JP2012199568A - Green compact, production method of green compact, reactor, converter, and power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low loss green compact, a production method of green compact capable of producing that green compact, a reactor with green compact, a converter, and a power converter.SOLUTION: The method of producing a green compact by using a coated soft magnetic powder where a plurality of coated soft magnetic particles coated with an insulating film are provided on the outer periphery of a soft magnetic particle includes a material preparation step, and an irradiation step. In the material preparation step, a material molding produced by pressure molding the coated soft magnetic powder is prepared. In the irradiation step, a part of the surface of the material molding is irradiated with a laser. Division points of a conductive part where the constituent materials of a plurality of soft magnetic particles are conducting on the surface of the material molding can be increased by irradiating a part of the surface of the material molding with a laser, and loss of the green compact can be reduced.

Description

  The present invention relates to a green compact formed by press-molding a coated soft magnetic powder, a method for producing the same, a reactor including the green compact, a converter including the reactor, and a power converter including the converter It is about. In particular, the present invention relates to a low-loss compact and a method for producing the same.

  A hybrid vehicle or the like includes a booster circuit in a power supply system to a motor. A reactor is used as one component of this booster circuit. The reactor has a configuration in which a coil is wound around a core. When the core is used in an alternating magnetic field, a loss called iron loss occurs in the core. The iron loss is generally represented by the sum of hysteresis loss and eddy current loss, and particularly increases significantly when used at high frequencies.

  In order to reduce iron loss in the core of the reactor, a core made of a green compact may be used. The compacted green body is formed by pressurizing coated soft magnetic powder composed of coated soft magnetic particles in which an insulating film is formed on the surface of soft magnetic particles, and the soft magnetic particles are insulated from each other by an insulating film. Highly effective in reducing eddy current loss.

  However, the green compact has a cavity formed by a relatively movable columnar first punch and a cylindrical die filled with coated soft magnetic powder, and the cavity is formed by the first punch and the columnar second punch. Since the coated soft magnetic powder is pressure molded, the insulating coating of the coated soft magnetic particles is damaged by the pressure during the pressure molding and the sliding contact with the mold when the molded product is removed. There is a fear. When the insulating coating is damaged, the soft magnetic particles may be exposed and spread, and as a result, the soft magnetic particles in the compacted body are electrically connected to each other to form a substantially film-like conductive part, resulting in an eddy current. Loss may increase.

  Therefore, in order to reduce the eddy current loss, for example, Patent Document 1 discloses that the surface of a molded material formed by pressurizing coated soft magnetic powder (soft magnetic powder) is subjected to surface treatment with concentrated hydrochloric acid. Have been described. Specifically, the material molded body is immersed in concentrated hydrochloric acid, and the conductive portion on the entire surface of the material molded body is removed to form a powder molded body.

JP 2006-229203 A

  By subjecting the entire surface of the material molded body to surface treatment as described above, a certain reduction in loss can be achieved. In this way, if the entire surface of the material molded body is surface-treated, the conductive portion can be removed, but on the other hand, the insulating coating of the coated soft magnetic particles that are not damaged by the insulating coating is also damaged. There is a possibility. As a result, the loss reduction effect may be reduced.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a low-loss compact.

  Another object of the present invention is to provide a method for producing a green compact that can efficiently produce a low-loss green compact.

  Another object of the present invention is to provide a green compact produced by the production method of the present invention.

  Another object of the present invention is to provide a reactor comprising the above compacted body.

  Still another object of the present invention is to provide a converter including the reactor and a power conversion device including the converter.

  In order to achieve the above-mentioned object, the present inventors diligently studied about a method for producing a green compact. Specifically, the cause of the reduced loss reduction effect was investigated by manufacturing a compacted body with various surface treatment areas selected. As a result, the following knowledge was obtained.

  When the surface treatment is performed on the entire surface of the material molded body, the conductive portion generated at the portion (sliding contact surface) that is in sliding contact with the die when the material molded body is demolded is removed. On the other hand, in the first place, the conductive portion is unlikely to be formed at a position (pressure contact surface) in contact with the punches of the material molded body, and when the surface treatment is performed there, the insulating coating may be destroyed. Therefore, the soft magnetic particles are exposed at the pressure contact surface, and the effect of reducing iron loss may be reduced. Accordingly, it has been found that the surface treatment may be performed on a part of the material molded body, and further on a part of the sliding contact surface, particularly on a region covering the entire length in the magnetic flux direction on the sliding contact surface.

  From the above knowledge, in order to efficiently produce a low-loss compacted body, the following method for subjecting a specific region of the material compact to surface treatment can be mentioned.

  The method for producing a green compact is a method for producing a green compact using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating coating. A preparation process and a surface treatment process are provided. In the material preparation step, a material molded body obtained by pressure-molding the coated soft magnetic powder is prepared. In the surface treatment step, the number of divided portions of the conducting portion where the constituent materials of the plurality of soft magnetic particles are conducted on the surface of the material molded body is increased. The increase in the part where the conductive part is divided is that the electrically interrupted part increases. In addition to the case where the middle part of the conductive part is deformed to form a discontinuous part, at least a part of the conductive part is removed. Including cases where The said surface treatment process is given to a part of surface of the said molded object. The surface treatment process here includes any surface treatment that can increase the number of breaks in the conductive part by chemical, mechanical, electrical, optical, thermal, or a combination of these treatments. It is. Specifically, cutting and grinding are mentioned as mechanical processing methods, and laser processing is mentioned as a thermal and optical method. Any of the processing methods is considered to be able to remove the conductive portion. In particular, in cutting and grinding, it is considered that the conductive portion is mechanically separated and removed. On the other hand, in the laser processing, it is considered that discontinuous portions are increased by melting and flowing of the conduction portion.

  As a more specific method, the following manufacturing method of the compacting body of this invention is mentioned.

  This manufacturing method is a method of manufacturing a compacted body using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating coating, and a raw material preparation step and an irradiation step With. In the material preparation step, a material molded body obtained by pressure-molding the coated soft magnetic powder is prepared. In the irradiation step, a laser is irradiated onto at least a part of the surface of the material molded body.

  According to the manufacturing method of the present invention, at least a part of the surface of the material molded body is irradiated with a laser, so that high energy is imparted to the conductive portion of the thin film body, or rapid heating and cooling are caused. It is considered that the number of parts where the conductive part is divided increases. By increasing the number of parts where the conductive portion is divided, it is possible to increase the electrical resistance of the conductive portion or to interrupt the conduction in the conductive portion. As a result, it is difficult for eddy currents to flow or the eddy currents can be interrupted, so that loss of the green compact can be reduced.

  In addition, by irradiating at least a part of the surface of the material molded body with a laser, the possibility of damaging the insulating coating of the coated soft magnetic particles whose insulating coating is not damaged is reduced, and the loss reduction effect is reduced. There is no. As a result, it is possible to produce a compacted product having a low loss comparable to that obtained when the entire surface of the material molded product is surface-treated. Furthermore, it can be set as a low-loss compacting body rather than the compacting body when the loss reduction effect becomes small, and a low-loss compacting body can be manufactured efficiently.

  Further, when the green compacts produced by various production methods were examined, an oxide film was present on at least a part of the surface of the green compact obtained by the production method of the present invention. It was found that the green compact in which the oxygen content in the surface portion of the area to be obtained is in a specific range has a low loss. Therefore, the present invention defines a green compact having the surface portion in which the oxygen content is in a specific range.

  Specifically, the green compact manufactured by the green compact of the present invention and the method of manufacturing the green compact of the present invention includes a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating coating. The coated soft magnetic powder is compression molded. An oxide film containing iron is provided on at least a part of the surface of the green compact. When the total content of iron and oxygen in the surface portion where the oxide film is provided is 100 mass%, the oxygen content is 9 mass% or more and 20 mass% or less.

  The green compact of the present invention can be a low-loss compact with low eddy current loss by providing the surface portion with the oxygen content within a predetermined range. For example, when used as a part of the magnetic core included in the reactor, a low-loss reactor can be obtained. Accordingly, the green compact of the present invention can be suitably used as a constituent member of a reactor, and the iron loss characteristics can be improved even when the coil is excited by high-frequency alternating current.

  As one form of the manufacturing method of this invention, it is mentioned that the said irradiation process is given to at least one part of the sliding contact surface with the metal mold | die in the said raw material molded object.

  According to said structure, since a conduction | electrical_connection part is easy to be formed in the sliding contact surface with a metal mold | die, an eddy current can be interrupted | blocked effectively by irradiating a laser to at least one part of a sliding contact surface.

  As one form of the manufacturing method of the present invention, the irradiation step may be performed on the surface of a material molded body that becomes at least a part of a plane parallel to the magnetic flux direction when the powder molded body is excited as a magnetic core. Can be mentioned.

  According to the above configuration, the laser is irradiated with the eddy current flowing in the circumferential direction with the magnetic flux direction as an axis, because the portion irradiated with the laser is at least a part of the plane parallel to the magnetic flux direction. It is thought that it can be cut off at the spot. Therefore, eddy current loss can be reduced, and a low-loss compacting body can be manufactured.

  As one form of the manufacturing method of this invention, the said irradiation process is at least one part of a parallel surface with a magnetic flux direction, when the said compacting body is excited as a magnetic core, and in the said parallel surface, the said compacting body of the said compacting body It is mentioned that it is applied to the surface of the material molded body that is a region extending over the entire length in the magnetic flux direction.

  According to said structure, the area | region which irradiates a laser is a surface which becomes an area | region over the magnetic flux direction full length of a compacting body in the parallel surface among the surfaces of a raw material molding at least one part of the said parallel surface. Thus, it is considered that the eddy current flowing in the circumferential direction with the magnetic flux direction as an axis can be blocked over the entire length. Therefore, the eddy current loss can be further reduced, and a green compact with lower loss can be manufactured.

One form of the manufacturing method of the present invention is that the laser is one kind of laser selected from a YAG laser, a YVO ₄ laser, and a fiber laser.

  According to said structure, it becomes easy to increase the parting part of the said conduction | electrical_connection part because the said laser is a laser selected from the above.

  As one form of the manufacturing method of this invention, it is mentioned that the wavelength of the said laser is a wavelength absorption area | region of the said soft-magnetic particle.

  According to said structure, while the parting location of the said conduction | electrical_connection part is easy to increase, the insulating film of the covering soft magnetic particle of places other than a conduction | electrical_connection part is hard to be damaged.

As one form of the manufacturing method of the present invention, the average output of the laser P (W), when the irradiation area of the laser and S (mm ^2), of the laser energy density ^{U (W / mm 2) =} P / S satisfies 37.0 ≦ U ≦ 450.0.

