Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
  • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
  • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
  • B09B3/30—Destroying solid waste or transforming solid waste into something useful or harmless involving mechanical treatment
  • B09B3/35—Shredding, crushing or cutting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
  • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
  • B09B5/00—Operations not covered by a single other subclass or by a single other group in this subclass
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/14—Treatment of metallic powder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/16—Metallic particles coated with a non-metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F8/00—Manufacture of articles from scrap or waste metal particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
  • H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
  • H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/24—Magnetic cores
  • H01F27/255—Magnetic cores made from particles
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F3/00—Cores, Yokes, or armatures
  • H01F3/08—Cores, Yokes, or armatures made from powder
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or 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

Definitions

• the present disclosure relates to a powder magnetic core, a stator for a motor, a motor, and a method for manufacturing the powder magnetic core.
• Powder magnetic cores have been used as magnetic cores for electrical equipment such as motors and reactors.
• Powder magnetic cores are compacts made by compressing soft magnetic powder, which has insulating films on the surfaces of soft magnetic particles.
• Patent Document 1 discloses a powder magnetic core used in motors.
• Patent Documents 2 and 3 disclose methods for recycling motors. They describe crushing a stator consisting of a magnetic core and a coil, separating the magnetic core and the coil, and then sorting them by material.
• the magnetic core material described in Patent Documents 2 and 3 is electromagnetic steel sheet, such as silicon steel sheet.
• the powder magnetic core disclosed herein contains recycled powder having insulating films on the surfaces of soft magnetic particles.
• the recycled powder is soft magnetic powder obtained by pulverizing used powder magnetic cores.
• FIG. 1 is a partial cross-sectional view that schematically shows a powder magnetic core according to an embodiment.
• FIG. 2 is a schematic perspective view showing an example of a powder magnetic core according to an embodiment.
• FIG. 3 is a schematic perspective view showing another example of a powder magnetic core according to the embodiment.
• FIG. 4 is a schematic perspective view showing yet another example of a powder magnetic core according to an embodiment.
• FIG. 5 is a schematic perspective view of a motor stator according to the embodiment.
• FIG. 6 is a schematic cross-sectional view of the motor according to the embodiment.
• FIG. 7 is a schematic cross-sectional view showing an example of a crusher.
• FIG. 8 is a graph showing the particle size distribution of the recycled powder and the new powder in Test Example 1.
• 9 is a diagram schematically illustrating the insulating film of the recycled powder used as the raw material for the dust core of Sample No. 2 in Test Example 2.
• 10 is a diagram schematically illustrating the insulating film of the recycled powder used as the raw material for the dust core of Sample No. 1 in Test Example 2.
• 11 is a partially enlarged view of a cross section of the powder magnetic core of Sample No. 100 in Test Example 2.
• 12 is a partially enlarged view of a cross section of the powder magnetic core of Sample No. 1 in Test Example 2.
• 13 is a partially enlarged view of a cross section of the powder magnetic core of Sample No. 2 in Test Example 2.
• An object of the present disclosure is to provide a powder magnetic core that can reduce the amount of CO 2 emissions generated during the production of the powder magnetic core.
• the powder magnetic core of the present disclosure can reduce the amount of CO 2 emissions generated during the production of the powder magnetic core.
• the powder magnetic core disclosed herein contains recycled powder having insulating films on the surfaces of soft magnetic particles.
• the recycled powder is soft magnetic powder obtained by pulverizing used powder magnetic cores.
• the powder core of the present disclosure can reduce the amount of new soft magnetic powder used.
• the CO2 emissions required to obtain the recycled powder are less than the CO2 emissions required to produce new soft magnetic powder. Therefore, by using recycled powder as a raw material, the powder core of the present disclosure can reduce the CO2 emissions generated during the production of the powder core.
• the average particle size of the soft magnetic particles may be 20 ⁇ m (micrometers) or more and 400 ⁇ m or less, and the average thickness of the insulating film may be 40 nm (nanometers) or more and 500 nm or less.
• the average particle size of the soft magnetic particles is 20 ⁇ m or more, it is easy to increase the density of the powder magnetic core.
• the average particle size of the soft magnetic particles is 400 ⁇ m or less, it is easy to reduce the eddy current loss of the powder magnetic core.
• the average thickness of the insulating film is 40 nm or more, it is easy to reduce the eddy current loss of the powder magnetic core.
• the average thickness of the insulating film is 500 nm or less, the magnetic properties of the powder magnetic core can be improved.
• the insulating film may have a plurality of cracks on its surface.
• the presence of multiple cracks on the surface of the insulating film indicates that the soft magnetic powder is not new, but recycled powder. Even if the insulating film has cracks, as long as it is not peeling off, the electrical insulation between the soft magnetic particles is maintained by the insulating film, thereby reducing the increase in eddy current loss.
