JP5195891B2 - Reactor core, reactor, and reactor manufacturing method - Google Patents

Description

  The present invention relates to a core, a reactor, and a reactor manufacturing method in which coils are arranged on the outer periphery and used for a reactor. In particular, the present invention relates to a reactor core that can reduce the size of the reactor and reduce the amount of coil used.

  In recent years, hybrid vehicles have been put into practical use from the viewpoint of protecting the global environment. A hybrid vehicle is a vehicle that includes an engine and a motor as drive sources and travels using one or both of them. Such a hybrid vehicle converts the direct current of the battery into alternating current with an inverter, and supplies the alternating current to a motor for traveling. Modern hybrid vehicles include a boost converter to reduce the size of the battery and motor. This converter has the role of boosting the voltage of the battery and supplying it to the inverter (motor), and the role of reducing the regenerative current from the generator (motor) to the battery voltage and charging the battery. One of the components of this converter is a reactor that can store electrical energy as magnetic energy.

  The reactor includes a core formed by laminating magnetic materials, typically silicon steel plates called electromagnetic steel plates, and a coil disposed on the outer periphery of the core. The core is typically an annular core formed by combining a plurality of divided pieces. Since silicon steel generally has a high relative permeability, a core made of an electromagnetic steel sheet is likely to be magnetically saturated. Therefore, in order to make it difficult for magnetic saturation, gaps (air gaps) are provided between divided pieces, or gap materials are provided.

  However, if there is a gap, there is a problem that noise and leakage magnetic flux are generated due to the gap. In order to solve this problem, Patent Document 1 does not use a high-permeability silicon steel sheet, but produces a split piece with a low magnetic permeability powder magnetic material and joins the split pieces with an adhesive to form an annular ring structure. Proposing the core.

  Patent Document 2 proposes a reactor in which a coil is embedded in a core made of a dust magnetic material. This reactor is manufactured by putting a powdery magnetic powder material and a coil into a mold and press-molding to form an integral core having a gapless structure and arranging the coil in the core. The integrated core covers a cylindrical inner core portion located inside the coil, a cylindrical outer core portion located outside the coil so as to cover the outer peripheral surface of the coil, and both ends of the coil, It is comprised from a pair of disk-shaped connection core part which connects a core part and an outer core part.

JP 2006-344868 JP 2006-210465 JP

  Since the reactor described in the cited document 2 is almost entirely covered with the core, the magnetic flux generated by the coil is less likely to leak to the outside of the core compared to the reactor including the annular core. Thus, the magnetic flux can be used efficiently. However, this reactor may use a large amount of coil.

  The powder magnetic material can be made to have a lower relative magnetic permeability than a silicon steel sheet by adjusting the ratio of the magnetic material. Therefore, a core having a low relative permeability can be formed using a magnetic material having a low magnetic permeability. Here, a core made of a magnetic material having a low magnetic permeability tends to have a low saturation magnetic flux density. The magnetic flux passing through the core is represented by the product of the magnetic flux density of the core and the cross-sectional area of the core. Therefore, when the core is formed of a magnetic material having a low magnetic permeability, it is necessary to increase the cross-sectional area of the core in order to obtain the same magnetic flux as that of a core made of a high magnetic permeability magnetic material such as a silicon steel plate. When the cross-sectional area of the core, particularly the cross-sectional area of the inner core portion where the coil is arranged, is increased, the length of the coil is increased per turn and the usage amount is increased. Increasing the amount of coil used is not preferable because loss (for example, copper loss) at the coil portion tends to increase. Further, a reactor mounted on a hybrid vehicle or the like is desired to be downsized in order to reduce the installation space, and an increase in the size of the reactor due to an increase in the cross-sectional area of the core is not preferable.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a reactor core capable of reducing the size of the reactor and reducing the amount of coil used. Another object of the present invention is to provide a reactor including the core and a method for manufacturing the reactor.

  The inventors of the present invention have studied a configuration that does not have a gap and can reduce the cross-sectional area of the core in the reactor core that includes the inner core portion, the outer core portion, and the connecting core portion. As a result, the present inventors have completed the present invention by obtaining the knowledge that instead of forming the entire core with a uniform magnetic material, the saturation magnetic flux density may be partially different. It came to.