According to said structure, the division | segmentation location of the said conduction | electrical_connection part can be increased reliably by setting the energy density U of a laser to 37.0 W / mm < ² > or more. By setting the energy density U of the laser to 450.0 W / mm ² or less, the contact between the soft magnetic particles due to excessive melting can be suppressed, and the loss reduction effect can be suppressed from being reduced.

  As one form of the manufacturing method of this invention, it is mentioned that the ratio of the irradiation interval with respect to the beam diameter of the said laser is 0.35 or less.

  According to said structure, since the unprocessed area | region which is not irradiated with a laser can be reduced by making the said ratio into 0.35 or less, it becomes easy to divide | segment a conduction | electrical_connection part.

  As one form of the manufacturing method of this invention, it is mentioned that the frequency | count of the said laser overlapping is 5 times or more.

  According to said structure, the said conduction | electrical_connection part can be reliably parted by irradiating a laser to the same area | region several times.

  As one form of this invention compacting body, providing the location where the content of the said oxygen is less than 6 mass% is mentioned further on the surface of a compacting body.

  According to said structure, the compacting body by which the low oxygen area | region whose oxygen content is less than 6 mass% and the high oxygen area | region of 9 mass% or more and 20 mass% or less were mixed on the surface of the compacting body. It can be. Thus, even if the low oxygen region is partially provided, the eddy current can be cut off in the high oxygen region, so that a low-loss compacted product can be obtained.

  As one form of this invention compacting body, it is mentioned that the said oxide film has a location whose thickness is 0.1 micrometer or more.

  According to said structure, when it uses as a part of magnetic core with which an oxide film is provided with a thick part with a thickness which is 0.1 micrometer or more, for example, a reactor, in the part It is possible to make eddy current difficult to flow.

  As one form of this invention compacting body, providing a parting area | region and a concentration part is mentioned. The divided region is a portion where the adjacent soft magnetic particles are electrically separated from each other in at least a part of the surface of the green compact. The concentrating portion is formed of an oxide film having a thickness on the center side larger than that on the outer peripheral edge side without straddling between adjacent particles on the surface of the soft magnetic particles adjacent to the dividing region.

  According to said structure, when using a compacting body as a part of magnetic core with which a reactor is provided, for example, an eddy current can be parted by the said division | segmentation area | region and a concentration part. Adjacent soft magnetic particles are electrically separated by this divided region, and the particles adjacent to the divided region are provided with the above-mentioned concentrating portion, whereby in addition to the insulation between the particles, the surface of the green compact is More reliable insulation.

  As one form of this invention compacting body, providing a parting area | region and an aggregation part is mentioned. The divided region electrically divides adjacent soft magnetic particles in at least a part of the surface of the green compact. The agglomerated portion protrudes toward the outer peripheral edge of the soft magnetic particle on the surface of the soft magnetic particle adjacent to the divided region, and is locally thick. And it has an oxide film in at least one part of the surface of the aggregation part.

  According to said structure, when a compacting body is utilized as a part of magnetic core with which a reactor is provided, for example, an eddy current can be parted by the said parting area | region and an aggregation part. Adjacent soft magnetic particles are electrically separated from each other by the divided region, and each end of the divided portion is covered with an insulating oxide film, so that the particles can be more reliably insulated from each other.

  As one form of the green compact of the present invention, when the agglomerated part is provided, the oxide film in the agglomerated part is provided with a portion having a thickness of 0.5 μm or more.

  According to said structure, in the aggregation part, by providing the thick location where thickness is 0.5 micrometer or more, for example, the compacting body was utilized as a part of magnetic core provided in a reactor. In this case, it is difficult to flow eddy current at that point.

As one form of the invention the green compact, the oxide film _{is, FeO, α-Fe 2 O} 3, include may include at least one of _γ-Fe 2 _{O 3,} and _Fe 3 _{O 4.}

  By using the green compact including the above compound, a low-loss reactor can be obtained as shown in a test example described later.

As one form of this invention compacting body, it is mentioned that the density d of a compacting body is 7.0 g / cm < ³ > or more.

  According to said structure, it can be set as the compacting body with a high magnetic flux density.

  As one form of this invention compacting body, it is mentioned that the said soft-magnetic particle consists of iron whose purity is 99 mass% or more.

  According to said structure, it can be set as the compacting body with a high magnetic permeability and magnetic flux density.

  The reactor of the present invention includes a coil formed by winding a winding, and a magnetic core that is disposed inside and outside the coil to form a closed magnetic circuit. At least a part of the magnetic core is formed of a powder compact, and this powder compact is the powder compact of the present invention.

  According to the reactor of this invention, it can be set as a low loss reactor by providing the compacting body which is excellent in the loss reduction effect.

  The reactor of the present invention can be suitably used as a component part of a converter. The converter of the present invention comprises a switching element, a drive circuit that controls the operation of the switching element, and a reactor that smoothes the switching operation, and converts the input voltage by the operation of the switching element. The reactor is the reactor of the present invention. This converter of the present invention can be suitably used as a component part of a power converter. The power converter of the present invention includes a converter that converts an input voltage and an inverter that is connected to the converter and converts between direct current and alternating current, and drives a load with the power converted by the inverter. The above converter is the converter of the present invention.

  According to said structure, a magnetic core is provided with this invention reactor which consists of a compacting body with a low loss, It is a low loss and can utilize suitably for vehicle-mounted components.

  The manufacturing method of the compacting body of this invention can reduce an eddy current loss, and can manufacture the compacting body of a low loss efficiently.

  The green compact of the present invention can be a low-loss compact with low eddy current loss.

  The reactor of the present invention has a low loss.

It is a figure which shows the compacting body which concerns on Embodiment 1, Comprising: It is a disassembled perspective view which shows the core for reactors which provides the compacting body. It is a schematic perspective view which shows the reactor which concerns on Embodiment 2. FIG. 1 is a schematic configuration diagram schematically showing a power supply system of a hybrid vehicle. It is a schematic circuit diagram which shows an example of this invention power converter device which provides this invention converter. In Experiment 3, it is a graph which shows the relationship between the energy density of the laser in each sample, and the loss of a compacting body. Sample No. It is a graph which shows the result of the X-ray diffraction in 1-1. Sample No. It is a graph which shows the result of the X-ray diffraction in 3-6. Sample No. It is a graph which shows the result of the X-ray diffraction in 1-3. Sample No. In the manufacturing process of the compacting body of 1-1, it is a SEM photograph which shows the surface state of the sample before laser irradiation, (A) shows the cross section in the surface vicinity, (B) shows the surface. Sample No. In the manufacturing process of the compacting body of 1-1, it is a SEM photograph which shows the surface state of the sample after laser irradiation, (A) shows the cross section in the surface vicinity, (B) shows the surface. Sample No. In the manufacturing process of the compacting body of 3-5, it is a SEM photograph which shows the surface state of the sample after laser irradiation, (A) shows the cross section in the surface vicinity, (B) shows the surface. Sample No. In the manufacturing process of the compacting body of 3-6, it is a SEM photograph which shows the surface state of the sample after laser irradiation, Comprising: (A) shows the cross section in the surface vicinity, (B) shows the surface. Sample No. In the manufacturing process of the compacting body of 3-8, it is a SEM photograph which shows the surface state of the sample after laser irradiation, (A) shows the cross section in the surface vicinity, (B) shows the surface. Sample No. In the manufacturing process of the compacting body of 3-9, it is a SEM photograph which shows the surface state of the sample after laser irradiation, Comprising: The cross section in the surface vicinity is shown.

  Embodiments of the present invention will be described below. First, a compacting body and its manufacturing method will be described, and then a reactor including the compacting body, a converter including the reactor, and a power conversion device will be described in this order.

<Embodiment 1>
<Green compact>
The green compact of the present invention is formed by press-molding a coated soft magnetic powder comprising a plurality of coated soft magnetic particles having an insulating coating coated on the outer periphery of the soft magnetic particles, and iron is applied to at least a part of the surface thereof. Contains oxide film. A feature of the green compact is that a specific amount of oxygen is contained in the surface portion of the portion having the oxide film. Hereinafter, in the detailed description, the above features will be mainly described, and the configuration of the soft magnetic powder itself will be described in the manufacturing method described later. The constituent elements of the green compact substantially maintain the properties and properties of the raw material.

  The surface of the green compact includes an oxide film containing iron at least in part. When the total content of iron and oxygen in the surface portion of the green compact formed with the oxide film is 100% by mass, the oxygen content is 9% by mass or more. Then, for example, when a compacted body is used as the core for the reactor, the eddy current can be divided or made difficult to flow at the location where this oxide film is formed, so the eddy current loss can be reduced and a low-loss reactor is constructed. it can. The surface portion refers to a region having a depth of about 1 μm from the surface of the green compact to the inside. The oxygen content refers to the measured value in that region. The measurement of the oxygen content can be performed, for example, by energy dispersive X-ray spectroscopy (EDX: Energy Dispersive X-ray spectroscopy). The upper limit of the oxygen content is 20% by mass or less. By doing so, it is possible to sufficiently reduce the loss.

  The surface of the green compact may further include a portion where the oxygen content is less than 6% by mass. That is, the surface of the green compact has a low oxygen region with an oxygen content of less than 6% by mass and a high oxygen region with 9% by mass or more and 20% by mass or less. Both regions can be formed by making the region to be irradiated with laser part of the surface of the green compact. The area | region which is not irradiating a laser among the surfaces of a compacting body becomes the said low oxygen area | region.

  The formation mechanism of the oxide film is considered as follows. On the surface of the green compact, a conductive portion is formed between the coated soft magnetic particles by rubbing with the mold in a molding step described later. The conductive part is a soft magnetic particle adjacent to the soft magnetic particle α, in which a metal portion of a certain soft magnetic particle α flows in a direction opposite to the direction in which the molded body is extracted from the die by sliding contact with the mold and is stretched into a thin film shape. It is formed so as to cover the particles β. The conduction part is melted by irradiating the surface of the green compact with a laser. The melted conduction part flows to each particle side so as to form a divided region between both particles, and as a result, the portion where the connection of the adjacent soft magnetic particles α and β by the conductive part is broken is the divided region. Become.

  When the laser energy density U is low, locally thick aggregates are formed. This agglomerated part is a solidified part of the soft magnetic particles α that is concentrated on the adjacent soft magnetic particles β before the molten metal is concentrated on the surface of the soft magnetic particles α that are integrally connected to the thin-film conducting part. The surface of the particle α may protrude toward the outer peripheral edge of the particle α and may cover the upper surface of the adjacent soft magnetic particles. The aggregated portion is often formed in a band shape. By melting the conductive portion, the conductive conductive portion is electrically separated, and an insulating oxide film is formed on at least a part of the aggregated portion. Therefore, the particles can be more reliably insulated. At this time, an oxide film is also formed on the surface excluding the agglomerated part of the soft magnetic particles having the agglomerated part. The agglomerated part may have a thicker oxide film than the surface excluding the agglomerated part of the soft magnetic particles having the agglomerated part.

