates the adhesive layer of the magnet structure 10 with the branches 3, this adhesive layer being shown enlarged to be more visible.
• the adhesive can be a layer of composite, a bonding resin, advantageously thermosetting or thermoplastic.
• the reference 6 designates a space filled with glue between two unit magnets 4, the glue between unit magnets 4 can be similar to the glue of the magnet structure 10 or of a large magnet between two branches 3.
• Each structure d the magnet 10 between two adjacent branches 3 can also be embedded in a layer of composite, the rotor 1 also being embedded in a layer of composite in its entirety.
• first layer of composite to surround the unitary magnets 4
• second layer of composite to individually surround the magnet structures 10
• third layer of composite to coat the rotor 1.
• each magnet structure 10 can integrate at least one mesh having meshes each delimiting a housing for a respective unitary magnet 4.
• Each housing can have sufficient internal dimensions sufficient to allow a unitary magnet 4 to be inserted into its interior while leaving a space between the housing and the unitary magnet 4 filled with a fiber-reinforced resin, the meshes being made of insulating material. fiber reinforced.
• the hoop 8 can be made of glass fibers or carbon fibers.
• the composite hoop 8 circumferentially surrounds the magnet structures 10 or the large magnets at an outer periphery of the rotor 1.
• the hoop 8 contributes, if necessary, to the radial maintenance of the magnet structures 10 or large magnets size in addition to that guaranteed by the external composite coating layer.
• the tapered points 3b of the branches 3 can be joined or not the hoop 8.
• Cover discs can be arranged on each circular face of the rotor 1 to prevent axial movement of the magnet structures 10 or large magnets between two arms 3.
• the invention also relates to a method of manufacturing such a rotor 1, in which the width I of each branch 3 at a point of its length extending radially from the external periphery of the hub 2 to the internal periphery of the hoop 8 at a known distance from the central axis 7 of rotation of the rotor 1 is determined from an evaluation of an admissible mechanical stress capable of being applied to the rotor 1, of a maximum admissible speed of rotation of the rotor 1 and mechanical resistance of the material of the branch.
• a decrease in the width I of each branch 3 away from the hub 2 is obtained by selecting for each branch 3 a width I for each point of its length allowing an iso-stress to be obtained inside the branch 3.
• FIG. 4 also referring to FIGS. 1 and 2, shows for example and without being limiting a curve giving the width I of a branch 3 in millimeters (mm) as a function of a distance from a point r taken in the length of the branch 3 relative to the central axis 7 of the rotor 1, r being expressed in millimeters (mm).
• This curve is established for a rotational speed of the rotor 1 chosen arbitrarily of 1,400 revolutions per minute or rpm, another speed which can also be chosen, in particular a maximum permissible rotational speed of the rotor 1.
• the width I of the branches 3 decreases more r therefore increases away from the central axis 7 of the rotor 1.
• the distance from the point r to the central axis 7 of the rotor 1 is between the radius of the hub 2 referenced ri for internal radius and the internal radius of the hoop 8 equivalent to the external radius re of each magnet structure 10.
• K being a constant varying according to a thickness of the hoop 8 and representative of the mechanical resistance of the material of the branch
• p a density of the magnet structure 10
• am an admissible mechanical stress capable of being applied to the rotor 1 and consequently on the branch
• Q an opening angle of each magnet structure 10, W the maximum permissible speed of rotation of the rotor 1 and r the distance from the point of the length taken relative to the center of the rotor, as before mentionned.
• the angle Q is visible in FIG. 2.
• an external face 10b of the magnet structure 10 adjacent to the hoop 8 is of larger size than the inner face 10a of the magnet structure 10, which means that there is more magnet surface towards the outer periphery of the rotor 1 than towards the hub 2.
• the invention finally relates to an electromagnetic motor or generator with axial flow comprising at least one such rotor 1, the electromagnetic motor or generator comprising at least one stator carrying at least one coil, the electromagnetic motor or generator comprising one or more air gaps between said at least one rotor 1 and said at least one stator.
• the electromagnetic motor or generator may preferably comprise at least one rotor 1 associated with two stators.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Permanent Field Magnets Of Synchronous Machinery (AREA)
• Iron Core Of Rotating Electric Machines (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=63209460

Family Applications (1)

Country Status (6)

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• 2018
  • 2018-06-22 FR FR1800691A patent/FR3083023B1/fr active Active
• 2019
  • 2019-06-17 WO PCT/IB2019/055036 patent/WO2019243996A1/fr active Application Filing
  • 2019-06-17 EP EP19756243.2A patent/EP3811498A1/de not_active Withdrawn
  • 2019-06-17 CN CN201980041544.3A patent/CN112703660A/zh active Pending
  • 2019-06-17 US US17/056,155 patent/US11804742B2/en active Active
  • 2019-06-17 JP JP2020564887A patent/JP2021528941A/ja not_active Ceased

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