Reactor, converter, and power conversion device

Abstract

To provide a reactor capable of securing high inductance even under a high current.SOLUTION: A reactor comprises a coil and a magnetic core consisting of a plurality of core pieces. The magnetic core is θ-shaped and the magnetic core includes: a middle core part which is disposed inside of the coil; side core parts which are disposed in parallel with the middle core part so as to hold the coil therebetween; and end core parts which are disposed so as to face both ends of the coil. The plurality of core pieces includes a low B core piece and a high B core piece, and the low B core piece and the high B core piece consist of materials of different saturated magnetic flux densities. The saturated magnetic flux density of the low B core piece is lower than the saturated magnetic flux density of the high B core piece, and a ratio BS of the magnetic core is 0.5 or more and 1.0 or less.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a reactor, a converter, and a power conversion device. [Background technology]

[0002] Patent Document 1 discloses a reactor including a coil and a magnetic core. The magnetic core in the reactor of Patent Document 1 is an assembly of a first core portion and a second core portion. The first core portion and the second core portion are formed of molded bodies made of different materials. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-141122 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to accommodate the increasing currents of converters, there is a demand for reactors that can maintain high inductance even at high currents.

[0005] An object of the present disclosure is to provide a reactor that can ensure high inductance even when a high current flows. [Means for solving the problem]

[0006] The reactor of the present disclosure includes: The magnetic coil includes a coil and a magnetic core formed of a plurality of core pieces. The magnetic core has a θ shape, The magnetic core is A middle core portion disposed inside the coil; side core portions arranged in parallel with the middle core portion so as to sandwich the coil; and end core portions arranged to face both ends of the coil, the plurality of core pieces include low B core pieces and high B core pieces, The low B core pieces and the high B core pieces are made of materials with different saturation magnetic flux densities, The saturation magnetic flux density of the low B core pieces is lower than the saturation magnetic flux density of the high B core pieces, The ratio BS of the magnetic core is 0.5 or more and 1.0 or less, The ratio BS is the ratio of the product BSm of the saturation magnetic flux density Bm and the cross-sectional area Sm in the middle core portion to the sum of the product BSe of the saturation magnetic flux density Be and the cross-sectional area Se in the end core portion and the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core portion. Effect of the Invention

[0007] The reactor of the present disclosure can ensure high inductance even at high currents. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view of a reactor according to an embodiment. [Diagram 2] FIG. 2 is a schematic plan view of the reactor according to the embodiment. [Diagram 3] FIG. 3 is a schematic plan view showing the configuration of a magnetic core provided in the reactor according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV of FIG. [Figure 6] FIG. 6 is a schematic plan view showing another example of the configuration of the magnetic core provided in the reactor according to the embodiment. [Figure 7] FIG. 7 is a schematic plan view showing another example of the configuration of the magnetic core provided in the reactor according to the embodiment. [Figure 8] FIG. 8 is a schematic plan view showing another example of the configuration of the magnetic core provided in the reactor according to the embodiment. [Figure 9] FIG. 9 is a schematic diagram showing the power supply system of a hybrid vehicle. [Figure 10] FIG. 10 is a circuit diagram that illustrates a power conversion device including a converter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described.

[0010] (1) The reactor of the present disclosure is The magnetic coil includes a coil and a magnetic core formed of a plurality of core pieces. The magnetic core has a θ shape, The magnetic core is A middle core portion disposed inside the coil; side core portions arranged in parallel with the middle core portion so as to sandwich the coil; and end core portions arranged to face both ends of the coil, the plurality of core pieces include low B core pieces and high B core pieces, The low B core pieces and the high B core pieces are made of materials with different saturation magnetic flux densities, The saturation magnetic flux density of the low B core pieces is lower than the saturation magnetic flux density of the high B core pieces, The ratio BS of the magnetic core is 0.5 or more and 1.0 or less, The ratio BS is the ratio of the product BSm of the saturation magnetic flux density Bm and the cross-sectional area Sm in the middle core portion to the sum of the product BSe of the saturation magnetic flux density Be and the cross-sectional area Se in the end core portion and the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core portion.

[0011] The reactor of the present disclosure can ensure high inductance even at high currents. A magnetic core with a ratio BS of 0.5 or more and 1.0 or less can delay magnetic saturation in the middle core portion, improving the inductance at high currents. "Delaying magnetic saturation" means suppressing magnetic saturation at a specific current value and preventing a decrease in inductance at that current value. For example, even if a reactor having a conventional configuration would be magnetically saturated at 300A, the reactor having the configuration of the present disclosure will cause magnetic saturation to occur at 350A. In this case, the reactor having the configuration of the present disclosure can maintain a high inductance at 300A. In this way, by delaying magnetic saturation, the current value at which magnetic saturation occurs can be increased.

[0012] In the reactor of the present disclosure, the magnetic core is not made of a single material. In the reactor of the present disclosure, the multiple core pieces that make up the magnetic core include high B core pieces and low B core pieces made of materials with different saturation magnetic flux densities. By making the magnetic core out of multiple materials, it is easy to adjust the magnetic properties of the entire magnetic core so as to obtain a predetermined inductance.

[0013] (2) In the reactor described in (1) above, The saturation magnetic flux density of the high B core piece is 1.0 T or more and 2.5 T or less, The low B core piece may have a saturation magnetic flux density of 0.5T or more and 1.7T or less.

[0014] The above configuration (2) makes it easy to obtain a predetermined inductance.

[0015] (3) In the reactor according to (1) or (2), The high B core piece may be formed of a compact of soft magnetic powder.

[0016] Generally, the saturation magnetic flux density of a powder compact of soft magnetic powder is high. By forming the high B core piece from a powder compact, it is easy to adjust the saturation magnetic flux density of the high B core piece to 1.0T or more and 2.5T or less.

[0017] (4) In the reactor according to any one of (1) to (3), The low B core pieces may be formed of a compact of a composite material in which soft magnetic powder is dispersed in a resin.

[0018] Generally, the saturation magnetic flux density of a composite material compact is low. By making the low B core piece from a composite material compact, it is easy to adjust the saturation magnetic flux density of the low B core piece to 0.5T or more and 1.7T or less.

[0019] (5) In the reactor according to any one of (1) to (4), The number of the core pieces is two, The number of the low B core pieces and the number of the high B core pieces may each be one.

[0020] The configuration of (5) above has a small number of core pieces, and therefore the manufacturability of the magnetic core is good.

[0021] (6) In the reactor described in (5) above, The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, the low B core piece is E-shaped and includes a portion of the middle core portion, the first end core portion, a portion of the first side core portion, and a portion of the second side core portion, The high B core piece may be E-shaped having a remainder of the middle core portion, the second end core portion, a remainder of the first side core portion, and a remainder of the second side core portion.

[0022] The above configuration (6) can provide a magnetic core that can ensure high inductance even when a high current flows. Even if the high B core pieces are powder compacts, they can be molded as long as they are E-shaped.

[0023] (7) In the reactor described in (5) above, The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, Either the low B core piece or the high B core piece has an E-shape and includes a part of the middle core piece, the first end core piece, the first side core piece, and the second side core piece, The remaining core piece of the low B core piece and the high B core piece may be T-shaped having the remainder of the middle core piece and the second end core piece.

[0024] The above configuration (7) can form a magnetic core that can ensure high inductance even at high currents. T-shaped core pieces are easier to mold than E-shaped core pieces. Even if the high B core pieces are powder compacts, they are easy to mold if they are T-shaped.

[0025] (8) In the reactor according to any one of (1) to (4), The number of at least one of the low B core pieces and the high B core pieces may be two or more.

[0026] In the above configuration (8), the number of at least one of the low B core pieces and the high B core pieces is two or more, which makes it easy to finely set the magnetic characteristics of the magnetic core.