  When the energy density U of the laser is high, the molten conducting portion further flows, and the molten metal further moves toward the center of each particle in an attempt to reduce the surface area due to surface tension. Thereby, a concentrating portion composed of an oxide film whose center side is thicker than its outer peripheral edge side is formed on the surface of each particle without straddling between adjacent particles. This condensing part is one in which the molten metal is solidified after concentrating on the surface of the soft magnetic particle α. The concentration part is flat and often has a shape close to a disk. That is, the portion that was the conductive portion changes to an oxide film. On the other hand, when the conduction portion does not melt or flow due to laser irradiation, an oxide film is generated on the surface of the film-like conduction portion as it is. As the oxidation further proceeds, the entire conductive portion becomes an oxide film.

  The oxide film includes a case where the oxide film is formed only on the surface of a single particle and a case where the oxide film straddles between adjacent particles. Both the former and the latter may be formed on the surface of the green compact, or only the former or the latter may be formed. In the former case, oxide films are scattered on the surface of the green compact. The higher the energy density U of the laser, the easier it is to enter the former state.

  The oxide film preferably has a portion having a thickness of 0.1 μm or more. Then, the eddy current can be hardly divided or flowed at the thick portion. It is preferable that the oxide film has a thick portion having a thickness of 0.5 μm or more, 1 μm or more, 3 μm or more, 5 μm or more, 7 μm or more, and particularly 10 μm or more. The thickness of the oxide film can be measured, for example, by observing a cross-section of the green compact with a scanning electron microscope (SEM).

The composition of the oxide film preferably includes at least one of FeO, α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ , and Fe ₃ O ₄ . Among them, FeO, and preferably contains a large amount of _Fe 3 _{O 4.} By using the green compact including the oxide film as a component of the reactor, a low-loss reactor can be obtained. The composition of the oxide film can be detected by, for example, X-ray diffraction (XRD: X-ray Diffraction).

  At least a part of the surface of the green compact is provided with a dividing region for electrically dividing adjacent soft magnetic particles. If it does so, when exciting a compacting body as a core for reactors, the eddy current which flows over the peripheral direction of the surface of a compacting object can be divided in a division field. The concentrating portion is provided on at least one of the surfaces of the soft magnetic particles adjacent to the divided region. That is, the concentration part is formed on a single particle surface. Moreover, the surface of the soft magnetic particle adjacent to the divided region may have the agglomerated portion. The agglomerated part may be generated when the conducting parts drawn from a plurality of soft magnetic particles are melted and aggregated together. Therefore, there may be a plurality of particles having an agglomerated part. For example, the agglomerated portion includes a portion where the thickness of the oxide film is 0.5 μm or more. In some cases, the surface of the green compact is dotted with the above-mentioned concentrated portions and aggregated portions.

[density]
The higher the density d (g / cm ³ ) of the green compact, the better. Then, it can be set as the compacting body with a high magnetic flux density. Specifically, the density d is 7.0 g / cm ³ or more. The upper limit of the density d is 7.55 g / cm ³ . This is because if the density d is too high, the insulation between the soft magnetic particles may be lowered.

<< Method for Producing Green Compact >>
The above-mentioned compacted body of the present invention can be produced, for example, by the following production method of the present invention. The production of the green compact of the present invention is a method of producing a green compact using a coated soft magnetic powder, and includes a material preparation step and an irradiation step. First, it demonstrates from the process of preparing the covering soft magnetic powder which is a constituent material of a compacting body, and demonstrates each said process in order.

[Material preparation process]
In the raw material preparation process, a coated soft magnetic powder constituting the green compact is prepared, and the powder is pressure-molded to produce a raw material compact, or a previously molded material compact is purchased in advance. Prepare. In the former case, a raw material preparation step and a raw material forming step of forming a raw material molded body from the raw material are provided. As the raw material preparation step, a coated soft magnetic powder constituting the green compact is prepared. The coated soft magnetic powder includes a plurality of coated soft magnetic particles in which an insulating coating is coated on the outer periphery of the soft magnetic particles.

[Raw material preparation process]
In the raw material preparation step, a coated soft magnetic powder is prepared. In this step, soft magnetic particles having the composition described below are prepared or manufactured, and the outer periphery of the soft magnetic particles is coated with an insulating film having the composition described later to produce a coated soft magnetic powder. Alternatively, a coated soft magnetic powder manufactured in advance may be purchased. When the soft magnetic particles are manufactured among the former, the coated soft magnetic powder can be manufactured through the soft magnetic particle manufacturing method and the insulating film coating method described below.

(Soft magnetic particles)
<composition>
The soft magnetic particles preferably contain 50% by mass or more of iron, and examples thereof include pure iron (Fe). In addition, iron alloys such as Fe-Si alloys, Fe-Al alloys, Fe-N alloys, Fe-Ni alloys, Fe-C alloys, Fe-B alloys, Fe-Co alloys, Fe An alloy composed of at least one selected from a -P alloy, an Fe-Ni-Co alloy, and an Fe-Al-Si alloy can be used. In particular, from the viewpoint of magnetic permeability and magnetic flux density, 99% by mass or more, more preferably 99.5% by mass or more of pure iron is preferable.

<Particle size>
The average particle diameter of the soft magnetic particles may be any size that contributes to low loss as a green compact. That is, although it can select suitably, without specifically limiting, For example, if it is 1 micrometer or more and 150 micrometers or less, it is preferable. By setting the average particle size of soft magnetic particles to 1 μm or more, the increase in coercive force and hysteresis loss of compacted compacts made from soft magnetic powder is suppressed without reducing the fluidity of soft magnetic powder. it can. Conversely, by setting the average particle size of the soft magnetic particles to 150 μm or less, eddy current loss that occurs in a high frequency region of 1 kHz or more can be effectively reduced. The average particle size of the soft magnetic particles is more preferably 40 μm or more and 100 μm or less. If the lower limit of the average particle diameter is 40 μm or more, an effect of reducing eddy current loss can be obtained, and handling of the coated soft magnetic powder becomes easy, and a molded body having a higher density can be obtained. The average particle diameter means a particle diameter of particles in which the sum of masses from particles having a small particle diameter reaches 50% of the total mass in the particle diameter histogram, that is, 50% particle diameter.

<shape>
The shape of the soft magnetic particles is preferably such that the aspect ratio is 1.2 to 1.8. The aspect ratio is the ratio between the maximum diameter and the minimum diameter of the particles. Soft magnetic particles having an aspect ratio in the above range can increase the demagnetizing factor when formed into a compact, compared to those having a small aspect ratio (close to 1.0), and have excellent magnetic properties. It can be set as a molded body. In addition, the strength of the green compact can be improved.

<Production method>
The soft magnetic particles are preferably produced by an atomizing method such as a water atomizing method or a gas atomizing method. Since the soft magnetic particles produced by the water atomization method have many irregularities on the particle surface, it is easy to obtain a high-strength molded product by meshing the irregularities. On the other hand, the soft magnetic particles produced by the gas atomization method are preferable because the particle shape is almost spherical, and there are few irregularities that break through the insulating coating.

(Insulation coating)
The insulating coating is coated on the outer periphery of the soft magnetic particles in order to insulate adjacent soft magnetic particles. By covering the soft magnetic particles with an insulating film, the contact between the soft magnetic particles can be suppressed, and the relative magnetic permeability of the compact can be suppressed low. In addition, the presence of the insulating coating can suppress the eddy current from flowing between the soft magnetic particles, thereby reducing the eddy current loss of the green compact.

<composition>
The insulating coating is not particularly limited as long as it has excellent insulating properties that can ensure insulation between soft magnetic particles. For example, examples of the material for the insulating film include phosphate, titanate, silicone resin, and two layers of phosphate and silicone resin.

  In particular, since the insulating coating made of phosphate is excellent in deformability, even when soft magnetic particles are deformed when a soft magnetic material is pressed to produce a compact, a deformation follows the deformation. Can do. The phosphate coating has high adhesion to iron-based soft magnetic particles and is difficult to drop off from the surface of the soft magnetic particles. As the phosphate, a metal phosphate compound such as iron phosphate, manganese phosphate, zinc phosphate, calcium phosphate, or aluminum phosphate can be used.

  In the case of an insulating coating made of a silicone resin, it is excellent in heat resistance, so that it is difficult to be decomposed in a heat treatment step to be described later, and the insulation between soft magnetic particles can be maintained well until the compacting body is completed.

  When the insulating coating has a two-layer structure of the phosphate and the silicone resin, it is preferable to coat the phosphate on the soft magnetic particle side and the silicone resin directly on the phosphate. Since the silicone resin is coated directly on the phosphate, the above-described characteristics of both the phosphate and the silicone resin can be provided.

<Film thickness>
The average thickness of the insulating coating may be a thickness that can insulate adjacent soft magnetic particles. For example, it is preferably 10 nm or more and 1 μm or less. By setting the thickness of the insulating coating to 10 nm or more, it is possible to effectively suppress contact between soft magnetic particles and energy loss due to eddy current. On the other hand, by setting the thickness of the insulating coating to 1 μm or less, the ratio of the insulating coating to the coated soft magnetic particles does not become too large, and the magnetic flux density of the coated soft magnetic particles can be prevented from significantly decreasing.

  The thickness of the insulating coating can be examined as follows. First, the film composition obtained by composition analysis (TEM-EDX: transmission electron microscopic energy dispersive X-ray spectroscopy), and the amount of inductively coupled plasma mass (ICP-MS) obtained by inductively coupled plasma Considering this, a considerable thickness is derived. Then, the film is directly observed with a TEM photograph, and the average thickness determined by confirming that the order of the equivalent thickness derived earlier is an appropriate value is used.

<Coating method>
The method of covering the soft magnetic particles with the insulating coating may be selected as appropriate. For example, the film may be formed by hydrolysis / polycondensation reaction. Soft magnetic particles and a material constituting the insulating coating are blended, and the blend is mixed in a heated state. By doing so, the soft magnetic particles can be sufficiently dispersed in the coating material, and the insulating coating can be coated on the outside of the individual soft magnetic particles.

  The heating temperature and mixing time may be appropriately selected. By selecting the heating temperature and mixing time, the soft magnetic particles can be more sufficiently dispersed, and it becomes easy to coat the individual particles with the insulating coating.

[Raw material forming process]
In the raw material forming step, a coated soft magnetic powder composed of a plurality of coated soft magnetic particles prepared in the raw material preparing step is pressure-molded to produce a raw material compact.

