Multi-layer magnet and method for its manufacture

Description

[0001] Method for manufacturing a multilayer magnet: Permanent magnet synchronous machines contain multiple permanent magnets. However, eddy currents are induced in these magnets by changes in the magnetic field, resulting in losses.

[0002] To reduce heat losses during operation, magnets are divided into electrically insulated segments, e.g., by sawing them apart. These segments are then glued back together.

[0003] However, this is complex and expensive.

[0004] Methods for producing composite materials by injection molding different powder materials, in particular two-component injection molding methods for magnetic and non-magnetic metal powders, are known, for example, from US 2003 / 0063993 A1, US 2013 / 0207756 A1, US 2013 / 0037633 A1, and CN 113600817 A. A manufacturing method for composite sintered parts with precise interface control by two-stage pressing of different materials and subsequent sintering is known, for example, from JP 2005089777 A. And a manufacturing method for thin material layers from particle suspension is known, for example, from US 2021 / 0320571 A1.

[0005] DARMANI MOSTAFA AHMADI ET AL: "Multilayer Bonded Magnets in Surface-Mounted PM Synchronous Machines", 2020 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE), IEEE, October 11, 2020 (2020-10-11), pages 1052-1059, XP033850746, DOI: 10.1109 / ECCE44975.2020.9235742, for example, is a study that investigates self-made, multilayer bonded magnets made of hard and soft permanent magnet materials in surface-mounted synchronous machines.

[0006] The invention is based on the objective of improving the production of magnets that have electrically insulated segments.

[0007] The problem is solved by claim 1, i.e., a method for producing a multilayer magnet (1) with a plurality of first layers and a plurality of second insulating layers alternating one another, wherein the first layer (2) is at least 1.5 mm and at most 4 mm thick, wherein the second insulating layer (3) is at least 0.01 mm and at most 0.1 mm thick, wherein a first layer (2) of a green body is formed by applying material to a base plate by injection molding, wherein the material is magnetic material, e.g., NdFeB powder and / or SmCo powder, and a binder, e.g.,plastic binder, wherein a second insulating layer (3) of the green body is formed by applying further material by injection molding adjacent to the first layer, wherein the further material is a poorly electrically conductive material with an electrical conductivity between 1x10 -8< and 1x10 -14< S / m, and / or is formed by oxidation of a surface of the first layer, wherein the surface of the first layer is oxidized by applying an oxidizing agent, e.g., an oxidizing agent comprising sodium peroxide and / or iron oxide, and / or is formed by applying the binder by injection molding.

[0008] Several layers are formed alternately. That is, preferably the first layer (which can also be called the magnetic layer) is formed, followed preferably by the second layer (which can also be called the insulating layer), then another magnetic layer, and subsequently another insulating layer. This is advantageously repeated until the desired magnet size is reached. A magnetic layer is preferably formed as the final layer.

[0009] The surface of the first layer is oxidized by applying an oxidizing agent, e.g., an oxidizing agent containing sodium peroxide and / or iron oxide. Other oxidizing agents are also conceivable.

[0010] Alternatively or in addition to applying the second material, it is advantageous to apply the oxidizing agent, which leads to oxidation.

[0011] The base plate serves advantageously as an aid during manufacturing and is preferably removed again.

[0012] Advantageously, the material for the first layer is in granular form, e.g., powder. This is advantageously melted and sprayed on.

[0013] Advantageously, the additional material for the second layer is available as a granular material, e.g., powder. This is advantageously melted and sprayed on.

[0014] Recycled material in the form of ground-up old magnets can be used for this purpose, requiring only a small amount of energy and resulting in minimal CO2 emissions. Other materials are also conceivable.

[0015] Furthermore, the material contains a binding agent (also called binder), e.g., plastic binder.

[0016] An advantageous embodiment is one in which the first layer is formed by means of powder injection molding.

[0017] Powder injection molding is also known as "MIM" (Metal Injection Molding). Powder injection molding advantageously comprises the following, particularly sequential, process steps: feedstock production, injection molding, debinding, and sintering. The resulting permanent magnet can be post-processed.

[0018] Feedstock production is advantageously achieved by mixing a metal powder, in particular magnetic powder, with a plastic, preferably a thermoplastic. The mixture can be referred to as feedstock.

[0019] The feedstock preferably contains other substances, for example the binder already explained, e.g. at least one organic binder.

[0020] Warming the feedstock is beneficial.

[0021] An advantageous embodiment is one in which the second insulating layer is formed by means of multi-component injection molding, in particular 2K injection molding.

