Core for coil part and coil part

Abstract

A core (40) contains a magnetic material and has a cylindrical shape centered on a virtual center axis (CA). The ratio of the height dimension H to the maximum value of the effective width dimension (EW) at a location where the effective width dimension (EW) is maximum is 1.5 or more.

Description

Cores for coil components and coil components

[0001] The present disclosure relates to a core for a coil component and the coil component.

[0002] The core for the coil component disclosed in Patent Document 1 is annular. When the core disclosed in Patent Document 1 is viewed in cross section along a plane including the central axis of the annular shape, the cross section of the core is substantially square. Furthermore, the material of the core disclosed in Patent Document 1 is Mn-Zn ferrite.

[0003] Japanese Patent Application Publication No. 03-012906

[0004] In cores for coil components such as those disclosed in Patent Document 1, the cross-sectional area of ​​the core may be increased to increase the inductance value. However, increasing the core dimensions to increase the cross-sectional area of ​​the core can easily cause so-called dimensional resonance. This dimensional resonance reduces the resonant frequency of the coil component. This reduction in the resonant frequency of the coil component can reduce impedance in frequency bands above the resonant frequency, potentially resulting in reduced noise suppression performance. Dimensional resonance is a phenomenon in which, when a magnetic field of a certain frequency is applied to the core of such a coil component, standing waves of electromagnetic waves are generated within the core, resulting in increased loss.

[0005] In order to solve the above problems, the present disclosure provides a core for a coil component that includes a magnetic material, is cylindrical and has a virtual central axis as its center, and when viewed in a plane in a direction along the central axis, the width dimension is the length of the shortest line segment connecting any point on the inner peripheral edge to the outer peripheral edge, the effective width dimension is the sum of the lengths of the ranges of the shortest line segments that are made up of the magnetic material, and when viewed in a plane in a direction perpendicular to the central axis, the height dimension is the length in a direction along the central axis from the end on the positive side along the central axis to the end on the negative side opposite to the positive direction, and the ratio of the height dimension at the point where the effective width dimension is maximum to the maximum value of the effective width dimension is 1.5 or more.

[0006] The present disclosure also provides a coil component including a cylindrical core containing a magnetic material and centered on an imaginary central axis, and a winding wound around the core, wherein, when the core is viewed in a plane in a direction along the central axis, the width dimension is the length of the shortest line segment connecting any point on the inner peripheral edge of the core to the outer peripheral edge, the effective width dimension is the sum of the lengths of the ranges of the shortest line segments formed by the magnetic material, and when the core is viewed in a plane in a direction perpendicular to the central axis, the height dimension is the length in a direction along the central axis from the end on the positive side along the central axis to the end on the negative side opposite to the positive direction, and the ratio of the height dimension at a point where the effective width dimension is maximum to the maximum value of the effective width dimension is 1.5 or greater.

[0007] When dimensional resonance occurs, the resonance frequency can be increased.

[0008] FIG. 1 is a perspective view of a coil component according to a first embodiment. FIG. 2 is a bottom view of the coil component according to the first embodiment. FIG. 3 is a top view of a core according to the first embodiment. FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3. FIG. 5 is a graph showing the relationship between resonant frequency and aspect ratio. FIG. 6 is a graph showing the relationship between DC resistance and aspect ratio. FIG. 7 is a top view of a core according to a second embodiment. FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 7. FIG. 9 is a cross-sectional view of a core according to a modified example. FIG. 10 is a top view of a core according to a modified example.

[0009] Hereinafter, a core for a coil component and a first and second embodiments of the coil component will be described. Note that the drawings are schematic diagrams for ease of understanding, and components may be enlarged or omitted. Therefore, the dimensional ratios of the components may differ from those of the actual components.

[0010] <First embodiment of a core for a coil component and a coil component> (Overall configuration of the coil component) As shown in Fig. 1 , a coil component 10 of this embodiment is a common mode choke coil. The coil component 10 includes a core 40, a first winding 21, and a second winding 22. As shown in Fig. 2 , the coil component 10 also includes a first electrode 31, a second electrode 32, a third electrode 33, and a fourth electrode 34.

[0011] As shown in Fig. 1, the core 40 is a so-called toroidal core. That is, the core 40 is cylindrical and has a virtual central axis CA as its center. More specifically, the core 40 has a rectangular cylindrical shape in which the boundary portions between adjacent outer side surfaces and the boundary portions between adjacent inner side surfaces are rounded and chamfered. The material of the core 40 is Mn-Zn ferrite. That is, the core 40 includes a ferromagnetic magnetic material.

[0012] The core 40 has four outer surfaces. The four outer surfaces are a top surface 41A, a bottom surface 41B, an inner peripheral surface 41C, and an outer peripheral surface 41D. The top surface 41A is an annular flat surface facing in one direction along the central axis CA. When the core 40 is viewed in a plan view facing the direction along the central axis CA, the shape of the outer peripheral edge of the top surface 41A is rectangular with two adjacent sides having rounded corners. The shape of the inner peripheral edge of the top surface 41A is similar to the shape of the outer peripheral edge. The bottom surface 41B is an annular flat surface facing in the opposite direction from the top surface 41A in the direction along the central axis CA. The size and shape of the bottom surface 41B are the same as those of the top surface 41A. The inner peripheral surface 41C is a cylindrical surface facing toward the central axis CA in a direction perpendicular to the central axis CA. The inner peripheral surface 41C connects the inner peripheral edge of the top surface 41A to the inner peripheral edge of the bottom surface 41B. The outer peripheral surface 41D is a cylindrical surface that faces in a direction perpendicular to the central axis CA and in the opposite direction from the central axis CA. The outer peripheral surface 41D connects the outer peripheral edge of the top surface 41A to the outer peripheral edge of the bottom surface 41B.

[0013] As shown in Fig. 3, when viewed in a plan view in a direction along the central axis CA, the inner peripheral edge of the top surface 41A is the inner peripheral edge E1 of the core 40. Furthermore, in this plan view, the outer peripheral edge of the top surface 41A is the outer peripheral edge E2 of the core 40. Note that Fig. 3 omits the windings and electrodes and illustrates only the core 40. Furthermore, when viewed in a plan view in a direction along the central axis CA, a virtual rectangle that has the smallest area among the rectangles circumscribing the outer peripheral edge E2 is defined as a circumscribing rectangle CR. Because the circumscribing rectangle CR is circumscribing the top surface 41A and the bottom surface 41B, the circumscribing rectangle CR is a rectangle in which the lengths of two parallel sides are longer than the lengths of the other two sides.