  In the raw material forming step, typically, the coated soft magnetic powder is injected into a molding die composed of a punch and die having a predetermined shape, and pressed and hardened. When the punch and die are used, the coated soft magnetic powder is pressure-molded so that the compact is not baked on the mold by pressurization and the insulating coating of the coated soft magnetic powder is not destroyed. As the means, an external lubrication molding method in which a lubricant is applied to a portion (inner wall) in contact with the coated soft magnetic powder of at least one of the punch and the die and the coated soft magnetic powder is pressed, or the coated soft magnetic powder is previously applied to the coated soft magnetic powder. An internal lubrication molding method may be used in which a mixture is prepared by mixing a lubricant, and the mixture is pressurized with a mold. In the former case, since the lubricant is applied to the inner wall, it is possible to reduce friction with the coated soft magnetic powder and to form a high-density compact. In the latter case, the lubricant adhering to the surface of the coated soft magnetic powder reduces friction between particles in the coated soft magnetic powder, so that the insulating coating of the coated soft magnetic particles can be prevented from being broken.

  Lubricant is a solid soap such as stearic acid, metal stearate such as lithium stearate, fatty acid amide such as stearic acid amide, higher fatty acid amide such as ethylene bis stearic acid amide, solid lubricant dispersed in liquid medium such as water And dispersion liquid, liquid lubricant, and inorganic lubricant having a hexagonal crystal structure.

  When pressurizing, the molding die may be heated and then press-molded. In that case, for example, the mold temperature is set to 50 to 200 ° C. A high-density molded body can be obtained by heating the mold.

The pressure to pressurize can be selected suitably. For example, if a green compact to be used as a reactor core is manufactured, the density d is preferably about 7.0 g / cm ³ or more, specifically about 490 to 1470 MPa, The pressure is preferably about 590 to 1079 MPa.

  By this pressurization, for example, a rectangular parallelepiped material molded body 10 shown in FIG. 1 (lower right) can be formed. Since the shape of the material molded body 10 can be changed as appropriate depending on the shape of the mold at the time of pressure molding, in addition to a rectangular parallelepiped shape, a columnar body having a trapezoidal surface, or a U having a U-shaped surface. Various shapes, such as a character-shaped body, are mentioned. Thus, when the raw material molded object 10 is a rectangular parallelepiped shape, the both end surfaces of the raw material molded object 10 are the pressurization surfaces 31p by a punch, and the other four side surfaces are the sliding contact surfaces 31s with a die | dye.

[Irradiation process]
In the irradiation step, a laser is irradiated to a part of the surface of the material molded body. By irradiating the laser, the number of divided portions of the conducting portion where the constituent materials of the plurality of soft magnetic particles are conducted on the surface of the material molded body is increased. That is, in this irradiation process, the conduction part is divided mainly by melting and flow of the conduction part.

  The surface of the material molded body to be irradiated with the laser may be at least a part of the sliding contact surface with the die on which the conductive portion is easily formed. When the manufactured material molded body 10 is excited as a magnetic core, for example, a reactor core 3 as shown in FIG. 1 (upper side), it is preferable to use at least a part of a plane (parallel plane) parallel to the magnetic flux direction. . FIG. 1 is an example of a reactor core 3 included in a reactor (FIG. 2), in an exploded state of an inner core portion 31 covered with a coil (FIG. 2) and an exposed core portion 32 exposed from the coil. Show. The inner core portion 31 is configured by laminating a core piece 31m and a gap material 31g. The core piece 31m may be configured by a powder compact 1 obtained by irradiating the raw material compact 10 with laser, or a powder compact 1 obtained by performing laser irradiation and heat treatment described later. Thus, if the compacting body 1 and a coil are combined and the coil is excited, the magnetic flux along the axial direction of a coil will be formed in a molding body. Therefore, for example, as shown in FIG. 1 (lower right), the direction of the arrow (I) is the magnetic flux direction, that is, the pressing surface 31p of the punch is a surface (orthogonal surface) orthogonal to the magnetic flux direction. When the powder compact 1 is combined with the coil so that the four slidable contact surfaces 31 s are parallel to the magnetic flux direction, the region of the material irradiated with the laser is the parallel surface (slidable contact surface 31 s). It may be at least part of the ten surfaces. In this way, by irradiating a part of the surface of the material molded body 10 which is parallel to the magnetic flux direction with the laser, the laser is irradiated with the eddy current flowing in the circumferential direction with the magnetic flux direction as an axis. It is thought that it can be blocked at the location. Therefore, eddy current loss can be reduced, and a low-loss compacting body can be manufactured. That is, if the region irradiated with the laser is at least a part of the surface that is the slidable contact surface 31s with the die and the parallel surface, it is possible to effectively manufacture a low-loss compact.

  On the other hand, when the direction of the arrow (II) is the magnetic flux direction, that is, when the pressing surface 31p of the punch is a parallel surface to the magnetic flux direction, the laser irradiation region is at least of the sliding surface 31so orthogonal to the magnetic flux direction. Some may be sufficient. By doing so, the eddy current flowing on the surface of the sliding contact surface 31so can be interrupted, so that it is considered that the eddy current loss can be further reduced. In addition, it is preferable to irradiate the laser to at least a part of the sliding contact surface 31sp parallel to the magnetic flux direction. If it does so, the eddy current of the circumference direction centering on a magnetic flux direction can be interrupted | blocked in the location which irradiated the laser of the sliding contact surface 31sp.

  When the material molded body is a cylinder, if the surface perpendicular to the magnetic flux direction is a pressurizing surface with a punch, the plane parallel to the magnetic flux direction is a cylindrical cylindrical surface. It may be at least a part of the surface of the formed material.

  The region irradiated with the laser is preferably a region extending over the entire length in the pressing direction of the punch on the sliding surface 31s. In particular, in the parallel plane, it is more preferable that the surface of the material molded body is a region extending over the entire length in the magnetic flux direction. For example, when the green compact 1 is combined with a coil so that the direction of the arrow (I) is the magnetic flux direction, the laser irradiation region is a region extending from one end surface side to the other end surface side in a parallel plane. It is preferable that the surface of the material molded body 10 is as follows. That is, when the pressing surface 31p of the punch is a surface (orthogonal surface) orthogonal to the magnetic flux direction, and the other four sliding contact surfaces 31s are parallel surfaces of the magnetic flux direction, the laser irradiation region is parallel. In the surface, it is preferable to use the surface of the material molded body 10 over the entire length in the pressing direction (the total length in the magnetic flux direction). If it does so, it is thought that the eddy current which flows into the circumferential direction centering on a magnetic flux direction can be interrupted | blocked over the said full length. That is, if the region to be surface-treated is the surface that is the slidable contact surface 31s with the die and the parallel surface, and is a region that extends over the entire length in the magnetic flux direction, a more compact low-loss compact is produced. it can.

  On the other hand, when the direction of arrow (II) is the magnetic flux direction, that is, when the pressing surface 31p of the punch is parallel to the magnetic flux direction, the laser irradiation region is one of the sliding contact surfaces 31so orthogonal to the magnetic flux direction. The region extending from one end face side to the other end face side, that is, between the long sides and the short sides of the sliding contact surface 31so may be used. Then, it is considered that the eddy current flowing on the surface of the sliding contact surface 31so can be interrupted. In addition, it is preferable to irradiate a laser to the area | region covering the magnetic flux direction full length of the slidable contact surface 31sp parallel to a magnetic flux direction. If it does so, the eddy current which flows into the circumferential direction centering on a magnetic flux direction can be interrupted | blocked over the said full length.

  When the material molded body is a cylinder, if the surface perpendicular to the magnetic flux direction is a pressurizing surface with a punch, the plane parallel to the magnetic flux direction is a cylindrical cylindrical surface. It is preferable that it is an area | region covering the pressurization direction full length (magnetic flux direction full length) of the surface of the raw material molded object which becomes.

  When irradiating a laser on a region extending from one end face side to the other end face side in the parallel plane, the green compact having a length in the direction parallel to the magnetic flux direction in the parallel plane as a length t and the magnetic flux direction as an axis. When the total length in the circumferential direction is l, the total area of the parallel surface is t × l, and the width of the region actually surface-treated on the parallel surface (the direction perpendicular to the magnetic flux direction) is defined as the processing width w. This area is represented as t × w. This treatment width w preferably satisfies d <w ≦ l, where d is the average particle diameter of the coated soft magnetic powder. By setting the processing width w within the above range, an effect of reducing eddy current loss can be effectively obtained. More preferably, the ratio w / l of the processing width w to the total length l is 30% or less, further 20% or less, 10% or less, and particularly 5% or less.

The kind of laser should just be a laser which can cut off the conduction part of the material fabrication object surface. Specific examples include a solid-state laser whose laser medium is solid, and for example, a laser selected from a YAG laser, a YVO ₄ laser, and a fiber laser is preferable. By doing so, the said conduction | electrical_connection part can be parted. Each of these lasers includes known lasers in which various materials are doped in the medium of each laser. That is, the YAG laser may be doped with Nd, Er, etc. in the medium, the YVO ₄ laser may be doped with Nd, etc., and the fiber laser is the medium. The core of the fiber is doped with a rare earth element, for example, doping with Yb or the like.

  The wavelength of the laser is more preferably in the wavelength absorption region of the soft magnetic particles (conduction part). By doing so, it becomes easy to divide the conduction part, and it is possible to suppress removal of parts other than the conduction part. Specifically, the wavelength is preferably about 532 nm to 1064 nm.

The energy density U (W / mm ² ) of the laser is expressed by U = P / S, where P (W) is the average output of the laser and S (mm ² ) is the irradiation area of the laser. Preferably satisfies 37.0 W / mm ² ≦ U ≦ 450.0 W / mm ² . By setting the energy density U to 37.0 W / mm ² or more, it is possible to reliably increase the number of disconnected portions of the conductive portion. On the other hand, when the energy density U is 450.0 W / mm ² or less, the contact between the soft magnetic particles due to excessive melting can be sufficiently suppressed. The energy density U is more preferably 50.0 W / mm ² or more and 300.0 W / mm ² or less.

Within this range, as the energy density U is increased, (1) the oxide film to be formed can be an oxide film containing a large amount of FeO or Fe ₃ O ₄ , and the oxygen content in the surface portion is increased. (2) A thick portion of the oxide film can be formed. Specifically, in the above (1), an increase in FeO and _Fe 3 _{O 4,} can increase the _Fe 3 _{O 4} than further FeO the energy density U increases. When the total content of iron and oxygen contained in the surface portion where the oxide film is provided is 100% by mass, the oxygen content can be 9% by mass or more by increasing the energy density U. . In the range of the above energy density U, the oxygen content can be about 20% by mass. In the above (2), the oxide film can have a thickness of 0.1 μm or more, and as the energy density U increases, 0.5 μm, 1.0 μm, 3 μm, further 5 μm, A thick portion having a thickness of 7 μm or more, particularly 10 μm or more can be formed. In the range of the above energy density U, the oxide film can have a thickness of about 15 μm.