[0027] (9) In the reactor described in (8) above, The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, The middle core portion is a first middle core portion connected to the first end core portion; a second middle core portion connected to the second end core portion; a third middle core portion disposed between the first middle core portion and the second middle core portion, The plurality of core pieces are A T-shaped first end core piece constituting the first middle core portion and the first end core portion; A T-shaped second end core piece constituting the second middle core portion and the second end core portion; an I-shaped middle core piece constituting the third middle core portion; an I-shaped first side core piece constituting the first side core portion; an I-shaped second side core piece constituting the second side core portion, The first end core piece and the second end core piece are either the low B core piece or the high B core piece, The middle core piece, the first side core piece and the second side core piece may be the remaining core pieces of the low B core piece and the high B core piece.

[0028] The above configuration (9) can form a magnetic core that can ensure high inductance even at high currents. T-shaped core pieces are easier to mold than E-shaped core pieces. Even if the high B core pieces are powder compacts, they are easy to mold if they are T-shaped.

[0029] (10) In the reactor described in (8) above, The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, The plurality of core pieces are An I-shaped first end core piece constituting the first end core portion; An I-shaped second end core piece constituting the second end core portion; an I-shaped middle core piece constituting the middle core portion; an I-shaped first side core piece constituting the first side core portion; an I-shaped second side core piece constituting the second side core portion, The first end core piece and the second end core piece are either the low B core piece or the high B core piece, The middle core piece, the first side core piece and the second side core piece may be the remaining core pieces of the low B core piece and the high B core piece.

[0030] The above configuration (10) can form a magnetic core that can ensure high inductance even at high currents. I-shaped core pieces are easy to mold. When the high B core pieces are powder compacts, they can be easily molded if they are I-shaped.

[0031] (11) In the reactor according to any one of (1) to (10), The middle core portion may have a gap portion.

[0032] The above configuration (11) makes it possible to adjust the inductance and suppress magnetic saturation by using the gap portion.

[0033] (12) In the reactor according to (11), The length of the gap may be 0.5 mm or more and 3 mm or less.

[0034] According to the above configuration (12), a predetermined inductance is easily obtained.

[0035] (13) The converter of the present disclosure comprises: The reactor according to any one of (1) to (12) above is included.

[0036] The converter of the present disclosure includes the reactor of the present disclosure, and therefore operates stably even at high currents.

[0037] (14) The power conversion device of the present disclosure includes: The converter is provided as described in (13) above.

[0038] The power conversion device of the present disclosure includes the converter of the present disclosure, and therefore operates stably even at high currents.

[0039] [Details of the embodiment of the present disclosure] Specific examples of the embodiments of the present disclosure will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or equivalent parts. Note that the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0040] [Embodiment] <Reactor> A reactor 1 according to an embodiment will be described with reference to Figs. 1 to 8. As shown in Fig. 1, the reactor 1 includes a coil 2 and a magnetic core 3. As shown in Fig. 2, the magnetic core 3 has a θ-shape. The magnetic core 3 includes a middle core portion 31, a side core portion 33, and an end core portion 35. As shown in Fig. 3, the magnetic core 3 is composed of a plurality of core pieces 4. The plurality of core pieces 4 include low B core pieces 4L and high B core pieces 4H. Fig. 1 is a perspective view of the reactor 1 as seen obliquely from above. Fig. 2 is a plan view of the reactor 1 as seen from above. In Fig. 2, the coil 2 is shown in cross section. Fig. 3 is a plan view of the magnetic core 3 as seen from above.

[0041] One of the features of the reactor 1 of the embodiment is that it satisfies the following requirements (a) and (b). (a) The low B core piece 4L and the high B core piece 4H are made of materials with different saturation magnetic flux densities. (b) The ratio BS of the magnetic core 3 is 0.5 or more and 1.0 or less.

[0042] "Middle core section", "side core section", and "end core section" refer to specific parts of a magnetic core. "Core piece" refers to a single part made of the same material. "Low B core piece" and "high B core piece" are names for core pieces classified according to the saturation magnetic flux density of the constituent materials. One core piece may make up all or part of one core section, or one core piece may make up multiple core sections. In the drawings, the boundaries between core pieces are shown with solid lines, and the boundaries between multiple core sections in one core piece are shown with two-dot chain lines.

[0043] The configuration of the reactor 1 will be described in detail below. In the following description, the X-direction, Y-direction, and Z-direction in the reactor 1 are defined as follows. The X-direction is a direction along the axis of the coil 2, and is a direction from the first end 2a to the second end 2b. A line parallel to the X-direction is the X-axis. The Y-direction is a direction perpendicular to the axis of the coil 2, that is, a direction perpendicular to the X-direction, and is a direction in which the middle core portion 31 and the side core portion 33 are arranged in parallel. Specifically, it is a direction from the second side core portion 332 to the first side core portion 331. A line parallel to the Y-direction is the Y-axis. The Z-direction is a direction perpendicular to both the X-direction and the Y-direction, and is a direction from the lower surface to the upper surface of the coil 2. The Z-direction is a direction perpendicular to the XY plane. A line parallel to the Z-direction is the Z-axis. The X-axis, the Y-axis, and the Z-axis are perpendicular to each other. In the following description, "height" refers to a length along the Z-direction.

[0044] <Coil> As shown in FIG. 1, the coil 2 is disposed in the middle core portion 31 of the magnetic core 3. The coil 2 is configured by winding a wire in a spiral shape. The winding is, for example, a coated rectangular wire having a conductor wire and an insulating coating that covers the conductor wire. The conductor wire is, for example, a rectangular wire made of copper. The insulating coating is, for example, made of enamel. The coil 2 in this example is an edgewise coil in which a coated rectangular wire is wound in a spiral shape.

[0045] The coil 2 has a tubular shape. The shape of the coil 2 may be a polygonal tube or a cylindrical shape. The polygonal tube shape means that the contour shape of the end face of the coil 2 is polygonal. The polygonal shape is, for example, a quadrangle, a hexagon, and an octagon. The quadrangle shape includes a rectangle. The rectangle shape also includes a square. For example, the quadrangle is not limited to a geometric quadrangle, but also includes a quadrangle with a detailed modification, such as a shape in which at least one of the four corners is rounded. The cylindrical shape means that the contour shape of the end face of the coil 2 is circular. The circular shape includes not only a perfect circle shape, but also an oval shape and an elliptical shape. In this example, the shape of the coil 2 is a rectangular tube.

[0046] The coil 2 has a first end 2a and a second end 2b. Although omitted in FIG. 1, ends of the winding are drawn out from the first end 2a and the second end 2b, respectively. The ends of the winding are drawn out, for example, upward in FIG. 1, i.e., in the Z-axis direction. The ends of the winding are connected to a bus bar (not shown). The bus bar connects the coil 2 to a power source (not shown). The bus bar is a long, thin, plate-shaped conductor made of metal.

[0047] <Magnetic core> The coil 2 is disposed in the magnetic core 3. As shown in Fig. 2, the magnetic core 3 of this example has middle core portions 31, side core portions 33, and end core portions 35. The magnetic core 3 has a θ-shape in a plan view.

[0048] A θ-shaped closed magnetic circuit is formed in the magnetic core 3. When a current is applied to the coil 2, a magnetic flux flows in the magnetic core 3. The magnetic flux generated by the coil 2 flows from the middle core portion 31, through the end core portions 35 and the side core portions 33, and back to the middle core portion 31.

[0049] (Middle core section) The middle core portion 31 is disposed in the coil 2. The number of the middle core portion 31 is one. The middle core portion 31 extends along the X direction. The length Lm of the middle core portion 31 is equal to or longer than the length of the coil 2. The length Lm of the middle core portion 31 refers to the length along the direction in which the middle core portion 31 extends, i.e., the X direction. Both ends of the middle core portion 31 may protrude from both ends of the coil 2. The protruding portions are also part of the middle core portion 31. The shape of the middle core portion 31 is a shape that generally corresponds to the inner shape of the coil 2. In this example, the shape of the middle core portion 31 is a substantially rectangular parallelepiped. The width Wm and height of the middle core portion 31 in this example are constant in the direction along the length of the middle core portion 31, i.e., in the X direction. The width Wm of the middle core portion 31 refers to the length along the Y direction.