[0014] In the following description, the axis perpendicular to the central axis CA and extending parallel to the long side of the circumscribing rectangle CR is referred to as the first axis X. The axis perpendicular to the central axis CA and extending parallel to the short side of the circumscribing rectangle CR is referred to as the second axis Y. The axis extending parallel to the central axis CA is referred to as the third axis Z. As shown in FIG. 1 , one of the directions along the first axis X is referred to as the first positive direction X1, and the direction opposite to the first positive direction X1 is referred to as the first negative direction X2. Furthermore, one of the directions along the second axis Y is referred to as the second positive direction Y1, and the direction opposite to the second positive direction Y1 is referred to as the second negative direction Y2. Furthermore, the direction along the third axis Z toward which the top surface 41A faces is referred to as the third positive direction Z1, and the direction opposite to the third positive direction Z1 is referred to as the third negative direction Z2.

[0015] As shown in FIG. 3, the core 40 has a first long side portion 42A, a second long side portion 42B, a first short side portion 43A, a second short side portion 43B, a first bent portion 44A, a second bent portion 44B, a third bent portion 44C, and a fourth bent portion 44D.

[0016] The first long side portion 42A is a portion of the core 40 that extends parallel to the long sides of the circumscribing rectangle CR. Specifically, when viewed in a plan view along the central axis CA, the center line CL of the first long side portion 42A of the core 40 is parallel to the long sides of the circumscribing rectangle CR. Note that the center line CL of the core 40 is the set of midpoints of the shortest line segments SL connecting any point on the inner peripheral edge E1 of the core 40 to the outer peripheral edge E2 when viewed in a plan view along the central axis CA. The dimension of the shortest line segment SL is the width dimension W of the core 40. The width dimension W of the first long side portion 42A is constant in the direction along the first axis X.

[0017] The second long side portion 42B is a portion of the core 40 that extends parallel to the long sides of the circumscribing rectangle CR. Therefore, the second long side portion 42B extends parallel to the first long side portion 42A. The second long side portion 42B is located on the second negative direction Y2 side of the first long side portion 42A. The width dimension W of the second long side portion 42B is the same as the width dimension W of the first long side portion 42A. The width dimension W of the second long side portion 42B is constant in the direction along the first axis X.

[0018] The first short side portion 43A is a portion of the core 40 that extends parallel to the short sides of the circumscribing rectangle CR. Specifically, in a plan view facing the center axis CA, the center line CL of the first short side portion 43A of the core 40 is parallel to the short sides of the circumscribing rectangle CR. Therefore, the first short side portion 43A extends in a direction perpendicular to the first long side portion 42A and the second long side portion 42B. The first short side portion 43A is located on the first negative direction X2 side relative to the first long side portion 42A and the second long side portion 42B. The width dimension W of the first short side portion 43A is smaller than the width dimension W of the first long side portion 42A and the width dimension W of the second long side portion 42B. The width dimension W of the first short side portion 43A is constant in the direction along the second axis Y.

[0019] The second short side portion 43B is a portion of the core 40 that extends parallel to the short sides of the circumscribing rectangle CR. The second short side portion 43B extends parallel to the first short side portion 43A. The second short side portion 43B is located on the first positive direction X1 side with respect to the first long side portion 42A and the second long side portion 42B. The width dimension W of the second short side portion 43B is the same as the width dimension W of the first short side portion 43A. The width dimension W of the second short side portion 43B is constant in the direction along the second axis Y.

[0020] The first bent portion 44A connects the end of the first long side portion 42A on the first negative direction X2 side of the core 40 to the end of the first short side portion 43A on the second positive direction Y1 side. The second bent portion 44B connects the end of the first long side portion 42A on the first positive direction X1 side of the core 40 to the end of the second short side portion 43B on the second positive direction Y1 side of the core 40. The third bent portion 44C connects the end of the second long side portion 42B on the first negative direction X2 side of the core 40 to the end of the first short side portion 43A on the second negative direction Y2 side of the core 40. The fourth bent portion 44D connects the end of the second long side portion 42B on the first positive direction X1 side of the core 40 to the end of the second short side portion 43B on the second negative direction Y2 side of the core 40.

[0021] When viewed in a plan view facing the third negative direction Z2, the first to fourth bent portions 44A to 44D are each generally fan-shaped and convex toward the outer peripheral edge E2. The width W of the first to fourth bent portions 44A to 44D is the same as the width W of the long side portions at the points where they connect to the long side portions. The width W of the first to fourth bent portions 44A to 44D decreases as they approach the short side portions, and is the same as the width W of the short side portions at the points where they connect to the short side portions.

[0022] As shown in Fig. 1, the first winding 21 is a winding that is wound as a whole around the first long side portion 42A of the core 40. The first winding 21 is made of a conductor such as copper. As shown in Fig. 2, the first winding 21 has a first straight pin S1 to a tenth straight pin S10 and a first bent pin B1 to a ninth bent pin B9.

[0023] The first linear pin S1 has a plate shape that is long in the direction along the second axis Y. The first linear pin S1 is located on the bottom surface 41B side of the first long side portion 42A of the core 40, i.e., on the third negative direction Z2 side. Therefore, when viewed in a plan view facing the third positive direction Z1, the first linear pin S1 is perpendicular to the first long side portion 42A. In addition, in this plan view, one end of the first linear pin S1 is located inside the inner peripheral edge E1. The other end of the first linear pin S1 is located outside the outer peripheral edge E2.

[0024] The second linear pin S2 to the tenth linear pin S10 have the same size and shape as the first linear pin S1. The first linear pin S1, the second linear pin S2, the third linear pin S3, the fourth linear pin S4, the fifth linear pin S5, the sixth linear pin S6, the seventh linear pin S7, the eighth linear pin S8, the ninth linear pin S9, and the tenth linear pin S10 are arranged in this order from the first negative direction X2 to the first positive direction X1.

