Coil parts

Abstract

This coil component 10 comprises a coil 200, a first core 32 having a first magnetic permeability, and a second core 34 which has a second magnetic permeability that is lower than the first magnetic permeability. The first core 32 is a pressed powder core. The first core 32 and the second core 34 form a magnetic path in which a magnetic flux circulates. In a plane including the magnetic path, the coil 200 forms two or more winding windows. In the same plane, the first core 32 is in contact with the entirety of one side that extends in a second direction of each of the winding windows, and protrudes from both ends of the one side in at least one of the winding windows. In the same plane, the second core 34 is in contact with three sides other than the one side of each of the winding windows. The surface resistance between two points, which are spaced apart by 20 mm in the first core, is 5 Ω or greater after a high-temperature storage test is performed. The driving frequency of the coil component 10 is 20 kHz or higher.

Description

[Technical field]

[0001] The present invention relates to a coil component, and more particularly to a coil component including a core formed by combining two types of core portions. [Background technology]

[0002] Patent Document 1 discloses a coil component having a core formed by combining two types of core parts. This coil component has an open case, a dust core placed at the bottom of the case, a coil placed on the dust core, and a cast core filled and hardened in the case so as to cover the coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6673711 Summary of the Invention [Problem to be solved by the invention]

[0004] In general, iron develops black rust in high-temperature environments. This is also true for the iron used in the cores of coil components. Note that black rust is more likely to develop in powder cores than in cast cores due to the difference in structure between cast cores and powder cores.

[0005] Black rust formed on the core changes the characteristics of the coil component. For example, black rust formed on the core increases eddy current loss in the core. Black rust formed on the core also increases the AC resistance of the coil component. The effect of such changes in characteristics due to black rust is greater the higher the driving frequency applied to the coil component.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a coil component having stable characteristics with little change even at high drive frequencies. [Means for solving the problem]

[0007] One aspect of the present invention provides a first coil component, A conductor that generates magnetic flux when current is passed through it; a core provided around the conductor and forming a magnetic path through which the magnetic flux circulates; a case that accommodates the conductor and the core; A coil component having The driving frequency of the coil component is 20 kHz or more, the conductor is a winding constituting one or more coils having an axis along a first direction; the conductor has a cross section that forms a rectangular winding window in a plane that includes the magnetic path, the plane includes the axis, The coil defines two or more winding windows in the plane, The winding windows are aligned in a second direction perpendicular to the first direction, The core has a first core having a first magnetic permeability and a second core having a second magnetic permeability lower than the first magnetic permeability, the first core is in contact with an entire side of each of the winding windows extending in the second direction in the plane, protrudes from both ends of the side of at least one of the winding windows in the second direction, and is located on the opposite side of the winding windows with respect to a straight line including the side of each of the winding windows, the second core is in contact with three sides other than the one side of each of the winding windows on the plane; The case has a bottom and a side extending in one direction from the bottom, The first core is in contact with the bottom portion, The first core is a dust core, The surface resistance between two points 20 mm apart of the powder core is 5 Ω or more after a high temperature storage test, The driving frequency is 20kHz or more. Coil components are provided. Effect of the Invention

[0008] According to the present invention, by using a dust core having a surface resistance of 5 Ω or more between two points 20 mm apart after a high-temperature storage test, a coil component having stable characteristics at high driving frequencies can be provided.

[0009] The objects of the present invention will be appreciated and its construction will become more completely understood by studying the following description of the best mode for carrying out the invention in conjunction with the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing a coil component according to an embodiment of the present invention, the coil component being cut along a plane including an axis of the coil and a magnetic path formed by a core. [Diagram 2] 2 is a schematic cross-sectional view showing a modified example of the coil device in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Although the present invention can be realized in various modifications and various forms, the following detailed description will be given of a specific embodiment as shown in the drawings, by way of example only, which is not intended to limit the present invention to the specific form disclosed herein, but to include all modifications, equivalents, and alternatives within the scope of the appended claims.

