Stator core of nanocrystal material and processing method for manufacturing stator core of nanocrystal material

Abstract

The invention relates to a stator core (1) of nanocrystal material for an axial flux electric machine, comprising an encapsulated nanocrystal material, where the encapsulation comprises at least two different encapsulation materials deposited over the nanocrystal material. The first encapsulation material includes a material capable of increasing the mechanical stiffness of the stator core, and the second encapsulation material includes a material capable of increasing the heat exchange capability of the electric machine.

Description

Technical Field

[0001] The present invention relates to a stator core of nanocrystalline material, and more particularly to a stator core of nanocrystalline material for an axial electromagnetic flux motor. Background Art

[0002] Axial electromagnetic flux motors are well known in the art and generally include at least one stator and at least one disk-shaped rotor, wherein the electromagnetic flux propagates axially along the axis of rotation of the machine.

[0003] The stator generally includes a laminated core, and coils of conductive material are wound over the laminated core.

[0004] The selection of materials for the motor directly affects the power, efficiency and cost of the device. The same is true for the selection of magnetic materials, where parameters such as permeability, saturation point, coercivity, magnetic loss, magnetostriction and process complexity are evaluated in the cost / benefit equation for component selection.

[0005] In particular, the materials selected for manufacturing the stator and rotor greatly affect the weight, volume, efficiency, heat dissipation and cost of the motor.

[0006] Commonly used are ferromagnetic materials such as permalloy, cobalt iron or iron-silicon alloys.

[0007] The search for higher efficiency and performance at lower cost has led to the exploration of other magnetic materials such as composites, amorphous and nanocrystalline materials.

[0008] Magnetic composites include particles of powder metal materials surrounded by insulating organic materials, such as iron or iron alloy powders. Although they have the advantage of allowing components to be constructed by compaction in different forms, these materials have a lower electrical resistance than laminated metal alloys.

[0009] Amorphous magnetic materials are the result of rapid cooling of metal alloys. The atoms of these materials are randomly arranged without periodic or spatial order, which makes them easy to magnetize. Although they have high mechanical resistance, they have low elasticity and are very brittle.

[0010] Nanocrystalline materials are produced by heat treatment of amorphous materials, by crystallization of amorphous materials (amorphous ribbons). These materials have high magnetic flux density, high permeability, magnetic stability and low coercivity and magnetostriction. However, they also exhibit low elasticity and are fragile.

[0011] Another characteristic of amorphous and nanocrystalline materials is their thin thickness, which together with their low elasticity brings complexity to the handling of the materials during the manufacture of magnetic components. For example, in the case of manufacturing a stator core, the thin thickness and low elasticity rule out the use of standard manufacturing processes.

[0012] A known solution to address this issue is core encapsulation, in which case the external mechanical stress is borne by the encapsulating material, thus ensuring the integrity of the core material.

[0013] For example, Document CN105490400 discloses a method for manufacturing a stator core of nanocrystalline or amorphous material for an axial flux motor, which includes the following steps: winding a nanocrystalline or amorphous alloy strip around an annular part, the strip being wound to form an annular part with a predetermined inner diameter and outer diameter; as the winding progresses, an adhesive layer on the strip surface binds adjacent alloy strip layers to form the annular part; performing a curing process; cutting the annular element to obtain an annular core with a concave structure, and performing annealing of the concave structure to obtain the completed stator core.

[0014] However, there are some inconveniences in the solutions described in the above-mentioned document. For example, continuous spraying of adhesive is required during stator winding, making the processing method complex. In addition, the annealing step of the concave structure after the cutting step of the annular element may cause deformation of the package associated with the heat treatment, compromising the guarantee of the final dimensions of the package.

[0015] Document CN102761175 discloses a method for manufacturing an amorphous alloy stator core, microcrystal and nanocrystal of an axial magnetic field motor with high performance using a mold box. The proposed manufacturing method includes the following steps: roll-cutting a wound alloy strip wideband along the length direction of the alloy wideband by a roll shear into an alloy strip with a width equal to the height of the completed stator core, rewinding the alloy strip to form an annular alloy core with a preset inner diameter and outer diameter; bundling the annular alloy iron core in a first annular protective box; performing slotting machining on the annular alloy iron core and the first protective box by a cutting machine processing method to form an alloy stator iron core with an axial slotting structure; annealing the annular alloy iron core; encapsulating the annealed annular alloy iron core into a second protective box corresponding to the axial slotting structure of the annular alloy iron core, and then bundling and fixing it to obtain the completed stator iron core.