[0025] Although not shown, the coil device 10 has a cover that covers the bottom surface 41B side of the core 40. The cover is made of, for example, insulating resin. Therefore, the bottom surface 41B of the core 40 and each of the linear pins are not in contact with each other.

[0026] As shown in FIG. 1 , the first bent pin B1 has a rod shape bent in a U-shape so that the center is convex toward the third positive direction Z1. The first bent pin B1 has a conductive core material and an insulating coating covering the core material. The insulating coating covers almost the entire core material except for both ends. The first bent pin B1 connects an end of the first straight pin S1 located on the inner circumferential surface 41C side to an end of the second straight pin S2 located on the outer circumferential surface 41D side, straddling the core 40 on the top surface 41A side. Specifically, the first bent pin B1 connects to the end of the first straight pin S1 located on the inner circumferential edge E1 side and has a portion extending in the third positive direction Z1 along the central axis CA. The first bent pin B1 connects to the end of the second straight pin S2 located on the outer circumferential edge E2 side and has a portion extending in the third positive direction Z1 along the central axis CA. The first bent pin B1 is located on the third positive direction Z1 side of the first long side portion 42A and has a portion that connects the ends of the two portions on the third positive direction Z1 side to each other.

[0027] 2, in a plan view facing the center axis CA, the end of the first bent pin B1 on the outer circumferential edge E2 side is located on the second positive direction Y1 side and the first positive direction X1 side relative to the end of the first bent pin B1 on the inner circumferential edge E1 side. In other words, in a plan view facing the third negative direction Z2, the first bent pin B1 diagonally intersects with the first long side portion 42A.

[0028] As shown in FIG. 1 , the second bend pin B2 to the ninth bend pin B9 have the same size and shape as the first bend pin B1. Furthermore, like the first bend pin B1, the second bend pin B2 to the ninth bend pin B9 have a core material and a coating. The first bend pin B1, the second bend pin B2, the third bend pin B3, the fourth bend pin B4, the fifth bend pin B5, the sixth bend pin B6, the seventh bend pin B7, the eighth bend pin B8, and the ninth bend pin B9 are arranged in this order from the first negative direction X2 to the first positive direction X1. Furthermore, when viewed in a plan view facing the third negative direction Z2, the first bend pin B1 to the ninth bend pin B9 are arranged approximately parallel to one another.

[0029] Therefore, the second bent pin B2 connects the end of the second straight pin S2 on the inner peripheral edge E1 side to the end of the third straight pin S3 on the outer peripheral edge E2 side. The third bent pin B3 connects the end of the third straight pin S3 on the inner peripheral edge E1 side to the end of the fourth straight pin S4 on the outer peripheral edge E2 side. The fourth bent pin B4 connects the end of the fourth straight pin S4 on the inner peripheral edge E1 side to the end of the fifth straight pin S5 on the outer peripheral edge E2 side. The fifth bent pin B5 connects the end of the fifth straight pin S5 on the inner peripheral edge E1 side to the end of the sixth straight pin S6 on the outer peripheral edge E2 side. The sixth bent pin B6 connects the end of the sixth straight pin S6 on the inner peripheral edge E1 side to the end of the seventh straight pin S7 on the outer peripheral edge E2 side. The seventh bent pin B7 connects the end of the seventh straight pin S7 on the inner peripheral edge E1 side to the end of the eighth straight pin S8 on the outer peripheral edge E2 side. The eighth bent pin B8 connects the end of the eighth straight pin S8 on the inner peripheral edge E1 side to the end of the ninth straight pin S9 on the outer peripheral edge E2 side. The ninth bent pin B9 connects the end of the ninth straight pin S9 on the inner peripheral edge E1 side to the end of the tenth straight pin S10 on the outer peripheral edge E2 side. Therefore, the total number of turns of the first winding 21 is nine.

[0030] As shown in Fig. 1, the second winding 22 is a winding that is wound as a whole around the second long side portion 42B of the core 40. The material of the second winding 22 is the same as that of the first winding 21, that is, a conductor such as copper. As shown in Fig. 2, the second winding 22 has an eleventh straight pin S11 to a twentieth straight pin S20 and an eleventh bent pin B11 to a nineteenth bent pin B19.

[0031] The eleventh linear pin S11 has a plate shape that is long in the direction along the second axis Y. The eleventh linear pin S11 is located on the bottom surface 41B side of the second long side portion 42B of the core 40, i.e., on the third negative direction Z2 side. Therefore, when viewed in a plan view facing the third positive direction Z1, the eleventh linear pin S11 is perpendicular to the second long side portion 42B. In addition, in this plan view, one end of the eleventh linear pin S11 is located inside the inner peripheral edge E1. The other end of the eleventh linear pin S11 is located outside the outer peripheral edge E2.

[0032] The twelfth linear pin S12 to the twentieth linear pin S20 have the same size and shape as the eleventh linear pin S11. The eleventh linear pin S11, the twelfth linear pin S12, the thirteenth linear pin S13, the fourteenth linear pin S14, the fifteenth linear pin S15, the sixteenth linear pin S16, the seventeenth linear pin S17, the eighteenth linear pin S18, the nineteenth linear pin S19, and the twentieth linear pin S20 are lined up in this order from the first negative direction X2 side to the first positive direction X1 side.

[0033] As shown in FIG. 1 , the 11th bent pin B11 has a rod shape bent in a U-shape so that the center is convex toward the third positive direction Z1. The 11th bent pin B11 has a conductive core material and an insulating coating covering the core material. The insulating coating covers almost the entire core material except for both ends. The 11th bent pin B11 connects an end of the 11th straight pin S11 located on the inner circumferential surface 41C side to an end of the 12th straight pin S12 located on the outer circumferential surface 41D side, straddling the core 40 on the top surface 41A side. Specifically, the 11th bent pin B11 connects to the end of the 11th straight pin S11 located on the inner circumferential edge E1 side and has a portion extending in the third positive direction Z1 along the central axis CA. The eleventh bent pin B11 is connected to the end of the twelfth straight pin S12 on the outer circumferential edge E2 side and has a portion extending in the third positive direction Z1 along the central axis CA. The eleventh bent pin B11 is located on the third positive direction Z1 side of the second long side portion 42B and has a portion connecting the ends of the two portions in the third positive direction Z1.

