Reactor, converter, and power conversion device

Abstract

This reactor comprises a coil and a magnetic core composed of a plurality of core pieces. The magnetic core is θ-shaped. The magnetic core includes: a middle core part disposed inside the coil; side core parts disposed in parallel with the middle core part so as to sandwich the coil; and end core parts disposed so as to face both ends of the coil. The plurality of core pieces include a low-B core piece and a high-B core piece. The low-B core piece and the high-B core piece are formed of materials having different saturation magnetic flux densities. The saturation magnetic flux density of the low-B core piece is lower than the saturation magnetic flux density of the high-B core piece. The magnetic core has a ratio BS of 0.5 to 1.0 inclusive.

Description

Reactors, converters, and power conversion devices

[0001] This disclosure relates to a reactor, a converter, and a power conversion device. This application claims priority to Japanese Patent Application No. 2023-123576 filed on July 28, 2023, and incorporates by reference all of the contents of that application.

[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 from molded bodies made of different materials.

[0003] Japanese Patent Application Laid-Open No. 2021-141122

[0004] The reactor of the present disclosure includes a coil and a magnetic core composed of multiple core pieces. The magnetic core has a θ-shape. The magnetic core includes a middle core portion arranged inside the coil, side core portions arranged parallel to the middle core portion so as to sandwich the coil, and end core portions arranged facing both ends of the coil. The multiple core pieces include low-B core pieces and high-B core pieces. The low-B core pieces and the high-B core pieces are formed of materials with different saturation magnetic flux densities. The saturation magnetic flux density of the low-B core pieces is lower than that of the high-B core pieces. The magnetic core has a ratio BS of 0.5 to 1.0. 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 BSs of the product BSe of the saturation magnetic flux density Be and the cross-sectional area Se in the end core pieces and the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core pieces.

[0005] FIG. 1 is a schematic perspective view of a reactor according to an embodiment. FIG. 2 is a schematic plan view of the reactor according to an embodiment. FIG. 3 is a schematic plan view showing the configuration of a magnetic core provided in the reactor according to an embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2. FIG. 5 is a cross-sectional view taken along line V-V of FIG. 2. FIG. 6 is a schematic plan view showing another example of the configuration of a magnetic core provided in the reactor according to an embodiment. FIG. 7 is a schematic plan view showing another example of the configuration of a magnetic core provided in the reactor according to an embodiment. FIG. 8 is a schematic plan view showing another example of the configuration of a magnetic core provided in the reactor according to an embodiment. FIG. 9 is a configuration diagram schematically showing a power supply system of a hybrid vehicle. FIG. 10 is a circuit diagram schematically showing a power conversion device including a converter.

[0006] [Problem to be Solved by the Present Disclosure] In order to cope with the increasing current of converters, there is a demand for a reactor that can obtain high inductance even at high currents.

[0007] An object of the present disclosure is to provide a reactor that can obtain high inductance even when a high current flows.

[0008] [Effects of the Present Disclosure] The reactor of the present disclosure can obtain high inductance even when a high current flows.

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

[0010] (1) A reactor according to the present disclosure includes a coil and a magnetic core composed of multiple core pieces. The magnetic core has a θ-shape. The magnetic core includes a middle core portion disposed inside the coil, side core portions disposed in parallel with the middle core portion so as to sandwich the coil, and end core portions disposed facing both ends of the coil. The multiple core pieces include low-B core pieces and high-B core pieces. The low-B core pieces and the high-B core pieces are formed of materials with different saturation magnetic flux densities. The saturation magnetic flux density of the low-B core pieces is lower than that of the high-B core pieces. The magnetic core has a ratio BS of 0.5 to 1.0. 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 BSs of the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core pieces and the product BSe of the product BSs of the product BSs of the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the end core pieces.

[0011] The reactor of the present disclosure achieves high inductance even at high currents. A magnetic core with a BS ratio of 0.5 or greater and 1.0 or less can delay magnetic saturation in the middle core portion, improving 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 with a conventional configuration would experience magnetic saturation at 300 A, a reactor with the configuration of the present disclosure will experience magnetic saturation at 350 A. In this case, a reactor with the configuration of the present disclosure can maintain high inductance at 300 A. In this way, delaying magnetic saturation can increase the current value at which magnetic saturation occurs.

[0012] In the reactor of the present disclosure, the magnetic core is not formed from 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 that are formed from materials with different saturation magnetic flux densities. By having the magnetic core made from multiple materials, it is easy to adjust the magnetic properties of the entire magnetic core to obtain a predetermined inductance.