• the insulating film may have an insulating layer containing phosphate, silica, or magnesia.
• the above insulating film tends to improve electrical insulation between adjacent soft magnetic particles.
• the mass ratio of the recycled powder to the mass of the powder magnetic core may be 1% by mass or more and 100% by mass or less.
• the mass proportion of recycled powder is 1% by mass or more, a CO2 reduction effect can be expected by reducing the amount of new soft magnetic powder used.
• the mass proportion of recycled powder is 100% by mass, the powder core contains only recycled powder 1. This powder core does not contain new soft magnetic powder, and therefore has a high CO2 reduction effect.
• any of the powder magnetic cores described above in (1) to (5) may contain new soft magnetic powder, and the mass ratio of the recycled powder to the total mass of the recycled powder and the new soft magnetic powder may be 1 mass% or more but less than 100 mass%.
• the soft magnetic particles may be formed from at least one metal selected from iron, iron-silicon alloy, iron-silicon-aluminum alloy, iron-aluminum alloy, iron-nickel alloy, and iron-cobalt alloy, each having a purity of 99% or more.
• the soft magnetic particles are made of iron with a purity of 99% or more, which makes it easier to increase the density of the powder magnetic core.
• the soft magnetic particles are made of at least one metal selected from iron-silicon alloy, iron-silicon-aluminum alloy, iron-aluminum alloy, iron-nickel alloy, and iron-cobalt alloy, which makes it easier to reduce eddy current loss in the powder magnetic core.
• the relative density of the powder magnetic core may be 85% or more.
• the magnetic properties of the powder magnetic core can be improved.
• a motor stator according to the present disclosure includes a powder magnetic core and a coil according to any one of (1) to (8) above.
• the motor stator of the present disclosure includes the powder magnetic core of the present disclosure, and therefore can reduce CO 2 emissions generated during production.
• the motor of the present disclosure includes the motor stator and rotor described above in (9).
• the motor of the present disclosure includes the motor stator of the present disclosure, and therefore can reduce CO 2 emissions generated during manufacturing.
• the method for producing a powder magnetic core disclosed herein comprises the steps of recovering used powder magnetic cores containing soft magnetic powder having insulating films on the surfaces of the soft magnetic particles, pulverizing the used powder magnetic cores to obtain recycled powder, and compression-molding the recycled powder.
• the method for producing a powder magnetic core according to the present disclosure can produce recycled powder by pulverizing used powder magnetic cores. By using recycled powder as a raw material, the method for producing a powder magnetic core according to the present disclosure can reduce CO2 emissions generated during the production of the powder magnetic core.
• the average particle size of the soft magnetic particles may be 20 ⁇ m or more and 400 ⁇ m or less, and the average thickness of the insulating film may be 40 nm or more and 500 nm or less.
• the average particle size of the soft magnetic particles is 20 ⁇ m or more, it is easy to increase the density of the powder magnetic core.
• the average particle size of the soft magnetic particles is 400 ⁇ m or less, it is easy to reduce the eddy current loss of the powder magnetic core.
• the average thickness of the insulating film is 40 nm or more, the insulating film is less likely to peel off when the powder magnetic core is pulverized.
• the average thickness of the insulating film is 500 nm or less, the magnetic properties of the powder magnetic core can be improved.
• the method for manufacturing a powder magnetic core according to (11) or (12) above may have the following configuration: In the step of obtaining the recycled powder, the used powder magnetic core is pulverized using a pulverizer equipped with a screen.
• the screen has a plurality of openings. The diameter of each of the plurality of openings is 1 mm or more and 15 mm or less.
• the step of obtaining the recycled powder may include a step of sieving the pulverized product obtained by pulverizing the used powder magnetic cores, and a step of sorting the recycled powder using a magnet.
• the above process allows recycled powder of a specified particle size to be selected and obtained.
• a lubricant may be added to the recycled powder in a content of 0.1% by mass or more and 1.0% by mass or less in the compression molding step.
• Adding a lubricant to recycled powder improves the lubrication of the recycled powder during compression molding, making it easier to achieve high density powder cores.
• the compression molding step may involve compression molding a mixed powder containing new soft magnetic powder having an insulating film on the surface of the soft magnetic particles and the recycled powder.
• a powder magnetic core 10 according to an embodiment will be described with reference to Figures 1 to 4.
• One of the features of the powder magnetic core 10 is that it contains recycled powder 1, as shown in Figure 1.
• the powder magnetic core 10 is a powder magnetic core that has been recycled using the recycled powder 1 as a raw material.
• the recycled powder 1 has an insulating film 3 on the surface of soft magnetic particles 2.
• the recycled powder 1 is a soft magnetic powder obtained by pulverizing used dust cores.