[0034] 2, in a plan view facing the center axis CA, the end of the 11 bent pin B11 on the outer circumferential edge E2 side is located on the second negative direction Y2 side and the first positive direction X1 side with respect to the end of the 11 bent pin B11 on the inner circumferential edge E1 side. In other words, in a plan view facing the third negative direction Z2, the 11 bent pin B11 diagonally intersects with the second long side portion 42B.

[0035] As shown in FIG. 1 , the twelfth to nineteenth bend pins B12 to B19 are similar in size and shape to the eleventh bend pin B11. Similarly to the eleventh bend pin B11, the twelfth to nineteenth bend pins B12 to B19 have a core material and a coating. The eleventh to nineteenth bend pins B11, B12, B13, B14, B15, B16, B17, B18, and B19 are arranged in this order from the first negative direction X2 to the first positive direction X1. When viewed in a plan view facing the third negative direction Z2, the eleventh to nineteenth bend pins B11 to B19 are arranged substantially parallel to one another.

[0036] Therefore, the twelfth bent pin B12 connects the end of the twelfth straight pin S12 on the inner peripheral edge E1 side to the end of the thirteenth straight pin S13 on the outer peripheral edge E2 side. The thirteenth bent pin B13 connects the end of the thirteenth straight pin S13 on the inner peripheral edge E1 side to the end of the fourteenth straight pin S14 on the outer peripheral edge E2 side. The fourteenth bent pin B14 connects the end of the fourteenth straight pin S14 on the inner peripheral edge E1 side to the end of the fifteenth straight pin S15 on the outer peripheral edge E2 side. The fifteenth bent pin B15 connects the end of the fifteenth straight pin S15 on the inner peripheral edge E1 side to the end of the sixteenth straight pin S16 on the outer peripheral edge E2 side. The 16th bent pin B16 connects the end of the 16th straight pin S16 on the inner peripheral edge E1 side to the end of the 17th straight pin S17 on the outer peripheral edge E2 side. The 17th bent pin B17 connects the end of the 17th straight pin S17 on the inner peripheral edge E1 side to the end of the 18th straight pin S18 on the outer peripheral edge E2 side. The 18th bent pin B18 connects the end of the 18th straight pin S18 on the inner peripheral edge E1 side to the end of the 19th straight pin S19 on the outer peripheral edge E2 side. The 19th bent pin B19 connects the end of the 19th straight pin S19 on the inner peripheral edge E1 side to the end of the 20th straight pin S20 on the outer peripheral edge E2 side. Therefore, the total number of turns of the second winding 22 is 9.

[0037] 2, the first electrode 31 to the fourth electrode 34 are each a rectangular plate. The first electrode 31 to the fourth electrode 34 are made of a conductor such as copper. The first electrode 31 to the fourth electrode 34 are each located on the bottom surface 41B side of the core 40, i.e., on the third negative direction Z2 side.

[0038] The first electrode 31 is located on the first negative direction X2 side and the second positive direction Y1 side of the core 40. The first electrode 31 is connected to the first straight pin S1 of the first winding 21. The second electrode 32 is located on the first positive direction X1 side and the second positive direction Y1 side of the core 40. The second electrode 32 is connected to the tenth straight pin S10 of the first winding 21. The third electrode 33 is located on the first negative direction X2 side and the second negative direction Y2 side of the core 40. The third electrode 33 is connected to the eleventh straight pin S11 of the second winding 22. The fourth electrode 34 is located on the first positive direction X1 side and the second negative direction Y2 side of the core 40. The fourth electrode 34 is connected to the twentieth straight pin S20 of the second winding 22. Therefore, the first electrode 31 and the second electrode 32 are electrically connected via the first winding 21. The third electrode 33 and the fourth electrode 34 are electrically connected via the second winding 22 .

[0039] (Core Dimensions) Next, the dimensions of the core 40 will be described. As shown in FIG. 3 , when viewed in a plan view in the third negative direction Z2, the effective width dimension EW is the sum of the lengths of the areas of the shortest line segment SL that are made up of magnetic material. In this embodiment, the width dimension W and the effective width dimension EW are the same. As shown in FIG. 4 , when viewed in a plan view in a direction perpendicular to the central axis CA, the height dimension H is the length along the central axis CA from the end on the third positive direction Z1 side to the end on the third negative direction Z2 side. The height dimension H of the core 40 in this embodiment is constant throughout.

[0040] In the core 40 of this embodiment, the effective width EW is greatest at the first long side portion 42A and the second long side portion 42B. The ratio of the height H at the location where the effective width EW is greatest to the maximum value of the effective width EW (height H / effective width EW) is 1.5 to 3.0. In other words, the height H at the location is 1.5 to 3.0 times the effective width EW at the same location. The product of the maximum value of the effective width EW and the height H at the location where the effective width EW is greatest is 80 mm. ２ In the following description, the "ratio of the height H at the point where the effective width EW is at its maximum to the maximum value of the effective width EW" will be referred to as the "aspect ratio."

[0041] In this embodiment, the aspect ratio is 2.4. The product of the effective width EW and height H that meets the above conditions is approximately 115.5 mm. ２ In this embodiment, the cross section of the core 40 perpendicular to the center line CL of the core 40 is rectangular. Therefore, the product of the effective width EW and the height H corresponds to the cross-sectional area of ​​the core 40 in a cross section perpendicular to the center line CL of the core 40 at the point where the effective width EW is maximum. This cross-sectional area refers to the area of ​​the cross section from the inner circumferential surface 41C to one of the outer circumferential surfaces 41D in the cross section. For example, as shown in FIG. 4 , when the entire core 40 is viewed in a cross section along the second axis Y and the third axis Z, two cross sections, i.e., the cross section of the first long side portion 42A and the cross section of the second long side portion 42B, can be observed. The "cross-sectional area of ​​the core 40" referred to above refers to the cross-sectional area of ​​one of these two cross sections.

[0042] 3, the maximum value of the effective width dimension EW at the first long side portion 42A is greater than the maximum value of the effective width dimension EW at the first short side portion 43A and the second short side portion 43B. Furthermore, the aspect ratio at each long side portion is 1.2 to 4.0 times the aspect ratio at each short side portion. As described above, in this embodiment, the height dimension H of the core 40 is constant throughout. Therefore, the above-mentioned magnification is the magnification of the maximum value of the effective width dimension EW at the first long side portion 42A relative to the maximum value of the effective width dimension EW at the first short side portion 43A. In this embodiment, the magnification is approximately 1.3 times.