[0050] The middle core portion 31 is disposed between the first end core portion 35a and the second end core portion 35b. The first end core portion 35a and the second end core portion 35b will be described later. A first end of the middle core portion 31 is joined to the first end core portion 35a. A second end of the middle core portion 31 is joined to the second end core portion 35b. "Joined" means that the core portions are integrated so as not to separate from each other. The joined core portions include a case where the core portions are integrally molded and a case where the core portions are joined to each other. When the core portions are integrally molded, there is no seam between the joined core portions. When the core portions are joined to each other, there is a seam between the joined core portions. In the latter case, for example, the core portions may be bonded to each other, or the core portions may be integrated to each other by a resin mold. The resin mold is a molded member formed in a continuous manner so as to cover at least a part of the outer circumferential surface of the magnetic core 3.

[0051] The middle core portion 31 of this example has a first middle core portion 31a and a second middle core portion 31b. The first middle core portion 31a and the second middle core portion 31b are arranged in series along the X-axis. The first middle core portion 31a is connected to the first end core portion 35a. The second middle core portion 31b is connected to the second end core portion 35b. The lengths of the first middle core portion 31a and the second middle core portion 31b can be set appropriately. The length of the first middle core portion 31a and the length of the second middle core portion 31b may be the same or different. In this example, the middle core portion 31 is equally divided into two portions, the first middle core portion 31a and the second middle core portion 31b, but the middle core portion 31 may not be divided, or may be divided into three or more portions.

[0052] The middle core portion 31 in this example is made of a single material. That is, the first middle core portion 31a and the second middle core portion 31b are made of the same material. Unlike this example, the first middle core portion 31a and the second middle core portion 31b may be made of different materials.

[0053] In this example, the middle core part 31 has a gap part 31g. The gap part 31g is disposed between the first middle core part 31a and the second middle core part 31b. The middle core part 31 has the gap part 31g, so that the inductance of the reactor 1 can be adjusted and magnetic saturation can be suppressed. The gap part 31g is located inside the coil 2. When the gap part 31g is located inside the coil 2, the leakage magnetic flux from the gap part 31g is reduced compared to when the gap part 31g is exposed from the coil 2. The gap part 31g may be an air gap. The gap part 31g may be made of a nonmagnetic material such as resin or ceramics. The gap part 31g may not be present. When the gap part 31g is not present, the first middle core part 31a and the second middle core part 31b are in contact with each other, and there is substantially no gap between the first middle core part 31a and the second middle core part 31b.

[0054] The length of the gap portion 31g is appropriately set so as to obtain a predetermined inductance. The length of the gap portion 31g is, for example, 0.5 mm or more and 3 mm or less. The length of the gap portion 31g refers to the length along the X direction. The length of the gap portion 31g may further be 1 mm or more and 2.5 mm or less, or 1 mm or more and 2 mm or less. The smaller the length of the gap portion 31g, the easier it is to reduce loss caused by leakage flux from the gap portion 31g. When the middle core portion 31 has the gap portion 31g, the length of the middle core portion 31 is the total length of the first middle core portion 31a, the length of the second middle core portion 31b, and the length of the gap portion 31g.

[0055] (Side core part) The side core portion 33 is disposed outside the coil 2. As shown in FIG. 2, the side core portion 33 is disposed in parallel with the middle core portion 31 so as to sandwich the coil 2. The side core portion 33 extends along the X direction. The side core portion 33 is disposed generally parallel to the middle core portion 31. The length Ls of the side core portion 33 is equal to the length Lm of the middle core portion 31. The length Ls of the side core portion 33 refers to the direction in which the side core portion 33 extends, i.e., the length along the X direction. In this example, the shape of the side core portion 33 is substantially rectangular parallelepiped. The width Ws and height of the side core portion 33 in this example are constant in the direction along the length of the side core portion 33, i.e., in the X direction. The width Ws of the side core portion 33 refers to the length along the Y direction.

[0056] The side core portion 33 is disposed between the first end core portion 35a and the second end core portion 35b. A first end of the side core portion 33 is joined to the first end core portion 35a. A second end of the side core portion 33 is joined to the second end core portion 35b.

[0057] The number of side core portions 33 is two. The side core portion 33 has a first side core portion 331 and a second side core portion 332. The first side core portion 331 and the second side core portion 332 are arranged in parallel with a gap in the Y direction. The first side core portion 331 and the second side core portion 332 are arranged line-symmetrically about the center of the middle core portion 31.

[0058] In this example, the first side core portion 331 and the second side core portion 332 are made of the same material. Unlike this example, the first side core portion 331 and the second side core portion 332 may be made of different materials. Furthermore, the first side core portion 331 and the second side core portion 332 in this example have the same shape and dimensions. The dimensions here refer to length, width, and height. Unlike this example, the first side core portion 331 and the second side core portion 332 may have different shapes and dimensions. For example, the first side core portion 331 and the second side core portion 332 may differ in either or both of the width Ws and the height.

[0059] (End core part) The end core portions 35 are disposed outside the coil 2. The end core portions 35 are disposed so as to face both ends of the coil 2. The end core portions 35 extend along the Y direction. The end core portions 35 are disposed so as to be generally perpendicular to the middle core portions 31 and the side core portions 33. In this example, the shape of the end core portions 35 is generally rectangular parallelepiped.

[0060] The number of end core portions 35 is two. The end core portion 35 has a first end core portion 35a and a second end core portion 35b. The first end core portion 35a and the second end core portion 35b are arranged in parallel with an interval in the X direction. The inner surface of the first end core portion 35a faces the first end 2a of the coil 2. The inner surface of the second end core portion 35b faces the second end 2b of the coil 2. The first end of the middle core portion 31, the first end of the first side core portion 331, and the first end of the second side core portion 332 are respectively joined to the inner surface of the first end core portion 35a. The second end of the middle core portion 31, the second end of the first side core portion 331, and the second end of the second side core portion 332 are respectively joined to the inner surface of the second end core portion 35b.

[0061] It is sufficient that the end core portion 35 has a length Le connecting the first side core portion 331 and the second side core portion 332. The length Le of the end core portion 35 refers to the length along the direction in which the end core portion 35 extends, i.e., the Y direction. The width We and height of the end core portion 35 in this example are constant in the direction along the length of the end core portion 35, i.e., the Y direction. The width We of the end core portion 35 refers to the length along the X direction.

[0062] In this example, the first end core portion 35a and the second end core portion 35b are made of the same material. Unlike this example, the first end core portion 35a and the second end core portion 35b may be made of different materials. Also, the first end core portion 35a and the second end core portion 35b in this example have the same shape and dimensions. Unlike this example, the first end core portion 35a and the second end core portion 35b may have different shapes and dimensions. For example, the first end core portion 35a and the second end core portion 35b may differ in either or both of the width We and the height.

[0063] The heights of the middle core portions 31, the side core portions 33 and the end core portions 35 may be the same or different. The widths of the side core portions 33 and the end core portions 35 may be the same or different.

[0064] <Core Piece> As shown in FIG. 3, the magnetic core 3 of this example is configured by combining multiple core pieces 4. Each core piece 4 is configured by a molding of a soft magnetic material. The multiple core pieces 4 include low B core pieces 4L and high B core pieces 4H. In FIG. 3, the low B core pieces 4L and the high B core pieces 4H are hatched differently for easy understanding. FIG. 3 also shows the coil 2. The configuration of the magnetic core 3 shown in FIG. 3 is an example of an arrangement form of the multiple core pieces 4. In this example, there are a total of six core pieces 4, two core pieces 4 are high B core pieces 4H, and four core pieces 4 are low B core pieces 4L.

[0065] (Saturation magnetic flux density of core piece) The low B core piece 4L and the high B core piece 4H are made of materials with different saturation magnetic flux densities. The saturation magnetic flux density of the low B core piece 4L is lower than that of the high B core piece 4H. The saturation magnetic flux density of the high B core piece 4H is, for example, 1.0T or more and 2.5T or less. The saturation magnetic flux density of the low B core piece 4L is, for example, 0.5T or more and 1.7T or less. If the saturation magnetic flux density of the high B core piece 4H and the saturation magnetic flux density of the low B core piece 4L are each within the above ranges, a predetermined inductance is easily obtained. The saturation magnetic flux density of the high B core piece 4H may further be 1.3T or more and 2.2T or less, or 1.5T or more and 2.0T or less. The saturation magnetic flux density of the low B core piece 4L may further be 0.7T or more and 1.5T or less, or 0.9T or more and 1.4T or less. The saturation magnetic flux density can be determined by applying a magnetic field of 10,000 Oe (Oersted) to the material and measuring the magnetic flux density when the material is magnetically saturated. 10,000 Oe is approximately 800 kA / m.

