JP2013201394A - Split magnetic core and method of molding dust core for split magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of molding a dust core for a split magnetic core that suppresses iron loss W.SOLUTION: A molding die comprises: a fixed die 10 having a through hole 11 forming a side face of a dust core; a movable die 20 fitted slidably in the through hole 11 of the fixed die 10 to form a die hole of its side face 21 and the through hole 11 of the fixed die 10, the side face 21 forming an end face crossing a magnetic path; a lower punch 30 fitted slidably in the die hole, an upper end surface thereof forming a lower surface of the dust core; and an upper punch 40 fitted slidably in the die hole, a lower end surface thereof forming an upper surface of the dust core. The molding die is used, material powder P is charged in a cavity formed of the die hole and the upper end surface of the lower punch 30, and the charged material powder P is pressed with the upper punch 40 and the lower punch 30 to be formed by compression. The lower punch 30 and the movable die 20 are synchronously elevated relatively to the fixed die 10 to extract a compression-molded body C from the die hole.

Description

  The present invention relates to a divided magnetic core in which a plurality of powder magnetic cores formed by compression molding magnetic powder are combined in a predetermined shape and a method for forming a powder magnetic core for a divided magnetic core.

  In recent years, development of low-emission vehicles such as fuel cell vehicles, electric vehicles, and hybrid vehicles has been promoted. In particular, hybrid vehicles are becoming increasingly popular in Japan and overseas. In such a hybrid vehicle or the like, when the voltage of the battery is lowered to the voltage for the electrical component or when the motor or the like is controlled by an inverter, conversion from a direct current to a high frequency alternating current power supply is performed via a switching power supply or the like. Done.

  In the circuit of the switching power supply as described above, a reactor including a magnetic core and a coil wound around the magnetic core is provided. As the performance of the reactor, in addition to being small in size, low loss and low noise, it is required to have stable inductance characteristics in a wide DC current range, that is, excellent in DC superimposition characteristics. Therefore, the core for the reactor is preferably a magnetic core that has a low iron loss and a stable permeability without decreasing the differential magnetic permeability from a low magnetic field to a high magnetic field, that is, a magnetic core having excellent constant magnetic permeability.

  In general, a reactor magnetic core is made of a silicon steel plate, but since it is a material with high magnetic permeability, the magnetic flux density is saturated on the high magnetic field side, and the differential magnetic permeability, which is the slope of the tangent to the magnetization curve, is reduced. . In order to apply such a magnetic core inferior to the constant magnetic permeability to the reactor, the magnetic core is divided into a plurality of divided cores, and the gap is adjusted so as to obtain a constant magnetic permeability by suppressing saturation of the magnetic flux density. .

  However, the silicon steel sheet is hard because it contains silicon that hardens iron to improve eddy current loss, and is difficult to bend. For this reason, in the case of a general magnetic core, a silicon steel sheet must be punched and produced by stacking the punched silicon steel sheets, and the moldability is poor. When manufacturing a reactor with such a silicon steel plate having poor workability, a silicon steel plate is wound around a core material to produce a wound iron core, and the wound silicon steel plate is bonded by welding or the like, and then cut into a plurality of It requires a large number of steps such as fine processing for adjusting the cut surface and adjusting the dimensions. In addition, since the silicon steel sheet has high magnetic permeability, it is necessary to increase the gap when forming a split core with a gap formed in the middle of the magnetic path. This will increase the size of the reactor and reactor.

  For this reason, in recent years, the application of powder magnetic cores produced by compression-molding soft magnetic metal powder such as iron has been advanced. Compared with a laminated magnetic core made of a silicon steel plate or the like, the dust core has a good material yield at the time of production and can reduce the material cost. In addition, the degree of freedom in shape is high, and it is possible to improve the characteristics by optimal design of the magnetic core shape. Furthermore, by mixing the metal powder with an electrical insulation material such as organic resin or inorganic powder, or by coating the surface of the metal powder with an electrical insulation coating, the electrical insulation between the metal powders is improved, thereby improving the vortex of the magnetic core. The current loss can be greatly reduced, and excellent magnetic properties can be obtained particularly in the high frequency range. Because of these characteristics, dust cores are attracting attention as reactor cores (Patent Documents 1, 2, etc.).

