JP2015228412A - Inductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductor element having little crack inside.SOLUTION: An inductor element includes: a coil (20) having a winding part (22) around which a conductor (20a) is wound in a coil shape and a lead part (24) pulled out from the winding part; a winding core body (30) having ferromagnetism, which supports winding of the conductor in the winding part; and an outer core part (40) which covers the winding part and the winding core body and is a compression molding body including a binder and magnetic powder. A recess (35) is formed on at least one of end surfaces (34a, 34b) in the axial direction of the winding core body.

Description

  The present invention relates to an inductor element in which a coil is embedded in a magnetic powder.

  As an inductor element, a surface-mount type inductor element used as a circuit element such as a DC / DC converter mounted on a personal computer or a portable electronic device is known.

  A conventional inductor element can be obtained, for example, by pressure-molding a powder containing a thermosetting resin as a binder and a magnetic powder as a powdery magnetic body with an air-core coil incorporated therein ( (See Patent Document 1). In addition, as another inductor element, a technique has been proposed in which a magnetic body having a higher permeability than the peripheral portion is arranged inside an air-core coil to aim at high inductance characteristics (see Patent Document 2, etc.).

JP 2010-10425 A JP 2003-168610 A

  However, in the method of manufacturing an inductor element in which a coil is incorporated in magnetic powder, it is difficult to uniformly pressurize the magnetic powder in the mold during pressure molding. For this reason, the conventional inductor element has a problem that a crack is generated particularly in an inner portion of the air-core coil, causing deterioration of characteristics. Moreover, in the prior art which embeds a magnetic body inside, there exists a problem which a layered crack arises on both sides of the compression direction adjacent to the said magnetic body.

  The present invention has been made in view of such a situation, and an object thereof is to provide an inductor element with few cracks.

In order to achieve the above object, an inductor element according to the present invention includes:
A coil having a winding portion in which a conductor is wound in a coil shape, and a lead portion drawn from the winding portion;
A ferromagnetic core that supports the winding of the conductor in the winding section;
An outer core part that covers the winding part and the core body and is a compression molded body containing a binder and magnetic powder;
A recess is formed on at least one end face in the axial direction of the core body.

  The inductor element according to the present invention does not use an air-core coil, but includes a ferromagnetic core body and a winding portion wound around the ferromagnetic core body in the outer core portion. Therefore, when pressure-molding the outer core portion, even if pressure transmission to the inner portion is hindered by the winding portion or the like, a winding core body that is separate from the outer core portion exists in this portion. Therefore, it is possible to prevent the occurrence of cracks in the inner part of the winding part. In addition, since the concave portion is formed on the end surface of the core body, the density distribution of the magnetic fluid that becomes the base point of the thin layered cracks on both sides in the compression direction adjacent to the core body when the outer core portion is pressed. Problems that are formed can be prevented. Thereby, the inductor element concerning this invention can prevent generation | occurrence | production of the layered crack in the both sides adjacent to a core body. In addition, since the concave portion is formed, the contact area between the core body and the outer core portion is increased, and the inductor element according to the present invention is excellent in adhesion and bonding between the core body and the outer core portion. Yes.

Further, for example, the winding core may be columnar, and may have an outer peripheral surface against which an inner peripheral surface of the winding portion is pressed,
The outer peripheral surface may be provided with irregularities along the shape of the inner peripheral surface of the winding portion.

  In the inductor element according to the present invention, the winding core body around which the winding portion is wound has little deformation or flow during pressure molding of the outer core portion, and the inner peripheral surface of the winding portion is the winding core body. Therefore, the winding shape is prevented from being disturbed during pressure molding, and an inductor element with less winding disturbance can be realized. In addition, the unevenness formed on the outer peripheral surface of the core increases the degree of adhesion between the inner peripheral surface of the winding and the outer peripheral surface of the core, and further reinforces the coupling between the core and the winding. To do.

  Further, for example, the core body may be a compression molded body including a magnetic powder different from the magnetic powder included in the binder and the outer core portion.

  By making the core body and the outer core portion into compression molded bodies containing different magnetic powders, it is possible to improve characteristics such as direct current superposition characteristics and oxidation resistance. Moreover, the problem that a clearance gap and a crack are formed between a core body and an outer core part can be prevented by making a core body into a compression molding body similarly to an outer core part.