[0016] The solution of Document CN102761175 has the same inconveniences as the cutting processing method before the heat treatment of the aforementioned amorphous, microcrystalline and nanocrystalline materials. In addition, the processing method proposed in the document requires the use of two protective boxes, one of which must be made of a material capable of withstanding a temperature of 380 °C or higher. This requirement increases the complexity of the processing method and raises the manufacturing cost.

[0017] Therefore, there is still a need in the prior art for a stator core of nanocrystalline material, the manufacturing processing method of which solves or at least reduces the inconveniences in the prior art solutions. Summary of the Invention

[0018] Object of the Invention

[0019] One object of the present invention is to provide a stator core of nanocrystalline material that allows for a simplified manufacturing process while ensuring the final dimensions of the stator package.

[0020] Another object of the present invention is to provide a stator core of nanocrystalline material that allows for grooving machining after heat treatment of the amorphous material.

[0021] Another object of the present invention is to provide a stator core of nanocrystalline material whose encapsulation can increase the mechanical resistance of the tooth region of the stator and increase the heat exchange capacity of the motor.

[0022] Another object of the present invention is to provide a manufacturing process for a stator core of nanocrystalline material that ensures the final dimensions of the stator package.

[0023] Another object of the present invention is to provide a manufacturing process for a stator core of nanocrystalline material in which grooving machining of the stator core is performed after heat treatment of the amorphous core. Summary of the Invention

[0025] The present invention relates to a stator core of nanocrystalline material for an axial flux motor, which comprises encapsulated and machined nanocrystalline material for forming stator teeth. In the solution of the present invention, the encapsulation comprises at least two different encapsulation materials deposited on top of the nanocrystalline material.

[0026] Preferably, at least one of the different encapsulation materials is a material capable of increasing the mechanical stiffness of the stator core, and at least another of the different encapsulation materials is a material capable of increasing the heat exchange capacity of the motor.

[0027] In a preferred embodiment of the present invention, the material capable of increasing the mechanical stiffness of the stator core is an epoxy structural resin composed of quartz or silica filler with a mass percentage of 10% to 50%, more preferably 40% by mass percentage, and the encapsulated stator core has an epoxy structural resin encapsulation material with a mass percentage of about 10% to 90%, preferably about 20% to 50%, and even more specifically 25% by mass percentage after its machining. As used herein, "encapsulation material mass" refers to the total mass of the encapsulation materials considering all the encapsulation materials used.

[0028] In a preferred embodiment of the present invention, the material capable of increasing the heat exchange capacity of the motor is an epoxy resin composed of alumina and silica fillers with a mass percentage of 30% to 80%, preferably 70%, and a minimum thermal conductivity of 0.5 W / m.K, and preferably higher than 1 W / m.K. Moreover, the encapsulating material of the encapsulated stator core after its machining is about 90% to 10% by mass percentage, preferably about 80% to 50% by mass percentage, and more preferably 75% by mass percentage.

[0029] The present invention also contemplates a method for machining a stator core of nanocrystalline material for manufacturing an axial flux motor, which comprises the following steps:

[0030] (a) Heat-treating the amorphous material to convert it into nanocrystalline material;

[0031] (b) Providing an encapsulating mold and depositing a first encapsulating material at the bottom of the encapsulating mold;

[0032] (c) Assembling the heat-treated nanocrystalline material in the encapsulating mold;

[0033] (d) Depositing a second encapsulating material in the encapsulating mold to form a raw stator core; and

[0034] (e) Machining the encapsulated raw stator core to form a plurality of grooves and teeth in the raw stator core.

[0035] Preferably, the first encapsulating material includes a material capable of increasing the mechanical stiffness of the stator core, and the second encapsulating material includes a material capable of increasing the heat exchange capacity of the motor.