[0043] (Relationship between Aspect Ratio and Resonant Frequency) Next, the relationship between aspect ratio and resonant frequency will be described. When dimensional resonance occurs, the relationship between the resonant frequency and the effective width EW and height H in a cross section perpendicular to the magnetic field passing through the core 40 is expressed by the following [Equation 1].

[0044]

[0045]

[0046] In Equation 1, f is the resonant frequency. The unit of the resonant frequency is "MHz (megahertz)." The unit of the effective width dimension EW and the height dimension H is "mm." The values ​​of A and B are constants determined by the magnetic permeability of the core 40. For example, when the magnetic permeability of the core 40 is 8500, the value of A is 2.48 and the value of B is 2.34. The smaller the magnetic permeability of the core 40, the larger the values ​​of A and B. The values ​​of A and B were calculated by experimentally obtaining the resonant frequency when the effective width dimension EW is changed relative to the height dimension H at which dimensional resonance occurs, and the resonant frequency when the height dimension H is changed relative to the effective width dimension EW at which dimensional resonance occurs, and then performing multiple regression analysis on these values.

[0047] Here, it is assumed that the product of the height dimension H and the effective width dimension EW is constant, and that the height dimension H is increased and the effective width dimension EW is decreased, i.e., the aspect ratio is increased. In this case, in the above [Equation 1], the value of A / H decreases as the height dimension H increases, and the value of B / EW increases as the effective width dimension EW decreases.

[0048] For example, when the magnetic permeability of the core 40 is 8500, it is assumed that the height dimension H is 8.94 mm and the effective width dimension EW is 8.94 mm. In this case, the product of the height dimension H and the effective width dimension EW, i.e., the cross-sectional area, is approximately 80 mm. ２ and the aspect ratio is 1. That is, the cross section of the core 40 in this assumption is square. Then, the theoretical value of the resonance frequency when dimensional resonance occurs is about 0.54 MHz according to the following [Equation 2].

[0049]

[0050] On the other hand, if the magnetic permeability of the core 40 is 8500, the height H is 14 mm, and the effective width EW is 5.7 mm, the product of these values, i.e., the cross-sectional area, is approximately 80 mm ２ The aspect ratio is about 2.5. The theoretical value of the resonance frequency when dimensional resonance occurs is about 0.59 according to the following [Equation 3].

[0051]

[0052] Therefore, as shown in Fig. 5, when dimensional resonance occurs and the product of the height dimension H and the effective width dimension EW is constant, the larger the aspect ratio, the higher the resonant frequency. In other words, the larger the aspect ratio is from 1, the higher the resonant frequency. Note that Fig. 5 shows the theoretical values ​​of the resonant frequency for the aspect ratio when the magnetic permeability of the core 40 is 5000, the theoretical values ​​of the resonant frequency for the aspect ratio when the magnetic permeability is 8500, and the theoretical values ​​of the resonant frequency for the aspect ratio when the magnetic permeability is 10000. In any case, when the cross-sectional area of ​​the core 40 is 80 mm ２ This is the theoretical value when

[0053] Furthermore, if the product of the height H and the effective width EW is kept constant and the height H is decreased and the effective width EW is increased, the value of A / H increases and the value of B / EW decreases. In other words, the resonant frequency increases even when the aspect ratio is smaller than 1. Therefore, a graph showing the relationship between the resonant frequency and the aspect ratio is parabolic, with a minimum value when the aspect ratio is 1.

[0054] When a relatively large current flows through the coil component 10, a high impedance is required in the range of 0.53 to 1.8 MHz, which includes the AM radio frequency band. Therefore, a resonant frequency of 0.53 MHz or higher is preferable. Assuming that the cross section of the core 40 is square, the larger the cross section, the higher the inductance value, and therefore the higher the impedance value. On the other hand, the resonant frequency is inversely proportional to the square root of the inductance. Therefore, the larger the cross section, the lower the resonant frequency. In other words, the resonant frequency may fall below the above-mentioned resonant frequency range. Furthermore, if dimensional resonance occurs, the resonant frequency will be even lower.

[0055] According to the above [Equation 1] to [Equation 3], when dimensional resonance occurs, the resonant frequency can be increased by increasing the aspect ratio even if the product of the height dimension H and the effective width dimension EW, i.e., the value of the cross-sectional area, is the same. In other words, increasing the cross-sectional area increases the inductance, and increasing the aspect ratio also increases the resonant frequency when dimensional resonance occurs. Furthermore, when the magnetic permeability is 10,000, the resonant frequency is smaller than when the magnetic permeability is 8,500. And, in the above [Equation 1], when the aspect ratio is 1.5, the resonant frequency is approximately 0.53 MHz. Therefore, when the cross-sectional area is 80 mm ２ Under the above conditions and under the condition that the magnetic permeability is 10,000 or less, the aspect ratio is 1.5 or more, so that the resonant frequency can be 0.53 MHz or more.

[0056] (Relationship Between Aspect Ratio and DC Resistance) Next, the relationship between the aspect ratio and the DC resistance (Rdc) generated in the coil component 10 will be described. When the aspect ratio is increased while the product of the height dimension H and the effective width dimension EW is kept constant, the circumferential length of the cross section of the core 40 increases. In this embodiment, since the cross section is rectangular, the circumferential length of the cross section of the core 40 is the sum of twice the height dimension H and twice the effective width dimension EW. As the circumferential length increases, the length of the winding that goes around the cross section, i.e., the length per turn of the winding, increases. Therefore, if the aspect ratio is changed while keeping the number of winding turns constant, the winding length increases as the aspect ratio increases. As a result, the DC resistance increases.

[0057] From this relationship, as shown in Fig. 6, the DC resistance increases as the aspect ratio increases from 1.0. Also, the DC resistance increases as the aspect ratio decreases from 1.0. In Fig. 6, the cross-sectional area of ​​the core 40 is 80 mm ２ The figure shows the theoretical value of DC resistance when the wire diameter of each of the first winding 21 and the second winding 22 is 2.7 mm, the number of turns of each winding is 9, and the distance between the core 40 and the winding is 0.5 mm. The unit of DC resistance is "mΩ." Under these conditions, if the aspect ratio is 3.0 or less, the DC resistance can be made 1.50 mΩ or less.