JP 2004-146804 A International Publication WO2011 / 118774

When used as a magnetic core for general without the dust core to form a gap in the middle of the magnetic path, the electrical insulating film formed on the metal powder surface is effectively functioning, greatly reduce the eddy current loss W _e of the magnetic core and it is possible to suppress lowering the iron loss W, when forming the divided cores forming a gap in the middle of the magnetic path increases the eddy current loss W _e is resulted a phenomenon that iron loss W are increased.

The iron loss W is the sum of the eddy current loss W _e and the hysteresis loss W _h . The eddy current loss W _e is expressed by the following formula 1, and the hysteresis loss W _h is expressed by the following formula 2, so the iron loss W is expressed by the following formula 3 As shown. Here, f is a frequency, B _m is an exciting magnetic flux density, ρ is a specific resistance value, t is a thickness of the material, and k ₁ and k ₂ are coefficients.

As these numbers 1-3 clear, eddy current loss W _e increases in proportion to the square of the frequency f, especially since the reactor is used in a high frequency range, the case of such a application, iron to reduce the losses W is essential suppression of eddy current loss W _e.

Accordingly, the present invention, when constituting the divided split core in the middle of the magnetic path in the dust core, by reducing the eddy current loss W _e, as well as providing a split magnetic core that suppresses the iron loss W, split core An object of the present invention is to provide a method for forming a dust core suitable for use.

  The split magnetic core of the present invention is divided in the middle of the magnetic path, and in the split magnetic core configured by combining a plurality of dust cores having end faces that cross the magnetic path, the surface of each of the dust cores is insulation-coated. After filling the raw material powder with the soft magnetic powder as a main raw material into the die hole and compression molding with a pair of upper and lower punches, the resulting molded body is molded by extracting from the die hole, It is characterized by comprising a dust core extracted from the die hole without rubbing the end face with the die hole. In the present invention, “rubbing” means that marks remain when members are rubbed against each other. In addition, “sliding” used in the following description means that the members rub against each other but no trace remains.

  In addition, the method for forming a powder magnetic core for a divided magnetic core according to the present invention comprises a powder magnetic core for a divided magnetic core configured by combining a plurality of powder magnetic cores having end faces that are divided in the middle of the magnetic path and intersect the magnetic path. A method for forming a powder magnetic core for at least one of the divided magnetic cores, comprising: a fixed die having a through hole forming a side surface adjacent to an end surface of the powder magnetic core; and a slidably fitted in the through hole of the fixed die The side surface and the through hole of the fixed die form a mold hole, the side surface is slidably fitted into the mold hole, and the upper end surface of the dust core is Using a molding die consisting of a lower punch that forms the lower surface and an upper punch that slidably fits in the mold hole and whose lower end surface forms the upper surface of the dust core, Soft magnetic powder whose surface is insulated and coated in the cavity formed from the end face The raw powder filled with the upper punch and the lower punch is pressed and compression molded, and the lower punch and the movable die are synchronized to rise relative to the fixed die. The body is extracted from the mold cavity.

  In the method of molding a powder magnetic core for a split magnetic core according to the present invention, a movable die and a lower punch are integrated to form an upper surface of a step portion that forms the lower surface of the powder magnetic core and an end surface that intersects the magnetic path of the powder magnetic core. A stepped lower punch having a corner side surface to be used may be used, and the molding die may include a core rod that forms the inner peripheral side surface of the dust core. Further, the movable die may include two side surfaces that form two end surfaces that cross the magnetic path of the dust core.

Since the split magnetic core of the present invention is composed of the dust core extracted from the die hole without rubbing the die end hole crossing the magnetic path, there is no damage to the insulating coating due to rubbing, can be eddy current loss W _e is a lower split core of iron loss W is suppressed. Further, in the method for forming a powder magnetic core for a split magnetic core according to the present invention, the powder magnetic core can be extracted from the die hole without rubbing the end face crossing the magnetic path with the die hole of the die. Therefore, plastic flow does not occur on the end face crossing the magnetic path, and the molding can be performed in a good state in which the insulating coating is maintained, which is suitable for molding the dust core constituting the split magnetic core.