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

[0014] The reactor according to (2) above is likely to achieve a predetermined inductance.

[0015] (3) In the reactor described in (1) or (2) above, the high-B core piece may be formed by a compact of soft magnetic powder.

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

[0017] (4) In the reactor described in any one of (1) to (3) above, the low-B core piece may be formed by a molding of a composite material in which soft magnetic powder is dispersed in a resin.

[0018] Generally, a composite material compact has a low saturation magnetic flux density. When the low B core pieces are formed from a composite material compact, the saturation magnetic flux density of the low B core pieces can be easily adjusted to 0.5 T or more and 1.7 T or less.

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

[0020] In the reactor according to (5) above, the number of core pieces is small, and therefore the manufacturability of the magnetic core is good.

[0021] (6) The reactor described in (5) above may be configured as follows: The side core portions have first side core portions and second side core portions. The end core portions have first end core portions and second end core portions. The low B core piece is E-shaped and has 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, and the high B core piece is E-shaped and has the remainder of the middle core portion, the second end core portion, the remainder of the first side core portion, and the remainder of the second side core portion.

[0022] The reactor according to (6) above includes a magnetic core that can obtain high inductance even at high currents. Even if the high B core pieces are powder compacts, they can be molded as long as they are E-shaped.

[0023] (7) The reactor described in (5) above may be configured as follows: The side core portions have first side core portions and second side core portions. The end core portions have first end core portions and second end core portions. Either of the low B core pieces or the high B core pieces has an E shape having a part of the middle core portion, the first end core portion, the first side core portion, and the second side core portion, and the remaining of the low B core pieces or the high B core pieces has a T shape having the remaining part of the middle core portion and the second end core portion.

[0024] The reactor according to (7) above includes a magnetic core that can obtain 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) above, 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 reactor according to (8) above, 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) The reactor described in (8) above may be configured as follows: 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 has a first middle core portion coupled to the first end core portion, a second middle core portion coupled to the second end core portion, and a third middle core portion disposed between the first middle core portion and the second middle core portion. The multiple core pieces have 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, and 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, and the middle core piece, the first side core piece and the second side core piece are the remaining core pieces either the low B core piece or the high B core piece.

[0028] The reactor according to (9) above includes a magnetic core that can obtain 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) The reactor described in (8) above may be configured as follows: 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 multiple core pieces have 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, and 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, and the middle core piece, the first side core piece, and the second side core piece are the remaining core pieces of the low B core piece and the high B core piece.

[0030] The reactor according to (10) above includes a magnetic core that can obtain high inductance even at high currents. I-shaped core pieces are easy to mold. When the high B core pieces are powder compacts, molding is easy if the high B core pieces are I-shaped.

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

[0032] The reactor according to (11) above can adjust the inductance and make magnetic saturation less likely to occur by using the gap portion.

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

[0034] The reactor according to (12) above is likely to achieve a predetermined inductance.

[0035] (13) A converter according to the present disclosure includes the reactor according to any one of (1) to (12) above.

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

[0037] (14) A power conversion device according to the present disclosure includes the converter 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 embodiments 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 defined 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 seen obliquely from above. FIG. 2 is a plan view of the reactor 1 seen from above. FIGS. 2, 3, and FIGS. 6 to 8, which will be described later, show the coil 2 in cross section. FIG. 3 is a plan view of the magnetic core 3 seen from above.

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

[0042] "Middle core portion," "side core portion," and "end core portion" refer to specific portions of the magnetic core. "Core piece" refers to a single component 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 material from which they are made. One core piece may constitute part or all of one core portion, or one core piece may constitute multiple core portions. In the drawings, the boundaries between core pieces are shown with solid lines, and the boundaries between multiple core portions in one core piece are shown with dashed double-dashed 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 of the reactor 1 are defined as follows: The X direction is a direction along the axis of the coil 2, from the first end 2a to the second end 2b. A line parallel to the X direction is defined as the X axis. The Y direction is a direction perpendicular to the axis of the coil 2, i.e., a direction perpendicular to the X direction, in which the middle core portions 31 and the side core portions 33 are arranged side by side. 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 defined as the Y axis. The Z direction is a direction perpendicular to both the X direction and the Y direction, from the bottom surface to the top surface of the coil 2. The Z direction is a direction perpendicular to the XY plane. A line parallel to the Z direction is defined as the Z axis. The X axis, Y axis, and Z axis are perpendicular to each other. In the following description, "height" refers to the 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 formed 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 covering 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 the coated rectangular wire is wound in a spiral shape.