  The reactor core of the present invention is a core used in a reactor mounted on a hybrid vehicle or an electric vehicle, and includes an inner core portion, an outer core portion, and a connecting core portion, and each core portion is integrated without a gap. Configured. The inner core portion is a portion arranged inside the coil constituting the reactor, the outer core portion is a portion arranged outside the coil, and the connecting core portion covers both ends of the coil, It is a part which connects an inner core part and an outer core part. And the saturation magnetic flux density of the inner core part is 1.7 T or more and 1.2 times or more of the saturation magnetic flux density of the outer core part and the connecting core part, and the average permeability of the entire reactor core is a relative permeability. The relative permeability of the inner core portion is 50 or more, and the relative permeability of the outer core portion and the connecting core portion is 3 or more and 50 or less. The reactor core of the present invention is a core having the same shape as the reactor core, and the core has an average magnetic permeability equal to that of the reactor core and a uniform saturation magnetic flux density. When the same magnetic flux as that of the comparison core is obtained when the comparison core is used, the entire core is smaller than the comparison core because the cross-sectional area of the inner core portion is smaller than the inner core portion of the comparison core.

  Since the reactor core according to the present invention has a gapless structure integrated without a gap, problems of noise and leakage magnetic flux due to the existence of the gap do not substantially occur. In addition, since the leakage magnetic flux hardly occurs, the core of the present invention can arrange the coil closer to the core than the core having a gap, that is, the interval between the coil and the core can be reduced, and the outer dimension of the reactor can be reduced. Can be small. Since the reactor in the constituent members of the above-described boost converter occupies a considerably large volume, the downsizing of the reactor is expected to greatly contribute to the reduction of the converter installation space.

  The core of the present invention has a structure in which the saturation magnetic flux density is partially different, specifically, the saturation magnetic flux density of the inner core portion arranged inside the coil is high, and the saturation magnetic flux density of the outer core portion and the connecting core portion. Is low. In addition, the core of the present invention has a relatively low relative permeability of the outer core portion and the connecting core portion, and the average permeability (effective permeability) of the entire core of the present invention is relatively low. In order to realize such characteristics, the core of the present invention is not entirely composed of a uniform magnetic material, but is partially composed of different magnetic materials. The core of the present invention having such a configuration obtains the same magnetic flux as a core of the same shape made of a magnetic material having a uniform low magnetic permeability as a whole (this core has a uniform saturation magnetic flux density). In this case, the cross-sectional area of the inner core portion can be reduced. That is, the core of the present invention can obtain a large magnetic flux even if the cross-sectional area of the inner core portion is reduced. Moreover, since the cross-sectional area of the inner core portion is small, the length per turn of the coil disposed on the outer periphery thereof can be shortened. Therefore, the reactor including the core of the present invention can reduce the amount of coil used, and problems such as an increase in loss accompanying an increase in the amount of coil used are unlikely to occur. Furthermore, since the cross-sectional area of the inner core portion is small, the core of the present invention can be made small, and the reactor of the present invention including the core of the present invention can also be reduced in size.

Hereinafter, the present invention will be described in more detail.
The core of the present invention is a magnetic member in which a closed magnetic path is formed when a coil disposed on the outer periphery thereof is excited, and an inner core portion, an outer core portion, and a pair of connecting core portions are integrated. Examples of such an integral core include a pot-type core having a columnar inner core portion, a cylindrical outer core portion, and a plate-like connecting core portion. Since the pot type core can substantially cover the entire surface of the coil, the reactor including this core can not only efficiently use the magnetic flux generated by the coil, but also the magnetic flux is difficult to leak out of the core. The influence of leakage magnetic flux in peripheral equipment can be reduced. In addition, a reactor having a pot-type core can directly or indirectly contact almost the entire surface of the coil with the core, and therefore can efficiently transfer the heat of the coil generated by energization to the core, and has excellent heat dissipation. .

  The core of the present invention can be obtained, for example, by forming a plurality of divided pieces and joining the divided pieces with a fastening member such as an adhesive or a bolt. Various divisions are possible for the divided pieces. For example, each of the inner core portion, the outer core portion, and the connecting core portion may be divided pieces. In addition, the inner core portion and one connecting core portion are composed of an integral divided piece, and the outer core portion and the other connecting core portion are composed of an integral divided piece, and the outer core portion is divided into two, Examples include a configuration in which one outer core piece and one connecting core portion include an integrated divided piece, and the other outer core piece and the other connecting core portion include an integrated divided piece. An epoxy adhesive or the like can be used as the adhesive.