  Further, for example, the winding portion may be disposed between the one end surface and the other end surface of the core body in the axial direction.

  Since the winding part is disposed between one end surface of the core body and the other end surface in the axial direction, the shape of the whole winding part is disturbed during pressure molding of the outer core part. It is possible to realize an inductor element that is prevented and has less winding disturbance.

Further, for example, the core body is a compression molded body containing magnetic powder,
The density of the magnetic powder in the core may be 4.5 to 7.0 g / cm ³ , and the density of the magnetic powder in the outer core may be 4.0 to 6.5 g / cm ^3. .

  By setting the density of the magnetic powder in the winding core and the outer core in the above range, an inductor element with few cracks and good electrical and magnetic characteristics can be realized.

  Further, for example, in the inductor element according to the present invention, a portion of the winding portion that is 50% or more of the entire axial length including the axial center position has a constant inner diameter where the inner diameter of the winding portion is constant. It may be a part.

  In the inductor element according to the present invention, the winding portion is wound around a winding core that is a separate body from the outer core portion. The constant inner diameter portion having a constant inner diameter occupies 50% or more of the entire winding portion, thereby suppressing variations in electrical characteristics.

FIG. 1 is an overall perspective view of an inductor element according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along the line II-II shown in FIG. FIG. 3 is a partially enlarged view of FIG. FIG. 4 is a flowchart showing the manufacturing process of the inductor element of the present invention. FIG. 5 is a conceptual diagram showing the manufacturing process of the inductor element of the present invention. FIG. 6 is a schematic perspective view of the core of the inductor element of the present invention. FIG. 7 is a plan view and a cross-sectional view illustrating a modified example of the core body. FIG. 8 is a schematic perspective view showing another modification of the core body.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
As shown in FIGS. 1 and 2, an inductor element 10 according to an embodiment of the present invention includes an outer core portion 40 that is a compression-molded body containing magnetic powder, and a winding core 30 that is built in the outer core portion 40. And the coil 20 having the winding part 22 incorporated in the outer core, and the terminal electrode 50 attached to the outer core part 40 and connected to the end of the lead part 24 of the coil 20.

  In the present embodiment, the lower surface of the outer core portion 40 is formed substantially parallel to a plane passing through the mutually perpendicular X axis and Y axis, and the winding axis of the winding portion 22 passes through the X axis and the Y axis. It is substantially parallel to the Z axis perpendicular to the plane. In the present embodiment, the upper surface of the outer core portion 40 is substantially parallel to the lower surface, and the side surface of the outer core portion 40 is substantially perpendicular to the upper surface and the lower surface. However, the outer shapes of the outer core portion 40 and the inductor element 10 are not particularly limited, and examples thereof include a hexahedron, a columnar shape, an elliptical column, and a polygonal column. it can.

  The size of the inductor element 10 of the present embodiment is not particularly limited. For example, the X-axis direction width is 1.0 to 20 mm, the Y-axis direction width is 1.0 to 20 mm, and the height is 1.0 to 10 mm.

  The inductor element 10 can be surface-mounted, and can be used as a circuit element such as a DC / DC converter mounted on a personal computer or a portable electronic device, for example.

  As shown in FIGS. 2 and 3, in the winding portion 22 of the coil 20, the conductor 20 a is wound around the outer peripheral surface 32 of the core body 30 in a coil shape. The lead part 24 is composed of a conductor 20 a drawn from the winding part 22. The conductor 20a is composed of, for example, a conductive wire and an insulating coating layer that covers the outer periphery of the conductive wire as necessary.

  As shown in FIG. 2, the winding portion 22 is a portion in which one or more conductors 20 a are wound in a coil shape. From the winding portion 22, at least a pair of lead portions 24 that are both ends of the conductor 20 a are provided. The outer core portion 40 is pulled out. In the illustrated embodiment, a pair of lead portions 24 are drawn from the winding portion 22 along the X-axis direction, and the tips of the lead portions 24 located outside the outer core portion 40 are on the outer surface of the outer core portion 40. It is bent along and connected to the pair of terminal electrodes 50. The leading end of the lead portion 24 is connected to the terminal electrode 50 by welding or a conductive adhesive. In the present embodiment, each terminal electrode 50 is made of a conductive plate material having a U-shaped cross-sectional shape, and is in close contact with and joined to the upper surface, the side surface, and the lower surface of the outer core portion 40.