It is a perspective view which shows one Embodiment of a division | segmentation magnetic core. It is the schematic which shows the general shaping die which shape | molds a side core. It is the schematic explaining the shaping | molding process at the time of using the general shaping die shown in FIG. 2, (a) is a filling stage, (b) is a compression stage, (c) is an extraction stage, (d) is a drawing stage. The schematic diagram which shows the structure | tissue of the side part surface of the extracted molded object, (e) is a SEM photograph of the side part surface of the extracted molded object. It is the schematic which shows the shaping die used in 1st Embodiment of this invention, (a) is a perspective view of each of a fixed die, a movable die, a lower punch, and an upper punch, (b) is a fixed die, The cross-sectional perspective view fractured | ruptured with the broken line in (a) at the time of combining a movable die, (c) is the top view. It is the schematic explaining the operation | movement state of each part in the AA 'line cross section of FIG.4 (c) for demonstrating the shaping | molding method of 1st Embodiment of this invention, (a) is a filling step, (b). Is a diagram showing a compression stage, and (c) is a drawing showing an extraction stage. It is a SEM photograph which shows the surface of the end surface crossing with respect to the magnetic path of the powder magnetic core shape | molded by the shaping | molding method of the powder magnetic core for division | segmentation magnetic cores of this invention. It is the schematic which shows the shaping die used in 2nd Embodiment of this invention, (a) is a perspective view of each of a fixed die, a stepped lower punch, and an upper punch, (b) is a fixed die and a step. The cross-sectional perspective view which fractured | ruptured with the broken line in (a) at the time of combining a subordinate punch, (c) is a top view of a fixed die. It is the schematic explaining the operation | movement state of each part in the AA 'line cross section of FIG.7 (c) for demonstrating the shaping | molding method of 2nd Embodiment of this invention, (a) is a filling step, (b ) Is the compression stage, and (c) is the drawing stage. FIG. 6 is a plan view of a fixed die 10 which is a modification of the embodiment of the present invention. It is the other modification of embodiment of this invention, (a) is a top view of a division | segmentation magnetic core, (b) is a perspective view of the magnetic core which comprises a division | segmentation magnetic core, (c) is shaping | molding which shape | molds the magnetic core of (b). It is a top view of a metal mold | die. It is the example which applied embodiment of this invention to shaping | molding of the middle core which comprises a division | segmentation magnetic core, (a) is a perspective view of the middle core shown in FIG. 1, (b) is the molding die which shape | molds the magnetic core of (a). Plan views (c) to (e) are cross-sectional views of the molding die taken along the line BB 'in (b). It is the schematic for demonstrating the shape of the middle core which comprises a division | segmentation magnetic core, and the shaping die which shape | molds a middle core, (a) is a perspective view of the middle core shown in FIG. 1, (b) is shaping | molding for shape | molding a middle core. It is a perspective view of each of the die | dye which comprises a metal mold | die, a lower punch, and an upper punch.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a split magnetic core 100 according to an embodiment. The split magnetic core 100 shown in this figure is configured by arranging a plurality of substantially rectangular middle cores 120 between a pair of substantially U-shaped side cores 110 having an outer peripheral surface (side surface) 112 and an inner peripheral surface (side surface) 113. Yes. Here, the end surface 121 (shaded portion) of the middle core 120 is disposed opposite to the end surface 111 (shaded portion) of the side core 110 or the end surface 121 of the adjacent middle core 120 to form a closed circuit. The magnetic path passes through the end faces 111 and 121 of each magnetic core to form a closed magnetic path. For this reason, the end surface 111 of the side core 110 and the end surface 121 of the middle core 120 serve as end surfaces that cross the magnetic path.

  Hereinafter, a method of forming the side core 110 and the middle core 120 of the split magnetic core 100 with a dust core will be described by taking the side core 110 as an example.

  The dust core constituting the side core 110 is generally molded using a molding die shown in FIG. 2A is a plan view of the die 10 that is a part of the molding die, and FIG. 2B is a perspective view of the die 10, the lower punch 30, and the upper punch 40. FIG. This molding die includes a die 10 having a through hole (die hole) 11 that forms an outer shape of the side core 110 (an outer peripheral surface 112, an inner peripheral surface 113, and an end surface 111 that crosses the magnetic path), and the side core 110. The lower punch 30 has an upper end surface 31 that forms the lower end surface, and the upper punch 40 has a lower end surface 41 that forms the upper end surface of the side core 110.

  It has been found that the eddy current loss increases in the split magnetic core using the dust core formed by using such a mold as the side core 110. When the present inventors examined the cause, the following knowledge was obtained.