  When the split pieces are joined together with an adhesive, the adhesive is interposed at the joint location of the split pieces. The adhesive is usually non-magnetic, but the adhesive here is not a gap material for adjusting the inductance of the reactor, but merely for joining the divided pieces. Therefore, even if an adhesive exists between the divided pieces in the core of the present invention, it is integrated without a gap.

  Alternatively, the core of the present invention can be manufactured by using a magnetic material that can be integrally molded. For example, when the core of the present invention is a compacted body, the core of the present invention and the coil are prepared by filling the molding die with a magnetic powder material so as to have desired characteristics and arranging and pressing the coil. Can be manufactured. When this manufacturing method is used, the formation of an integral core having a gapless structure and the placement of the coil on the core can be performed simultaneously, and the connection work using an adhesive or an adhesive is unnecessary.

  When the core of the present invention is used as a green compact, it is possible to easily form a desired three-dimensionally divided piece or integral core, and adjust the materials and manufacturing conditions so as to have the desired characteristics as described above. Thus, the core of the present invention can be obtained.

  As another form of an outer core part and a connection core part, a sintered compact and the shaping | molding hardening body of resin are mentioned. The molded and hardened body is obtained by molding a mixture of magnetic powder and fluid resin and curing the resin of the obtained molded body. Even in the case of using these sintered bodies and molded cured bodies, it is possible to easily form a desired three-dimensional segment. The outer core portion and the connecting core portion may be the same material or different materials.

  As another form of the inner core portion, a laminate formed by laminating electromagnetic steel sheets can be mentioned. By using an electromagnetic steel sheet, an inner core part having a high saturation magnetic flux density can be easily formed.

  The core of the present invention has a gapless structure as described above. However, if the entire core is made of a low magnetic material having a uniform relative magnetic permeability in order to obtain a gapless structure, the cross-sectional area of the inner core portion increases as described above. Therefore, in the core of the present invention, the outer core portion and the connecting core portion are made of a magnetic material having a relatively low relative permeability, and the inner core portion is made of a magnetic material that increases the saturation magnetic flux density. It is preferable to select a magnetic material so that the overall average magnetic permeability (effective magnetic permeability) is relatively low. Specifically, the average permeability of the entire core of the present invention is 5 to 50 in terms of relative permeability.

The inner core portion is made of a high permeability material having a relative permeability of 50 or more, and the outer core portion and the connecting core portion are made of a material having a lower relative permeability than the inner core portion. When the material is composed of a low permeability material of 3 or more and 50 or less, the average permeability of the entire core of the present invention can be set to 5 to 50 in terms of relative permeability. Moreover, it is preferable that the whole outer core part and the whole connection core part are comprised from the magnetic material of uniform relative magnetic permeability. The outer core portion or the connecting core portion may be composed of a low permeability material in the above range so that the relative permeability of a part thereof is small and the relative permeability of the remaining portion is large. A magnetic material having a relative magnetic permeability is preferable because the magnetic flux passes through the core portion uniformly. The relative permeability μ _r is the ratio μ / μ ₀ between the material permeability μ and the vacuum permeability μ ₀ (vacuum permeability μ ₀ = 4π × 10 ⁻⁷ H / m). Moreover, the relative magnetic permeability of the electromagnetic steel sheet is about 4000 to 8000. If the entire core is made of such a high magnetic permeability material, it is difficult to form a gapless structure.

  In order to adjust the relative magnetic permeability of the magnetic material constituting the outer core portion and the connecting core portion within the above range, the following method may be mentioned. In any case, the relative permeability of the material can be adjusted according to the size of the core portion.