  Since the winding part 22 is wound around the core body 30 which is a separate body from the outer core part 40, the winding part 22 is not disturbed despite being incorporated in the outer core part 40 which is a compression molded body. Few. In particular, it is preferable that a portion of the winding portion 22 that is 50% or more of the entire axial length L including the center position A in the winding axis direction is a constant inner diameter portion in which the inner diameter D of the winding portion 22 is constant. More preferably, the portion of 5% or more of the entire axial length L is a constant inner diameter portion. In the present specification, the constant inner diameter portion where the inner diameter D of the winding portion 22 is constant is a portion where the difference between the maximum value and the minimum value of the inner diameter D (twice the inner radius) is equal to or less than the diameter of the conductor 20a. Is defined as being.

  The conducting wire is made of, for example, Cu, Al, Fe, Ag, Au, phosphor bronze, or the like. The insulating coating layer is made of, for example, polyurethane, polyamideimide, polyimide, polyester, polyester-imide, polyester-nylon, or the like. The cross-sectional shape of the conductor 20a is not particularly limited, and examples thereof include a circular shape and a rectangular shape.

  As shown in FIG. 2, the core body 30 is disposed inside the winding portion 22. The winding core 30 supports the winding of the conductor 20 a in the winding portion 22. The winding core 30 is formed separately from the outer core portion 40 and has an outer peripheral surface 32 against which the inner peripheral surface 22a of the winding portion 22 is pressed. As shown in FIG. 6, the outer shape of the core body 30 is a cylindrical shape. However, the outer shape of the winding core 30 is not particularly limited as long as it is a columnar shape capable of forming the winding portion 22 by winding the conductor 20a, and may be another shape such as an elliptical columnar shape or a polygonal columnar shape. Moreover, you may provide C surface in a core body in order to reduce the crack of a corner | angular part of a core body, and a chip.

  As shown in FIGS. 2 and 6, the upper end surface 34 a and the lower end surface 34 b, which are end surfaces in the winding axis direction (Z-axis direction) of the core body 30, are located at the center of the upper end surface 34 a and the lower end surface 34 b. A recess 35 is formed. As shown in FIG. 7 (a), the recess 35 only needs to have a shape recessed toward the center of the core body 30, and the depth and size are not particularly limited. The length of the core body 30 in the winding axis direction can be about 1/4 to 1/40, and the opening diameter of the recess 35 can be about 30% to 80% of the diameter of the end faces 34a and 34b.

  As shown in FIG. 3, irregularities 32 a are formed on the outer peripheral surface 32 of the core body 30 along the shape of the inner peripheral surface 22 a of the winding portion 22. The height of the unevenness 32a (the radial length from the bottom of the concave portion closest to the central axis to the apex of the convex portion farthest from the central axis in the unevenness 32a) is not particularly limited, but is 1 of the diameter of the conductor 20a. It is about / 10 to 1/2. Since the irregularities 32 a are formed along the inner peripheral surface 22 a of the winding part 22, the outer peripheral surface 32 of the winding core 30 is in a state of biting into the inner peripheral surface 22 a of the winding part 22. As a result, the adhesiveness and bondability of the core body 30 are improved. In other drawings except FIG. 3, the irregularities 32a of the outer peripheral surface 32 are not shown because they have a detailed structure.

  As shown in FIG. 2, the winding portion 22 has a winding axis direction (Z-axis direction) from the upper end surface 34 a to the lower end surface 34 b in the winding axis direction (Z-axis direction) of the winding core 22. It is preferable to arrange | position between. Unlike the illustrated embodiment, when a part of the winding portion 22 exists above the upper end surface 34a or below the lower end surface 34b, the winding core 30 supports the conductor 20a in the radial direction for the portion. It is difficult. On the other hand, by arranging the winding part 22 between the upper end face 34a and the lower end face 34b as in the embodiment shown in FIG. The winding portion 22 is supported and functions as a winding core for the entire winding portion 22.