[0058] (Effects of the First Embodiment) According to the above embodiment, the following effects can be obtained. (1-1) In the above embodiment, the ratio of the height dimension H of the core 40 to the effective width dimension EW is 1.5 or more. According to the above [Equation 1], when the product of the height dimension H and the effective width dimension EW is constant, the larger the ratio of the height dimension H to the effective width dimension EW, the higher the resonant frequency will be when dimensional resonance occurs. In particular, if the aspect ratio is 1.5 or more, there is a high possibility that the resonant frequency can be made considerably high, such as 0.53 MHz or more.

[0059] (1-2) According to the above embodiment, the product of the height H and the effective width EW, i.e., the cross-sectional area of ​​the core 40, is 80 mm ２ The larger the cross-sectional area, the larger the inductance, and therefore the lower the resonant frequency.２ Under the above conditions, an aspect ratio of 1.5 or more is particularly preferable in that it makes the resonant frequency a sufficiently large value that does not pose any practical problems.

[0060] (1-3) In the above embodiment, the aspect ratio is 3.0 or less. As described above, when the aspect ratio is changed while keeping the cross-sectional area constant, the larger the aspect ratio, the greater the DC resistance of the winding. As described above, an aspect ratio of 3.0 or less prevents the DC resistance of the winding from becoming excessively large. In particular, if the aspect ratio is 3.0 or less under the above conditions, the DC resistance can be suppressed to approximately 1.5 mΩ or less.

[0061] (1-4) In the above embodiment, the circumscribing rectangle CR of the core 40 is rectangular. That is, the core 40 has a so-called racetrack shape. If the circumscribing rectangle CR is square, that is, if it is a so-called ring shape, the center of the space surrounded by the inner circumferential surface 41C of the core 40 tends to become a dead space where no windings exist. Therefore, with this configuration, when the coil component 10 is mounted on a substrate or the like, the area occupied by the entire coil component 10 on the substrate or the like can be reduced.

[0062] (1-5) In the above embodiment, the aspect ratio of the first long side portion 42A is 1.2 times or more the aspect ratios of the first short side portion 43A and the second short side portion 43B. This allows the effect of (1-1) above to be achieved in the first long side portion 42A when a winding is wound around the first long side portion 42A. Furthermore, because the aspect ratios of the short side portions are small, i.e., the effective width EW is relatively small, the size of the core 40 can be reduced. Meanwhile, the aspect ratio of the first long side portion 42A is 4.0 times or less the aspect ratios of the first short side portion 43A and the second short side portion 43B. If the difference in aspect ratio between the long side portion and the short side portion is within this range, there is no need to significantly change the width W at each bend.

[0063] <Second embodiment of the core for the coil component and the coil component> Next, a second embodiment of the coil component will be described. The coil component 100 according to the second embodiment differs from the coil component 10 according to the first embodiment in that the core 400 has two slits. In the following, among the components of the coil component 100 according to the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted. However, although the same reference numerals are also used for dimensions, the specific numerical values ​​of the dimensions may differ from those in the first embodiment.

[0064] 7 , the core 400 of the coil device 100 according to the second embodiment has a first slit 401 and a second slit 402. Each slit is located at a position where the width dimension W is maximum, i.e., at the first long side portion 42A and the second long side portion 42B of the core 400.

[0065] As shown in Fig. 8, the first slit 401 is located in the first long side portion 42A. The first slit 401 is a through-hole that penetrates from the top surface 41A to the bottom surface 41B. That is, the first slit 401 is recessed along the central axis CA of the core 400. The inside of the first slit 401 is hollow and does not contain any magnetic material.

[0066] The shortest distance from the outer edge of the first slit 401 on the second positive direction Y1 side to the outer peripheral edge E2 of the core 400 is defined as a first division dimension SW1, and the shortest distance from the outer edge of the first slit 401 on the second negative direction Y2 side to the inner peripheral edge E1 of the core 400 is defined as a second division dimension SW2. In this case, the effective width dimension EW of the first long side portion 42A is the sum of the first division dimension SW1 and the second division dimension SW2. As a result, the width dimension W and the effective width dimension EW do not coincide with each other in the first long side portion 42A.

[0067] 7, in a plan view facing the third negative direction Z2, the outer edge shape of the first slit 401 is a rectangle that is elongated in the direction along the first axis X. In this plan view, both ends of the first slit 401 substantially coincide with both ends of the first long side portion 42A.

[0068] In the above plan view, the first slit 401 extends on the center line CL of the core 400. That is, the first slit 401 extends along the center line CL. In other words, a line passing through the center of the first slit 401 is parallel to the center line CL of the core 400. More specifically, the first division dimension SW1 and the second division dimension SW2 are substantially equal. Furthermore, the first division dimension SW1 and the second division dimension SW2 are substantially constant from one end to the other end of the first slit 401.

[0069] 8, the second slit 402 is located in the second long side portion 42B. The second slit 402 is a through-hole that penetrates from the top surface 41A to the bottom surface 41B. That is, the second slit 402 is recessed along the central axis CA of the core 400. The interior of the second slit 402 is hollow and does not contain any magnetic material.

[0070] As shown in FIG. 7 , when viewed in a plan view facing the third negative direction Z2, the outer edge shape of the second slit 402 is a rectangle elongated in the direction along the first axis X. In this plan view, both ends of the second slit 402 substantially coincide with both ends of the second long side portion 42B. Also, in this plan view, the second slit 402 extends on the center line CL of the core 400. That is, the second slit 402 extends along the center line CL. In other words, a line passing through the center of the second slit 402 is parallel to the center line CL of the core 400.

[0071] In the second embodiment, the effective width EW is maximum near the boundary between each bent portion and the long side portion. Also in the core 400 of the second embodiment, the ratio of the height H at the point where the effective width EW is maximum to the maximum value of the effective width EW is 1.5 or more. The effective width EW at each long side portion is smaller than the maximum value of the effective width EW. Therefore, since the height H of the core 400 is constant throughout, the ratio of the height H to the effective width EW at each long side portion is greater than 1.5.