[0045] The coil 2 has a cylindrical shape. The shape of the coil 2 may be a polygonal cylindrical shape or a cylindrical shape. A polygonal cylindrical shape means that the contour shape of the end face of the coil 2 is polygonal. Examples of polygonal shapes include a quadrilateral shape, a hexagonal shape, and an octagonal shape. A quadrilateral shape includes a rectangular shape. A rectangular shape also includes a square shape. For example, a quadrilateral is not limited to a geometric quadrilateral, but also includes quadrilaterals with minor modifications, such as a shape in which at least one of the four corners is rounded. A cylindrical shape means that the contour shape of the end face of the coil 2 is circular. A circular shape includes not only a perfect circular shape, but also an oval shape and an elliptical shape. In this example, the shape of the coil 2 is a rectangular cylindrical shape.

[0046] The coil 2 has a first end 2a and a second end 2b. Although not shown 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 the coil 2 is energized, magnetic flux flows through 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 Portion) The middle core portion 31 is disposed within the coil 2. There is one middle core portion 31. The middle core portion 31 extends along the X direction. The length Lm of the middle core portion 31 is equal to or greater 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. These protruding portions are also part of the middle core portion 31. The shape of the middle core portion 31 roughly corresponds to the internal 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 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 connected to the first end core portion 35a. A second end of the middle core portion 31 is connected to the second end core portion 35b. "Connected" means that the core portions are integrated so as not to separate from each other. Connected core portions include cases where the core portions are integrally molded and cases where the core portions are joined together. When the core portions are integrally molded, there is no seam between the joined core portions. When the core portions are joined together, there is a seam between the joined core portions. In the latter case, for example, the core portions may be glued together, or the core portions may be integrated together by a resin mold. The resin mold is a molded member formed in a continuous manner so as to cover at least a portion of the outer circumferential surface of the magnetic core 3.

[0051] In this example, the middle core portion 31 includes 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 aligned in series along the X-axis. The first middle core portion 31a is coupled to the first end core portion 35a. The second middle core portion 31b is coupled 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 as appropriate. The lengths of the first middle core portion 31a and 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. However, the middle core portion 31 need not be divided, and may be divided into three or more portions.

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

[0053] In this example, the middle core portion 31 has a gap portion 31g. The gap portion 31g is located between the first middle core portion 31a and the second middle core portion 31b. The gap portion 31g in the middle core portion 31 can adjust the inductance of the reactor 1 and make it less likely for magnetic saturation to occur. The gap portion 31g is located within the coil 2. When the gap portion 31g is located within the coil 2, leakage magnetic flux from the gap portion 31g is reduced compared to when the gap portion 31g is exposed from the coil 2. The gap portion 31g may be an air gap. The gap portion 31g may be formed of a non-magnetic material such as resin or ceramics. The gap portion 31g may be omitted. When the gap portion 31g is not present, the first middle core portion 31a and the second middle core portion 31b are in contact with each other, and there is substantially no gap between the first middle core portion 31a and the second middle core portion 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 shorter the length of the gap portion 31g, the easier it is to reduce loss due to leakage magnetic flux from the gap portion 31g. When the middle core portion 31 has a gap portion 31g, the length of the middle core portion 31 is the sum of the 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 Portion) The side core portion 33 is disposed outside the coil 2. As shown in FIG. 2 , the side core portion 33 is disposed parallel to the middle core portion 31 so as to sandwich the coil 2 therebetween. 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 length along 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 approximately 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., the X direction. The width Ws of the side core portion 33 refers to the length along the Y direction.

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

[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 with respect to 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 formed of the same material. Unlike this example, the first side core portion 331 and the second side core portion 332 may be formed of different materials. Furthermore, in this example, the first side core portion 331 and the second side core portion 332 have the same shape and dimensions. Here, dimensions 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 have different widths Ws and / or heights.

[0059] (End Core Portions) The end core portions 35 are arranged outside the coil 2. The end core portions 35 are arranged to face both ends of the coil 2. The end core portions 35 extend along the Y direction. The end core portions 35 are arranged 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 a substantially 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 a gap 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. A first end of the middle core portion 31, a first end of the first side core portion 331, and a first end of the second side core portion 332 are respectively coupled to the inner surface of the first end core portion 35a. A second end of the middle core portion 31, a second end of the first side core portion 331, and a second end of the second side core portion 332 are respectively coupled to the inner surface of the second end core portion 35b.