  The magnetic properties of the core 30 are ferromagnetic, and it is particularly preferable that the core 30 be a soft magnetic material suitable as a magnetic core material. The core body 30 of the embodiment is a compression-molded body including a binder and magnetic powder, and the magnetic powder is not particularly limited, but pure iron (Fe), Mn—Zn ferrite, Ni—Cu—Zn, and the like. Examples thereof include ferrites such as ferrite, sendust (Fe—Si—Al alloy), Fe—Si—Cr alloy, permalloy (Fe—Ni alloy), and the like. The binder is not particularly limited, and examples thereof include epoxy resins, phenol resins, polyimides, polyamide imides, silicon resins, and combinations thereof. Note that the materials illustrated may contain impurities within a range that satisfies the required characteristics.

  As shown in FIGS. 1 and 2, the outer core portion 40 covers the winding portion 22 and the core body 30 of the coil 20. On the upper surface and the lower surface of the outer core portion 40, electrode recesses for engaging the terminal electrodes 50 are formed at both ends.

  The outer core portion 40 is a compression-molded body including a binder and a magnetic powder, and the magnetic powder is not particularly limited, but ferrite, sendust (Fe-Si, etc.) such as Mn—Zn and Ni—Cu—Zn. -Al-based alloy), Fe-Si-Cr-based alloy, permalloy (Fe-Ni-based alloy) and the like. The binder is not particularly limited, and examples thereof include epoxy resins, phenol resins, polyimides, polyamide imides, silicon resins, and combinations thereof. The magnetic properties of the outer core portion 40 are ferromagnetic as in the core body 30, and are preferably soft magnetic materials suitable as magnetic core materials.

  The magnetic powder contained in the core body 30 and the magnetic powder contained in the outer core portion 40 may be the same or different. By including the magnetic powder different from the magnetic powder contained in the outer core portion 40, the core body 30 can adjust the characteristics of the core body 30 and the outer core portion 40 and improve the performance of the inductor element 10. . For example, by using pure iron as the magnetic powder contained in the core 30 and using an alloy containing Fe and Si as the magnetic powder contained in the outer core portion 40, the core loss of the inductor element 10 can be reduced and direct current superposition can be achieved. While improving a characteristic, oxidation resistance can be improved.

The density of the magnetic powder in the core 30 and the outer core 40 is not particularly limited. For example, the density of the magnetic powder in the core 30 is 4.5 to 7.0 g / cm ³ , and the outer The density of the magnetic powder in the core part 40 is preferably 4.0 to 6.5 g / cm ³ . By adjusting the density of the magnetic powder in the core body 30 and the outer core portion 40 to a predetermined range, the occurrence of cracks in the inductor element 10 can be prevented, the initial permeability can be increased, and the DC superposition characteristics can be improved. Is possible.

Next, a method for manufacturing the inductor element 10 shown in FIGS. 1 to 3 will be described with reference to FIGS.
FIG. 4 is a flowchart illustrating an example of a method for manufacturing the inductor element 10, and FIGS. 5A to 5E are conceptual diagrams illustrating the manufacturing method indicated by the flowchart. In step S01, a winding core for winding the conductor 20a is prepared. FIG. 5A shows a cross section of the core body 130 before curing, which is the core body prepared in step S01. The core body 130 before curing has substantially the same shape as that of the core body 30 after curing, except for the shape of the outer peripheral surface described later, and at the center of the upper end surface 134a and the lower end surface 134b, A recess 135 is formed. The core body 130 before being cured is obtained, for example, by pressure-molding granules composed of magnetic powder and a binder.

The magnetic powder contained in the granules used in the pressure forming (step S01) of the core body 130 is metal magnetic particles (preferably Fe particles), and the outer periphery of the particles is preferably coated with an insulating film. Examples of the insulating film include a metal oxide film and a resin film. The particle size of the magnetic powder is preferably 0.5 to 50 μm. The applied pressure when forming the core body 130 before curing is preferably 0.5 to 6 ton / cm ² (4.9 × 10 ^{1 to} 5.88 × 10 ² MPa) or less.