[0012] Referring to FIG. 1, a coil device 10 according to one embodiment of the present invention includes a conductor 20 that generates magnetic flux when current is passed through it, a core 30 that is provided around the conductor 20 and forms a magnetic path through which the magnetic flux circulates, and a case 40 that houses the conductor 20 and the core 30.

[0013] As can be seen from FIG. 1, the conductor 20 is a winding that is wound around an axis along the vertical direction (first direction) to form the coil 200. In this embodiment, the number of the coils 200 is one. However, the present invention is not limited to this. The number of the coils 200 may be more than one. The multiple coils 200 may be arranged in the vertical direction, or in a horizontal direction (second direction) perpendicular to the vertical direction. In either case, the multiple coils 200 may be arranged so as to be magnetically coupled to each other, or so as not to be magnetically coupled to each other. In this embodiment, the vertical direction is the Z direction, the +Z direction is the upper side, and the -Z direction is the lower side. The horizontal direction is the X direction.

[0014] As can be seen from Fig. 1, in this embodiment, the conductor 20 is a rectangular wire having a substantially rectangular cross section. The coil 200 is a flatwise coil made by winding a rectangular wire in the thickness direction. For example, a polyamide-imide wire (AIW) in which a copper wire is covered with an insulating film can be used as the rectangular wire. In addition, the outer surface of the coil 200 may be further covered with an insulating film (not shown).

[0015] 1, the coil 200 has a pair of end faces 202, 204, and an inner circumferential surface 206 and an outer circumferential surface 208 connecting the end faces 202, 204. When viewed in the vertical direction, the shape of the end face 202 or 204 is an annular polygon or a circle. In this embodiment, when viewed in the vertical direction, the shape of the end face 202 or 204 is an annular rounded rectangle.

[0016] As shown in Fig. 1, when the coil component 10 is cut in a plane including the magnetic path and the axis of the coil 200, the coil 200 has two cross sections. These two cross sections each form a winding window. In the present invention, the winding window refers to a cross section of the coil 200 around which a circulating magnetic flux is formed in a plane including the magnetic path and the axis of the coil 200. In this embodiment, the shape of each winding window is substantially rectangular. That is, each winding window has two sides extending in the vertical direction and two sides extending in the horizontal direction.

[0017] As shown in FIG. 1, when the number of coils 200 is one, the number of winding windows is two. When the number of coils 200 is multiple, the number of winding windows depends on the number of coils 200 and their arrangement. For example, when two coils 200 of the same shape are stacked vertically with their axes aligned, the cross sections of the multiple coils 200 that are vertically adjacent form one winding window. In this case, the number of winding windows is two. When two coils 200 of the same shape are juxtaposed so that their axes are parallel, the cross sections of the coils 200 that are adjacent to each other form one winding window. In this case, the number of winding windows is three. Note that the cross sections of the multiple coils 200 that form one winding frame do not necessarily have to be in contact with each other. The cross sections of the coils 200 that are adjacent to each other form one winding frame even if there is a gap between them. In addition, when an insulating coating or the like that covers the outer surface of the coil 200 exists, the insulating coating or the like is also included in the winding window. In any case, the coil device 10 forms two or more winding windows in a plane that includes the magnetic path and the axis of the coil 200. Two or more roll windows are aligned horizontally.

[0018] 1, the core 30 has a first core 32 and a second core 34. The first core 32 is disposed below the coil 200 in the up-down direction and is in contact with an end face 204. The first core 32 exists only below the end face 204 of the coil 200 and is not present above the end face 204. In other words, the first core 32 is located on the opposite side of the winding window with respect to a straight line including one side that is in contact with the coil 200 in a plane including the magnetic path.