<For compacted compact>
When the outer core portion and the connecting core portion are formed of a compacted body, usually, a soft magnetic powder having an insulating coating on the surface and a binder resin are mixed, and after molding the mixed powder, the heat resistance temperature of the insulating coating or lower is reached. Bake with. And the relative magnetic permeability can be adjusted by adjusting the mixing ratio of the soft magnetic powder and the binder resin. Specifically, by increasing the blending amount of the binder resin, the ratio of the magnetic material (soft magnetic powder) to the cross section through which the magnetic flux passes in the core portion is reduced. A small percentage of the magnetic material results in a low saturation magnetic flux density. In addition, the relative magnetic permeability of the material constituting the core portion can be adjusted by changing the pressure at the time of forming the mixed powder. There is a tendency that the relative permeability of the core portion is lower when the amount of the binder resin is larger or when the molding pressure of the mixed powder is lower. Unlike a sintered body, which will be described later, in the green compact, a binder resin remains after firing, and the soft magnetic powders are insulated from each other by this resin. Therefore, the core part which consists of a compacting body can reduce an eddy current loss compared with the core part which consists of a sintered compact when it uses for a reactor, and is suitable for use when a high frequency is supplied with a coil.

  Soft magnetic powder is Fe group metal powder such as Fe, Co, Ni, Fe-based alloy powder such as Fe-Si, Fe-Ni, Fe-Al, Fe-Co, Fe-Cr, Fe-Si-Al, Or rare earth metal powder, ferrite powder, etc. can be used. Examples of a method for producing such a powder include an atomizing method (gas or water) and a mechanical grinding method. In particular, when a powder made of a nanocrystalline material whose crystals are nano-sized, preferably a powder made of an anisotropic nanocrystalline material, a core portion having high anisotropy and low coercive force can be obtained. The insulating coating formed on the soft magnetic powder is preferably composed of a phosphoric acid compound, a silicon compound, a zirconium compound or a boron compound. The binder resin preferably uses a thermoplastic resin, a non-thermoplastic resin, or a higher fatty acid.

<For sintered body>
When the outer core portion and the connecting core portion are made into a sintered body, a mixed powder of nonmagnetic powder and binder resin and soft magnetic powder are usually mixed, and the mixed powder is molded and then sintered at a high temperature. During sintering, the binder resin almost disappears and the soft magnetic powder and the nonmagnetic powder are sintered. Therefore, by adjusting the mixing ratio of the soft magnetic powder and the nonmagnetic powder, a core portion made of a low magnetic permeability material can be obtained as in the case of the above-described powder compact. In addition, the relative permeability of the core portion can be adjusted by changing the pressure at the time of forming the mixed powder. There is a tendency that the relative permeability of the core portion can be lowered when the blending amount of the nonmagnetic powder is large or when the molding pressure of the mixed powder is low.

As the soft magnetic powder, iron group metal powder, Fe-based alloy powder, rare earth metal powder, ferrite powder or the like can be used as in the above compacted body. The nonmagnetic powder can be based on a single element such as Cu, Al, Si, or a compound such as Al ₂ O ₃ or SiO ₂ . As the binder resin, a thermoplastic resin, a non-thermoplastic resin, or a higher fatty acid can be suitably used.

<In the case of molded hardened body>
In the case where the outer core portion and the connecting core portion are formed of a molded cured body, methods for obtaining the molded cured body include injection molding and cast molding. Injection molding usually involves mixing soft magnetic powder (mixed powder with non-magnetic powder added if necessary) and fluid binder resin, and pouring this mixed fluid into a mold under pressure. After molding, the binder resin is cured. On the other hand, in cast molding, after obtaining a fluid mixture similar to that of injection molding, the fluid mixture is injected into a mold without applying pressure to be molded and cured. In any molding technique, a thermosetting resin such as an epoxy resin, a phenol resin, or a silicone resin can be suitably used as the binder resin. When a thermosetting resin is used as the binder resin, the molded body is heated to thermoset the resin. A normal temperature curable resin or a low temperature curable resin may be used as the binder resin. In this case, the molded body is allowed to stand at a normal temperature to a relatively low temperature to be cured. In addition, after injection molding, the molded body may be heat treated at a high temperature to sinter soft magnetic powders or soft magnetic powder and nonmagnetic powder (MIM: Metal Injection Molding). Even when using injection molding or cast molding, if not sintered, soft magnetic powder (non-magnetic powder) and binder resin are mixed, and when sintering, soft magnetic powder and non-magnetic powder The relative magnetic permeability of the constituent material of the core part can be adjusted by changing the composition of. For example, when the blending amount of the soft magnetic powder is reduced, the relative permeability tends to decrease.