[0022] Advantageously, at least two components are melted and applied, preferably under pressure. For example, a ceramic or yttrium oxide with organic binders, such as terpineols, can be used.

[0023] The surface is only adversely affected during a sintering process at a later time.

[0024] For example, if a first layer, which may contain NdFeB, is treated with iron oxide, the iron oxide is deposited on the first layer and / or neodymium oxide particles form on the surface of the first layer. In this way, an insulating layer can be created.

[0025] An advantageous design is one in which the other material is ceramic, e.g. aluminum oxide.

[0026] Oxide ceramics are particularly preferred. Lanthanide oxides, such as the cost-effective cerium oxide, are advantageous.

[0027] Other materials are also conceivable that would ensure isolation between two magnetic layers.

[0028] An advantageous method is one in which the binder is expelled from the green body to obtain a brown body, particularly by means of debinding.

[0029] During debinding, the binder is removed from the green body using thermal and / or catalytic debinding.

[0030] Preferably, the green part, i.e., the injection-molded part, is placed in a debinding oven. After this process, it can be referred to as a brown part. Thermal debinding is advantageously carried out in the debinding oven. In this way, the binder decomposes effectively.

[0031] Sintering is then advantageously carried out afterwards.

[0032] An advantageous design involves compacting and hardening the browning material by means of sintering.

[0033] The problem can also be solved by a magnet having a plurality of layers, at least a first layer and a second insulating layer, manufactured according to the described method.

[0034] According to the present invention of the magnet, the first layer has a thickness of at least 1.5 mm and at most 4 mm. on.

[0035] A magnetic layer thickness is advantageously between 1.5 mm and 4 mm. A thickness of at least 3 mm and at most 3.5 mm is particularly advantageous. Below 3 mm, the magnetic properties deteriorate significantly. A compromise is advantageously reached between minimizing eddy current losses in the magnet and maintaining full magnetic properties.

[0036] This process allows for the production of very thin magnetic layers, also called magnetic segment layers. The described thickness offers the following advantage: very low eddy currents are generated in the magnet during operation.

[0037] The magnetic layers that can be produced using the described method can be significantly thinner than those that can be produced using conventional methods.

[0038] According to the present invention, the first layer is thicker than the second insulating layer.

[0039] According to the present invention, the second insulating layer has a thickness of at least 0.01 mm and at most 0.1 mm.

[0040] This results in only a small amount of magnetically active volume being replaced by magnetically inactive volume.

[0041] The problem can also be solved by a dynamo-electric machine, in particular a permanent magnet synchronous machine, having at least one such magnet.

[0042] Preferably, the machine has a plurality of such magnets.

[0043] The segmentation made possible by this process also allows for the segmentation of complex magnet geometries, such as bowl magnets. For example, magnets with thin edges (e.g., bread loaf magnets or magnets with recessed edges) can be manufactured effectively.

[0044] The procedure is less complex than the previous procedure.

[0045] The described magnet can be used in the high-frequency range, e.g., in high-speed machining motors, electric vehicle motors, and in motors and generators in aircraft.

[0046] The invention will now be described and explained in more detail with reference to the exemplary embodiments shown in the figures. The figures show: FIG 1 a magnet, FIG 2 a machine, FIG 3 a method for manufacturing.

[0047] FIG 1 shows a magnet 1.

[0048] The magnet in the figure has multiple layers. A first layer 2 and a second insulating layer 2 are shown. The first layer 2 is advantageously a magnetic layer.

[0049] Advantageously, the magnet has several magnetic layers, with an insulating layer 3 formed between two magnetic layers.

[0050] FIG2 shows a dynamoelectric rotary machine 10.

[0051] This has a stator 11, a rotor 12 and a shaft 13.

[0052] FIG 3 shows the manufacturing process.

[0053] In process step S0, feedstock production takes place. Feedstock production is advantageously achieved by mixing the magnetic powder with a binder. Other substances may also be included. Heating the feedstock is beneficial.

[0054] In process step S1, the material is applied to a base plate to form a first layer by injection molding, in particular by metal injection molding. This creates a magnetic layer.

[0055] In process step S2, a second insulating layer (also called insulation layer) is formed by applying further material adjacent to the first layer by means of injection molding, in particular by means of 2K injection molding, wherein the material is a poorly conductive material.

[0056] Alternatively or additionally, the second insulating layer can be formed by oxidizing a surface of the first layer.

[0057] Alternatively or additionally, the second insulating layer can be formed by applying the binder using injection molding.