[0019] As can be seen from FIG. 1, the outer shape of the first core 32 is larger than the outer shape of the coil 200 when viewed in the vertical direction. In other words, when viewed in the vertical direction, the coil 200 is disposed inside the outer periphery of the first core 32. In a plane including the magnetic path, the first core 32 is in contact with an entire side extending in the horizontal direction of the winding window and protrudes outward in the horizontal direction from both ends of the side. However, the present invention is not limited to this. It is sufficient that the first core 32 is in contact with an entire side extending in the horizontal direction of each winding window and protrudes outward in the horizontal direction from both ends of one side of at least one winding frame.

[0020] 1, the second core 34 is disposed above the first core 32 and the coil 200 in the up-down direction. When viewed in the up-down direction, the outer shape of the second core 34 substantially matches the outer shape of the first core 32. The second core 34 is formed so as to cover the coil 200, and is in contact with an end face 202, an inner peripheral surface 206, and an outer peripheral surface 208 of the coil 200. In other words, the second core 34 is in contact with three sides of the winding window other than the side in contact with the first core 32 in a plane including the magnetic path.

[0021] The first core 32 and the second core 34 have different magnetic permeabilities (μ). When the first core 32 has a first magnetic permeability μ1, the second core 34 has a second magnetic permeability μ2 lower than the first magnetic permeability μ1. In other words, the first core 32 is a high μ core, and the second core 34 is a low μ core. In this embodiment, the first core 32 is a dust core, and the second core 34 is a cast core. Here, the dust core is a soft magnetic alloy powder compressed and molded together with a binder. The cast core is a hardened slurry containing a soft magnetic alloy powder and a binder (resin), etc. In general, the dust core can have a higher magnetic permeability (μ) than the cast core.

[0022] As can be seen from FIG. 1, the case 40 is an open case having a bottom 42 and a side 44 protruding upward from the periphery of the bottom 42. In other words, the case 40 has an opening 46 that opens upward. The case 40 is made of a metal such as aluminum. The first core 32 is in contact with at least the bottom 42 of the case 40. This allows the heat generated in the coil 200 to be efficiently transferred to the case 40 via the first core 32. Usually, the case 40 is connected to a heat dissipation mechanism or the like (not shown). However, the present invention is not limited to this. Instead of the opening 46 that opens upward, the case 40 may have an opening that opens in a direction perpendicular to the vertical direction. For example, as shown in FIG. 2, the case 40 may have an opening 46A that opens in a horizontal direction. The opening that opens in a direction perpendicular to the vertical direction can be used to pull out the end 22 of the conductor 20 to the outside of the case 40.

[0023] Referring to FIG. 2, the opening 46A is provided with a cap member 24 that surrounds the end 22 of the conductor 20 so that the end 22 of the conductor 20 does not come into direct contact with the first core 32 and the second core 34. The cap member 24 extends in the lateral direction from the outside of the opening 46 to the outer circumferential surface of the first core 32 or its vicinity. The second core 34 is provided between the first core 32 and the opening 46A so that the first core 32 does not come into contact with the outside air. However, the boundary between the cap member 24 and the second core 34 can be a path through which the outside air can enter the first core 32 from the outside of the case 40. In particular, if the length (shortest distance) of the entry path is shorter than 5 mm, the possibility that the outside air will reach the first core 32 increases. The outside air that reaches the first core 32 can cause black rust to form on the surface of the first core 32.

[0024] 1, the magnetic flux generated by energizing the coil 200 passes mainly through the inside of the first core 32 and the second core 34. In other words, the first core 32 and the second core 34 form a magnetic path through which the magnetic flux circulates.

[0025] An AC voltage having a frequency of 20 kHz or more, for example, 30 kHz, is applied to the coil 200. In other words, the drive frequency of the coil component 10 is 20 kHz or more. In order to obtain stable characteristics for such a high drive frequency, in the present invention, the surface resistance of the first core 32 is set to a predetermined value or more. In detail, the surface resistance between two points 20 mm apart on the first core 32 is set to 5 Ω (room temperature) or more after a high-temperature storage test. More preferably, the surface resistance between two points 20 mm apart on the first core 32 is 30 Ω (room temperature) or more after a high-temperature storage test. By giving the first core 32 a surface resistance of a predetermined value or more in this way, changes in the characteristics of the coil component 10 are suppressed even when the drive frequency is high.