[0066] (Core piece material) The material of each core piece 4 is, for example, a compressed powder compact of soft magnetic powder or a compact of a composite material. Since the magnetic core 3 is made of multiple materials, it is easier to adjust the magnetic characteristics of the entire magnetic core to obtain a predetermined inductance, compared to a magnetic core made of a single material.

[0067] The powder compact is formed by compressing raw material powder containing soft magnetic powder. The powder compact has high magnetic properties because of a relatively high content of soft magnetic powder. The magnetic properties are, for example, relative permeability and saturation magnetic flux density. The relative permeability of the powder compact is, for example, 100 to 500. The saturation magnetic flux density of the powder compact is, for example, 1.0 T to 2.5 T. The powder compact may contain, for example, at least one of a binder resin and a molding aid. The content of the soft magnetic powder in the powder compact is, for example, more than 80 vol% and 99.99 vol% or less, when the powder compact is taken as 100 vol%. The content of the soft magnetic powder in the powder compact may further be 85 vol% to 99 vol%.

[0068] The composite material compact is formed by dispersing soft magnetic powder in resin. The composite material compact is formed by filling a raw material in which soft magnetic powder is dispersed in unsolidified resin into a mold, and solidifying the resin. The content of the soft magnetic powder in the composite material compact can be easily adjusted. Therefore, the magnetic properties of the composite material compact can be easily adjusted. The content of the soft magnetic powder in the composite material compact is, for example, 30% by volume or more and 80% by volume or less, when the composite material compact is 100% by volume. The content of the soft magnetic powder in the composite material may further be 50% by volume or more, or 60% by volume or more.

[0069] The composite material compact contains less soft magnetic powder than the powder compact. Therefore, the composite material compact has lower magnetic properties than the powder compact. The composite material compact has a relative permeability of, for example, 5 to 50. The composite material compact has a saturation magnetic flux density of, for example, 0.5 T to 1.7 T. The composite material compact has a structure in which soft magnetic powder is dispersed in resin, and therefore has a smaller iron loss than the powder compact.

[0070] The content of the soft magnetic powder is regarded as equivalent to the area ratio of the soft magnetic powder in the cross section of the molded body constituting the core piece 4. The content of the soft magnetic powder can be determined as follows. The cross section of the molded body is observed with a scanning electron microscope (SEM) to obtain an observation image. The magnification of the SEM is, for example, 200 times or more and 500 times or less. Ten or more observation images are obtained. The total area of ​​the observation images is 0.1 cm. 2 That is all. One observation image may be acquired per cross section, or multiple observation images may be acquired per cross section. Each acquired observation image is subjected to image processing to extract the contours of the soft magnetic particles. The image processing is, for example, a binarization process. The total area of ​​the soft magnetic particles in each observation image is calculated, and the area ratio of the soft magnetic powder in each observation image is determined. The average value of the area ratios in all observation images is regarded as the content of the soft magnetic powder.

[0071] The particles constituting the soft magnetic powder are at least one selected from the group consisting of soft magnetic metal particles, coated particles having an insulating coating on the outer periphery of soft magnetic metal particles, and soft magnetic nonmetal particles. The soft magnetic metal is, for example, pure iron or an iron-based alloy. The iron-based alloy is, for example, an Fe (iron)-Si (silicon) alloy or an Fe-Ni (nickel) alloy. The insulating coating is, for example, a phosphate. The soft magnetic nonmetal is, for example, a ferrite.

[0072] The resins used in the composite materials may be thermoplastic or thermosetting. Thermoplastic resins include, for example, polyphenylene sulfide resin, polytetrafluoroethylene resin, liquid crystal polymer, polyamide resin, polybutylene terephthalate resin, or acrylonitrile-butadiene-styrene resin. Polyamide resins include, for example, nylon 6, nylon 66, or nylon 9T. Thermosetting resins include, for example, unsaturated polyester resin, epoxy resin, urethane resin, or silicone resin.

[0073] In this example, the high B core pieces 4H are formed of a powder compact. The low B core pieces 4L are formed of a composite material compact. If the high B core pieces 4H are powder compacts, it is easy to adjust the saturation magnetic flux density of the high B core pieces 4H to 1.0T or more and 2.5T or less. If the low B core pieces 4L are composite material compacts, it is easy to adjust the saturation magnetic flux density of the low B core pieces 4L to 0.5T or more and 1.7T or less.

[0074] (Core piece arrangement) <First arrangement> In the magnetic core 3 of this example, the middle core portion 31, the side core portion 33, and the end core portion 35 are each composed of independent core pieces 4. The arrangement of the core pieces 4 shown in FIG. 3 is called a first arrangement. The multiple core pieces 4 have a middle core piece 41, a first side core piece 431, a second side core piece 432, a first end core piece 45a, and a second end core piece 45b. The "middle core piece", the "first side core piece", the "second side core piece", the "first end core piece", and the "second end core piece" are names of core pieces classified according to the core portions that constitute them. The middle core piece 41 is an I-shaped core piece 4 that constitutes the middle core portion 31. The middle core portion 31 of this example has a first middle core piece 41a that constitutes the first middle core portion 31a, and a second middle core piece 41b that constitutes the second middle core portion 31b. The first side core piece 431 is an I-shaped core piece 4 that constitutes the first side core portion 331. The second side core piece 432 is an I-shaped core piece 4 constituting the second side core portion 332. The first end core piece 45a is an I-shaped core piece 4 constituting the first end core portion 35a. The second end core piece 45b is an I-shaped core piece 4 constituting the second end core portion 35b.

[0075] As shown in FIG. 3, the middle core portion 31 is composed of two core pieces 4, a first middle core piece 41a and a second middle core piece 41b, and a gap portion 31g. The first side core portion 331 and the second side core portion 332, and the first end core portion 35a and the second end core portion 35b are each composed of one core piece 4. The first side core portion 331 and the second side core portion 332 are each composed of a first side core piece 431 and a second side core piece 432. The first end core portion 35a and the second end core portion 35b are each composed of a first end core piece 45a and a second end core piece 45b. The first end core piece 45a and the second end core piece 45b are high B core pieces 4H. That is, the first end core portion 35a and the second end core portion 35b are composed of a powder compact. The first middle core piece 41a and the second middle core piece 41b, and the first side core piece 431 and the second side core piece 432 are low B core pieces 4L. That is, the first middle core portion 31a and the second middle core portion 31b are formed of a composite material molded body. The first side core portion 331 and the second side core portion 332 are formed of a composite material molded body.

[0076] The high B core pieces 4H and the low B core pieces 4L may be interchanged. In other words, the first end core piece 45a and the second end core piece 45b may be low B core pieces 4L formed by a composite material molding, and the first middle core piece 41a and the second middle core piece 41b, and the first side core piece 431 and the second side core piece 432 may be high B core pieces 4H formed by a powder compact.

[0077] 3, the number of low B core pieces 4L and the number of high B core pieces 4H are each at least two. By having at least one of the low B core pieces 4L and the high B core pieces 4H be two or more, it is easy to finely set the magnetic properties of the entire magnetic core 3.

[0078] (Magnetic core ratio BS) The ratio BS of the magnetic core 3 is 0.5 or more and 1.0 or less. This ratio BS is the ratio of the sum of the product BSe of the saturation magnetic flux density Be and the cross-sectional area Se in the end core portions 35 and the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core portions 33 to the product BSm of the saturation magnetic flux density Bm and the cross-sectional area Sm in the middle core portions 31. By setting the ratio BS to 0.5 or more and 1.0 or less, it is possible to delay magnetic saturation in the middle core portions, and the inductance at high currents is improved. Therefore, high inductance can be ensured even at high currents. The ratio BS may further be 0.5 or more and 0.9 or less, 0.6 or more and 0.9 or less, or 0.6 or more and 0.8 or less.