  As shown in the above-described mechanism, a divided region that electrically divides adjacent soft magnetic particles can be formed on at least a part of the surface of the compact formed body irradiated with the laser by laser irradiation. A divided region is formed, and the oxide film is formed in a surface region located on the surface of the green compact in the surface of the soft magnetic particles adjacent to the divided region. When a laser having a low energy density U is irradiated, a divided region is formed, and the agglomerated portion is formed on the surface of the soft magnetic particle adjacent to the divided region. The thickness of the oxide film in the agglomerated portion increases as the energy density U of the laser increases. On the other hand, when the laser is irradiated at a high energy density U, a divided region is formed, and the above-described concentrated portion is formed on the surface of the soft magnetic particle adjacent to the divided region. As the energy density U of the laser increases, the concentration portion of the concentration portion can be made thicker and the center side can be made thicker than the outer peripheral side. This is because, depending on the magnitude of the energy density U of the laser, the amount of melting or the fluidity of the molten metal can be different, and if the surface area of the constituent material of the soft magnetic particles is reduced due to surface tension, the degree of aggregation will be different.

  The ratio of the irradiation interval to the laser beam diameter is preferably small. The beam diameter refers to the diameter of the laser on the surface of the green compact. The irradiation interval refers to the distance that the laser beam moves in the scanning direction during the irradiation time of one pulse of laser. If the ratio of the irradiation interval to the laser beam diameter is small, when the laser is scanned on the surface of the green compact, the unprocessed area where the laser is not irradiated can be reduced, and the conductive part can be easily divided. . Specifically, the ratio is preferably 0.35 or less, and particularly preferably 0.30 or less.

  A smaller ratio of the scanning interval to the laser beam diameter is also preferable. The scanning interval refers to the distance when moving the line scanned by the laser to the adjacent line. That is, if the ratio of the scanning interval to the laser beam diameter is small, the region not irradiated with the laser can be reduced as described above, and the conducting portion can be easily divided.

  The number of laser overlaps is preferably a plurality of times. The number of overlaps refers to the number of times the same area is processed (scanned) with a laser. The greater the number of laser overlaps, the better. If it does so, the said conduction | electrical_connection part can be divided reliably. Specifically, the number of times of overlapping is 5 times or more, and particularly preferably 10 times or more.

  The method of irradiating the surface of the material molded body with laser is not particularly limited as long as it is a method capable of irradiating a desired portion of the surface with laser.

[Other processes]
(Heat treatment process)
The material molded body may be subjected to a heat treatment for heating in order to remove strains and dislocations introduced into the soft magnetic particles in the material molding process.

  Since the higher the heat treatment temperature is, the more strain can be removed, the heat treatment temperature is preferably 300 ° C. or higher, particularly 400 ° C. or higher, and the upper limit is preferably about 800 ° C. With such a heat treatment temperature, not only strain can be removed, but also lattice defects such as dislocations introduced into the soft magnetic particles during pressurization can be removed. Thereby, the hysteresis loss of a compacting body can be reduced effectively.

  What is necessary is just to select suitably the time which performs heat processing according to the said heat processing temperature and the volume of a raw material molded object so that the distortion, dislocation, etc. which were introduce | transduced into the soft-magnetic particle in the raw material formation process may fully be removed. For example, in the above temperature range, it is preferably 10 minutes to 1 hour.

  The atmosphere at the time of performing the heat treatment may be in the air, but it is particularly preferable to apply in an inert gas atmosphere. As a result, adhesion of soot or the like to the material molded body due to combustion of the lubricant can be suppressed.

  This heat treatment process may be performed on the material molded body before the irradiation process, or may be performed on the material molded body after the irradiation process.

<Effect>
According to embodiment mentioned above, there exist the following effects.

  (1) A low-loss reactor can be obtained by using a green compact having an oxide film on at least a part of the surface and having an oxygen content of 9% by mass or more at the surface part. When the green compact having the above-mentioned divided region is excited as a reactor core, the eddy current flowing over the circumferential direction of the surface of the green compact can be divided or hardly flowed. Therefore, eddy current loss can be reduced, and a low-loss reactor can be obtained. Therefore, the compacting body of this invention can be utilized suitably for the structural member of a reactor.

  (2) According to the manufacturing method described above, by irradiating the conducting part with laser, high energy is imparted to the conducting part of the thin film-like body, or rapid heating and cooling (temperature change) can be caused. it can. At this time, the thin film-like body is melted and the molten metal flows or agglomerates due to surface tension to form a lump (aggregation part) or a concentration part as shown in a test example described later. Thereby, the middle part of the conduction part is separated, and it is considered that the same parting occurs at various parts of the conduction part, thereby increasing the number of parts where the conduction part is divided. By increasing the number of parts where the conductive portion is divided, it is possible to increase the electrical resistance of the conductive portion or to interrupt the conduction in the conductive portion. As a result, it is difficult for eddy currents to flow, or eddy currents can be interrupted. Therefore, a low-loss compacting body with little eddy current loss can be manufactured.

  (3) The above-mentioned compacting body or the compacting body manufactured by the above-mentioned manufacturing method can be utilized suitably for the core for reactors. As will be described in detail later, in that case, for example, a coil having a pair of coil elements and arranged side by side so that the axes of the coil elements are parallel to each other, and a pair of columnar inner core portions in which the coil elements are respectively disposed (Middle core portion) and a reactor including a magnetic core having an outer core portion (side core portion) that is connected to the inner core portion and forms a closed magnetic circuit without being arranged with a coil element, is suitable for the inner core portion. Can be used. When the inner core portion is configured by combining a plurality of divided core pieces, at least one, preferably all of the divided core pieces can be formed by the green compact of the present invention. At this time, in the inner core portion or the split core piece, the region to be irradiated with the laser is at least a part of a surface parallel to the magnetic flux direction when the coil is excited. Here, the parallel surface is a sliding surface with the die. When the reactor is assembled with the split core pieces, the surface of the split core pieces irradiated with the laser faces the inner peripheral surface of the coil. Thereby, when the coil is excited, the eddy current generated in the circumferential direction of the inner core portion is cut off in the region irradiated with the laser, and the eddy current loss can be reduced. For example, if this laser is applied to the inner core portion or a region extending from one end surface side to the other end surface side of each divided core piece in the parallel plane, when the reactor is assembled, the region is the inner core portion. Extends over the entire length of the magnetic flux direction. Therefore, since the eddy current can be interrupted over the entire length of the inner core in the magnetic flux direction, the eddy current loss can be further reduced. The outer core portion is typically U-shaped or trapezoidal in the end surface. Also in this outer core part, you may use the compacting body of this invention, or the compacting body obtained by the manufacturing method of this invention.

  (4) Since the part to be surface-treated by irradiating the laser is a part of the surface of the material molded body, the processing steps and the processing time can be shortened, and the manufacturing process of the green compact can be simplified. . Therefore, the manufacturing cost of a compacting body can also be reduced.

<Embodiment 2>
《Reactor》
The above-mentioned compacting body and the compacting body manufactured by the manufacturing method of the above-mentioned compacting body can be used suitably as a constituent member of a reactor. For example, the reactor includes a coil formed by winding a winding, and a magnetic core that is disposed inside and outside the coil to form a closed magnetic path, and at least a part of the magnetic core is formed of a powder compact. The green compact of the present invention can be used for the green compact. That is, the feature of the reactor of the present invention is that at least a part of the magnetic core included in the reactor is provided with the above-described compacted body. Hereinafter, an example of the reactor will be described with reference to FIGS. Here, the case where the inner core part 31 arrange | positioned inside the coil 2 among the magnetic cores 3 with which the reactor 100 is comprised is comprised by the compacting body of this invention is demonstrated to an example. For the configuration other than the core piece 31m constituting the inner core portion 31, a known reactor configuration can be used. Of course, you may comprise the exposed core 32 among the magnetic cores 3 by this invention compacting body.

(coil)
As shown in FIG. 2, the coil 2 includes a pair of coil elements 2 a and 2 b formed by spirally winding a single continuous winding 2 w without a joint portion, and a connection for connecting both the coil elements 2 a and 2 b. Part 2r. Each coil element 2a, 2b is a hollow cylindrical body having the same number of turns, and is arranged in parallel (side-by-side) so that the respective axial directions are parallel to each other, and is wound on the other end side (right side in FIG. 2) of the coil 2 A part of 2w is bent into a U shape to form a connecting portion 2r. With this configuration, the winding directions of both coil elements 2a and 2b are the same.

  The winding 2w is preferably a covered wire having an insulating layer made of an insulating material (typically an enamel layer made of polyamideimide) on the outer periphery of a conductor made of a conductive material such as copper, aluminum, or an alloy thereof. Available. As the conductor of the winding 2w, a rectangular wire having a rectangular cross section can be suitably used in addition to a round wire having a circular cross section. The coil elements 2a and 2b are edgewise coils formed by edgewise winding a covered rectangular wire having an insulating layer.

(Magnetic core)
The magnetic core will be described with reference to FIG. The magnetic core 3 includes a pair of columnar inner core portions 31 covered by the coil elements 2 a and 2 b (FIG. 2) and a pair of exposed core portions that are exposed from the coil 2 without the coil 2 (FIG. 2). 32. Each inner core portion 31 is a columnar body (here, substantially a rectangular parallelepiped) having an outer shape along the inner peripheral shape of each coil element 2a, 2b, and each exposed core portion 32 is a pair of trapezoidal shapes. A columnar body having a surface. The reactor core 3 has an exposed core portion 32 disposed so as to sandwich the inner core portion 31 disposed in parallel, and the end surface of each inner core portion 31 and the inner end surface of the exposed core portion 32 are contacted to form an annular shape. Is done.

  The inner core portion 31 alternately includes a core piece 31m made of a magnetic material and a gap material 31g made of a material having a lower magnetic permeability than the core piece (for example, a nonmagnetic material such as alumina) for adjusting the inductance. It is the laminated body comprised by laminating | stacking. The exposed core portion 32 is also a core piece made of a magnetic material. For the integration of the core pieces and the integration of the core piece 31m and the gap material 31g, for example, an adhesive or an adhesive tape can be used.

  Each of the core pieces 31m of the inner core portion 31 is constituted by the above-described green compact of the present invention. The region irradiated with the laser in the core piece 31m (inner core portion 31) is preferably arranged so as to be parallel to the magnetic flux direction when the coil 2 is excited. That is, when the reactor 100 is assembled with the core piece 31m, the surface of the core piece 31m irradiated with the laser faces the inner peripheral surface of the coil 2. Thereby, when the coil 2 is excited, the eddy current loss generated in the circumferential direction of the inner core portion 31 around the magnetic flux direction can be cut off in the region irradiated with the laser, and the eddy current loss can be reduced. When all the core pieces 31m which comprise the inner core part 31 are comprised with the core piece 31m (the compacting body of this invention) to which the laser was irradiated like this example, the one end surface side of the inner core part 31 It is preferable to arrange each core piece 31m so that the region irradiated with the laser is lined up in the region extending from to the other end face side. Then, when the reactor is assembled, the region irradiated with the laser extends over the entire length of the inner core portion 31 in the magnetic flux direction. Therefore, since the eddy current can be interrupted over the entire length of the inner core portion 31 in the magnetic flux direction, the eddy current loss can be further reduced.