  That is, the dust core constituting the side core 110 is formed in the cavity formed by the through hole 11 of the die 10 and the upper end surface 31 of the lower punch 30 as shown in FIG. The raw material powder P mainly composed of the soft magnetic powder whose surface is insulated and coated is filled (FIG. 3A), and the raw material powder P filled by the upper punch 40 and the lower punch 30 is pressed and compression molded. After (FIG. 3B), the molded body C is molded by being extracted from the through hole 11 of the die 10 and taken out (FIG. 3C).

  In such a molding process, as shown in FIG. 3B, the raw material powder P is compression-molded under the pressure of the upper punch 40 and the lower punch 30 at the time of compression molding. Inside C, a pressure is generated to expand the inner peripheral surface of the through hole 11. As shown in FIG. 3C, when the molded body C in which pressure to expand on the inner peripheral surface side of the through hole 11 is thus extracted from the through hole 11 of the die 10, The outer periphery of C receives friction due to the pressure of this expansion. As a result, as shown in FIG. 3 (d), the inside of the molded body C maintains the insulation coating I formed on the surface of the soft magnetic powder MP and ensures electrical insulation. The surface is plastically flowed and the insulating coating I formed on the surface of the soft magnetic powder MP is peeled off, and the soft magnetic powder MPs are connected to each other.

An SEM photograph of the outer peripheral surface of the dust core C molded as described above is shown in FIG. As shown in this photograph, the outer peripheral surface of the dust core C is formed with scratch marks with the through-holes 11 of the die 10, and the soft magnetic powder MPs are plastically flowed and connected to each other. I understand. Thus, when and if the soft magnetic powder MP is connected by plastic flow, when used as a reactor, a large eddy current is generated in the connection portion, it is believed that eddy current loss W _e is increased .

However, when a dust core is applied to a magnetic core that does not form a gap in the middle of the magnetic path, for example, even in a ring-shaped dust core, plastic flow occurs in the outer peripheral portion in the same manner as described above. The eddy current loss We does not increase as in the case where the magnetic core is applied. When both are compared, in the ring-shaped dust core, there is no end face crossing the magnetic path, whereas in the split magnetic core, there is an end face crossing the magnetic path. Therefore, the electrical insulation peeled off the insulation coating of the end surface transverse to the magnetic path is lost is considered to cause an increase in eddy current loss W _e. Therefore, by etching only the end faces 111 and 121 that cross the magnetic path of the dust core produced by molding as described above, the soft magnetic powder MP that is plastically flowed and connected to the surface layer is removed, and the split magnetic core is formed. was constructed, it was confirmed that the increase of eddy current loss W _e does not occur.

As described above, when a dust core is applied to the split magnetic core, the end surfaces 111 and 121 crossing the magnetic path are not removed from the through-hole 11 of the die 10 and the dust core is extracted from the through-hole 11 of the die 10. If configured, the end faces 111 and 121 traversing the magnetic paths of the respective powder magnetic cores are not formed with scratch marks of the through-holes 11 of the die 10 and become end faces in which the insulation coating is maintained, and the eddy current loss We is _reduced . It has been found that a split magnetic core with reduced iron loss W can be provided.

  FIG. 4 shows a molding die according to the first embodiment of the present invention that can be extracted from the through-hole of the die without rubbing the end face crossing the magnetic path as described above without rubbing with the through-hole of the die. 4A is a perspective view of the fixed die 10, the movable die 20, the lower punch 30 and the upper punch 40 constituting the molding die, and FIG. 4B is a view when the fixed die 10 and the movable die 20 are combined ( The cross-sectional perspective view fractured | ruptured with the broken line in a), (c) is the top view.

  A through-hole 11 is formed in the fixed die 10 from the upper surface to the lower surface. The through hole 11 forms an outer shape excluding the end surface 111 that traverses the magnetic path of the dust core having the shape of the side core 110, that is, the outer peripheral surface 112 and the inner peripheral surface 113, and corresponds to the shape of the side core 110. Thus, it is substantially U-shaped. Further, unlike the die 10 in the general molding die shown in FIG. 2, the through-hole 11 is movable to a position corresponding to the end surface 111 crossing the magnetic path of the dust core having the shape of the side core 110. An extra space for accommodating the die 20 is provided.