• the soft magnetic particles 2 are formed of, for example, iron or an iron-based alloy.
• the iron has a purity of, for example, 99% or more. Iron with a purity of 99% or more contains 99% or more by mass of iron.
• the iron-based alloy is, for example, at least one selected from an iron-silicon alloy (silicon steel), an iron-silicon-aluminum alloy (sendust), an iron-aluminum alloy, an iron-nickel alloy (permalloy), and an iron-cobalt alloy.
• the soft magnetic particles 2 in this example are formed of iron with a purity of 99% or more. Iron with a purity of 99% or more is softer than an iron-based alloy.
• the powder core 10 can be easily densified by compression molding. Densifying the powder core 10 can improve the magnetic properties of the powder core.
• the magnetic properties include, for example, relative permeability and saturation magnetic flux density.
• An iron-based alloy has higher electrical resistance than iron. When the soft magnetic particles 2 are made of the iron-based alloy, eddy current loss that occurs when magnetic flux flows through the powder magnetic core 10 can be easily reduced.
• the average particle diameter of the soft magnetic particles 2 is, for example, 20 ⁇ m or more and 400 ⁇ m or less.
• the average particle diameter of the soft magnetic particles 2 is 20 ⁇ m or more, the recycled powder 1 can be easily compression-molded, and the powder core 10 can be easily densified.
• the magnetic properties of the powder core can be improved.
• the average particle diameter of the soft magnetic particles 2 is 45 ⁇ m or more, high magnetic properties are easily obtained.
• the average particle diameter of the soft magnetic particles 2 is 90 ⁇ m or more, even higher magnetic properties are easily obtained.
• the average particle diameter of the soft magnetic particles 2 is 150 ⁇ m or more, even higher magnetic properties are easily obtained.
• the average particle diameter of the soft magnetic particles 2 When the average particle diameter of the soft magnetic particles 2 is 200 ⁇ m or more, even higher magnetic properties are easily obtained. Furthermore, when the average particle diameter of the soft magnetic particles 2 is 400 ⁇ m or less, eddy current loss is easily reduced. When the average particle diameter of the soft magnetic particles 2 is 300 ⁇ m or less, eddy current loss is easily reduced even more.
• the average particle diameter of the soft magnetic particles 2 may be 45 ⁇ m or more and 300 ⁇ m or less, or even 90 ⁇ m or more and 300 ⁇ m or less.
• the average particle diameter of the soft magnetic particles 2 can be determined as follows.
• the dust core 10 is pulverized into powder.
• the particle size distribution of the pulverized powder is measured using a laser diffraction particle size distribution measuring device.
• the measured particle diameters are multiplied by their frequency, and the sum of these values is considered to be the average particle diameter of the soft magnetic particles 2.
• the frequency is the ratio of the number of particles in each particle size range to the total number of particles, expressed as a percentage.
• a particle size range is an individual division into a specified particle size range that divides the entire range from the minimum to maximum particle diameter.
• the range from greater than 15 ⁇ m to less than 25 ⁇ m is considered to be the 20 ⁇ m particle size range
• the range from greater than 25 ⁇ m to less than 35 ⁇ m is considered to be the 30 ⁇ m particle size range
• the range from greater than 35 ⁇ m to less than 45 ⁇ m is considered to be the 40 ⁇ m particle size range.
• the frequency of particles falling within the 20 ⁇ m particle size interval is 20%
• the frequency of particles falling within the 30 ⁇ m particle size interval is 50%
• the frequency of particles falling within the 40 ⁇ m particle size interval 30%
• the width of the particle size interval is set to 10 ⁇ m, but the width of an actual particle size interval is, for example, between 5 ⁇ m and 40 ⁇ m.
• the insulating film 3 provides electrical insulation between adjacent soft magnetic particles 2. Having the insulating film 3 on the surface of the soft magnetic particles 2 can increase the electrical resistance of the powder core 10 and reduce eddy current loss in the powder core 10.
• the insulating film 3 is formed from, for example, phosphate, silica, or magnesia.
• the phosphate is, for example, zinc phosphate, iron phosphate, manganese phosphate, or calcium phosphate.
• the insulating film 3 may have a single-layer structure having only one type of insulating layer, or a multilayer structure having two or more types of insulating layers stacked together.
• the insulating film 3 having a multilayer structure may have an insulating layer containing phosphate, silica, or magnesia.
• An insulating layer containing phosphate has high adhesion to the soft magnetic particles 2. Furthermore, an insulating layer containing phosphate is easily deformed.
• An insulating film 3 having an insulating layer containing phosphate is less likely to peel off because it easily follows the deformation of the soft magnetic particles 2 when the recycled powder 1 is compression-molded.
• An insulating layer containing silica or magnesia is hard.