  On the other hand, in order to increase the saturation magnetic flux density of the inner core portion, for example, it is possible to use a high magnetic permeability material having a large relative magnetic permeability. For example, the inner core portion is formed using a magnetic steel sheet as described above. When the inner core portion is formed of a powder compact, it may be formed of a magnetic material having a relative magnetic permeability of 50 or more, particularly 300 to 500. At this time, contrary to the case of obtaining the outer core part and the connecting core part made of the low magnetic permeability material described above, the blending amount of the soft magnetic powder is increased in the mixed powder of the soft magnetic powder and the binder resin, or the mixed powder is molded. By increasing the pressure, the relative permeability of the inner core portion tends to be increased. In addition, it is preferable that the inner core portion is made of a magnetic material having a uniform relative permeability as a whole because the magnetic flux passes uniformly through the core portion.

  The saturation magnetic flux density of the inner core portion is set to 1.7 T or higher, and is 1.2 times higher than that of the outer core portion and the connecting core portion. If it is less than 1.2 times, the degree of reduction of the cross-sectional area of the inner core is small, and it is difficult to reduce the amount of coil used. Further, the saturation magnetic flux density of the inner core portion is preferably as high as possible, and is preferably 1.8 T or more, and particularly preferably 2.0 T or more.

  The core for reactor of the present invention can be suitably used as a reactor by arranging a coil on the outer periphery of the inner core portion. The coil is formed by winding a winding. The winding is typically composed of a metal wire having an insulating coating. The metal wire has various shapes such as a polygonal shape such as a quadrangle and a hexagon in addition to a circular cross-sectional shape, and any shape may be used. The shape of the coil is preferably in a form adapted to the outer shape of the inner core portion where the coil is disposed. The metal wire is preferably made of copper or copper alloy having high conductivity, and examples of the insulating coating include enamel.

  The coil is preferably fixed to the core of the present invention using an adhesive or the like in order to reduce noise caused by vibration of the coil when excited. For example, an epoxy resin or a urethane resin can be used as the adhesive.

  When the reactor in which the insulator is disposed at the portion where the core of the present invention and the coil are in contact is provided, the coil and the core of the present invention can be more reliably insulated, and even if a large current flows through the coil, the dielectric breakdown occurs. And generation of eddy currents can be prevented. Examples of the insulating material constituting the insulator include resins such as PPS (Poly Phenylene Sulfide) and LCP (Liquid Crystal Polymer). It is preferable to add an inorganic filler such as glass (silicon dioxide), alumina (aluminum oxide), or titanium oxide to such a resin to enhance the thermal conductivity so that the heat of the coil can be easily transferred to the core of the present invention. The amount of the inorganic filler added may be appropriately selected. It is preferable that this insulator is easily arranged in the core of the present invention when the divided pieces are combined and integrated.

The following manufacturing method is mentioned as a manufacturing method of the reactor which provides this invention core. A method for manufacturing a reactor according to the present invention is a method for manufacturing a reactor mounted on a hybrid vehicle or an electric vehicle, including a coil formed by winding a coil and a reactor core on which the coil is arranged. The process is provided.
(1) a coil, a columnar inner core portion disposed inside the coil, a hollow cylindrical outer core portion disposed outside the coil, an inner core portion covering both ends of the coil, and A step of preparing a pair of plate-like connecting core parts for connecting the outer core parts.
(2) A step of arranging the coil in the outer core portion.
(3) A step of positioning and joining the inner core portion to the one connecting core portion.
(4) A step of fitting the inner core portion inside the coil and joining one end surface of the outer core portion and the one connecting core portion.
(5) A step of joining the other end surface of the outer core portion and the other connecting core portion.
By the said process, the reactor with which each said core part was integrated without passing through a gap is manufactured.
However, the reactor core shall satisfy the following (I) to (IV).
(I) The saturation magnetic flux density of the inner core part is 1.7 T or more and 1.2 times or more of the saturation magnetic flux density of the outer core part and the connecting core part.
(II) The average permeability of the entire reactor core is 5 to 50 in terms of relative permeability.
(III) The relative permeability of the inner core portion is 50 or more, and the relative permeability of the outer core portion and the connecting core portion is 3 or more and 50 or less.
(IV) When the core having the same shape as the core for the reactor, the average permeability of the entire core is equal to the core for the reactor, and the core having the uniform saturation magnetic flux density is the comparison core, In the case where the same magnetic flux as that of the comparison core is obtained, the core for reactor is assumed to be smaller than the comparison core because the cross-sectional area of the inner core portion is smaller than the inner core portion of the comparison core.