[0072] (Effects of the Second Embodiment) According to the second embodiment, in addition to the above (1-1) to (1-5), the following effects can be obtained. Note that, although the effects of the first slit 401 will be described below, the second slit 402 also provides the same effects.

[0073] (2-1) In the above embodiment, the core 400 has the first slits 401. The effective width dimension EW is small in the portion having the first slits 401. This allows the aspect ratio, which is the value of the effective width dimension EW relative to the height dimension H, to be increased.

[0074] (2-2) In the above embodiment, the first slit 401 extends on the center line CL of the first long side portion 42A. If the first slit 401 is not positioned on the center line CL, the shortest distance from the outer edge of the first slit 401 on the second positive direction Y1 side to the outer peripheral edge E2 of the core 400 will be different from the shortest distance from the outer edge of the first slit 401 on the second negative direction Y2 side to the inner peripheral edge E1 of the core 400. The larger the dimension, the more likely dimensional resonance will occur, and the greater the decrease in resonant frequency will be. Therefore, by making the shortest distances approximately equal, the decrease in resonant frequency due to dimensional resonance can be prevented.

[0075] (2-3) In the above embodiment, the first slit 401 is located in the first long side portion 42A where the width dimension W is maximum. The larger the width dimension W, the more likely dimensional resonance occurs, and the more significant the decrease in resonant frequency. Therefore, by locating the first slit 401 in such a location, the aspect ratio at that location can be increased. As a result, the resonant frequency can be increased when dimensional resonance occurs.

[0076] <Modifications> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0077] The coil component 10 is not limited to a common mode choke coil. For example, the coil component 10 may be a transformer. Furthermore, the coil component 10 does not have to have two windings.

[0078] The materials of the components of the coil device 10 are not limited to those described in the above embodiment. For example, the magnetic material of the core 40 is not limited to those described in the above embodiment. For example, Ni-Zn ferrite, iron, nickel, permalloy, etc. may be used.

[0079] The shape of the core 40 is not limited to the examples of the above embodiments, as long as it is at least cylindrical and has an aspect ratio of 1.5 or greater. For example, the shape of the core 40 may be ring-shaped instead of toroidal. In other words, the circumscribing rectangle CR of the core 40 may be square. Furthermore, for example, the shape of the outer peripheral edge E2 of the core 40 may be rectangular when viewed in a plan view facing the third negative direction Z2. Furthermore, the cross-sectional shape of the core 40 does not have to be rectangular and may be, for example, elliptical.

[0080] The width W of the long side portions may be smaller than the width W of the short side portions. The aspect ratio of the long side portions may be smaller than 1.2 times or larger than 4.0 times the aspect ratio of the short side portions. Even in such a case, the resonant frequency can be increased when dimensional resonance occurs.

[0081] The top surface 41A and the bottom surface 41B of the core 40 do not have to be flat. For example, the top surface 41A may have an uneven surface. Furthermore, for example, the boundary between the top surface 41A and the inner peripheral surface 41C of the core 40 may be rounded.

[0082] The structures of the first winding 21 and the second winding 22 are not limited to those in the above embodiment. For example, each winding may be a string-like wire wound around the core 40 so as to contact the core 40. The number of turns of the first winding 21 and the second winding 22 is not limited to those in the above embodiment. The number of turns may be less than or greater than 9 turns. Furthermore, the number of turns of each winding does not have to be the same.

[0083] The product of the maximum value of the effective width dimension EW and the height dimension H at the point where the effective width dimension EW is maximum is 80 mm ２ Regardless of the product, the larger the aspect ratio, the lower the resonant frequency can be when dimensional resonance occurs.

[0084] The aspect ratio may be greater than 3.0. Even in such a case, the resonant frequency can be increased at least when dimensional resonance occurs. In the second embodiment, the number of slits in the core 400 is not limited to two. It may be one, or three or more.

[0085] In the second embodiment, the slits may be located on the short side portions. The slits do not have to be located on the long side portions. As shown in Fig. 9, the first slits 401 and the second slits 402 do not have to be through holes. When viewed in a cross section along the central axis CA of the core 400, the dimension NPH of the non-penetrating portion NP in the direction along the central axis CA is preferably the same as the first division dimension SW1 and the second division dimension SW2.

[0086] The shape of each slit is not limited to the example of the second embodiment. For example, when viewed in a plan view facing the third negative direction Z2, the outer edge shape of the slit may be elliptical. For example, as shown in FIG. 10 , when viewed in a plan view facing the direction along the central axis CA, the first slit 401 may extend in an annular shape. This makes it easier to prevent dimensional resonance from occurring around the entire circumference of the core 400. In this case, the first slit 401 is a blind hole.

[0087] In the second embodiment, the first slits 401 do not have to extend along the center line CL. Even in this case, the effective width dimension EW can be reduced, making it easy to increase the aspect ratio. The same applies to the second slits 402.

[0088] <Supplementary Notes> The technical ideas that can be understood from the above embodiments and modified examples will be described below. [1] A core for a coil component that includes a magnetic material, has a cylindrical shape centered on a virtual central axis, and when viewed in a plan view in a direction along the central axis, defines a width dimension as the length of the shortest line segment connecting any point on the inner periphery to the outer periphery, defines an effective width dimension as the sum of the lengths of the sections of the shortest line segment that are made up of the magnetic material, and defines a height dimension as the length in a direction along the central axis from an end on a positive side along the central axis to an end on a negative side opposite to the positive direction, where the ratio of the height dimension at a point where the effective width dimension is maximum to the maximum value of the effective width dimension is 1.5 or more.

[0089] [2] The product of the maximum value of the effective width dimension and the height dimension at the point where the effective width dimension is maximum is 80 mm ２ [3] The core for a coil component according to [1] or [2], wherein a ratio of the height dimension at a point where the effective width dimension is maximum to the maximum value of the effective width dimension is 3.0 or less.

[0090] [4] A core for a coil component described in any one of [1] to [3], wherein when viewed in a plane facing the direction along the central axis, the circumscribing rectangle is a virtual rectangle that has the smallest area among the rectangles circumscribing the outer peripheral edge, and the circumscribing rectangle is a rectangle in which the lengths of two sides are longer than the lengths of the other two sides.