• An insulating film 3 having an insulating layer containing silica or magnesia is less likely to be damaged or become too thin when the recycled powder 1 is compression-molded.
• the insulating film 3 has a two-layer structure, it has a first insulating layer and a second insulating layer in this order.
• the first insulating layer is in contact with the surface of the soft magnetic particles 2.
• the second insulating layer is disposed on top of the first insulating layer and in contact with the first insulating layer.
• the first insulating layer contains phosphate or silica
• the second insulating layer contains any of phosphate, silica, and magnesia.
• the material of the first insulating layer is phosphate
• the material of the second insulating layer is silica or magnesia. If the material of the first insulating layer is silica, the material of the second insulating layer is phosphate or magnesia.
• the insulating film 3 in this example has a two-layer structure in which the first insulating layer and the second insulating layer are stacked in order.
• the first insulating layer is made of phosphate.
• the second insulating layer is made of silica.
• the average thickness of the insulating film of the soft magnetic powder contained in a conventional powder magnetic core is 20 nm or more and 30 nm or less.
• the average thickness of the insulating film 3 is, for example, 40 nm or more and 500 nm or less.
• the average thickness of the insulating film 3 is 40 nm or more, the eddy current loss of the powder magnetic core 10 is easily reduced.
• the average thickness of the insulating film 3 is 40 nm or more, the insulating film 3 is less likely to peel off, making it easier to achieve the effect of reducing eddy current loss by the insulating film 3.
• the average thickness of the insulating film 3 is 80 nm or more and 350 nm or less, the variation in magnetic properties is likely to be small, and if it is 100 nm or more and 300 nm or less, the variation in magnetic properties is small and higher magnetic properties are likely to be obtained.
• the average thickness of the insulating film 3 may be 120 nm or more, 150 nm or more, or even 200 nm or more.
• the thickness of the insulating film 3 is the combined thickness of all the insulating layers that make up the insulating film 3.
• the average thickness of the insulating film 3 can be determined as follows.
• the cross section of the powder magnetic core 10 is observed using a microscope, and the observed image is subjected to image analysis.
• the microscope may be a scanning electron microscope (SEM) or a transmission electron microscope (TEM). 20 or more fields of view are observed. The magnification is, for example, 50,000 times or more and 200,000 times or less.
• the average thickness of the insulating film 3 in each field of view is determined by image analysis. In each field of view, the thickness of the insulating film 3 is measured at five or more locations and the average is determined. The average thickness of the insulating film 3 over all 20 or more fields of view is determined, and this average is taken as the average thickness of the insulating film 3.
• the relative density of the powder core 10 is, for example, 85% or more.
• the high magnetic properties of the powder core 10 contribute to improving the performance of electrical equipment such as motors and reactors.
• the relative density of the powder core 10 may be 90% or more, 93% or more, or even 95% or more.
• the upper limit of the relative density of the powder core 10 is not particularly limited, but is, for example, 99%.
• the relative density is the apparent density divided by the true density, expressed as a percentage.
• the theoretical density of the soft magnetic powder is taken as the true density.
• the insulating film 3 of recycled powder 1 has cracks 3c, but there are almost no peeled-off portions. In this way, the presence or absence of multiple cracks 3c on the surface of the insulating film 3 can be used as an indicator to determine whether or not the powder is recycled.
• the powder core 10 can reduce the amount of new soft magnetic powder used.
• a powder core 10 manufactured using recycled powder 1 as a raw material can reduce the amount of CO2 emissions generated during the manufacture of the powder core 10.
• the powder core 10 may further include new soft magnetic powder.
• the new soft magnetic powder has an insulating film on the surface of the soft magnetic particles.
• the structure of the new soft magnetic powder is basically the same as the structure of the recycled powder described above.
• the new soft magnetic powder is unused soft magnetic powder in the state in which it is manufactured.
• the mass proportion of the recycled powder 1 relative to the mass of the powder core 10 is, for example, 1 mass% or more and 100 mass% or less.
• a CO2 reduction effect can be expected by reducing the amount of new soft magnetic powder used.
• This CO2 reduction effect can be expected the greater the mass proportion of the recycled powder.
• the mass proportion of the recycled powder 1 is 100 mass%, the powder core 10 contains only the recycled powder 1. In other words, this powder core 10 is manufactured using only the recycled powder 1 as a raw material. Because it does not contain new soft magnetic powder, it has a high CO2 reduction effect.
• the mass proportion of the recycled powder 1 relative to the total mass of the recycled powder 1 and the new soft magnetic powder is, for example, 1 mass% or more and less than 100 mass%.
• the mass proportion of the recycled powder 1 is 1 mass% or more, a CO2 reduction effect can be expected by reducing the amount of new soft magnetic powder used.