(Other components)
In addition, in order to improve the insulation between the coil 2 and the reactor core 3, an insulator (not shown) made of an insulating resin is provided, or the outer periphery of the combination of the coil 2 and the reactor core 3 is provided. The integrated body covered with the insulating resin, the combined body can be stored in a case made of a metal material, or the combined body stored in the case can be covered with a sealing resin.

  According to said structure, when the inner core part 31 is comprised with the above-mentioned compacting body and it arrange | positions so that it may become parallel to a magnetic flux direction when the coil 2 is excited, the magnetic flux direction is used as an axis | shaft of the inner core part 31. The eddy current loss generated in the circumferential direction can be cut off to reduce the eddy current loss. Therefore, the reactor 100 with a low loss can be obtained.

<Embodiment 3>
<Converter and power converter>
The above-described reactor can be used, for example, as a component part of a converter mounted on a vehicle or the like, or a component part of a power conversion device including the converter.

  For example, a vehicle 1200 such as a hybrid vehicle or an electric vehicle is used for traveling by being driven by a main battery 1210, a power converter 1100 connected to the main battery 1210, and power supplied from the main battery 1210 as shown in FIG. Motor (load) 1220. The motor 1220 is typically a three-phase AC motor, which drives the wheel 1250 when traveling and functions as a generator during regeneration. In the case of a hybrid vehicle, vehicle 1200 includes an engine in addition to motor 1220. In addition, in FIG. 3, although an inlet is shown as a charge location of the vehicle 1200, it can also be set as the form which provides a plug.

  Power conversion device 1100 includes converter 1110 connected to main battery 1210 and inverter 1120 connected to converter 1110 and performing mutual conversion between direct current and alternating current. Converter 1110 shown in this example boosts the DC voltage (input voltage) of main battery 1210 of about 200V to 300V to about 400V to 700V and supplies power to inverter 1120 when vehicle 1200 is traveling. In addition, converter 1110 steps down DC voltage (input voltage) output from motor 1220 via inverter 1120 to DC voltage suitable for main battery 1210 during regeneration, and causes main battery 1210 to be charged. The inverter 1120 converts the direct current boosted by the converter 1110 into a predetermined alternating current when the vehicle 1200 is running, and supplies the motor 1220 with electric power. During regeneration, the alternating current output from the motor 1220 is converted into direct current and output to the converter 1110. doing.

  As shown in FIG. 4, the converter 1110 includes a plurality of switching elements 1111, a drive circuit 1112 that controls the operation of the switching elements 1111, and a reactor L, and converts input voltage by ON / OFF repetition (switching operation). (In this case, step-up / down pressure). For the switching element 1111, a power device such as FET or IGBT is used. The reactor L has the function of smoothing the change when the current is going to increase or decrease by the switching operation by utilizing the property of the coil that prevents the change of the current to flow through the circuit. As this reactor L, the above-mentioned reactor is provided. By providing the low-loss reactor 100, the power converter 1100 and the converter 1110 can also achieve a low loss as a whole.

  Vehicle 1200 is connected to converter 1110, power supply converter 1150 connected to main battery 1210, sub-battery 1230 serving as a power source for auxiliary machinery 1240, and main battery 1210. Auxiliary power supply converter 1160 for converting high voltage to low voltage is provided. The converter 1110 typically performs DC-DC conversion, while the power supply device converter 1150 and the auxiliary power supply converter 1160 perform AC-DC conversion. Some power supply device converters 1150 perform DC-DC conversion. The reactor of the power supply device converter 1150 and the auxiliary power supply converter 1160 can have a configuration similar to that of the above-described reactor and the like, and the reactor whose size and shape are appropriately changed can be used. In addition, the above-described reactor or the like can be used for a converter that performs conversion of input power and that only performs step-up or only performs step-down.

<< Test Example 1 >>
As Test Example 1, the green compacts of Samples 1-1 to 1-3 below were produced, and the tests described below were performed for the magnetic properties of the samples.

[Sample 1-1]
The green compact of Sample 1-1 is produced through the following steps in the order of step a → step b → step c → step d.
Step a: Raw material preparation step of preparing coated soft magnetic powder.
Step b: A material molding step for producing a material molded body by press-molding the coated soft magnetic powder.
Step c: a heat treatment step of heating the material molded body to produce a heat treated molded body.
Step d: An irradiation step of irradiating the surface of the heat-treated molded body with a laser.

(Process a)
As a constituent material of the green compact, the coated soft magnetic powder in which the surface of soft magnetic particles made of iron powder was coated with an insulating coating made of iron phosphate contained 0.6% by mass of a lubricant made of zinc stearate. A mixed material was prepared. The iron powder was produced by a water atomization method and had a purity of 99.8% or more. The soft magnetic particles had an average particle size of 50 μm and an aspect ratio of 1.2. This average particle size was determined from the particle size of particles in which the sum of masses from particles with small particle sizes reached 50% of the total mass, that is, 50% particle size, in the particle size histogram. The insulating coating substantially covered the entire surface of the soft magnetic particles, and the average thickness was 20 nm.

(Process b)
The mixed material prepared in step a was poured into a mold having a predetermined shape, and pressure-molded by applying a pressure of 730 MPa without heating the mold to produce a material molded body. Here, a plurality of rectangular parallelepiped material molded bodies were produced.

(Process c)
The material molded body produced in step b was heat-treated at 400 ° C. for 30 minutes in a nitrogen atmosphere to obtain a plurality of heat-treated molded bodies.

(Process d)
In step d, a plurality of rectangular parallelepiped heat treatment molded bodies obtained in step c are combined in a ring shape to produce a test piece for evaluating iron loss, and at least the heat treatment molded body is irradiated with a laser. Here, the laser was irradiated to a part of the surface of the heat-treated molded body on which the coil is arranged in the magnetic property measurement test described later among the surfaces of the heat-treated molded body. In that case, the area | region covering the magnetic flux direction full length of the surface (parallel surface) parallel to the direction of the magnetic flux which arises in a sample was irradiated on the conditions shown below. As a result, the ratio w / l of the treatment width w irradiated with the laser with respect to the total length l in the circumferential direction of the heat-treated molded body with the magnetic flux direction as an axis was 7%. A heat treatment molded body on which no coil is disposed may be irradiated with a laser. The heat-treated molded body irradiated with this laser is a green compact, and this green compact is designated as Sample 1-1.

<Laser irradiation conditions>
Type: Fiber laser Wavelength: 1064nm
Ratio of irradiation interval to beam diameter: 0.15
Pulse width: 200ns
Ratio of scanning interval to beam diameter: 0.08
Number of stacking times: 10 times Energy density U: 61.1 W / mm ²

[Sample 1-2]
The compacted body of the sample 1-2 differs from the sample 1-1 in the order of performing each step, and is manufactured through the respective steps in the order of the step a → step b → step d → step c. The region irradiated with laser in step d was the same as that of sample 1-1.

[Sample 1-3]
The compacted green body of Sample 1-3 differs from Sample 1-1 in that the surface of the green body is not irradiated with laser. That is, the green compact of Sample 1-3 is manufactured through each step in the order of the above step a → step b → step c.

[Evaluation 1]
A plurality of powder compacts of each of the samples 1-1 to 1-3 were combined in a ring shape to produce a test magnetic core. A measuring member for measuring magnetic characteristics was prepared by arranging coils each composed of a winding on each test magnetic core, and the following magnetic characteristics were evaluated.

[Magnetic property test]
For each measurement member, the hysteresis loss Wh (W) and eddy current loss We (W) of the sample at an excitation magnetic flux density Bm: 1 kG (= 0.1 T) and measurement frequency: 5 kHz are obtained using an AC-BH curve tracer. The loss W (W) of each sample was calculated.

  The characteristic values obtained from the above tests are listed in Table 1.

"result"
By irradiating a part of the surface of the heat-treated molded body with the laser after the heat treatment like the sample 1-1, the eddy current loss can be greatly reduced as compared with the sample 1-3 not subjected to the laser irradiation. It was. In addition, eddy current loss was similarly reduced in Sample 1-2 that was heat-treated after laser irradiation.

  Based on the above test results, laser irradiation reduces eddy current loss and loss when applied to a part of the surface of the heat-treated molded body, particularly a part parallel to the magnetic flux direction when excited as a reactor core. It turns out to be effective.

  A sample that was not heat-treated before or after laser irradiation was prepared, and the sample was subjected to the same test as described above. The sample 1 was heat-treated before or after laser irradiation. 1 and 1-2, it was effective in reducing eddy current loss.

<< Test Example 2 >>
As Test Example 2, in preparing samples in the same process order as Samples 1-1 and 1-2 prepared in Test Example 1, sample 2-1 with different laser irradiation conditions in step d was used. 2-2 was produced. The magnetic characteristics of these samples were evaluated in the same manner as in Evaluation 1 above. The laser irradiation conditions are shown below, and the obtained characteristic values are shown in Table 2. Here, Sample 1-3 produced in Test Example 1 is also shown.

<Laser irradiation conditions>
Type: Fiber laser Wavelength: 1064nm
Ratio of irradiation interval to beam diameter: 0.07
Pulse width: 120ns
Ratio of scanning interval to beam diameter: 0.05
Number of times of stacking: 40 times Energy density U: 123.6 W / mm ²

"result"
Similar to Test Example 1, Samples 2-1 and 2-2 in which a part of the surface was irradiated with laser were able to reduce eddy current loss compared to Sample 1-3 that was not irradiated with laser.

<< Test Example 3 >>
In producing the same sample as the sample 2-1 produced in the test example 2 as the test example 3, the energy density U is variously changed among the irradiation conditions of the laser irradiated in the step d, and the conditions other than the energy density U Prepared Samples 3-1 to 3-10 in the same manner as Sample 2-1. The magnetic characteristics were evaluated for each sample in the same manner as in Evaluation 1. The energy density U irradiated to each sample and the obtained characteristic values are shown in Table 3 and FIG.

"result"
Samples 3-1 to 3-10 were all able to reduce eddy current loss as compared to Sample 1-3 (Test Example 1). In addition, Samples 3-3 to 3-9 can reduce eddy current loss more than Samples 3-1, 3-2, and 3-10. Among them, Samples 3-4 to 3-8 have eddy current loss. In particular, it was reduced.