[0079] The ratio BS of the magnetic core 3 is calculated by the following formula. Ratio BS=[(product BSe)+(product BSs)] / (product BSm) Product BSm=Bm×Sm Product BSe=Be×Se Product BSs=Bs×Ss The product BSm means the product of the saturation magnetic flux density Bm and the cross-sectional area Sm in the middle core portion 31. The product BSe means the product of the saturation magnetic flux density Be and the cross-sectional area Se in the end core portion 35. The product BSs means the product of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core portion 33.

[0080] The cross-sectional area of ​​each core part refers to the area of ​​a cross section perpendicular to the direction in which magnetic flux flows in each core part when a closed magnetic circuit is formed in the magnetic core 3. The direction in which magnetic flux flows in each core part coincides with the direction in which each core part extends, i.e., the direction along the length of each core part.

[0081] The cross-sectional area Sm of the middle core portion 31 in this example is the area of ​​a cross section 31x perpendicular to the X direction, as shown in FIG. 4. The cross section 31x of the middle core portion 31 in this example is rectangular. The cross-sectional area Sm of the middle core portion 31 is the product of the width Wm and height Hm of the middle core portion 31. The cross-sectional area Sm is constant in the X direction. The cross-sectional area Ss of the side core portion 33 in this example is the area of ​​a cross section 33x perpendicular to the X direction. The cross-sectional area Ss is the area of ​​the cross section 33x of one side core portion 33. The cross section 33x of the side core portion 33 in this example is rectangular. The cross-sectional area Ss of the side core portion 33 is the product of the width Ws and height Hs of the side core portion 33. The cross-sectional area Ss is constant in the X direction. The cross-sectional area Se of the end core portion 35 in this example is the area of ​​a cross section 35x perpendicular to the Y direction, as shown in FIG. 5. The cross-sectional area Se is the area of ​​the cross section 35x of one end core portion 35. In this example, the shape of the cross section 35x of the end core portion 35 is rectangular. The cross-sectional area Se of the end core portion 35 is the product of the width We and the height He of the end core portion 35. The cross-sectional area Se of the end core portion 35 is the cross-sectional area of ​​a portion corresponding to a portion between the middle core portion 31 and the side core portion 33. The cross-sectional area Se is constant in the Y direction.

[0082] In this example, the height Hm of the middle core portion 31, the height Hs of the side core portion 33, and the height He of the end core portion 35 are substantially equal. Also, the width Ws of the side core portion 33 and the width We of the end core portion 35 are substantially equal. Unlike this example, the height Hm of the middle core portion 31, the height Hs of the side core portion 33, and the height He of the end core portion 35 may be different.

[0083] The saturation magnetic flux density of each core part is determined by the material of the core pieces 4 that constitute the core part. The saturation magnetic flux density Bm of the middle core part 31 and the saturation magnetic flux density Bs of the side core part 33 in this example are the saturation magnetic flux densities of the low B core pieces 4L formed by a composite material compact, as shown in Fig. 3. The saturation magnetic flux density Be of the end core part 35 in this example is the saturation magnetic flux density of the high B core pieces 4H formed by a powder compact.

[0084] Unlike this example, for example, the first middle core portion 31a and the second middle core portion 31b in the middle core portion 31 may be made of materials with different saturation magnetic flux densities. That is, either the first middle core piece 41a or the second middle core piece 41b may be the low B core piece 4L. In this case, the product BSm of the middle core portion 31 is calculated as follows. The ratio of each of the first middle core portion 31a and the second middle core portion 31b is calculated when the total volume of the first middle core portion 31a and the second middle core portion 31b is set to 1. In this example, the ratio of the first middle core portion 31a corresponds to the ratio of the length of the first middle core portion 31a to the length of the middle core portion 31. The ratio of the second middle core portion 31b corresponds to the ratio of the length of the second middle core portion 31b to the length of the middle core portion 31. However, here, the length of the middle core portion 31 excludes the length of the gap portion 31g. The product of the saturation magnetic flux density Bma and the cross-sectional area Sm in the first middle core portion 31a is multiplied by the ratio of the first middle core portion 31a to obtain the product BSma. The product of the saturation magnetic flux density Bmb and the cross-sectional area Sm in the second middle core portion 31b is multiplied by the ratio of the second middle core portion 31b to obtain the product BSmb. The sum of the product BSma of the first middle core portion 31a and the product BSmb of the second middle core portion 31b is regarded as the product BSm of the middle core portion 31.

[0085] In this example, the first side core portion 331 and the second side core portion 332 are made of the same material and also have the same shape and dimensions. That is, the first side core piece 431 and the second side core piece 432 have the same configuration. In this case, the product BSs of the side core portion 33 can be found from the saturation magnetic flux density Bs and the cross-sectional area Ss of one of the first side core portion 331 and the second side core portion 332.

[0086] Unlike this example, for example, the first side core portion 331 and the second side core portion 332 may be made of materials with different saturation magnetic flux densities. That is, either the first side core piece 431 or the second side core piece 432 may be a high-B core piece 4H. In this case, the product BSs of the side core portion 33 is calculated as follows. The product BSs1 of the saturation magnetic flux density Bs1 and the cross-sectional area Sm in the first side core portion 331 and the product BSs2 of the saturation magnetic flux density Bs2 and the cross-sectional area Sm in the second side core portion 332 are calculated. Then, the average value of the product BSs1 of the first side core portion 331 and the product BSs2 of the second side core portion 332 is regarded as the product BSs of the side core portion 33.

[0087] Also, unlike this example, for example, when the width Ws of the first side core portion 331 and the width Ws of the second side core portion 332 are different, the product BSs of the side core portion 33 is calculated as follows. The product BSs1 of the saturation magnetic flux density Bs and the cross-sectional area Ss1 in the first side core portion 331 and the product BSs2 of the saturation magnetic flux density Bs and the cross-sectional area Ss2 in the second side core portion 332 are calculated. Then, the average value of the product BSs1 of the first side core portion 331 and the product BSs2 of the second side core portion 332 is regarded as the product BSs of the side core portion 33.

[0088] In this example, the first end core portion 35a and the second end core portion 35b are made of the same material and also have the same shape and dimensions. That is, the first end core piece 45a and the second end core piece 45b have the same configuration. In this case, the product BSe of the end core portion 35 can be calculated from the saturation magnetic flux density Be and the cross-sectional area Se of one of the first end core portion 35a and the second end core portion 35b.

[0089] Unlike this example, for example, the first end core portion 35a and the second end core portion 35b may be made of materials with different saturation magnetic flux densities. In other words, either the first end core piece 45a or the second end core piece 45b may be a low-B core piece 4L. In this case, the product BSe of the end core portion 35 is calculated as follows. The product BSe of the saturation magnetic flux density Bea and the cross-sectional area Se in the first end core portion 35a and the product BSe of the saturation magnetic flux density Beb and the cross-sectional area Se in the second end core portion 35b are calculated. Then, the average value of the product BSe of the first end core portion 35a and the product BSe of the second end core portion 35b is regarded as the product BSe of the end core portion 35.

[0090] Also, unlike this example, for example, when the width We of the first end core portion 35a and the width We of the second end core portion 35b are different, the product BSe of the end core portion 35 is calculated as follows. The product BSea of ​​the saturation magnetic flux density Be and the cross-sectional area Sea in the first end core portion 35a and the product BSeb of the saturation magnetic flux density Be and the cross-sectional area Seb in the second end core portion 35b are calculated. Then, the average value of the product BSea of ​​the first end core portion 35a and the product BSeb of the second end core portion 35b is regarded as the product BSe of the end core portion 35.