[0036] In one embodiment of the invention, the first encapsulating material comprises an epoxy structural resin composed of quartz or silica fillers with a mass percentage of 10% to 50%, and the second encapsulating material comprises an epoxy resin composed of silica and alumina fillers with a mass percentage of 30% to 80% and a minimum thermal conductivity of 0.5 W / m.K.

[0037] After step (c) and after step (d), the machining method of the present invention may further include the step of thermally curing the first encapsulating material and the heat-treated nanocrystalline material assembled on the encapsulating mold at a temperature of about 150 °C for about 90 minutes.

[0038] In one embodiment, after step (d) and before step (e), the machining method includes: a vacuum process for removing air from the encapsulated raw stator core and from the encapsulating mold; and a thermal curing step of the encapsulated raw stator core at a temperature of about 150 °C for about 16 hours. Description of the Drawings

[0039] The present invention will now be described in more detail with reference to the accompanying drawings, in which:

[0040] Figure 1 is a perspective view of a stator core of encapsulated and machined nanocrystalline material according to an embodiment of the present invention;

[0041] Figure 2 is a perspective view of a stator core of encapsulated and machined nanocrystalline material according to an embodiment of the present invention, showing the encapsulated material before machining;

[0042] Figure 3a is Figure 2 a top view of the mold in , showing the A-A cutting line;

[0043] Figure 3b is a cross-sectional view taken along the A-A cutting line;

[0044] Figure 4 is a perspective view of an encapsulation mold for a stator core of nanocrystalline material according to an embodiment of the present invention, showing the nanocrystalline material and the first encapsulating material at the bottom of the mold;

[0045] Figure 5a is Figure 4 a top view of the mold in , showing the B-B cutting line; and

[0046] Figure 5b is a cross-sectional view taken along the B-B cutting line. DETAILED DESCRIPTION

[0047] Figure 1 Shows a laminated stator core 1 made of nanocrystalline material for an axial flux motor according to an embodiment of the present invention. As is well known to those skilled in the art, the stator core 1 includes grooves 2 for winding coils of conductive material. The grooves forming the teeth 3 of the core 1 are typically formed by machining.

[0048] The machined stator core 1 is made of a nanocrystalline alloy material, which is a soft magnetic alloy and is typically provided in the form of a longitudinally continuous strip having a certain width. In the solution of the present invention, the stator core of the nanocrystalline alloy is made using a nanocrystalline alloy strip with a thickness of 20 ± 1 μm, a width of 40 mm, and a smooth surface, and a nominal chemical composition of Fe 84 Cu 1 Nb 5.5 Si 8.2 B 1.3 . Of course, those skilled in the art will understand that the present invention can be applied to nanocrystalline alloys with different chemical compositions.

[0049] Although the present invention has been described with reference to an electric motor, it should be understood that it can equally be applied to the stator of other axial flux motors (e.g., such as axial flux generators).

[0050] In the solution of the present invention, two different materials with different thermal and mechanical properties are used to encapsulate the stator core.

[0051] The first encapsulating material is a material capable of increasing the mechanical resistance in the tooth region of the stator. In a preferred embodiment of the present invention, the material is an epoxy structural resin composed of quartz or silica filler with a mass percentage of 10% to 50%, preferably 40%. The epoxy structural resin enables machining processes.

[0052] The second encapsulating material is a material capable of increasing the heat exchange capacity of the motor. In a preferred embodiment of the present invention, the material is an epoxy resin composed of alumina and silica filler with a mass percentage of 30% to 80%, preferably 70%, and a minimum thermal conductivity of 0.5 W / m.K, preferably higher than 1 W / m.K. Therefore, this second material increases the dissipation of heat generated by the external winding of the machine, and its epoxy resin load provides thermal capacity and mechanical resistance for the machining process.