  The movable die 20 has a side surface 21 that forms an end surface that traverses the magnetic path of the dust core having the shape of the side core 110, and in the surplus space provided in the through hole 11 of the fixed die 10. It is fitted so as to be slidable in the vertical direction. By combining the fixed die 10 and the movable die 20 as described above, a mold hole for forming the outer shape of the dust core having the shape of the side core 110 is formed by the through hole 11 of the fixed die 10 and the side surface 21 of the movable die 20. To do. Note that there are two end faces 111 that cross the magnetic path of the side core 110, and the side faces 21 that form these may be configured by two separate movable dies 20, and are integrated at the bottom as shown in FIG. May be configured.

  The lower punch 30 and the upper punch 40 are each slidably fitted into a mold hole formed by the through hole 11 of the fixed die 10 and the side surface 21 of the movable die 20, and the side core 110 is formed at the upper end surface 31 of the lower punch 30. The lower end surface of the dust core having the shape is formed, and the upper end surface of the dust core having the shape of the side core 110 is formed by the lower end surface 41 of the upper punch 40, respectively. The shapes of the lower punch 30 and the upper punch 40 are the same as those of the general mold apparatus shown in FIG.

  A molding method using a molding die comprising the fixed die 10, the movable die 20, the lower punch 30, and the upper punch 40 will be described with reference to FIG. FIG. 5 is a cross-sectional view taken along line A-A ′ of the molding die shown in FIG. First, as shown in FIG. 5A, the movable die 20 is fitted into the through hole 11 of the fixed die 10, and a mold hole is formed by the through hole 11 of the fixed die and the side surface 21 of the movable die 20, The lower punch 30 is fitted into this mold hole. In this state, a raw material whose main raw material is a soft magnetic powder whose surface is insulation-coated in a cavity formed by the through hole 11 of the fixed die, the side surface 21 of the movable die 20, and the upper end surface 31 of the lower punch 30 Fill with powder P.

  Next, as shown in FIG. 5 (b), the upper punch 40 is lowered and the fixed die 10 is lowered to raise the lower punch 30 relative to the fixed die 10. 41 and the upper end surface 31 of the lower punch 30 press and compress the raw material powder P filled in the cavity. At this time, the movable die 20 is driven by the movable die driving means 22 such as a fluid pressure cylinder or a servo motor so as to move down in conjunction with the lowering of the fixed die 10.

  When the forming is completed, as shown in FIG. 5C, the upper punch 40 is raised and retracted, and the lower die 30 is further lowered relative to the fixed die 10 by further lowering the fixed die 10. Then, the molding formed from the through hole 11 of the fixed die 10 is extracted. At this time, the movable die 20 is raised relative to the fixed die 10 in synchronization with the lower punch 30. In the state shown in FIG. 5B, the lower punch 30 does not move and the fixed die 10 is lowered, so that the lower punch 30 is raised relative to the fixed die 10, so that the movable die 20 is also moved to the lower punch. If it is immovable like 30, the movable die 20 rises relative to the fixed die 10 in synchronization with the lower punch 30. In the molded body (powder magnetic core) C having the shape of the side core 111 extracted in this way, the end surface 111 crossing the magnetic path is formed by the side surface 21 of the movable die 20, and the magnetic path is crossed when extracted. The molded body C is extracted without the end surface 111 to be scraped against the side surface 21 of the movable die 20. For this reason, the end surface 111 crossing the magnetic path does not generate plastic flow as in the prior art, and as shown in FIG. 6, the insulating coating is maintained in a good state.

  The operating condition of the molding die is based on the withdrawal method that is common in the powder metallurgy method, but the lower punch 30 and the movable die 20 may be driven with the fixed die 10 fixed. In the above, as shown in FIG. 5B, the movable die 20 is lowered in conjunction with the lowering of the fixed die 10 in the molding stage, but the movable die 20 and the lower punch 30 are completely synchronized. That is, it may be immovable in FIG.

  Next, a molding die for carrying out the second embodiment of the present invention is shown in FIG. 7A is a perspective view of each of the fixed die 10, the lower punch 32, and the upper punch 40 constituting the molding die, and FIG. 7B is a view in (a) when the fixed die 10 and the lower punch 32 are combined. The cross-sectional perspective view fractured | ruptured with the broken line, (c) is the top view. In the molding die of the second embodiment of the present invention, the movable die 20 and the lower punch 30 in the molding die of the first embodiment of the present invention are integrated into a stepped lower punch 32. In the second embodiment, the fixed die 10 and the upper punch 40 are the same as those in the first embodiment.