[0091] [Variations] The arrangement of the core pieces 4 constituting the magnetic core 3 can be changed as appropriate. Modified examples of the magnetic core 3 will be described with reference to Figs. 6 to 8. The following description will focus on the differences from the configuration of the magnetic core 3 of this example shown in Fig. 3. In Figs. 6 to 8, the boundaries between the core pieces 4 are indicated by solid lines, and the boundaries between the core parts of one core piece 4 are indicated by two-dot chain lines. The coil 2 is also shown in Figs. 6 to 8.

[0092] (Variation 1) <Second arrangement> The configuration of the magnetic core 3 shown in FIG. 6 shows a second arrangement mode. In the magnetic core 3 shown in FIG. 6, the middle core portion 31 has a first middle core portion 31a, a second middle core portion 31b, and a third middle core portion 31c. The third middle core portion 31c is arranged between the first middle core portion 31a and the second middle core portion 31b. The first middle core portion 31a, the third middle core portion 31c, and the second middle core portion 31b are arranged in series along the X-axis. The lengths of the first middle core portion 31a, the second middle core portion 31b, and the third middle core portion 31c can be set appropriately. In the example shown in FIG. 6, a gap portion 31g is arranged between the third middle core portion 31c and the second middle core portion 31b. The first middle core portion 31a and the third middle core portion 31c are in contact with each other. Unlike the example shown in FIG. 6, the gap portion 31g may be arranged between the third middle core portion 31c and the first middle core portion 31a. Furthermore, the gap portion 31g may be disposed between the third middle core portion 31c and the first middle core portion 31a, and between the third middle core portion 31c and the second middle core portion 31b. The gap portion 31g may not be present.

[0093] In the example shown in FIG. 6, the multiple core pieces 4 include a middle core piece 41, a first side core piece 431, a second side core piece 432, a first end core piece 45a, and a second end core piece 45b. The first end core piece 45a is a T-shaped core piece 4 constituting the first middle core portion 31a and the first end core portion 35a. The second end core piece 45b is a T-shaped core piece 4 constituting the second middle core portion 31b and the second end core portion 35b. The middle core piece 41 is an I-shaped core piece 4 constituting the third middle core portion 31c. The first side core piece 431 is an I-shaped core piece 4 constituting the first side core portion 331. The second side core piece 432 is an I-shaped core piece 4 constituting the second side core portion 332.

[0094] As shown in FIG. 6, the middle core portion 31 is composed of a part of the first end core piece 45a, a part of the second end core piece 45b, the middle core piece 41, and the gap portion 31g. The first end core piece 45a and the second end core piece 45b are high B core pieces 4H. That is, the first middle core portion 31a and the first end core portion 35a are composed of an integrally molded powder compact. The second middle core portion 31b and the second end core portion 35b are composed of an integrally molded powder compact. The middle core piece 41, the first side core piece 431, and the second side core piece 432 are low B core pieces 4L. That is, the third middle core portion 31c is composed of a composite material compact. The third middle core portion 31c is composed of a material different from the first middle core portion 31a and the second middle core portion 31b. The first side core portion 331 and the second side core portion 332 are composed of a composite material compact.

[0095] The high B core piece 4H and the low B core piece 4L may be interchanged. In other words, the first end core piece 45a and the second end core piece 45b may be low B core pieces 4L formed by a composite material molding, and the middle core piece 41, the first side core piece 431 and the second side core piece 432 may be high B core pieces 4H formed by a powder compact.

[0096] The magnetic core 3 shown in Fig. 6 has two or more low B core pieces 4L and two or more high B core pieces 4H, similar to the magnetic core 3 shown in Fig. 3. By having two or more of at least one of the low B core pieces 4L and the high B core pieces 4H, it is easy to finely set the magnetic properties of the magnetic core 3 as a whole.

[0097] (Variation 2) <Third arrangement> The configuration of the magnetic core 3 shown in FIG. 7 shows a third arrangement mode. The magnetic core 3 shown in FIG. 7 is composed of an E-shaped low B core piece 4L and an E-shaped high B core piece 4H. In the magnetic core 3 shown in FIG. 7, the first side core portion 331 and the second side core portion 332 are each divided into two, and each has a first portion 331a, 332a and a second portion 331b, 332b. The first portion 331a and the second portion 331b in the first side core portion 331 are arranged in series along the X-axis. The first portion 332a and the second portion 332b in the second side core portion 332 are arranged in series along the X-axis. The first portions 331a, 332a are connected to the first end core portion 35a. The second portions 331b, 332b are connected to the second end core portion 35b. The lengths of the first portions 331a, 332a and the second portions 331b, 332b can be set appropriately. In the example shown in Fig. 7, the first portions 331a, 332a and the second portions 331b, 332b are in contact with each other. Unlike the example shown in Fig. 7, there may be gaps between the first portions 331a, 332a and the second portions 331b, 332b.

[0098] In the example shown in Fig. 7, the low B core piece 4L is an E-shaped core piece 4 having a first middle core portion 31a, a first end core portion 35a, a first portion 331a of the first side core portion 331, and a first portion 332a of the second side core portion 332. In other words, the first middle core portion 31a, the first end core portion 35a, the first portion 331a of the first side core portion 331, and the first portion 332a of the second side core portion 332 are configured by an integrally molded composite material molding. The high B core piece 4H is an E-shaped core piece 4 having a second middle core portion 31b, a second end core portion 35b, a second portion 331b of the first side core portion 331, and a second portion 332b of the second side core portion 332. That is, the second middle core portion 31b, the second end core portion 35b, the second portion 331b of the first side core portion 331, and the second portion 332b of the second side core portion 332 are configured as an integrally molded powder compact. In the example shown in Fig. 7, the first middle core portion 31a corresponds to a portion of the middle core portion 31, and the second middle core portion 31b corresponds to the remaining portion of the middle core portion 31. The first portion 331a of the first side core portion 331 corresponds to a portion of the first side core portion 331, and the second portion 331b corresponds to the remaining portion of the first side core portion 331. The first portion 332a of the second side core portion 332 corresponds to a portion of the second side core portion 332, and the second portion 332b corresponds to the remaining portion of the second side core portion 332.

[0099] When the first portions 331a, 332a and the second portions 331b, 332b are made of materials with different saturation magnetic flux densities, the product BSs of the side core portion 33 is calculated as follows. The product BSs1 of the saturation magnetic flux density Bs1 and the cross-sectional area Sm in the first side core portion 331 and the product BSs2 of the saturation magnetic flux density Bs2 and the cross-sectional area Sm in the second side core portion 332 are calculated. The product BSs1 of the first side core portion 331 is calculated as follows. The ratios of the first portion 331a and the second portion 331b are calculated when the total volume of the first portion 331a and the second portion 331b is set to 1. In the example shown in FIG. 7, the ratio of the first portion 331a corresponds to the ratio of the length of the first portion 331a to the length of the first side core portion 331. The ratio of the second portion 331b corresponds to the ratio of the length of the second portion 331b to the length of the first side core portion 331. The product of the saturation magnetic flux density and the cross-sectional area in the first portion 331a is multiplied by the ratio of the first portion 331a to calculate a product BSs1a. The product of the saturation magnetic flux density and the cross-sectional area in the second portion 331b is multiplied by the ratio of the second portion 331b to calculate a product BSs1b. The sum of the product BSs1a of the first portion 331a and the product BSs2b of the second portion 331b is regarded as the product BSs1 of the first side core portion 331. The product BSs2 of the second side core portion 332 is determined in the same manner as the product BSs1 of the first side core portion 331. The average value of the product BSs1 of the first side core portion 331 and the product BSs2 of the second side core portion 332 is regarded as the product BSs of the side core portion 33.

[0100] (Variation 3) <Fourth arrangement> The configuration of the magnetic core 3 shown in Fig. 8 shows a fourth arrangement mode. The magnetic core 3 shown in Fig. 8 is composed of an E-shaped low B core piece 4L and a T-shaped high B core piece 4H.