  The binder content in the magnetic powder is preferably about 2.0 to 5.0 parts by weight of the binder with respect to 100 parts by weight of the magnetic powder. In addition to the magnetic powder and binder, the granules may contain a solvent, a plasticizer, a lubricant, an antioxidant, a flame retardant, a heat stabilizer, and the like.

  In step S02, the conductor 20a is wound around the core body 130 before curing to form the coil 20 having the winding portion 22 and the lead portion 24 (FIG. 5B). The winding of the conductor 20a is started, for example, while pressing the conductor 20a against the outer peripheral surface of the core body 130. After forming the inner peripheral surface 22a of the winding portion 22, the conductor 20a is overlapped on the outer peripheral side as necessary. It progresses by winding. Note that when the coil 20 is formed in step S02 of the embodiment, the outer peripheral surface of the core body 130 is flat, and the unevenness 32a as shown in FIG. 3 is not formed.

  FIG.5 (c) is a schematic sectional drawing of the metal mold | die 160 in the state of step S03. As shown in FIGS. 5 (c) to 5 (e), the mold 160 of this embodiment includes a lower punch 162 and an upper punch 164 that are relatively movable up and down in the Z-axis direction that is the winding axis direction. Have A cavity is formed by combining the lower punch 162, the upper punch 164, and the outer frame.

  In step S03, the first filling of the granules 142 forming the outer core portion 40 is performed. In the first filling of the granules 142, as shown in FIG. 5C, a part of the total amount of the granules to be finally filled in the cavity is filled. Then, in step S04, the coil 20 having the winding core 22 wound around the core body 130 and the core body 130 before curing is placed inside the cavity.

  FIG.5 (d) is a schematic sectional drawing of the metal mold | die 160 in the state of step S05. In step S05, the second filling of the granules 142 forming the outer core portion 40 is performed. In the second filling of the granules 142, as shown in FIG. 5 (d), the remainder of the total amount of the granules to be filled in the cavity is filled.

  The granules 142 used in the first filling (step S03) and the second filling (step S05) are composed of the same magnetic powder and binder, and the type, particle size, structure, and content ratio of the magnetic powder are the same. The type and content of the binder are the same. The magnetic powder contained in the granule 142 is a metal magnetic particle (preferably an alloy particle containing Fe and Si), and the outer periphery of the particle is preferably coated with an insulating film. Examples of the insulating film include a metal oxide film and a resin film. The particle size of the magnetic powder is preferably 0.5 to 50 μm.

  The binder content in the magnetic powder is preferably about 2.0 to 5.0 parts by weight of the binder with respect to 100 parts by weight of the magnetic powder, as in the granule used in step S01. Further, the granules 142 may contain a solvent, a plasticizer, a lubricant, an antioxidant, a flame retardant, a heat stabilizer and the like in addition to the magnetic powder and the binder. However, the magnetic powder contained in the granules used for the core body 130 is preferably different from the magnetic powder contained in the granules 142 forming the outer core portion 40. For example, the magnetic powder contained in the core 130 can be pure iron powder, and the magnetic powder contained in the outer core portion 40 can be Fe-Si-Cr alloy powder.

In step S06 shown in FIG. 4, pressure molding with the mold 160 is performed. As shown in FIG. 5E, the upper and lower punches 162 and 164 are moved in directions close to each other to pressurize the inside of the cavity. The applied pressure in this case is preferably 4.0 ton / cm ² (3.92 × 10 ² MPa) or less.

  By the pressurization in step S06, the granules 142 are flowed and compressed, and are formed into the shape of the outer core portion 40. In addition, since the core body 130 is not completely cured at this stage, deformation and flow of constituent particles may occur due to the pressurization in step S06, whereby the core body 130 is cured on the outer peripheral surface. A concavo-convex shape to be the concavo-convex 32a later is formed. However, since the core body 130 before curing is press-molded in advance, the flow generated in the core body 130 is smaller than the flow of the granules 142 forming the outer core portion 40.