  By using the reactor core of the present invention, the amount of coil used in the reactor can be reduced.

1 shows an example of a reactor including a reactor core according to the present invention, in which (A) is an external perspective view, (B) is a longitudinal sectional view, and (C) is a transverse sectional view. FIG. 2 is an exploded perspective view of the reactor of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Example 1)
FIG. 1 shows an example of a reactor having a pot-type reactor core, (A) is an external perspective view, (B) is a longitudinal sectional view, (C) is a transverse sectional view, and FIG. 2 is a view of the reactor. It is a disassembled perspective view. Reactor L has a cylindrical outer appearance, and includes a core 1 made of a magnetic material and a coil C disposed on the outer periphery of core 1. The core 1 includes a columnar inner core portion 11, a hollow cylindrical outer core portion 12, and a pair of disk-shaped connecting core portions 13.

  The inner core portion 11 is arranged inside the coil C, the outer core portion 12 is arranged outside the coil C so as to cover the outer peripheral surface of the coil C, and both the core portions 11 and 12 are arranged concentrically. ing. The connection core portion 13 covers both ends of the coil C, and includes an upper connection core portion 13u that covers one end side (the upper end side in FIGS. 1 and 2) and a lower connection core portion that covers the other end side (the same lower end side). It consists of 13d. The outer diameter of the outer core portion 12 and the outer diameters of both the connecting core portions 13u and 13d are substantially the same.

  Each of the core parts 11, 12, and 13 is a split piece that can be split. The core 1 has a gapless structure in which these divided pieces are joined together by an adhesive and integrated, and no gap is formed between the divided pieces. Each of these divided pieces is composed of a green compact.

  The core 1 is characterized in that the inner core portion 11 has a higher saturation magnetic flux density than the outer core portion 12 and the connecting core portion 13. In order to increase the saturation magnetic flux density, the inner core portion 11 is configured such that the ratio of the binder resin to the magnetic material powder is smaller than the same ratio in the outer core portion 12 and the connecting core portion 13, that is, the magnetic material powder increases. It is made like this. Therefore, the inner core portion 11 has a higher relative magnetic permeability than the outer core portion 12 and the connecting core portion 13, and as a result, the saturation magnetic flux density is also higher.

A procedure for assembling the reactor L using the core 1 composed of such divided pieces will be described.
As shown in FIG. 2, a coil C formed by winding a winding is prepared in advance, and the coil C is fitted inside the outer core portion 12. On the upper and lower end surfaces of the outer core portion 12, a notch 12c is formed for pulling out both end portions We of the windings constituting the coil C, and both ends We of the windings are fitted into the notches 12c. The coil C is positioned in the outer core portion 12. A coil C shown in FIG. 2 is formed by so-called edgewise winding of a rectangular metal winding having a rectangular cross section, and has a hollow cylindrical shape corresponding to the columnar inner core portion 11.

  Next, the inner core part 11 is positioned with respect to the connecting core part 13d so that the center of the lower connecting core part 13d and the center of the inner core part 11 coincide with each other, and both parts 13d and 11 are joined. As the coil C is fitted into the inner core part 11, the outer core part 12 fitted with the coil C is positioned and joined on the lower connecting core part 13d.

  Then, the upper connecting core portion 13u is joined to the upper end surface of the outer core portion 12 to form the core 1, and the coil C is accommodated in the core 1. Thus, a reactor L having a pot-shaped core 1 is obtained, and a closed magnetic path that returns to the inner core portion 11 through the inner core portion 11, the upper connecting core portion 13u, the outer core portion 12, and the lower connecting core portion 13d. Is formed. This closed magnetic circuit has no gap formed in the middle.