[0101] In the example shown in FIG. 8, the low B core piece 4L is an E-shaped core piece 4 having a first middle core portion 31a, a first end core portion 35a, a first side core portion 331, and a second side core portion 332. That is, the first middle core portion 31a, the first end core portion 35a, the first side core portion 331, and the second side core portion 332 are constituted by a molded body of a composite material molded integrally. The high B core piece 4H is a T-shaped core piece 4 having a second middle core portion 31b and a second end core portion 35b. That is, the second middle core portion 31b and the second end core portion 35b are constituted by a powder compact molded integrally. In the example shown in FIG. 8, the first middle core portion 31a corresponds to a part of the middle core portion 31, and the second middle core portion 31b corresponds to the remaining part of the middle core portion 31.

[0102] The shapes of the high B core piece 4H and the low B core piece 4L may be interchanged. That is, the high B core piece 4H may be an E-shaped core piece 4 having the first middle core portion 31a, the first end core portion 35a, the first side core portion 331, and the second side core portion 332, and the low B core piece 4L may be a T-shaped core piece 4 having the second middle core portion 31b and the second end core portion 35b.

[0103] 7 and 8, the magnetic core 3 has two core pieces 4. Since the number of low B core pieces 4L and the number of high B core pieces 4H are one each, the number of core pieces 4 is small, and the manufacturability of the magnetic core 3 is good.

[0104] <Converter / power conversion device> The reactor 1 of the embodiment can be used in applications that satisfy the following energization conditions. The energization conditions are, for example, a maximum DC current of about 100 A to 1000 A, an average voltage of about 100 V to 1000 V, and an operating frequency of about 5 kHz to 100 kHz. The reactor 1 of the embodiment can be used as a component of a converter mounted on a vehicle, such as an electric vehicle or a hybrid vehicle, and as a component of a power conversion device including the converter.

[0105] As shown in Fig. 9, a vehicle 1200 such as a hybrid vehicle or an electric vehicle includes a main battery 1210, a power conversion device 1100 connected to the main battery 1210, and a motor 1220 that is driven by power supplied from the main battery 1210 and used for traveling. The motor 1220 is typically a three-phase AC motor. The motor 1220 drives wheels 1250 during traveling and functions as a generator during regeneration. In the case of a hybrid vehicle, the vehicle 1200 includes an engine 1300 in addition to the motor 1220. Although Fig. 9 shows an inlet as a charging point for the vehicle 1200, a form including a plug may be used.

[0106] The power conversion device 1100 includes a converter 1110 connected to a main battery 1210, and an inverter 1120 connected to the converter 1110 and performing mutual conversion between direct current and alternating current. The converter 1110 shown in this example boosts the input voltage of the main battery 1210, which is about 200V to 300V, to about 400V to 700V when the vehicle 1200 is running, and supplies power to the inverter 1120. During regeneration, the converter 1110 lowers the input voltage output from the motor 1220 via the inverter 1120 to a direct current voltage suitable for the main battery 1210, and charges the main battery 1210. The input voltage is a direct current voltage. When the vehicle 1200 is running, the inverter 1120 converts the DC boosted by the converter 1110 into a predetermined AC and supplies it to the motor 1220. During regeneration, the inverter 1120 converts the AC output from the motor 1220 into DC and outputs it to the converter 1110.

[0107] As shown in FIG. 10, the converter 1110 includes a plurality of switching elements 1111, a drive circuit 1112 that controls the operation of the switching elements 1111, and a reactor 1115, and converts the input voltage by repeatedly switching on and off. The conversion of the input voltage means stepping up and down the voltage here. The switching elements 1111 are power devices such as field effect transistors and insulated gate bipolar transistors. The reactor 1115 utilizes the properties of a coil that prevents changes in the current flowing through the circuit, and has a function of smoothing out changes when the current increases or decreases due to switching operations. The reactor 1115 includes the reactor 1 of the embodiment.

[0108] In addition to the converter 1110, the vehicle 1200 includes a power supply converter 1150 connected to the main battery 1210, and an auxiliary power converter 1160 connected to the sub-battery 1230 serving as a power source for the auxiliary devices 1240 and the main battery 1210 to convert the high voltage of the main battery 1210 to a low voltage. The converter 1110 typically performs DC-DC conversion, while the power supply converter 1150 and the auxiliary power converter 1160 perform AC-DC conversion. Some of the power supply converters 1150 perform DC-DC conversion. The reactors of the power supply converter 1150 and the auxiliary power converter 1160 may have the same configuration as the reactor 1 of the embodiment, and may be of a different size or shape as appropriate. The reactor 1 of the embodiment may also be used as a converter that converts input power and that only boosts or only lowers the voltage.

[0109] [Test Example 1] The inductance and loss were evaluated for a reactor having a similar configuration to the reactor 1 of the embodiment.

[0110] In test example 1, a magnetic core 3 having the configuration shown in Fig. 3 was used. The first middle core piece 41a and the second middle core piece 41b constituting the middle core portion 31 are low B core pieces 4L constituted by a composite material molding. The first side core piece 431 and the second side core piece 432 constituting the side core portion 33 are low B core pieces 4L constituted by a composite material molding. The first end core piece 45a and the second end core piece 45b constituting the end core portion 35 are high B core pieces 4H constituted by a powder compact.

[0111] In Test Example 1, reactor models No. 1-0 to No. 1-5 shown in Table 1 were designed. No. 1-0 to No. 1-5 are models in which the magnetic cores were designed so that the ratio BS was 1.2 to 0.4. The magnetic core No. 1-0, which was designed so that the ratio BS was 1.2, was used as the reference. The configuration of the reference magnetic core is shown below.

[0112] (Magnetic core dimensions) Magnetic core length L: 77mm Magnetic core width W: 82mm Magnetic core height H: 30mm Length L is the dimension in the X direction as shown in Figure 1. Width W is the dimension in the Y direction. Height H is the dimension in the Z direction.

[0113] (Dimensions of each core part) Length of middle core Lm: 47mm Width of middle core Wm: 30mm Gap length: 1.5mm Side core length Ls: 47mm Side core width Ws: 15mm End core length Le: 82mm End core width We: 15mm The height of each core is 30 mm.

[0114] (Materials of the core pieces that make up each core section) Middle core: Composite material molding Side core: Composite material molding End core: Powder compact The saturation magnetic flux density B of the powder compact is 1.7 T. The saturation magnetic flux density B of the composite material compact is 1.2 T.

[0115] No.1-1 to No.1-5 are models in which the magnetic core ratio BS has been adjusted by reducing the width of each of the side core parts and end core parts compared to the reference magnetic core No.1-0. The length and width of the magnetic cores No.1-0 to No.1-5, as well as the width and cross-sectional area of ​​each core part, are shown in Table 1. Table 1 also shows the product of the saturation magnetic flux density and the cross-sectional area of ​​each core part.

[0116] [Table 1]

[0117] An analysis of inductance and loss was performed for reactor models No.1-0 to No.1-5. To analyze the inductance and loss, JMAG-Designer22.0, a commercially available electromagnetic field analysis software made by JSOL Corporation, was used to perform a magnetic field transient response analysis.

[0118] (Inductance Analysis) The inductance was analyzed when currents of 250A and 300A were passed through the coil. The maximum inductance value was found from the amount of magnetic flux linkage in the coil when the current values ​​were 250A and 300A. Table 2 shows the inductance at 250A and 300A for each model. The inductance shown in Table 2 is shown as a percentage, with the inductance of No.1-0 as the reference (100%). Inductance of 99% or more is considered to be equal to or better than No.1-0.

[0119] (Loss Analysis) We analyzed the losses when a DC current of 0A, an input voltage of 300V, an output voltage of 600V, and a frequency of 20kHz were applied to the coil. These losses include iron loss in the magnetic core and loss in the coil. Table 2 shows the losses in each model. The losses are shown as a percentage, with the coil loss of No.1-0 taken as the reference (100%).

[0120] [Table 2]

[0121] As shown in Table 2, No.1-1 to No.1-4 have improved inductance at 250A and 300A compared to No.1-0. In other words, models with magnetic cores designed so that the ratio BS is between 0.5 and 1.0 have high inductance at high currents. In particular, No.1-2 and No.1-3 have higher inductance at 250A and 300A than No.1-1. No.1-1 to No.1-4 also have smaller losses compared to No.1-0. Furthermore, as shown in Table 1, No.1-1 to No.1-4 have smaller magnetic core lengths and widths, and smaller magnetic core sizes, compared to No.1-0.