• the mass proportion of the recycled powder 1 is less than 100 mass%, an improvement in magnetic properties can be expected by including new soft magnetic powder.
• the mass proportion of the recycled powder 1 may be, for example, 5 mass% or more, 10 mass% or more, 20 mass% or more, 40 mass% or more, 50 mass% or more, 70 mass% or more, or even 90 mass% or more.
• the powder magnetic core 10 can take various shapes depending on the application.
• the powder magnetic core 10 can be used as a magnetic core for electrical equipment such as motors and reactors.
• the powder magnetic core 10a shown in Figure 2 is a circular stator core used in the stator of an axial gap motor.
• the powder magnetic core 10a includes a yoke 20 and teeth 30.
• the yoke 20 and teeth 30 are integrally molded.
• the yoke 20 is shaped like an annular plate.
• a plurality of teeth 30 are arranged in an annular pattern at equal intervals on the upper surface of the yoke 20. Each tooth 30 protrudes from the upper surface of the yoke 20.
• the teeth 30 are shaped like a column. In this example, there are 12 teeth 30.
• the teeth 30 in this example are shaped like a triangular column.
• a coil (not shown) is attached to the outer periphery of each tooth 30.
• the number of teeth 30 is not particularly limited and is set appropriately depending on the specifications of the motor.
• the shape of the teeth 30 can be any shape other than a triangular prism, such as a trapezoidal prism or other quadrangular prism.
• the powder magnetic core 10b shown in Figure 3 is a split core obtained by splitting the stator core described above with reference to Figure 2 around the axis.
• the split core constitutes part of the stator core.
• the stator core is constructed by combining split cores in an annular shape.
• the powder magnetic core 10b comprises a fan-shaped yoke 20 and a triangular prism-shaped tooth 30 protruding from the top surface of the yoke 20. There is one tooth 30.
• the annular stator core is constructed by combining 12 powder magnetic cores 10b.
• the powder magnetic core 10c shown in Figure 4 is another example of a split core obtained by splitting the stator core described above with reference to Figure 2 around the axis.
• the powder magnetic core 10c has three teeth 30 arranged on one yoke 20.
• the yoke 20 is fan-shaped.
• the teeth 30 are triangular prism-shaped.
• a circular stator core is formed by combining four powder magnetic cores 10c.
• the powder core 10 may include a resin mold (not shown).
• the resin mold covers at least a portion of the powder core 10.
• the resin mold is provided, for example, on a portion of the powder core 10 that comes into contact with the coil.
• the resin mold may be provided so as to cover the coil arranged on the powder core 10. In this case, the resin mold can integrate the coil with the powder core 10.
• a motor stator 200 according to an embodiment will be described with reference to FIG. 5 .
• the motor stator may be simply referred to as a "stator.”
• the stator 200 shown in FIG. 5 is used in an axial gap motor.
• the stator 200 includes a powder magnetic core 10 and a coil 210.
• the powder magnetic core 10 shown in FIG. 5 has the same configuration as the powder magnetic core 10a shown in FIG. 2.
• the coils 210 are arranged on each of the teeth 30.
• a motor 300 according to an embodiment will be described with reference to Fig. 6.
• the motor 300 includes a stator 200 and a rotor 250.
• the motor 300 shown in Fig. 6 is an axial gap motor in which the stator 200 and the rotor 250 are disposed facing each other in a direction along a rotation axis 330.
• the rotor 250 is arranged to face the end faces of each tooth 30 of the stator 200.
• the rotor 250 comprises a plurality of flat magnets 260 and an annular retaining plate 270 that supports these magnets 260.
• the end faces of each tooth 30 and each magnet 260 face each other at a predetermined interval in the direction along the rotation shaft 330.
• the retaining plate 270 is fixed to the rotation shaft 330 and rotates together with the rotation shaft 330.
• Each magnet 260 is embedded in the retaining plate 270.
• the multiple magnets 260 are arranged at equal intervals around the axis of the rotation shaft 330.
• Each magnet 260 is magnetized in the direction along the rotation shaft 330.
• the magnetization directions of adjacent magnets 260 are opposite to each other.
• the stator 200 and rotor 250 are housed in a cylindrical case 310.
• Disk-shaped plates 320 are attached to both ends of the case 310.
• a through-hole is formed in the center of each plate 320, and a rotating shaft 330 passes through the case 310.
• the stator 200 is fixed to the case 310 by fitting the outer surface of the yoke 20 into the inner surface of the case 310.
• An annular bearing 340 that rotatably supports the rotating shaft 330 is attached to the inner surface of the yoke 20.
• the powder magnetic core 10 can be manufactured by a method for manufacturing a powder magnetic core according to an embodiment.
• the method for manufacturing a powder magnetic core can manufacture recycled powder by pulverizing used powder magnetic cores.