From the above test results, it has been found that if the energy density U of the laser to be irradiated is 37.0 W / mm ² or more and 450.0 W / mm ² or less, it is more effective in reducing eddy current loss.

<< Test Example 4 >>
As a test example 4, in producing the same sample as the sample 2-1 produced in the test example 2, the ratio of the irradiation interval to the beam diameter was variously changed among the irradiation conditions of the laser irradiated in the step d. Samples 4-1 to 4-10 were produced in the same manner as in Sample 2-1, except for the above conditions. Each sample was evaluated for magnetic properties in the same manner as in Evaluation 1. Table 4 shows the ratio of the irradiation interval to the beam diameter of the laser irradiated to each sample, and the obtained characteristic values.

"result"
Samples 4-1 to 4-10 were all able to reduce eddy current loss as compared to Sample 1-3 (Test Example 1). Samples 4-1 to 4-7 were able to reduce eddy current loss more than samples 4-8 to 4-10, and samples 4-1 to 4-6 were particularly able to reduce eddy current loss.

  From the above results, it is possible to reduce the eddy current loss by reducing the ratio of the irradiation interval to the beam diameter of the irradiating laser. In particular, the eddy current can be reduced by setting the ratio to 0.35 or less, and further to 0.30 or less. It has been found to be more effective in reducing losses.

<< Test Example 5 >>
As a test example 5, in producing the same sample as the sample 2-1 produced in the test example 2, among the laser irradiation conditions irradiated in the step d, the number of times of overlapping is variously changed. Samples 5-1 to 5-9 were prepared in the same manner as Sample 2-1. The magnetic characteristics were evaluated for each sample in the same manner as in Evaluation 1. Table 5 shows the number of times the laser was irradiated to each sample and the obtained characteristic values.

"result"
Samples 5-1 to 5-8 can reduce eddy current loss compared to sample 5-9, and samples 5-1 to 5-6 can reduce eddy current loss more than samples 5-7 and 5-8. It was. In particular, Samples 5-1 to 5-5 were able to further reduce eddy current loss.

  From the above results, it was found that eddy current loss can be reduced by increasing the number of overlapping lasers, and more effective for reducing eddy current loss, especially by setting it to 5 times or more, and even 10 times or more. .

<< Test Example 6 >>
As Test Example 6, the surface components of Samples 1-1 and 3-6 were measured with a parallel optical X-ray diffractometer using a multilayer mirror. In this component measurement, components in the laser irradiation regions of Sample 1-1 and Sample 3-6 were measured. The components on the sliding surface of Sample 1-3 were also measured. Measurement conditions are shown below, and each result of Samples 1-1, 3-6, and 1-3 is shown in FIGS. In the figure, ◯ represents Fe ₃ O ₄ , Δ represents FeO, and x represents α-Fe.

<Measurement condition>
Equipment used: X-ray diffractometer (X'pert manufactured by PANalytical)
X-ray used: Cu-Kα
Excitation conditions: 45 kV 40 mA
Measurement method: θ-2θ measurement

"result"
Sample 1-1 (FIG. 6) and sample 3-6 (FIG. 7) have less α-Fe, more FeO, and Fe ₃ O ₄ than sample 1-3 (FIG. 8). When comparing the sample 1-1 and the sample 3-6, the sample 3-6 having a higher energy density U of the irradiated laser has less α-Fe than the sample 1-1. Sample 1-1 is that the FeO is detected more than _Fe 3 _{O 4,} samples 3-6 were detected many towards _Fe 3 _{O 4} than FeO.

From the above results, by irradiating with laser, α-Fe is decreased and FeO and Fe ₃ O ₄ are increased. It was found that increasing the laser energy density U increases Fe ₃ O ₄ over FeO. In addition, as shown in Test Examples 1 and 3, since Samples 1-1 and 3-6 have less loss than Sample 1-3, at least FeO and Fe ₃ O ₄ are formed on the surface of the green compact. It has been found that providing an oxide film containing one can reduce loss, and in particular, loss can be further reduced by containing more Fe ₃ O ₄ than FeO.

<< Test Example 7 >>
As a test example 7, in producing the same sample as the sample 2-1 produced in the test example 2, the energy density U is variously changed among the irradiation conditions of the laser irradiated in the step d, and conditions other than the energy density U Prepared Samples 7-1 to 7-4 in the same manner as Sample 2-1. Further, Sample 7-5 similar to Sample 1-3 manufactured in Test Example 1 was manufactured. And the oxygen content in the surface of each sample was measured by energy dispersive X-ray spectroscopy (EDX) using the following apparatus. Specifically, in Samples 7-1 to 7-4, the portion irradiated with the laser was measured, and in Sample 7-5, a part of the slidable contact surface with the die and a part of the pressure contact surface in contact with the punch were measured. . The oxygen content indicates a ratio when the total content of iron and oxygen in the region from the surface of each sample to the depth of about 1 μm into the sample is 100% by mass. Table 6 summarizes the surface treatments, measurement locations, and results.

<Measurement condition>
Equipment used: Scanning electron microscope (SEM) (SUPRA35VP manufactured by ZEISS)
Energy dispersive X-ray analyzer (EDX system) (GENESIS 4000 manufactured by EDAX)
Acceleration voltage: 15 kV
Measurement area: 1.80 × 0.835 mm ²

"result"
Samples 7-1 to 7-4 had a smaller loss than Sample 7-5, and Samples 7-1 to 7-3 having an oxygen content of 9% by mass or more had particularly small losses. On the other hand, the sliding contact surface and the pressure contact surface of Sample 7-5 both had an oxygen content of less than 6% by mass.

  In Samples 7-1 to 7-4, the surface of the green compact was oxidized by laser irradiation to form an oxide film, so that the oxygen content was higher than that of Sample 7-5. In particular, the higher the energy density U of the laser was, the more oxidized, and therefore it is considered that Samples 7-1 to 7-3 had an increased oxygen content. As a result of the formation of the oxide film in addition to the division of the conduction part, it is considered that the eddy current can be sufficiently cut off and the loss is reduced. From the above, it was found that the loss can be further reduced by setting the oxygen content on the surface to 9% by mass or more.

  Hereinafter, as a reference example, green compacts of the following samples 7-11 to 7-13 were prepared, and the oxygen content on the surface of each sample was measured in the same manner as in Test Example 7.

[Sample 7-11]
The compact formed body of Sample 7-11 was subjected to the following electrolytic treatment on the surface of the heat treated formed body instead of irradiating the laser in step d after passing through each step in the order of step a → step b → step c. Made.

(Electrolytic treatment)
The electrolytic treatment is performed by immersing the heat-treated molded body in a liquid tank containing sodium nitrate having a concentration of 20% by mass, bringing the Pt electrode of the anode into contact with the portion to be subjected to the electrolytic treatment, and immersing the cathode Pt electrode in the electrolytic solution. Then, it is brought into contact with other portions of the heat-treated molded body. In that state, a voltage of 65 V was applied and a current of 40 A was applied for 35 seconds. The ratio w / l in the electrolytic treatment was 7%. After the electrolytic treatment, the green compact was washed with water.

[Sample 7-12]
In the same manner as the sample 7-11, the compact formed body of the sample 7-12 is subjected to each step in the order of step a → step b → step c, and then, on the surface of the heat treated formed body, instead of irradiating the laser in step d. It produced by performing the acid treatment shown below.

(Acid treatment)
In the acid treatment, a part of the surface of the heat-treated molded article was immersed for 20 minutes in a liquid tank containing concentrated hydrochloric acid having a pH of 1 and a temperature of 26 ° C. while stirring the concentrated hydrochloric acid. The ratio w / l in the acid treatment was 7%. After the acid treatment, the green compact was washed with water.

[Sample 7-13]
The green compact of Sample 7-13 is produced through each step in the order of step a → step b → step c. Here, the kind of the coated soft magnetic powder to be prepared is different from the process a in Test Example 1, and the process b is different from the process b in that an external lubrication molding method in which a lubricant is applied to the mold is adopted. In other words, the above-described external lubrication molding method can provide a sufficient lubrication effect so that the conductive portion is not easily generated on the sliding contact surface with the mold.

  Specifically, the insulating coating coated on the surface of the soft magnetic particles in step a was made into a multilayer structure. First, a chemical conversion treatment is performed on soft magnetic particles to form an inner film (thickness: about 20 nm or less) made of a metal phosphate compound containing hydrated water. Particles including the inner film and a commercially available resin material (Momentive silicone XC96-B0446 (which becomes a silicone resin by hydrolysis / condensation polymerization reaction)) is mixed in a heated atmosphere (80 ° C. to 150 ° C.), and the inner membrane made of a metal phosphate compound and the silicone resin are mixed. An insulating layer having a multilayer structure with the outer layer (total average thickness: 500 nm) was formed. When injecting the coated soft magnetic powder into the mold, a lubricant made of ethylenebisstearic acid amide is applied to the inner wall of the mold that comes into contact with the coated soft magnetic powder, and pressure-molded by applying a pressure of 950 MPa. A green compact was produced. When the slidable contact surface with the mold in the produced green compact was observed on the surface, no generation of the conductive part was observed.

  In the produced samples 7-11 and 7-12, the amount of oxygen was measured in the same manner as described above with respect to the place where each treatment was performed, and in the sample 7-13 with respect to the pressure contact surface. Table 7 summarizes the surface treatment performed, the measurement location, and the oxygen content.

"result"
In Samples 7-11 and 7-12 subjected to electrolytic treatment and acid treatment instead of the laser, the surface oxygen amount was about 4% by mass. That is, it has been found that even when electrolytic treatment and acid treatment are performed, a surface portion containing a predetermined amount of oxygen is not formed on the surface of the green compact. On the other hand, in the sample 7-13 composed of powder having a large amount of oxygen at the raw material stage as compared with Samples 7-1 to 7-3, the insulating coating covering the soft magnetic particles of the raw material of the green compact is thick. The amount of oxygen on the surface was about 8% by mass and did not exceed 9% by mass. That is, it has been found that even when a compacted body is produced using a coated soft magnetic powder having a large amount of oxygen at the raw material stage, the oxygen content on the surface does not become 9% by mass or more.

<< Test Example 8 >>
As Test Example 8, before and after laser irradiation of Sample 1-1, and the surfaces of Samples 3-5, 3-6, 3-8, and 3-9 were observed with a microscope. This surface observation was performed by taking an enlarged photograph of the surface of each sample with an SEM. The enlarged photographs are shown in FIGS. 9A to 13A show cross sections of the samples 3-5, 3-6, and 3-8 before and after laser irradiation of the sample 1-1, and FIG. 9B shows the surface of the sample. FIG. 14 shows a cross section of Sample 3-9.