  The stepped lower punch 32 has a stepped portion upper surface 33 corresponding to the upper end surface 31 of the lower punch 30 of the first embodiment. Moreover, it has the corner | angular part (horn) part 34 equivalent to the movable punch 20 of 1st Embodiment, and the corner | angular part 34 is slidable in the surplus space provided in the through-hole 11 of the fixed die 10. It is mated. The side surface 35 of the corner portion 34 corresponds to the side surface 21 of the movable punch 20 of the first embodiment, and forms an end surface 111 that crosses the magnetic path.

  A molding method using the molding die of the second embodiment will be described with reference to FIG. FIG. 8 is a cross-sectional view taken along line A-A ′ of the molding die shown in FIG. First, as shown in FIG. 8A, the stepped lower punch 32 is fitted into the through hole 11 of the fixed die 10, and the through hole 11 of the fixed die 10 and the side surface 35 of the corner portion 34 of the lower punch 32. Then, a cavity is formed by the stepped upper surface 33 of the stepped lower punch 32, and a raw material powder P whose main material is soft magnetic powder whose surface is insulated and coated is filled in the cavity.

  Next, as shown in FIG. 8 (b), the upper punch 40 is lowered and the fixed die 10 is lowered to raise the stepped lower punch 32 relative to the fixed die 10. The raw material powder P filled in the cavity is pressed and compressed by the lower end surface 41 and the stepped upper surface 33 of the stepped lower punch 32. As a result, the outer peripheral surface 112 and the inner peripheral surface 113 of the dust core having the shape of the side core 110 are used as the through holes 11 of the fixed die 10, and the end surface 111 crossing the magnetic path of the dust core is used as the stepped lower punch 32. At the side surface 35 of the corner portion 34, the lower end surface of the dust core is formed by the stepped upper surface 33 of the stepped lower punch 32, and the upper end surface of the dust core is formed by the lower end surface 41 of the upper punch 40.

  When the forming is completed, as shown in FIG. 8C, the upper punch 40 is raised and retracted, and the fixed die 10 is further lowered to bring the stepped lower punch 32 relative to the fixed die 10. Further, the molded body (powder magnetic core) C formed from the through hole 11 of the fixed die 10 is extracted. In the molded body C having the shape of the side core 110 extracted in this way, the end surface 111 crossing the magnetic path is formed by the side surface 35 of the corner portion 34 of the stepped lower punch 32, and the magnetic path is The transverse end face 111 is extracted without rubbing against the side face 35. For this reason, the end surface 111 crossing the magnetic path does not generate plastic flow as in the conventional case, and is in a good state in which the insulation coating is maintained.

  FIG. 9 shows a modification of the molding die of the present invention for molding a dust core having the shape of the side core 110. 9A shows a change in the shape of the movable die 20 shown in FIG. 4 (or the corner 34 of the stepped lower punch 32 shown in FIG. 7), and the side surface 21 of the movable die 20 (or the stepped lower punch 32). This is an example in which the inner peripheral surface 113 is formed together with the end surface 111 crossing the magnetic path of the dust core having the shape of the side core 110 at the side surface 35) of the corner portion 34.

  FIG. 9B shows the side surface 21 (or stepped lower punch 32) of the movable die 20 (or the corner 34 of the stepped lower punch 32) integrated with the end surface 111 that crosses the magnetic path of the two side cores 110. In this example, the inner peripheral surface 113 of the side core 110 is formed by the outer peripheral surface 51 of the core rod 50 by arranging the core rod 50.

  The above is an example of the shape of the side core 110 shown in FIG. 1 as a dust core for a split magnetic core. However, the method for forming a dust core for a split magnetic core according to the present invention is not limited to this shape. Is also applicable. An example in which the shape of such a dust core is changed is shown in FIG. FIG. 10A is a plan view showing the configuration of the split magnetic core. In this divided magnetic core, the middle core 120 is the same as the divided magnetic core shown in FIG. 8, but instead of the side core 110 shown in FIG. 1, a side core 130 obtained by dividing the middle core 120 into two is used. As shown in FIG. 10B, the side core 130 has two end faces 131 that cross the magnetic path arranged so as to be substantially perpendicular to each other.