• the method for manufacturing a powder magnetic core includes a recovery step, a pulverization step, and a pressing step. Each step will be described in detail below.
• the recovery process is a process of recovering used powder magnetic cores.
• Used powder magnetic cores contain soft magnetic powder having insulating films on the surfaces of the soft magnetic particles.
• the composition of the soft magnetic powder in used powder magnetic cores is basically the same as the composition of the recycled powder described above.
• Used powder magnetic cores may be powder magnetic cores that have never been recycled, or may be powder magnetic cores that have been recycled at least once.
• a powder magnetic core that has never been recycled is a powder magnetic core manufactured using only new soft magnetic powder as raw materials.
• a recycled powder magnetic core is a powder magnetic core that contains recycled powder.
• "used" does not necessarily mean that the core has actually been used as an electrical device.
• Used powder magnetic cores may also be cores that have been manufactured as powder magnetic cores and then collected without being used as electrical equipment. In other words, a core that has once been molded from soft magnetic powder is included in the category of used powder magnetic cores, regardless of whether it has been used as an actual electrical device. Used powder magnetic cores may also be powder magnetic cores that have been collected as defective products during the production of powder magnetic cores.
• the average particle diameter of the soft magnetic particles in used powder magnetic cores is, for example, 20 ⁇ m or more and 400 ⁇ m or less.
• the average particle diameter of the soft magnetic particles may be 45 ⁇ m or more and 300 ⁇ m or less, or even 90 ⁇ m or more and 300 ⁇ m or less.
• the average thickness of the insulating film in used powder magnetic cores is, for example, 40 nm or more and 500 nm or less.
• the average thickness of the insulating film may be 50 nm or more and 400 nm or less, 80 nm or more and 350 nm or less, or even 100 nm or more and 300 nm or less.
• the average thickness of the insulating film in conventional powder magnetic cores is 20 nm or more and 30 nm or less.
• the average thickness of the insulating film is set to 40 nm or more and 500 nm or less to prevent peeling of the insulating film when the powder magnetic core is pulverized in the pulverization step described below.
• Used powder magnetic cores are collected from used electrical equipment. Used powder magnetic cores may still have accessories such as coils attached, or may remain covered in a resin mold. Therefore, there is no need to remove attached parts such as coils from used powder magnetic cores, or to remove the resin mold.
• the pulverization process is a process in which used powder cores are pulverized to obtain recycled powder.
• the recycled powder is soft magnetic powder contained in used powder cores.
• adjacent soft magnetic particles are not metallurgically bonded to each other.
• the inventors discovered that when a powder core is pulverized, the soft magnetic particles separate from each other and become dispersed, i.e., powdered, and that the particle size of the powdered particles is substantially the same as the particle size of the soft magnetic powder contained in the powder core before pulverization. In other words, even when the powder core is pulverized, the particle size of the soft magnetic powder is substantially maintained.
• the insulating film in a used powder core is thin, the insulating film may peel off due to the impact caused when the powder core is pulverized. If the insulating film is thick, cracks may occur in the insulating film when the powder core is pulverized, but peeling of the insulating film is unlikely to occur. If the average thickness of the insulating film before pulverization is 40 nm or more, the insulating film is unlikely to peel off when the powder core is pulverized.
• the average particle diameter of the recycled powder is, for example, 20 ⁇ m or more and 400 ⁇ m or less.
• the average particle diameter of the recycled powder is the average particle diameter of soft magnetic particles including insulating films.
• the average particle diameter of the recycled powder is the particle diameter D50 at which the cumulative mass is 50% in the particle size distribution measured using a laser diffraction particle size analyzer.
• the average particle diameter of the recycled powder may be 45 ⁇ m or more and 300 ⁇ m or less, or even 90 ⁇ m or more and 300 ⁇ m or less.
• the average thickness of the insulating film in the recycled powder is, for example, 40 nm or more and 500 nm or less.
• the average thickness of the insulating film in the recycled powder may be 50 nm or more and 400 nm or less, 80 nm or more and 350 nm or less, or even 100 nm or more and 300 nm or less.
• Used powder magnetic cores can be pulverized using a known pulverizer.
• the pulverizer used is, for example, a cutter-type pulverizer, a hammer-type pulverizer, or a chain-type pulverizer.
• a cutter-type pulverizer pulverizes the powder magnetic cores by scraping them off with a rotating blade.
• a hammer-type pulverizer pulverizes the powder magnetic cores by smashing them with a rotating hammer.
• a chain-type pulverizer pulverizes the powder magnetic cores by smashing them with a rotating chain.
• the powder magnetic cores may be crushed using a crusher equipped with a screen.
• An example of a crusher 100 will be described with reference to Figure 7.
• Figure 7 is a schematic diagram of the configuration of the crusher 100.