[0122] [Test Example 2] In test example 2, in the magnetic core 3 having the configuration shown in Fig. 3, the high B core pieces 4H and low B core pieces 4L were replaced. The first middle core piece 41a and the second middle core piece 41b constituting the middle core portion 31 are the high B core pieces 4H constituted by a powder compact. The first side core piece 431 and the second side core piece 432 constituting the side core portion 33 are the high B core pieces 4H constituted by a powder compact. The first end core piece 45a and the second end core piece 45b constituting the end core portion 35 are the low B core pieces 4L constituted by a composite material compact.

[0123] In Test Example 2, reactor models No. 2-0 to No. 2-5 shown in Table 3 were designed. No. 2-0 to No. 2-5 are models in which the magnetic cores were designed so that the ratio BS was 1.2 to 0.4. The magnetic core No. 2-0, which was designed so that the ratio BS was 1.2, was used as the reference. The configuration of the reference magnetic core is shown below.

[0124] (Magnetic core dimensions) Magnetic core length L: 89mm Magnetic core width: 94mm Magnetic core height H: 30mm

[0125] (Dimensions of each core part) Length of middle core Lm: 47mm Width of middle core Wm: 30mm Gap length: 1.5mm Side core length Ls: 47mm Side core width Ws: 21mm End core length Le: 94mm End core width We: 21mm The height of each core is 30 mm.

[0126] (Materials of the core pieces that make up each core section) Middle core: Powder compact Side core: Powder compact End core: Composite material molding The saturation magnetic flux density B of the powder compact is 1.7 T. The saturation magnetic flux density B of the composite material compact is 1.2 T.

[0127] No.2-1 to No.2-5 are models in which the magnetic core ratio BS has been adjusted by reducing the width of each of the side core parts and end core parts compared to the reference magnetic core No.2-0. The length and width of the magnetic cores No.2-0 to No.2-5, as well as the width and cross-sectional area of ​​each core part, are shown in Table 3. Table 3 also shows the product of the saturation magnetic flux density and the cross-sectional area of ​​each core part.

[0128] [Table 3]

[0129] The inductance and loss were analyzed for reactor models No. 2-0 to No. 2-5. The inductance and loss in each model were determined in the same manner as in Test Example 1. The results are shown in Table 4.

[0130] [Table 4]

[0131] As shown in Table 4, the inductance at 250A for No.2-1 to No.2-4 is 99% or more, which is equal to or greater than that of No.2-0. The inductance at 300A for No.2-1 to No.2-4 is improved compared to No.2-0. In other words, models with magnetic cores designed so that the ratio BS is 0.5 to 1.0 have high inductance at high currents. In particular, No.2-1 to No.2-3 have higher inductance at 250A and 300A than No.2-0. Furthermore, No.2-1 to No.2-4 have smaller losses compared to No.2-0. Furthermore, as shown in Table 3, No.2-1 to No.2-4 have smaller magnetic core lengths and widths, and smaller magnetic core sizes, compared to No.2-0. [Explanation of symbols]

[0132] 1 Reactor 2 Coil 2a first end, 2b second end 3. Magnetic core 31 Middle Core Division 31a first middle core part, 31b second middle core part, 31c third middle core part 31g Gap section 31x cross section 33 Side core part 331 first side core portion, 332 second side core portion 331a,332a first part, 331b,332b second part 33x cross section 35 End Core Section 35a first end core portion, 35b second end core portion 35x cross section 4 Core pieces 4H high B core piece, 4L low B core piece 41 Middle core piece 41a first middle core piece, 41b second middle core piece 431 first side core piece, 432 second side core piece 45a first end core piece, 45b second end core piece 1100 Power Converter, 1110 Converter 1111 switching element, 1112 drive circuit 1115 Reactor, 1120 Inverter 1150 Converter for power supply device, 1160 Converter for auxiliary power supply 1200 vehicles 1210 Main battery, 1220 Motor 1230 Sub-battery, 1240 Auxiliary equipment, 1250 Wheels, 1300 Engine L length, W width, H height Lm, Ls, Le length Wm, Ws, We Width Hm, Hs, He height

Claims

1. The magnetic coil includes a coil and a magnetic core formed of a plurality of core pieces. The magnetic core has a θ shape, The magnetic core is A middle core portion disposed inside the coil; side core portions arranged in parallel with the middle core portion so as to sandwich the coil; and end core portions arranged to face both ends of the coil, the plurality of core pieces include low B core pieces and high B core pieces, The low B core pieces and the high B core pieces are made of materials with different saturation magnetic flux densities, The saturation magnetic flux density of the low B core pieces is lower than the saturation magnetic flux density of the high B core pieces, The ratio BS of the magnetic core is 0.5 or more and 1.0 or less, the ratio BS is a ratio of the product BSm of the saturation magnetic flux density Bm and the cross-sectional area Sm in the middle core portion to the sum of the product BSe of the saturation magnetic flux density Be and the cross-sectional area Se in the end core portions and the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core portions; Reactor.

2. The saturation magnetic flux density of the high B core piece is 1.0 T or more and 2.5 T or less, 2. The reactor according to claim 1, wherein the saturation magnetic flux density of the low B core piece is 0.5 T or more and 1.7 T or less.

3. 3. The reactor according to claim 1, wherein the high B core piece is formed of a compact of soft magnetic powder.

4. 3. The reactor according to claim 1, wherein the low-B core piece is formed of a molded body of a composite material in which soft magnetic powder is dispersed in a resin.

5. The number of the core pieces is two, The reactor according to claim 1 or 2, wherein the number of the low B core pieces and the number of the high B core pieces are each one.

6. The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, the low B core piece is E-shaped and includes a portion of the middle core portion, the first end core portion, a portion of the first side core portion, and a portion of the second side core portion, The reactor according to claim 5, wherein the high B core piece is E-shaped having a remainder of the middle core portion, the second end core portion, a remainder of the first side core portion, and a remainder of the second side core portion.

7. The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, Any one of the low B core piece and the high B core piece has an E-shape including a part of the middle core piece, the first end core piece, the first side core piece, and the second side core piece, The reactor according to claim 5 , wherein the remaining core piece of the low B core piece and the remaining core piece of the high B core piece is T-shaped and has the remainder of the middle core portion and the second end core portion.

8. The reactor according to claim 1 or 2, wherein the number of at least one of the low B core pieces and the high B core pieces is two or more.

9. The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, The middle core portion is a first middle core portion connected to the first end core portion; a second middle core portion connected to the second end core portion; a third middle core portion disposed between the first middle core portion and the second middle core portion, The plurality of core pieces are a T-shaped first end core piece constituting the first middle core portion and the first end core portion; A T-shaped second end core piece constituting the second middle core portion and the second end core portion; an I-shaped middle core piece constituting the third middle core portion; an I-shaped first side core piece constituting the first side core portion; an I-shaped second side core piece constituting the second side core portion, The first end core piece and the second end core piece are either the low B core piece or the high B core piece, The reactor according to claim 8 , wherein the middle core piece, the first side core piece, and the second side core piece are remaining core pieces among the low B core piece and the high B core piece.

10. The side core portion has a first side core portion and a second side core portion, The end core portion has a first end core portion and a second end core portion, The plurality of core pieces are An I-shaped first end core piece constituting the first end core portion; An I-shaped second end core piece constituting the second end core portion; an I-shaped middle core piece constituting the middle core portion; an I-shaped first side core piece constituting the first side core portion; an I-shaped second side core piece constituting the second side core portion, The first end core piece and the second end core piece are either the low B core piece or the high B core piece, The reactor according to claim 8 , wherein the middle core piece, the first side core piece, and the second side core piece are remaining core pieces among the low B core piece and the high B core piece.

11. The reactor according to claim 1 or 2, wherein the middle core portion has a gap portion.

12. The reactor according to claim 11, wherein the length of the gap is not less than 0.5 mm and not more than 3 mm.

13. A reactor comprising the reactor according to claim 1 or 2. converter.

14. A converter comprising: Power conversion equipment.

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