[0091] [5] A core for a coil component according to [4], comprising a long side portion extending parallel to the long side of the circumscribing rectangle and a short side portion extending parallel to the short side of the circumscribing rectangle, wherein the maximum value of the width dimension at the long side portion is greater than the maximum value of the width dimension at the short side portion, and the ratio of the height dimension at the point where the effective width dimension is maximum to the maximum value of the effective width dimension at the long side portion is 1.2 to 4.0 times the ratio of the height dimension at the point where the effective width dimension is maximum to the maximum value of the effective width dimension at the short side portion.

[0092] [6] A core for a coil component described in any one of [1] to [5], which has a slit recessed along the central axis, and when the set of midpoints of the shortest line segments is taken as the center line, the slit extends along the center line when viewed in a plane facing in a direction along the central axis.

[0093] [7] The core for a coil component according to [6], wherein the slit extends on the center line. [8] The core for a coil component according to [6] or [7], wherein the slit is located at a position where the width dimension is maximum.

[0094] [9] The core for a coil component according to any one of [6] to [8], wherein, when viewed in a plane along the central axis, the slit extends in an annular shape.

[10] A coil component comprising: a cylindrical core containing a magnetic material and centered on a virtual central axis; and a winding wound around the core, wherein, when viewed in a plane along the central axis, the length of the shortest line segment connecting an arbitrary point on the inner peripheral edge of the core to the outer peripheral edge of the core is defined as a width dimension, and the sum of the lengths of the sections of the shortest line segment formed by the magnetic material is defined as an effective width dimension. When viewed in a plane along the central axis, the length from the end on the positive side along the central axis to the end on the negative side opposite to the positive direction is defined as a height dimension, and the ratio of the height dimension at a point where the effective width dimension is maximum to the maximum value of the effective width dimension is 1.5 or more.

[0095]

[11] A core for a coil component that contains a magnetic material and is cylindrical with a virtual central axis as its center, and when viewed in a plane in a direction along the central axis, the width dimension is the length of the shortest line segment connecting any point on the inner peripheral edge to the outer peripheral edge, the sum of the lengths of the ranges of the shortest line segment that are made up of the magnetic material is the effective width dimension, and when viewed in a plane in a direction perpendicular to the central axis, the height dimension is the length in a direction along the central axis from the end on the positive side along the central axis to the end on the negative side opposite to the positive direction, and the ratio of the maximum value of the effective width dimension to the height dimension at the point where the effective width dimension is maximum is 1.5 or more.

[0096] 10... Coil component 21... First winding 22... Second winding 31... First electrode 32... Second electrode 33... Third electrode 34... Fourth electrode 40... Core 41A... Top surface 41B... Bottom surface 41C... Inner peripheral surface 41D... Outer peripheral surface E1... Inner peripheral edge E2... Outer peripheral edge CA... Central axis SL... Shortest line segment CL... Center line W... Width dimension EW... Effective width dimension H... Height dimension CR... Circumscribed rectangle 100... Coil component 400... Core 401... First slit 402... Second slit

Claims

1. A core for a coil component that contains a magnetic material and is cylindrical with a virtual central axis as its center, and when viewed in a plane in a direction along the central axis, the width dimension is the length of the shortest line segment connecting any point on the inner periphery to the outer periphery, and the sum of the lengths of the areas of the shortest line segment that are made up of the magnetic material is the effective width dimension, and when viewed in a plane in a direction perpendicular to the central axis, the height dimension is the length in a direction along the central axis from the end on the positive side along the central axis to the end on the negative side opposite to the positive direction, and the ratio of the height dimension at the point where the effective width dimension is maximum to the maximum value of the effective width dimension is 1.5 or more.

2. The product of the maximum value of the effective width dimension and the height dimension at the point where the effective width dimension is maximum is 80 mm ２ The core for a coil component according to claim 1 .

3. A core for a coil component according to claim 1 or 2, wherein the ratio of the height dimension at the point where the effective width dimension is at its maximum to the maximum value of the effective width dimension is 3.0 or less.

4. A core for a coil component according to any one of claims 1 to 3, wherein when viewed in a plane in a direction along said central axis, the circumscribing rectangle is defined as a virtual rectangle that has the smallest area among the rectangles circumscribing said outer periphery, and said circumscribing rectangle is a rectangle in which the lengths of two sides are longer than the lengths of the other two sides.

5. A core for a coil component according to claim 4, comprising: long side portions extending parallel to the long sides of the circumscribing rectangle; and short side portions extending parallel to the short sides of the circumscribing rectangle, wherein the maximum value of the width dimension at the long side portions is greater than the maximum value of the width dimension at the short side portions, and the ratio of the height dimension at the point where the effective width dimension is maximum to the maximum value of the effective width dimension at the long side portions is 1.2 to 4.0 times the ratio of the height dimension at the point where the effective width dimension is maximum to the maximum value of the effective width dimension at the short side portions.

6. A core for a coil component according to any one of claims 1 to 5, having a slit recessed along said central axis, and when the collection of midpoints of said shortest line segments is taken as a center line, said slit extends along said center line when viewed in a plane facing in a direction along said central axis.

7. A core for a coil component according to claim 6, wherein the slit extends on the center line.

8. A core for a coil component according to claim 6 or 7, wherein the slit is located at a position where the width dimension is maximum.

9. A core for a coil component according to any one of claims 6 to 8, wherein the slit extends in an annular shape when viewed in a plan view facing the direction along the central axis.

10. A coil component comprising: a cylindrical core containing a magnetic material and centered on an imaginary central axis; and a winding wound around said core; wherein, when said core is viewed in a plane in a direction along said central axis, the width dimension is the length of the shortest line segment connecting any point on the inner peripheral edge of said core to the outer peripheral edge, and the sum of the lengths of the range of said shortest line segment formed by said magnetic material is the effective width dimension; and when viewed in a plane in a direction perpendicular to said central axis, the height dimension is the length in a direction along said central axis from the end on the positive side along said central axis to the end on the negative side opposite to said positive direction, and the ratio of the height dimension at the point where said effective width dimension is maximum to the maximum value of said effective width dimension is 1.5 or more.

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