  An example of a molding die for molding the powder magnetic core having the shape of the side core 130 is shown in FIG. The fixed die 10 forms an outer peripheral surface 132 and an inner peripheral surface 133 of the dust core having the shape of the side core 130, and an excess space for accommodating the movable die 20 (or the corner portion 34 of the stepped lower punch 32). It has the formed through hole 11. The movable die 20 (or the corner portion 34 of the stepped lower punch 32) is slidably fitted into this excess space, and the side surface 21 (or the corner portion 34 of the stepped lower punch 32) (or An end surface 131 that crosses the magnetic path of the dust core having the shape of the side core 130 is formed by the side surface 35) of the corner portion 34 of the stepped lower punch 32. When molding is performed as described above using such a molding die, the end surface 131 that crosses the magnetic path can be extracted from the through-hole 11 of the fixed die 10 without rubbing against the fixed die 10, and the magnetic path In the end surface 131 that crosses the surface, the conventional plastic flow does not occur, and the insulating coating is maintained in a good state.

  Here, when molding the dust core having the shape of the middle core 120, in FIG. 10C, the movable dies 20 (or the corners 34 of the stepped lower punch 32) are arranged to face each other and face each other. You may form the end surface 121 which cross | intersects the magnetic path of a powder magnetic core by a surface. That is, as shown in FIG. 11A, end surfaces 121 crossing the magnetic path of the dust core of the middle core 120 face opposite sides, and the end surfaces 121 are extracted without rubbing against the fixed die 10. As shown in FIG. 11B, the movable dies 20 (or the corners 34 of the stepped lower punch 32) are arranged to face each other. In this case, as shown in FIG. 11C, both end surfaces 121 of the middle core 120 facing opposite to each other may be formed by the side surface 21 of the movable die 20. 11D, one end surface 121 of the middle core 120 is formed by the side surface 21 of the movable die 20, and the other end surface 121 is formed by the side surface 35 of the corner portion 34 of the stepped lower punch 32. You may make it shape | mold. Further, as shown in FIG. 11 (e), two corner portions 34 are formed opposite to the stepped lower punch 32, and the end surface 121 of the middle core 120 is formed by the side surfaces 35 of the opposed corner portions 34. May be. In these embodiments, the end surface 121 that crosses the magnetic path of the dust core of the middle core 120 is extracted in a state protected by the corner portion 34 of the movable die 20 or the stepped lower punch 32. Large plastic flow is prevented. However, the molded body extracted from the die 10 is sandwiched between the opposing movable die 20 and / or the corner 34 of the stepped lower punch 32. When this is taken out, there is a possibility that rubbing will occur although it is very slight.

  When molding a dust core having the shape of the middle core 120 while preventing such slight rubbing, a general molding die is used and the end surface 121 crossing the magnetic path of the middle core 120 is used as a punch surface. What is necessary is just to shape | mold. That is, the middle core 120 in FIG. 1 has a rectangular parallelepiped shape having end faces 121 that traverse parallel magnetic paths, and a pair of parallel magnetic paths as shown in FIG. , And a pair of upper surfaces (122) and a lower surface (123), and a pair of side surfaces (124) adjacent to the end surface 121 that crosses the pair of magnetic paths. Here, as shown in FIG. 12B, the shape of the through hole (mold hole) 11 of the die 10 is a rectangle composed of an upper surface, a lower surface, and a pair of side surfaces adjacent to the end surface 121 crossing the magnetic path. These surfaces are formed by the through holes 11 of the die 10, and the end surface 121 that crosses the magnetic path of the middle core 120 is formed by the lower end surface 41 of the upper punch 40 and the upper end surface 31 of the lower punch 30 to form a rectangular compact. Mold the magnetic core. At this time, the upper surface, the lower surface, and the pair of side surfaces adjacent to the end surface 121 that traverses the magnetic path undergo friction during extraction and cause plastic flow, but cross the opposing magnetic path formed by the upper punch and the lower punch. Since the end face 121 is not subjected to friction during extraction, plastic flow does not occur and the insulating coating is maintained in a good state.