[0053] The formation of the nanocrystalline material core is achieved by the heat treatment of the amorphous material. In the solution of the present invention, the heat treatment process includes the following steps: 1) placing the amorphous alloy stator core in a furnace, inserting and filling the furnace with nitrogen (N 2 ), heating it to 480 °C at a heating rate of 8 °C / min, and holding it at this temperature for 30 minutes; 2) next, heating it to 575 °C at a heating rate of 2 °C / min, and holding it at this temperature for 60 minutes; 3) and then, starting the rapid cooling device to cool the furnace body, cooling it to 180 °C at a speed of 20 °C / min, and taking out the nanocrystalline alloy stator core. During the heat treatment, a magnetic flux for increasing the magnetic permeability of the nanocrystalline material may or may not be applied to the nanocrystalline alloy core.

[0054] In the present invention, before the encapsulation process, the treatment of converting the amorphous material into nanocrystals is performed.

[0055] Therefore, in the present invention, the amorphous material forming the core will be heat-treated to be converted into nanocrystalline material before being inserted into Figures 2 to 5b the encapsulation mold 4 as shown. In an embodiment of the present invention, the mold 4 is made of a thermoplastic material, e.g., such as polybutylene terephthalate.

[0056] To assemble the core in the encapsulation mold 4, the bottom of the mold is initially filled with a material that can increase the mechanical resistance of the tooth region of the stator. The material preferably comprises an epoxy resin having structural properties and having a quartz or silica filler in a mass percentage of 10% to 50%, preferably 40% by mass percentage, which increases the mechanical stiffness of the setting to allow future machining on the nanocrystalline material.

[0057] Next, the heat-treated nanocrystalline material core is placed in the encapsulation mold, and then the epoxy structural resin is thermally cured at a temperature of 150 °C for 90 minutes.

[0058] Figures 4 to 5b The encapsulation mold 4 with the cured epoxy structural resin (first encapsulation material) and the nanocrystalline material core N is shown before performing the second encapsulation.

[0059] After the curing process of the epoxy structural resin in the encapsulation mold with the stator core of the nanocrystalline material, an encapsulation process is performed on the stator core 1 using a material (second encapsulation material) that can increase the heat exchange capacity of the motor.

[0060] The material is inserted into the encapsulation mold. The material is preferably a thermally conductive epoxy resin composed of alumina and silica fillers in a mass percentage of 30% to 80%, preferably 70%.

[0061] Next, a vacuum process is carried out, reaching about 0.5 mbar for about 30 minutes to remove all the air in the epoxy resin and the encapsulation mold. Finally, the epoxy resin is thermally cured at a temperature in the range of 150 °C for about 16 hours. Thus, different encapsulation materials are deposited above the previously heat-treated nanocrystalline material.

[0062] Figures 2 to 3b The encapsulation mold 4 with at least two different encapsulation materials E deposited before machining the groove 2 is shown.

[0063] Therefore, after the encapsulation process of the stator core 1 with at least two different encapsulation materials, the machining of the groove 2 can be performed. Since the machining is carried out after the heat treatment of the core, there is no risk of dimensional change, thus ensuring the final dimensions of the stator package.

[0064] The machining of the groove is carried out without the need to demold the encapsulated core.

[0065] In an embodiment of the present invention, the encapsulated and machined stator core 1 preferably has an encapsulating material of a first encapsulating material in an amount of about 10% to 90% by mass, more preferably 20% to 50% by mass, and an encapsulating material of a second encapsulating material in an amount of about 90% to 10% by mass, more preferably 80% to 50% by mass. Thus, during the deposition of the first encapsulating material in the mold, the encapsulating material in an amount of 10% to 90% by mass is completed, and during the deposition of the second encapsulating material in the mold, the encapsulating material in an amount of 90% to 10% by mass is completed.

[0066] In a preferred embodiment, considering the total mass of the encapsulating material, the encapsulated and machined stator core 1 has a first encapsulating material in an amount of about 25% by mass and a second encapsulating material in an amount of about 75% by mass.

[0067] Considering the total mass of the stator, which includes the mass of the encapsulating material and the nanocrystalline core, the material that can improve the mechanical stiffness of the stator core is about 1% to about 10% relative to the total mass after machining of the stator core, more specifically 3% by mass, and the material that can improve the heat exchange capacity of the motor is about 5% to 15% relative to the total weight after machining of the stator core, more specifically 11% by mass.