  Here, as shown in FIG. 5 (e), when a core body that is sufficiently less in flow than the granule 142 or that does not generally flow is disposed inside the mold, it is assumed that the core body has a recess. Is not formed, there is a problem that the density distribution of the magnetic fluid serving as the base point of the thin layered crack is formed between the end face of the core body and the punches 162 and 164 by pressure molding. In particular, when the distance from the upper and lower end surfaces of the core to the punches 162 and 164 is short, cracks are likely to occur in this portion. However, since the recesses 135 are formed in the end faces 134a and 134b of the core body 130 of the embodiment, the density distribution of the magnetic fluid between the end faces 134a and 134b and the punches 162 and 164 is perpendicular to the winding axis. It is hard to become constant along. As described above, in the concave portion 135 formed in the end surfaces 134a and 134b, a density distribution of the magnetic fluid serving as a base point of the thin layered crack is formed between the end surfaces 134a and 134b of the core body 130 and the punches 162 and 164. Can be prevented.

  In step S07 shown in FIG. 4, the molded body formed in step S06 is taken out from the mold 160, and heat treatment is performed. By the heat treatment in step S07, the binder contained in the core body 130 and the granules 142 is cured, and the core body 30 and the outer core portion 40 shown in FIG. 4 are formed.

  Thereafter, in step S08, the terminal element 50 shown in FIGS. 1 and 2 is attached to the outer core portion 40 and the lead portion 24 is connected to the terminal electrode 50, whereby the inductor element 10 shown in FIGS. Get. The connection between the lead portion 24 and the terminal electrode 50 can be performed by welding, bonding with a conductive adhesive, soldering, or the like, but is not particularly limited as long as it is a connection method that can ensure conduction.

  In the inductor element 10 described above, the coil 20 is formed by using a core body 130 that has been separately pressure-molded before being cured, and this is placed in the cavity and subjected to insert molding. The problem that the amount of compression of the core body 130 that occurs at the time of pressure forming (step S007) is small and the inner portion of the winding portion 22 is insufficiently pressurized is also solved. Therefore, the occurrence of cracks in the inner part of the winding part 22 can be prevented, and the inner peripheral surface 22a of the winding part 22 is supported by the outer peripheral surface 32 of the core body 30 with little deformation. Thus, it is possible to realize the inductor element 10 with less winding disturbance. In addition, the coil 20 is formed using the core body 130 before being cured, and the binder contained in the core body 30 is cured simultaneously with the curing of the binder contained in the outer core portion 40, whereby the core body is obtained. The generation of cracks at the interface between the outer core portion 40 and the outer core portion 40 can be prevented.

  Furthermore, since the recesses 35 and 135 are formed in the end faces 34a, 34b, 134a, and 134b of the core bodies 30 and 130, the outer core is located on both sides in the winding axis direction of the end faces 34a and 34b of the core body 30. A thin layered crack can be prevented from being formed in the portion 40. In addition, since the contact area between the core body 30 and the outer core portion 40 is increased by the concave portion 135, the inductor element 10 is excellent in adhesion and binding between the core body 30 and the outer core portion 40.

  Further, the inductor element 10 does not apply excessive pressure to the coiled conductor 20a existing inside the core, and the coiled conductor 20a is less likely to be crushed. Therefore, the insulation coating breakdown in the coiled conductor 20a is reduced. Is less likely to occur, and short circuit defects are less likely to occur. Furthermore, the unevenness 32a formed on the outer peripheral surface 32 of the core body 30 increases the degree of adhesion between the inner peripheral surface 22a of the winding part 22 and the outer peripheral surface 32 of the core body 30, and the core body 30 and the winding The connection with the portion 22 is reinforced.

  Furthermore, in the inductor element 10 obtained by the method of the present embodiment, the initial magnetic permeability and the direct current superposition characteristics are improved by setting the density of the magnetic powder of the winding core 30 and the outer core portion 40 within a predetermined range. be able to. The density of the magnetic powder in the core 30 and the outer core 40 is different in the particle size of the contained magnetic powder between the core 30 and the outer core 40, or the core 130 before curing is formed. By making the pressure at the time of (step S01) different from the pressure at the time of insert molding (step S06), it can be within an appropriate range.