• the crusher 100 is a cutter-type crusher.
• the crusher 100 comprises a crushing chamber 110, a rotary blade 120, a fixed blade 130, and a screen 140.
• the crushing chamber 110 has an inlet 111. Used powder magnetic cores 10 are loaded into the crushing chamber 110 through the inlet 111.
• the rotary blade 120 is disposed within the crushing chamber 110.
• the rotary blade 120 is attached to a rotating shaft 121.
• a plurality of rotary blades 120 are attached in a line along the rotating shaft 121.
• the rotary blades 120 rotate as the rotating shaft 121 rotates.
• the fixed blade 130 is disposed within the crushing chamber 110. A predetermined clearance is provided between the rotary blade 120 and the fixed blade 130.
• the powder magnetic core 10 is sheared by the rotary blade 120 and the fixed blade 130.
• the screen 140 is attached to the discharge outlet of the crushing chamber 110. The crushed material sheared by the rotary blade 120 and the fixed blade 130 is crushed and pulverized between the rotary blade 120 and the screen 140.
• the screen 140 is a plate with multiple openings 141.
• the powder cores 10 are pulverized to a size that can pass through the openings 141. As described above, when the powder cores 10 are pulverized, the soft magnetic particles break down into powder.
• the recycled powder 1 obtained by pulverizing the powder cores 10 is discharged through the openings 141.
• the shape of each opening 141 is, for example, circular.
• the diameter of each of the multiple openings 141 can be selected appropriately depending on the size of the powder cores 10 to be pulverized.
• the diameter of the openings 141 is, for example, 1 mm or more and 15 mm or less.
• the diameter of the openings 141 is 2 mm or more and 10 mm or less, the powder cores 10 are easily pulverized and the recycled powder 1 is easily obtained.
• the diameter of the openings 141 may be 2 mm or more and 10 mm or less.
• the powder magnetic core 10 When a used powder magnetic core 10 with a coil attached or resin molded is pulverized, the powder magnetic core 10 is pulverized to a particle size similar to that of the soft magnetic powder used as the raw material. In contrast, the coil and resin mold are pulverized to a size similar to the diameter of the openings 141 in the screen 140.
• the particle size of the recycled powder 1 obtained by pulverizing the powder magnetic core 10 is sufficiently smaller than the size of the pulverized coil and resin mold. Therefore, the recycled powder 1 can be easily separated from the pulverized coil and resin mold using a sieve. Furthermore, since the recycled powder 1 is attracted to a magnet, it can also be separated using a magnet.
• the pulverization process may include a step of classifying the pulverized powder obtained by pulverizing the powder magnetic core 10 using a sieve, and a step of sorting the recycled powder 1 using a magnet. By performing the sieving process and the magnetic sorting process, it is possible to select and obtain only recycled powder 1 of a predetermined particle size.
• the pressing step is a step of compression molding the recycled powder.
• a recycled powder core is obtained.
• the average particle diameter of the recycled powder is 20 ⁇ m or more and 400 ⁇ m or less, the recycled powder is easy to handle and compression mold.
• the higher the molding pressure when compressing the recycled powder the higher the density of the powder core can be.
• the molding pressure is, for example, 500 MPa or more and 1500 MPa or less.
• a lubricant may be added to the recycled powder before compression molding. Adding a lubricant improves the lubricity of the recycled powder during compression molding, facilitating the densification of the powder core.
• Solid lubricants such as fatty acid amides and metal soaps can be used as lubricants.
• fatty acid amides include stearic acid amide and ethylene bisstearic acid amide.
• metal soaps include metal stearates such as zinc stearate and lithium stearate.
• the lubricant content is, for example, 0.1% to 1.0% by mass, where the total of the recycled powder and lubricant is 100% by mass.
• a lubricant content of 0.1% by mass or more sufficiently improves the lubricity of the recycled powder, thereby enabling the densification of the powder core.
• a lubricant content of 1.0% by mass or less prevents a decrease in the proportion of soft magnetic powder contained in the powder core, thereby improving the magnetic properties of the powder core.
• the lubricant content may be 0.3% to 0.6% by mass.
• only recycled powder may be compression-molded, or a mixed powder containing new soft magnetic powder and recycled powder may be compression-molded.
• a mixed powder containing new soft magnetic powder and recycled powder as a raw material can improve the magnetic properties of the powder core and reduce the eddy current loss of the powder core compared to using only recycled powder as a raw material.
• the mass ratio of the recycled powder to the total mass of the recycled powder and new soft magnetic powder is, for example, 1 mass% or more and less than 100 mass%. By using a mass ratio of recycled powder of 1 mass% or more, a CO2 reduction effect can be expected by reducing the amount of new soft magnetic powder used.