[0026] In this embodiment, the high-temperature storage test is performed in accordance with the high-temperature test method defined in JIS (Japanese Industrial Standards) C 60068-2-2:2010. More specifically, the high-temperature storage test is performed by introducing the coil component 10, setting the temperature in a test tank to 200° C., and maintaining the temperature for 500 hours or more. The maintenance time may be 1000 hours or more, for example, 2000 hours, but the change in surface resistance is often saturated by the time the time exceeds 500 hours. Therefore, a maintenance time of 500 hours is considered sufficient.

[0027] In order to make the surface resistance of the first core 32 equal to or greater than a predetermined value, a magnetic powder with a high electrical resistivity can be used. The magnetic powder used for the first core 32 can be a magnetic powder with an electrical resistivity of 20 μΩcm (at room temperature) or more. An example of such a magnetic powder is an Fe-Si alloy. An Fe-Si alloy exhibits a higher electrical resistivity than pure iron. For example, while the electrical resistivity of pure iron is 10 μΩcm, an Fe-Si alloy containing 1 wt% Si has an electrical resistivity of about 20 μΩcm. Also, an Fe-Si alloy containing 3 wt% Si has an electrical resistivity of about 50 μΩcm.

[0028] An index related to the surface resistance of the first core 32 is the initial electrical resistivity of the first core 32. If the initial electrical resistivity of the first core 32 is equal to or greater than a predetermined value, the change in the characteristics of the coil component 10 is suppressed even when the driving frequency is high. 10 The initial electrical resistivity of the powder core made of pure iron is preferably 10 9 Therefore, the first core 32 has an initial electrical resistivity that is at least one order of magnitude higher than that of the first core 32. For example, the initial electrical resistivity of the dust core using the Fe-Si alloy described above is 10 12 It is more than μΩcm.

[0029] In order to suppress the generation of black rust on the first core 32, the surface of the first core 32 may be covered with a coating material. In this case, the first core 32 may be formed by covering the surface of a dust core made of pure iron with a coating material, or the first core 32 may be formed by covering the surface of a dust core made of an Fe-Si alloy or the like with a coating material. The gas permeability coefficient of the coating material is 100 cc(STP)cm / (cm 2 .·sec·cmHg or less. For example, epoxy resin or polyamide resin can be used as such a coating material. The coating material suppresses the generation of black rust on the first core 32, so that changes in the characteristics of the coil component 10 can be suppressed even at high drive frequencies.

[0030] The effect of making the surface resistance of the first core 32 equal to or greater than a predetermined value is remarkable when the component ratio of the coil 200 itself in the AC resistance Rac of the coil component 10 is small. In other words, when the component ratio of the coil 200 itself in the AC resistance Rac of the coil component 10 is large, the effect of the present invention is limited. Therefore, it is desirable that the component ratio of the coil 200 itself in the AC resistance Rac of the coil component is small. Here, the component ratio of the coil 200 itself in the AC resistance Rac of the coil component depends on the number of turns of the coil. That is, in this embodiment, it is preferable that the number of turns of the coil 200 is small. Specifically, it is preferable that the number of turns of the coil 200 is 30 or less.

[0031] The effect of the number of turns of the coil 200 on the effect of the present invention is limited when the effect of the core 30 on the magnetic properties of the coil component 10 is small. In other words, the present invention is particularly effective when the effect of the core 30 on the magnetic properties of the coil component 10 is large. Specifically, the present invention is particularly effective when the ratio of the inductance of the coil component 10 to the inductance of the coil 200 itself is 4 or more.