"result"
[Sample No. 1-1]
In FIG. 9A, Sample 1-1 is obtained by extracting the molded body toward the right side of FIG. 9A. The right-side particle in each broken-line circle is the soft magnetic particle α, and the left adjacent particle is the soft magnetic particle. Let particle β. The same applies to FIG. The surface before laser irradiation is in a state where the thin film-like body formed on each particle α reaches the adjacent left-side particle β and becomes conductive, as shown by each broken-line circle. In particular, it is clear that the thin-film body (conduction part) is formed so that the rightmost particle α is stretched in a thin film shape and covered on the surface of the particle β on the left side in the place surrounded by the broken line circle on the right side. Is shown in Due to the partial overlap between the adjacent particles, almost no part of the thin film-like body is seen ((B) in the figure). In the surface after laser irradiation, as shown by each broken-line circle in FIG. 10A, the thin film-like body formed in each particle is melted and fluidized to form a divided region. For example, the surface of the left particle β in the right dashed circle is the segmented region. A split region is formed, and a lump (aggregation part) that protrudes so as to partially cover the upper surface of the adjacent particle β from the particle α is formed. A thick oxide film (dark gray portion) is formed on the aggregated portion, and an oxide film thinner than the aggregated portion is formed on the surface excluding the aggregated portion of the particles α having the aggregated portion. The core of the agglomerated part shown in the broken line circle on the left side remains in the state of the metal constituting the soft magnetic particles without being oxidized. And as shown to the same figure (B), the area | region of a thin film-like body is few compared with laser irradiation (FIG. 9 (B)), the part of a division | segmentation has increased, and it can confirm between each particle | grain.

[Sample No. 3-5]
As shown in FIG. 11A, the sample 3-5 has a thin film-like body (for example, a broken line circle in FIG. 9A) formed on the surface of the sample between adjacent particles. When irradiated, it melted and flowed to form an oxide film covering the surface of each particle. And the surface side between adjacent particles is in a non-contact state with each other, and a cleaved region is formed between the surface sides of adjacent particles. Further, as shown in FIG. 11B, the area of the thin film-like body is smaller than that of the sample 1-1, and the number of divided portions is increased, so that the space between the particles can be confirmed.

[Sample No. 3-6]
In Sample 3-6, as shown in FIG. 12A, a cleaved region is formed between adjacent particle surfaces on the sample surface, and an oxide film covering the surface of each particle is formed. Has been. In FIG. 12A, dark gray on the surface of the particles is an oxide film. The same applies to FIGS. 13 and 14 below. When a thin film-like body (for example, a broken line circle in FIG. 9A) formed between adjacent particles is irradiated with a laser, it is melted and flown as shown in the center particle in the figure. A central portion is formed of a thick oxide film that is thicker than both sides. In particular, the thickness of the oxide film formed on the particle surface on the left side of the figure is as thick as about 0.75 μm. In addition, as shown in FIG. 12B, the area of the thin film-like body is smaller than that of the sample 3-5, and the number of divided portions is increased.

[Sample No. 3-8]
In the sample 3-8, a thin film-like body (for example, a broken line circle in FIG. 9A) formed between adjacent particles is melted and fluidized by irradiation with a laser, and the sample 3-8 in FIG. As shown in Fig. 2), on the sample surface, a crevice-shaped segmented region is formed between the surface sides of adjacent particles, and the particles are concentrated on the center side of the particles and are composed of an oxide film that is thicker than both sides. Forming part. In particular, the thickness of the oxide film formed on the particle surface on the right side of the center of the figure is as thick as about 3.0 μm. Further, as shown in FIG. 13B, the area of the thin film-like body is smaller than that of the sample 3-6, and the number of divided portions is increased.

[Sample No. 3-9]
In Sample 3-9, a mountain-shaped oxide film (concentration part) is formed in the center of FIG. 14, and the thickness thereof is about 10 μm.

Prior to laser irradiation of sample 1-1, the insulating film on the surface of the molded body was damaged by rubbing with the mold in the molding process, and the soft magnetic particles were spread to cause conduction between the soft magnetic particles on the surface. It is considered that the portion is formed, and in Sample 1-1, the heat generated by irradiating the laser hardly diffuses in the conduction portion, and the high temperature state is easily maintained. As a result, it is considered that the conducting part was melted and divided. In Sample 1-1, the energy density U of the irradiated laser is smaller than that of the other samples, so that the thin film remains between the chunks, and an oxide film covering the outer periphery of the chunk is formed. It is thought. On the other hand, in Sample 3-5, the energy density U of the irradiated laser was 88.1 W / mm ² which was higher than that of Sample 1-1, and in Sample 3-6, the energy density U of the irradiated laser was 123. 6W / mm ² was higher than Sample 3-5, and Sample 3-8 was higher in energy density U of the irradiated laser than 290.8 W / mm ² and Sample 3-6, The lump formed in Sample 1-1 and the thin film-like body remaining between the lump in Sample 1-1 were also oxidized. As a result, it is considered that an oxide film covering the surface was formed. In particular, the higher the energy density, the easier the high temperature state of the thin film body is maintained and the thin film body is further melted. The constituent material of the molten thin film is aggregated due to surface tension, and the surface area tends to be reduced. As a result, it is considered that the thickness of the oxide film at the center has increased.

[Summary]
As the energy density U of the laser is higher, the conduction part is more likely to be divided. In addition, it has been found that the area of the oxide film covering the surface of each particle can be increased, and a portion having a thick oxide film can be provided.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.

  The manufacturing method of this invention compacting body can be utilized suitably for preparation of various magnetic cores. Further, the green compact of the present invention can be suitably used as a core material for a transformer or a choke coil in addition to a booster circuit such as a hybrid vehicle or a reactor used in power generation / transforming equipment. The reactor of the present invention can be used for components of power conversion devices such as DC-DC converters and air conditioner converters mounted on vehicles such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, and fuel cell vehicles.

DESCRIPTION OF SYMBOLS 100 Reactor 1 Compacting body 10 Material molding 2 Coil 2a, 2b Coil element 2r Connecting part 2w Winding 3 Magnetic core (core for reactor)
31 Inner core portion 31m Core piece 31g Gap material 32 Exposed core portion 31p Pressure surface 31s, 31so, 31sp Sliding contact surface 1100 Power conversion device 1110 Converter 1111 Switching element 1112 Drive circuit L reactor 1120 Inverter 1150 Power supply device converter 1160 Auxiliary power supply Converter 1200 Vehicle 1210 Main battery 1220 Motor 1230 Sub battery 1240 Auxiliaries 1250 Wheel

Claims (22)

A compacted body formed by pressure-molding a coated soft magnetic powder comprising a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating coating,
Comprising an oxide film containing iron on at least a part of the surface of the green compact,
Powder compacting, wherein the content of oxygen is 9% by mass or more and 20% by mass or less when the total content of iron and oxygen in the surface portion of the portion having the oxide film is 100% by mass body.   Furthermore, the surface of the said compacting body provides the location where oxygen content is less than 6 mass%, The compacting body of Claim 1 characterized by the above-mentioned.   The green compact according to claim 1 or 2, wherein the oxide film has a portion having a thickness of 0.1 µm or more. At least part of the surface of the green compact, a divided region that electrically separates adjacent soft magnetic particles, and
In the surface of the soft magnetic particle adjacent to the segmented region, the central portion includes a concentrating portion formed of an oxide film having a thickness larger than that of the outer peripheral edge without crossing between adjacent particles. The compacting body of any one of Claims 1-3. At least part of the surface of the green compact, a divided region that electrically separates adjacent soft magnetic particles, and
On the surface of the soft magnetic particle adjacent to the segmented region, it protrudes to the outer peripheral edge side of the soft magnetic particle, and comprises a locally thick aggregated portion,
The compacted article according to any one of claims 1 to 4, wherein the oxide film is provided on at least a part of the agglomerated part.   The green compact according to claim 5, wherein the oxide film in the agglomerated portion includes a portion having a thickness of 0.5 μm or more. The pressure according to claim 1, wherein the oxide film includes at least one of FeO, α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ , and Fe ₃ O _4. Powder molded body. The density d of the said compacting body is 7.0 g / cm < ³ > or more, The compacting body of any one of Claims 1-7 characterized by the above-mentioned.   The green compact according to any one of claims 1 to 8, wherein the soft magnetic particles are made of iron having a purity of 99% by mass or more. A method for producing a green compact using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles each having an insulating film coated on the outer periphery of the soft magnetic particles,
A material preparation step of preparing a material molded body obtained by pressure-molding the coated soft magnetic powder;
And a step of irradiating at least a part of the surface of the material molded body with a laser.   The said irradiation process irradiates a laser to at least one part of the slidable contact surface with the metal mold | die in the said raw material molded object, The manufacturing method of the compacting body of Claim 10 characterized by the above-mentioned.   The said irradiating step irradiates a surface of a material molded body that becomes at least a part of a plane parallel to a magnetic flux direction when the powder compacted body is excited as a magnetic core. The manufacturing method of the compacting body of description.   The said compacting body of the compacting body of Claim 12 which irradiates a laser to the surface of the raw material molding body used as the area | region covering the magnetic flux direction full length of the said compacting body in the said parallel surface. Production method. Said laser, producing a green compact according to any one of claims 10 to 13, wherein the YAG laser, YVO ₄ laser, and is a type of laser chosen from fiber laser Method.   The method for producing a green compact according to any one of claims 10 to 14, wherein a wavelength of the laser is a wavelength absorption region of the soft magnetic particles. When the average output of the laser is P (W) and the irradiation area of the laser is S (mm ² ), the energy density U (W / mm ² ) = P / S of the laser is 37.0 ≦ U ≦ 450.0 is satisfied, The manufacturing method of the compacting body of any one of Claims 10-15 characterized by the above-mentioned.   The method of manufacturing a green compact according to any one of claims 10 to 16, wherein a ratio of an irradiation interval to a beam diameter of the laser is 0.35 or less.   The method for producing a green compact according to any one of claims 10 to 17, wherein the number of times the laser is overlapped is 5 or more.   A green compact formed by the method for manufacturing a green compact according to any one of claims 10 to 18. A reactor comprising a coil formed by winding a winding and a magnetic core disposed inside and outside the coil to form a closed magnetic path,
At least a part of the magnetic core consists of a green compact,
The said compacting body is a compacting body of any one of Claims 1-9 and Claim 19, The reactor characterized by the above-mentioned. A converter comprising a switching element, a drive circuit that controls the operation of the switching element, and a reactor that smoothes the switching operation, and converts the input voltage by the operation of the switching element,
The converter according to claim 20, wherein the reactor is a reactor according to claim 20. A converter for converting an input voltage, and an inverter connected to the converter for converting between direct current and alternating current, and for driving a load with electric power converted by the inverter,
The power converter according to claim 21, wherein the converter is the converter according to claim 21.