• the mass proportion of the recycled powder may be, for example, 5 mass% or more, 10 mass% or more, 20 mass% or more, 40 mass% or more, 50 mass% or more, 70 mass% or more, or even 90 mass% or more.
• the mass proportion of the recycled powder in the mixed powder is maintained even after compression molding. In other words, the mass proportion of the recycled powder in the powder core manufactured using the mixed powder as a raw material is equivalent to the mass proportion of the recycled powder in the mixed powder used as a raw material.
• the method for manufacturing a powder magnetic core may include a heat treatment step after the pressing step.
• the heat treatment step is a step of heat treating the compacted powder magnetic core.
• the heat treatment temperature is, for example, 300°C or higher and 900°C or lower.
• the lubricant added in the pressing step is eliminated by the heat treatment.
• the dust core was manufactured using new soft magnetic powder as a raw material.
• new soft magnetic powder will be referred to as "new powder.”
• the new powder is iron powder with an insulating film on the surface of soft magnetic particles made of iron.
• the soft magnetic particles are made of iron with a purity of 99% or more.
• the average particle diameter of the soft magnetic particles was approximately 250 ⁇ m.
• the insulating film has a two-layer structure consisting of a first insulating layer, which is the inner layer, and a second insulating layer, which is the outer layer, stacked in that order.
• the first insulating layer is made of phosphate.
• the second insulating layer is made of silica.
• the average thickness of the insulating film was approximately 80 nm.
• the powder magnetic core is a circular stator core as shown in Figure 2.
• the outer diameter d of the stator core is approximately 52 mm.
• the thickness t of the stator core is approximately 19 mm.
• the thickness t of the stator core is the total thickness of the yoke and the teeth.
• the particle size distribution of the recycled powder obtained by crushing powder magnetic cores is nearly identical to the particle size distribution of new powder at the raw material stage. This shows that by crushing used powder magnetic cores, it is possible to crush them to a particle size similar to that of the soft magnetic powder used as the raw material.
• Sample No. 1 is a powder magnetic core using the recycled powder of Test Example 1 as the raw material.
• the average thickness of the insulating film at the raw material stage is approximately 80 nm.
• the powder magnetic core of Sample No. 1 was manufactured as follows: 0.3 mass% of lubricant was added to the recycled powder.
• the recycled powder was compression-molded to obtain a powder magnetic core.
• the molding pressure was approximately 850 MPa.
• the compression-molded powder magnetic core was heat-treated.
• the heat treatment temperature was 600°C, and the holding time was 15 minutes.
• the manufactured powder magnetic core was a ring-shaped toroidal core.
• Sample No. 2 is a dust core that uses recycled powder as a raw material.
• the recycled powder for Sample No. 2 was obtained by pulverizing a dust core, similar to Sample No. 1. However, in Sample No. 2, the average thickness of the insulating film at the raw material stage was approximately 25 nm. Sample No. 2 was manufactured in the same manner as Sample No. 1, except that recycled powder with an average insulating film thickness different from that of Sample No. 1 was used.
• Sample No. 100 is a powder magnetic core manufactured using only new powder as a raw material. In Sample No. 100, the average thickness of the insulating film of the new powder is approximately 25 nm.
• the powder magnetic core of Sample No. 100 was manufactured in the same manner as the powder magnetic core of Sample No. 1, except that new powder was used as a raw material.
• the loss of the powder core of each sample was measured.
• the loss of the powder core was measured as follows. A primary coil and a secondary coil were each wound around the powder core. The number of turns of the primary coil was 300, and the number of turns of the secondary coil was 30.
• the iron loss when a current was passed through the primary coil to magnetize the powder core was measured using the secondary coil.
• the measured loss of the powder core was the iron loss [W/kg] at a frequency of 1 kHz and a magnetic flux density of 1.0 T.
• the loss of each powder core of Sample No. 1 and Sample No. 2 is shown below. The loss of the powder core is shown as a ratio based on the loss of the powder core of Sample No. 100. Sample No. 1: 112% Sample No. 2: 442%
• the loss of sample No. 1 is almost the same as that of sample No. 100. This shows that sample No. 1 has performance equivalent to that of sample No. 100.
• Figure 11 is a schematic enlarged view of the cross section of the powder magnetic core of sample No. 100. As shown in Figure 11, in sample No. 100, the surface of the soft magnetic particles 2 was covered with an insulating film 3.
• Figure 12 is a schematic enlarged view of the cross section of the powder magnetic core of sample No. 1. As shown in Figure 12, in sample No. 1, cracks 3c were found in the insulating film 3, but almost no peeling of the insulating film 3 was observed.
• Figure 13 is a schematic enlarged view of the cross section of the powder magnetic core of sample No. 2. As shown in Figure 13, in sample No. 2, there were many peeling areas 3f in the insulating film 3.

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