[0058] Therefore, only the described binder or a material mixture consisting predominantly of the binder can be applied. A debinding process (see process step S3) and a preferably subsequent sintering process advantageously produce a porous metal compound layer with low electrical conductivity. High mechanical strength can be achieved through advantageous subsequent infiltration of adhesive.

[0059] Process steps S1 and S2 are advantageously repeated until the desired magnet size is reached. A magnetic layer is preferably formed as the final layer.

[0060] According to the present invention, the magnet has a plurality of magnetic layers and a plurality of insulating layers that alternate one another.

[0061] In process step S3, debinding takes place, i.e., the removal of binding agent.

[0062] Debinding is preferably carried out at a temperature of 200°C to 400°C.

[0063] Sintering takes place in process step S4.

[0064] Sintering preferably takes place at a temperature of 900°C to 1100°C.

[0065] This ensures that magnet 1 is firmly bonded.

[0066] The described method allows the in FIG 1 Magnet 1 shown is manufactured.

[0067] In other words, the invention can also be explained as follows: The magnets are advantageously manufactured using the MIM injection molding process, preferably anisotropically. A magnetic feedstock advantageously comprises recycled NdFeB powder and a binder, in particular a plastic binder. The binder is advantageously completely removed from the magnetic body during the thermal debinding process. Preferably, several layers are injection molded. Advantageously, insulating layers are created between the layers. The insulating layers are preferably produced by a 2K injection molding process, for example, by injecting a thin layer, consisting essentially of or comprising a poorly or non-conductive material, onto the first magnetic layer. Magnetic and insulating layers are injection molded alternately. An insulating material orThe insulating layer is preferably made of a ceramic material, such as aluminum oxide. Alternatively or additionally, the insulating layer is created by superficially oxidizing the surface of the magnetic layer. Alternatively or additionally, binder is injected as an intermediate step. During the debinding process and the advantageously subsequent sintering process, a porous metal compound layer with low electrical conductivity is advantageously formed. High mechanical strength can be achieved through subsequent infiltration of adhesive.

Claims

1. Method for producing a multilayered magnet (1) with a plurality of first layers and a plurality of second insulating layers which follow one another alternately, wherein the first layer (2) is at least 1.5 mm and at most 4 mm thick, wherein the second insulating layer (3) is at least 0.01 mm and at most 0.1 mm thick, wherein a first layer (2) of a green body is formed by applying material by means of injection moulding to a base plate, wherein the material has magnetic material, for example NdFeB powder and / or SmCo powder, and a binder, for example plastic binder, wherein a second insulating layer (3) of the green body is formed by applying further material by means of injection moulding adjacent to the first layer, wherein the further material is an electrically poorly conducting material with an electrical conductivity which is between 1·10-8 and 1·10-14 S / m, and / or is formed by oxidizing a surface of the first layer, wherein the surface of the first layer is oxidized by applying an oxidizing agent, for example an oxidizing agent having sodium peroxide and / or iron oxide, and / or is formed by applying the binder by means of injection moulding.

2. Method according to claim 1, wherein the first layer (2) is formed by means of powder injection moulding.

3. Method according to one of the preceding claims, wherein the second insulating layer (3) is formed by means of multicomponent injection moulding, in particular 2K injection moulding.

4. Method according to one of the preceding claims, wherein the further material is ceramic, for example aluminium oxide.

5. Magnet (1), having a plurality of layers (2, 3), with a plurality of first layers (2) and a plurality of second insulating layers (3) which follow one another alternately, wherein the first layer (2) is at least 1.5 mm and at most 4 mm thick, wherein the second insulating layer (3) is at least 0.01 mm and at most 0.1 mm thick, produced according to a method according to one of claims 1 to 4, wherein the first layer (2) of a green body is formed by applying material by means of injection moulding to a base plate, wherein the material has magnetic material, for example NdFeB powder and / or SmCo powder, and a binder, for example plastic binder, wherein the second insulating layer (3) of the green body is formed by applying further material by means of injection moulding adjacent to the first layer, wherein the further material is an electrically poorly conducting material with an electrical conductivity which is between 1·10-8 and 1·10-14 S / m and / or is formed by oxidizing a surface of the first layer, wherein the surface of the first layer is oxidized by applying an oxidizing agent, for example an oxidizing agent having sodium peroxide and / or iron oxide and / or is formed by applying the binder by means of injection moulding.

6. Dynamoelectric machine (10), in particular permanently excited synchronous machine, having at least one magnet (1) according to claim 5.