<Test example>
The core 1 and the comparison core were prepared so that the same magnetic flux was obtained in the core 1 with partially different saturation magnetic flux density and the core with uniform saturation magnetic flux density (hereinafter referred to as a comparison core). The size of the inner core part was compared. Here, all the cores were pot-shaped, and the material was adjusted so that the magnetic flux was equal as described above.

[Core 1]
Water atomized pure iron powder (average particle size of about 100 μm) is prepared as a soft magnetic powder, and polyethylene (powder) is prepared as a binder resin. The iron powder and polyethylene are mixed so that the resin amount ratio (the mass of the resin / the total mass of the resin and the iron powder) is 4%. This mixed powder is filled in a predetermined mold and molded at a molding pressure of 980 MPa. And a molded object is heat-processed at 250 degreeC x 60 minutes, and the outer core part which consists of a compacting body, and a pair of connection core part are obtained.

  On the other hand, by using a mixed powder obtained by mixing iron powder and polyethylene so that the resin amount ratio is 0.3%, molding and heat treatment are performed under the same conditions as described above to obtain an inner core portion made of a compacted body.

  When the relative permeability and saturation magnetic flux density of each of the obtained core parts were measured, the outer core part and the connecting core part had a relative magnetic permeability of 20, a saturation magnetic flux density of 0.95 T, and the inner core part had a relative magnetic permeability: 300, saturation magnetic flux density: 1.7 T (about 1.8 times the outer core portion and the connected core portion). The average magnetic permeability of the entire core 1 was 30 in terms of relative permeability. The relative permeability and saturation magnetic flux density were measured using a BH tracer manufactured by Riken Denshi Co., Ltd.

[Comparison core]
On the other hand, using a mixed powder in which iron powder and polyethylene are mixed so that the resin content ratio is 3%, molding and heat treatment are performed under the same conditions as above, and an inner core portion and an outer core made of a compacted body are formed. And a pair of connecting core parts. That is, each of these core portions is formed of a compacted body made of a material having the same resin amount ratio. With respect to this comparative core, the relative magnetic permeability and the saturation magnetic flux density were measured in the same manner as the core 1, and the relative magnetic permeability was 30 and the saturation magnetic flux density was 1.0T.

About the obtained core 1 and the comparative core, when comparing the cross-sectional area of the inner core portion 11 (the area of the circular surface shown in FIG. 1 (C)), the inner core portion 11 of the core 1 is 700 mm ² The inner core part of the core was 1000 mm ² . That is, the inner core portion 11 of the core 1 has a cross-sectional area that is approximately 30% smaller than the inner core portion of the comparative core.

  From the above, it can be seen that the core 1 including the inner core portion having a saturation magnetic flux density higher than that of the outer core portion and the connecting core portion can reduce the cross-sectional area of the inner core portion 11 as compared with the comparative core. Because the cross-sectional area of the inner core portion 11 is small, the coil disposed on the outer periphery of the inner core portion 11 of the core 1 has a longer length per turn than the coil disposed on the outer periphery of the inner core portion of the comparison core. Can be shortened. Therefore, the reactor L including the core 1 can reduce the amount of use of the coil as compared with the reactor including the comparison core, and loss due to an increase in the amount of use of the coil is less likely to occur. In addition, since the cross-sectional area of the inner core portion 11 is small, the core 1 can also be made small. Therefore, the reactor L including the core 1 can be made smaller than the reactor including the comparison core.

  Furthermore, since the reactor L including the core 1 has a gapless structure, problems of noise and leakage magnetic flux due to the existence of the gap do not substantially occur.

(Example 2)
In Example 1 described above, the configuration in which all of the inner core portion, the outer core portion, and the connecting core portion are formed of a green compact. Another embodiment includes a configuration in which the inner core portion is formed of a compacted body, and the outer core portion and the connecting core portion are formed of a sintered body. At this time, the material and manufacturing conditions of the sintered body are adjusted so that the saturation magnetic flux density of the inner core portion is higher than that of the outer core portion and the connecting core portion.

(Example 3)
Furthermore, as another embodiment, a configuration in which the inner core portion is made of a compacted molded body and the outer core portion and the connecting core portion are made of a resin-molded and cured body can be mentioned. At this time, the material and manufacturing conditions of the molded cured body are adjusted so that the saturation magnetic flux density of the inner core portion is higher than that of the outer core portion and the connecting core portion.