As described above, the divided magnetic cores configured by combining a plurality of dust cores that are divided in the middle of the magnetic path and have end faces that cross the magnetic path are all arranged so that the end faces that cross the magnetic path are parallel and opposite to each other. In the case where the powder core is not divided magnetic core (for example, when the middle core 120 is not provided), all the powder magnetic cores for the divided core are molded according to the present invention using the molding die described above. In all of the powder magnetic cores for divided magnetic cores, the end face 121 crossing the opposing magnetic path is not subjected to friction during extraction, so that plastic flow does not occur and the insulation coating is maintained. since it a state, by reducing the eddy current loss W _e, can be divided magnetic core that suppresses the iron loss W.

In addition, a split magnetic core configured by combining a plurality of dust cores that are divided in the middle of the magnetic path and have end faces that cross the magnetic path is divided so that the end faces that cross the magnetic path are parallel and opposite to each other. In the case of including a magnetic core for a magnetic core, the other powder magnetic core for a divided magnetic core, i.e., a powder magnetic core for a divided magnetic core whose end faces crossing the magnetic path are not arranged in parallel and facing each other, For the powder magnetic core for a split magnetic core in which the end surfaces crossing the magnetic path are arranged in parallel and facing each other, the end surface crossing the magnetic path is formed as a punch surface. , the end face 121 transverse to the magnetic path is also facing this case, since not subject to friction during extraction, does not occur plastic flow, it is possible to a satisfactory state where the insulating coating is maintained, reducing the eddy current loss W _e And reduced iron loss W A split magnetic core can be used.

  The split magnetic core of the present invention can be used as a reactor used in a voltage boosting circuit, a high voltage circuit, or a conversion circuit from a direct current to a high frequency alternating current, for example, in an electric vehicle or a hybrid vehicle.

DESCRIPTION OF SYMBOLS 10 ... Fixed die 11 ... Through hole of fixed die 20 ... Movable die 21 ... Side surface of movable die 30 ... Lower punch 31 ... Upper end surface of lower punch 32 ... Lower punch with step 33 ... Upper surface of step with lower step with step 34 ... Corner part of stepped lower punch 35 ... Side face of corner part of stepped lower punch 40 ... Upper punch 41 ... Lower end face of upper punch 100 ... Divided core 110 ... Side core 111 ... End face transverse to magnetic path of side core 120 ... Middle core 121 ... End face crossing the magnetic path of the middle core 130 ... Side core 131 ... End face crossing the magnetic path of the side core

Claims (5)

In a split magnetic core configured by combining a plurality of dust cores having end faces that are divided in the middle of the magnetic path and intersect the magnetic path,
Each dust core is filled with a raw material powder mainly composed of a soft magnetic powder whose surface is insulated and coated in a die hole and compression-molded with a pair of upper and lower punches. The mold core is formed by being extracted from the mold hole, and is configured by a dust core extracted from the mold hole of the die without rubbing the end surface with the mold hole of the die. Split magnetic core. A method of forming a powder magnetic core for at least one divided magnetic core among powder magnetic cores for a divided magnetic core, which is configured by combining a plurality of powder magnetic cores divided in the middle of a magnetic path and having end faces that cross the magnetic path. There,
A fixed die having a through hole forming a side surface adjacent to the end surface of the dust core;
A movable die that is slidably fitted into the through hole of the fixed die, forms a mold hole with the side surface and the through hole, and the side surface forms the end surface;
A lower punch that is slidably fitted into the mold hole and whose upper end surface forms the lower surface of the dust core;
Using a molding die that is slidably fitted into the mold hole, and whose lower end surface forms an upper surface of the dust core,
Filling the cavity formed from the mold hole and the upper end surface of the lower punch with raw material powder whose main raw material is soft magnetic powder whose surface is insulated,
Press and compress the raw material powder filled with the upper punch and the lower punch,
A method for forming a powder magnetic core for a split magnetic core, wherein the lower punch and the movable die are synchronized with each other, and a molded body that is raised relative to the fixed die and is compression-molded is extracted from the mold hole.   A stepped lower punch having a stepped upper surface that forms the lower surface of the dust core by integrating the movable die and the lower punch, and a corner side surface that forms the end surface that intersects the magnetic path of the dust core. The method for forming a powder magnetic core for a split magnetic core according to claim 2, wherein the method is used.   The method for molding a powder magnetic core for a split magnetic core according to claim 2 or 3, wherein the molding die includes a core rod that forms an inner peripheral side surface of the powder magnetic core.   The movable die has two side surfaces forming the two end faces traversing the magnetic path of the dust core, and the dust for a split magnetic core according to any one of claims 2 to 4 Magnetic core forming method.

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