  In the manufacturing method described above, a part of the whole amount of the granule 142 to be filled in the cavity is filled in the cavity, and then wound around the core 130 as an insert member and the inside of the mold 160. The coil 20 is placed and then the cavity is filled with granules 142. By filling the granule 142 into the cavity in this order, the insert member having the winding portion 22 and the core body 130 can be easily placed in the cavity without using a spacer, and the manufacturing cost can be reduced. Contribute.

The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
For example, in the above-described embodiment, the lower punch 162 and the upper punch 164 of the mold 160 are arranged vertically above and below the Z-axis direction, but horizontally or vertically and horizontally along the Z-axis direction. You may arrange | position in the angle direction between.

  In addition, the core body 130 before curing is subjected to drying or preliminary heat treatment after the pressure molding and before the coil 20 is formed, whereby the fluidity of the granules contained in the core body 130 is determined. May be adjusted. However, the heat treatment temperature (first temperature) for the core body 130 before curing before forming the coil 20 is preferably a temperature that does not completely cure the binder contained in the core body 130, for example, the outer core portion. It is preferable that the temperature is lower than the heat treatment temperature (second temperature) in forming 40 (step S07).

  In the above-described embodiment, the recesses 35 and 135 are formed on both end surfaces 34a, 34b, 134a, and 134b of the core body 30, but may be formed on only one of them. For example, when the core body 30 is disposed so as to be biased up or down from the center of the inductor element 10, the concave portion 35 may be formed only on the end surface in the direction in which the core body 30 is skewed. Furthermore, the shape of the recessed part formed in the end surface of a core is not limited to the shape dented in the shape of a truncated cone like the recessed part 35 shown to Fig.7 (a), It can be set as arbitrary shapes. For example, a concave shape like a concave portion 81 shown in FIG. 7B, a mortar shape like a concave portion 82 shown in FIG. 7C, or a concave portion 83 shown in FIG. Examples of such a shape are a pyramid shape or a conical shape.

  Moreover, although a recessed part may be arrange | positioned in the center part in the end surface of a core body, it may arrange | position a recessed part in positions other than the center of a core like the core bodies 85 and 88 shown in FIG. good. In the core body 85, two concave portions 87 are arranged along the diameter of the end face 86a. The two recesses 87 are arranged at a substantially equidistant position from the center of the end face 86a. In the core body 88, three concave portions are arranged at substantially equal intervals along the diameter of the end face 89a. Of the three recesses, the middle recess 90 is disposed at the center of the end face 89a.

  Further, the core body may be already cured at the time of coil formation, or may be formed by casting or processing other than the compression molded body.

DESCRIPTION OF SYMBOLS 10 ... Inductor element 20 ... Coil 20a ... Conductor 22 ... Winding part 24 ... Lead part 30 ... Core body 32 ... Outer peripheral surface 32a ... Concavity and convexity 35 ... Concavity

Claims (6)

A coil having a winding portion in which a conductor is wound in a coil shape, and a lead portion drawn from the winding portion;
A ferromagnetic core that supports the winding of the conductor in the winding section;
An outer core part that covers the winding part and the core body and is a compression molded body containing a binder and magnetic powder;
An inductor element, wherein a recess is formed on at least one end face in the axial direction of the core body. The winding core is columnar and has an outer peripheral surface against which an inner peripheral surface of the winding portion is pressed;
2. The inductor element according to claim 1, wherein the outer peripheral surface is provided with irregularities along the shape of the inner peripheral surface of the winding portion.   3. The inductor element according to claim 1, wherein the winding core is a compression-molded body including a magnetic powder different from the magnetic powder included in the binder and the outer core portion.   The said winding part is arrange | positioned between the said one end surface in the said core body from the other end surface regarding the axial direction, The Claim 1 characterized by the above-mentioned. Inductor element. The core body is a compression molded body containing magnetic powder,
The density of the magnetic powder in the core is 4.5 to 7.0 g / cm ³ , and the density of the magnetic powder in the outer core is 4.0 to 6.5 g / cm ^3. The inductor element according to any one of claims 1 to 4.   The portion of 50% or more of the entire axial length including the axial center position in the winding portion is a constant inner diameter portion in which the inner diameter of the winding portion is constant. The inductor element according to claim 5.

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