(Example 4)
Furthermore, as another embodiment, the inner core portion is made of a laminated body in which electromagnetic steel sheets are laminated, and the outer core portion and the connecting core portion are made of any one of a green compact, a sintered body, and a resin molded and hardened body. A configuration is mentioned. In general, an electromagnetic steel sheet tends to have a higher saturation magnetic flux density than any of a green compact, a sintered body, and a molded and hardened resin. Therefore, the outer core portion and the connecting core portion can be appropriately selected from a compacted body, a sintered body, and a molded and cured body of resin. In addition, since the magnetic steel sheet has a high relative permeability, the inner core portion of this embodiment has a smaller cross-sectional area than the above-described Examples 1 to 3 in which the inner core portion is formed of a green compact. can do.

  The above-described embodiments can be appropriately changed without departing from the gist of the present invention, and are not limited to the above-described configuration. For example, the resin amount ratio in Example 1 can be changed.

  The reactor core according to the present invention can be suitably used as a magnetic member of a reactor provided in a boost converter mounted on a hybrid vehicle or an electric vehicle. The reactor of the present invention can be suitably used for a reactor provided in a boost converter mounted on a hybrid vehicle or an electric vehicle. The manufacturing method of this invention reactor can be utilized for manufacture of the said reactor.

1 Reactor core 11 Inner core 12 Outer core 12c Notch
13 Connecting core part 13u Upper connecting core part 13d Lower connecting core part
L Reactor C Coil We End of coil

Claims (3)

A reactor core used in a reactor mounted on a hybrid vehicle or an electric vehicle,
This core
An inner core portion arranged inside the coil constituting the reactor, an outer core portion arranged outside the coil, and a connecting core portion that covers both ends of the coil and connects the inner core portion and the outer core portion. Each core part is integrated without a gap,
The saturation magnetic flux density of the inner core portion is 1.7 T or more, and 1.2 times or more of the saturation magnetic flux density of the outer core portion and the connecting core portion,
The average permeability of the reactor core as a whole is 5 to 50 in terms of relative permeability,
The relative permeability of the inner core part is 50 or more, and the relative permeability of the outer core part and the connecting core part is 3 or more and 50 or less,
When a core having the same shape as the reactor core, the average permeability of the entire core is equal to that of the reactor core and the saturation magnetic flux density of the entire core is uniform, the comparison core is used. When the same magnetic flux is obtained, the reactor core is characterized in that the cross-sectional area of the inner core portion is smaller than the inner core portion of the comparison core, so that the entire core is smaller than the comparison core.   2. A reactor comprising the reactor core according to claim 1, and a coil disposed on an outer periphery of the inner core portion. A reactor manufacturing method comprising a coil formed by winding a coil and a reactor core on which the coil is arranged, and manufacturing a reactor mounted on a hybrid vehicle or an electric vehicle,
A coil, a columnar inner core portion disposed inside the coil, a hollow cylindrical outer core portion disposed outside the coil, and an inner core portion and an outer core portion covering both ends of the coil Preparing a pair of plate-like connecting core portions for connecting
Disposing the coil on the outer core portion;
Positioning and joining the inner core portion to the one connecting core portion;
Fitting the inner core part inside the coil and joining one end surface of the outer core part and the one connecting core part;
Joining the other end surface of the outer core portion and the other connecting core portion,
A reactor manufacturing method, wherein the core unit is manufactured without an intervening gap.
However, the reactor core shall satisfy the following (1) to (4).
(1) The saturation magnetic flux density of the inner core part is 1.7 T or more and 1.2 times or more of the saturation magnetic flux density of the outer core part and the connecting core part.
(2) The average permeability of the entire reactor core is 5 to 50 in terms of relative permeability.
(3) The relative permeability of the inner core portion is 50 or more, and the relative permeability of the outer core portion and the connecting core portion is 3 or more and 50 or less.
(4) When the core having the same shape as the core for the reactor, the average permeability of the entire core is equal to the core for the reactor, and the core having a uniform saturation magnetic flux density is used as the comparison core, In the case where the same magnetic flux as that of the comparison core is obtained, the core for reactor is assumed to be smaller than the comparison core because the cross-sectional area of the inner core portion is smaller than the inner core portion of the comparison core.

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