[0068] Since the heat treatment is performed before the encapsulation process, the encapsulation mold 4 does not have to be made of a material that resists high temperatures during the heat treatment.

[0069] In fact, using the encapsulating material allows the treated nanocrystalline material core to withstand the tension applied to the material during the machining process.

[0070] Furthermore, by using two different encapsulating materials, the present invention achieves an encapsulating material that has sufficient mechanical resistance to withstand the machining process of the core, while having a sufficiently high thermal conductivity that does not affect the performance of the motor.

[0071] After describing the preferred exemplary embodiments of the present invention, it must be understood that the scope of the present invention covers other possible variations of the described inventive concept, and the scope of the present invention is limited only by the content of the appended claims and the potential equivalents contained therein.

Claims

1. A stator core (1) of nanocrystalline material for an axial flux electric machine, comprising encapsulated and machined nanocrystalline material for forming teeth (3) of the stator, characterized in that The encapsulation includes at least two different encapsulation materials deposited over the nanocrystalline material.

2. The stator core (1) according to claim 1, characterized in that: At least one of the different encapsulation materials is a material capable of increasing the mechanical rigidity of the stator core.

3. The stator core (1) according to claim 2, characterized in that: The material capable of increasing the mechanical rigidity of the stator core is an epoxy structural resin composed of quartz or silica filler in an amount of 10% to 50% by mass.

4. The stator core (1) according to claim 3, characterized in that: The encapsulated stator core has an epoxy structural resin encapsulation material of about 10% to 90% by weight after machining thereof.

5. The stator core (1) according to any one of claims 1 to 4, characterized in that: At least one of the different encapsulation materials is a material capable of increasing the heat exchange capabilities of the electric machine.

6. The stator core (1) according to claim 5, characterized in that: The material capable of increasing the heat exchange capacity of the motor is a thermal performance epoxy resin composed of 30% to 80% by mass of alumina and silica fillers with a minimum thermal conductivity of 0.5 W / mK.

7. The stator core (1) according to claim 6, characterized in that: The encapsulated stator core has a thermal performance epoxy resin encapsulation material of about 90% to 10% by weight after machining thereof.

8. A method for manufacturing a stator core of a nanocrystalline material for an axial flux motor, characterized in that: The following steps are involved: (a) heat treating an amorphous material to convert it into a nanocrystalline material; (b) providing an encapsulation mold (4) and depositing a first encapsulation material in the bottom of the encapsulation mold, wherein the first encapsulation material comprises a material capable of increasing the mechanical stiffness of the stator core; (c) assembling the heat-treated nanocrystalline material in the encapsulation mold; (d) depositing a second encapsulating material in the encapsulating mold (4) to form an original stator core, wherein the second encapsulating material comprises a material capable of increasing the heat exchange capacity of the motor, and (e) machining the encapsulated original stator core to form a plurality of grooves (2) and teeth (3) on the original stator core.

9. The processing method according to claim 8, characterized in that: The first encapsulating material includes an epoxy structural resin composed of 10% to 50% by mass of quartz or silica fillers, and the second encapsulating material includes a thermal performance epoxy resin composed of 40% to 80% by mass of alumina and silica fillers with a minimum thermal conductivity of 0.5 W / mK.

10. The processing method according to claim 9, characterized in that: The encapsulated stator core has about 10% to 90% by weight of epoxy structural resin encapsulation material and about 90% to 10% by weight of thermal performance epoxy resin encapsulation material after machining thereof.

11. The processing method according to any one of claims 8 to 10, characterized in that: The encapsulation mold (4) is made of a thermoplastic material, namely polybutylene terephthalate.

12. The processing method according to any one of claims 8 to 11, characterized in that: After step (c) and before step (d), the processing method includes the step of thermally curing the first encapsulating material and the heat-treated nanocrystalline material assembled in the encapsulating mold at a temperature of about 150° C. for about 90 minutes.

13. The processing method according to any one of claims 8 to 12, characterized in that: After step (d) and before step (e), the processing method comprises: A vacuum process for removing air from the encapsulated raw stator core and the encapsulation mold; and The encapsulated raw stator core is subjected to a heat curing step at a temperature of about 150° C. for about 16 hours.

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