[0032] In the case where the coil component 10 includes a plurality of coils 200 that are magnetically coupled to one another, when the coil component 10 is driven, for example, in a two-phase interleaved manner, the frequency of change in magnetic flux is twice as high as when the coil component 10 is driven in a single-phase manner. The present invention is particularly effective for a coil component 10 that includes a plurality of coils 200 that are magnetically coupled to one another.

[0033] As described above, the present invention provides a coil component having stable characteristics with little change in characteristics even when the driving frequency is high.

[0034] Although the present invention has been described above with reference to several embodiments, the present invention is not limited to the above embodiments, and various modifications and changes are possible without departing from the spirit of the present invention. For example, the coil 200 may be an edgewise coil. Furthermore, the cross section of the conductor 20 is not limited to a rectangular shape, and may be a circular or square shape.

[0035] Although the best mode for carrying out the present invention has been described, it will be apparent to those skilled in the art that modifications can be made to the present invention without departing from the spirit of the present invention, and such modifications are within the scope of the present invention. [Explanation of symbols]

[0036] 10,10A coil parts 20 Conductor 22 End 24 Cap member 200 Coil 202,204 End face 206 Inner surface 208 Outer surface 30 cores 32 First core (powder core) 34 Second core (cast core) 40 cases 42 Bottom 44 Side 46,46A opening

Claims

1. A conductor that generates magnetic flux when current is passed through it; a core provided around the conductor and forming a magnetic path through which the magnetic flux circulates; an open-top case that houses the conductor and the core; A coil component having the conductor is a winding constituting one or more coils having an axis along a first direction; the conductor has a cross section that forms a rectangular winding window in a plane that includes the magnetic path, the plane includes the axis, The coil defines two or more winding windows in the plane, The winding windows are aligned in a second direction perpendicular to the first direction, The core has a first core having a first magnetic permeability and a second core having a second magnetic permeability lower than the first magnetic permeability, the first core is in contact with an entire side of each of the winding windows extending in the second direction in the plane, protrudes from both ends of the side of at least one of the winding windows in the second direction, and is located on the opposite side of the winding windows with respect to a straight line including the side of each of the winding windows, the second core is in contact with three sides other than the one side of each of the winding windows on the plane; The open-top case has a bottom and a side extending in one direction from the bottom, The first core is in contact with the bottom portion, The first core is a dust core, The surface resistance between two points 20 mm apart of the powder core is 5 Ω or more after a heating test of 200 ° C. x 500 hours or more as a high temperature storage test, The surface of the dust core is covered with a coating material made of an epoxy resin or a polyamide resin, The gas permeability coefficient of the coating material is 100 cc(STP)cm / (cm 2 ·sec·cmHg) or less; the open case has an opening that opens in a direction perpendicular to the first direction, An end of the conductor is extended to the outside of the open case, a cap member is provided in the opening to surround an end of the conductor so that the end of the conductor does not come into direct contact with the first core and the second core; the cap member extends from an outside of the opening to an outer circumferential surface of the first core or a vicinity thereof in a direction perpendicular to the first direction, the second core is provided between the first core and the opening so as to prevent the first core from contacting outside air; The shortest distance of the boundary between the cap member and the second core is 5 mm or more. Coil parts.

2. The coil component according to claim 1 , The electrical resistivity of the magnetic powder used in the dust core is 20 μΩcm or more. Coil parts.

3. The coil component according to claim 1 or 2, The initial electrical resistivity of the powder core is 10 １０ μΩcm or more Coil parts.

4. A coil component according to any one of claims 1 to 3, The number of turns of the coil is 30 or less. Coil parts.

5. A coil component according to any one of claims 1 to 4, The number of the coils is plural, The coils are magnetically coupled to each other. Coil parts.

6. A coil component according to any one of claims 1 to 5, The surface resistance between two points 20 mm apart on the powder core is 30Ω or more after the high-temperature storage test. Coil parts.

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