[0061] It is sufficient that the end core portions 35 have a length Le that connects the first side core portions 331 and the second side core portions 332. The length Le of the end core portions 35 refers to the length along the direction in which the end core portions 35 extend, i.e., the Y direction. The width We and height of the end core portions 35 in this example are constant in the direction along the length of the end core portions 35, i.e., the Y direction. The width We of the end core portions 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 formed from the same material. Unlike this example, the first end core portion 35a and the second end core portion 35b may be formed from different materials. Also, in this example, the first end core portion 35a and the second end core portion 35b 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 have different widths We and / or heights.

[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 Pieces> 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 formed from a molded body of a soft magnetic material. The multiple core pieces 4 include low B core pieces 4L and high B core pieces 4H. For ease of understanding, the low B core pieces 4L and the high B core pieces 4H are hatched differently in FIG. 3 . The coil 2 is also shown in FIG. 3 . The configuration of the magnetic core 3 shown in FIG. 3 is an example of an arrangement of multiple core pieces 4. In this example, there are a total of six core pieces 4, two of which are high B core pieces 4H and four of which are low B core pieces 4L.

[0065] (Saturation Magnetic Flux Density of Core Laminations) The low B core laminations 4L and the high B core laminations 4H are formed of materials with different saturation magnetic flux densities. The saturation magnetic flux density of the low B core laminations 4L is lower than that of the high B core laminations 4H. The saturation magnetic flux density of the high B core laminations 4H is, for example, 1.0 T or more and 2.5 T or less. The saturation magnetic flux density of the low B core laminations 4L is, for example, 0.5 T or more and 1.7 T or less. If the saturation magnetic flux densities of the high B core laminations 4H and the low B core laminations 4L are each within the above ranges, a predetermined inductance is easily obtained. The saturation magnetic flux density of the high B core laminations 4H may further be 1.3 T or more and 2.2 T or less, or 1.5 T or more and 2.0 T or less. The saturation magnetic flux density of the low B core laminations 4L may further be 0.7 T or more and 1.5 T or less, or 0.9 T or more and 1.4 T or less. The saturation magnetic flux density can be determined by applying a magnetic field of 10,000 Oe (oersteds) 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 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 properties 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 compression molding raw material powder containing soft magnetic powder. The powder compact has high magnetic properties due to the relatively high content of soft magnetic powder. The magnetic properties include, 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 mold with raw material in which soft magnetic powder is dispersed in unsolidified resin, and then 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 are 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 taken as 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 a smaller amount of 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 or more and 50 or less. The composite material compact has a saturation magnetic flux density of, for example, 0.5 T or more and 1.7 T or less. The composite material compact has a structure in which soft magnetic powder is dispersed in resin, and therefore has lower iron loss than the powder compact.

[0070] The content of the soft magnetic powder is considered to be equivalent to the area ratio of the soft magnetic powder in the cross section of the molded body forming 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. The number of observation images obtained is 10 or more. The total area of ​​the observation images is 0.1 cm. ２ That's 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. Image processing may be, for example, binarization processing. 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 considered to be the content of soft magnetic powder.

[0071] The particles contained in the soft magnetic powder are at least one type selected from the group consisting of soft magnetic metal particles, coated particles with an insulating coating on the outer periphery of soft magnetic metal particles, and soft magnetic non-metal 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 non-metal is, for example, ferrite.

[0072] The resin used in the composite material may be a thermoplastic resin or a thermosetting resin. Examples of the thermoplastic resin include polyphenylene sulfide resin, polytetrafluoroethylene resin, liquid crystal polymer, polyamide resin, polybutylene terephthalate resin, and acrylonitrile butadiene styrene resin. Examples of the polyamide resin include nylon 6, nylon 66, and nylon 9T. Examples of the thermosetting resin include unsaturated polyester resin, epoxy resin, urethane resin, and silicone resin.

[0073] In this example, the high B core pieces 4H are formed of powder compacts. The low B core pieces 4L are formed of composite material compacts. 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 between 1.0 T and 2.5 T. 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 between 0.5 T and 1.7 T.

[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 referred to as the first arrangement. 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 terms "middle core piece," "first side core piece," "second side core piece," "first end core piece," and "second end core piece" refer to the names of core pieces categorized by the core portion they comprise. 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 that constitutes the second side core portion 332. The first end core piece 45a is an I-shaped core piece 4 that constitutes the first end core portion 35a. The second end core piece 45b is an I-shaped core piece 4 that constitutes 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, respectively. 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, respectively. The first end core piece 45a and the second end core piece 45b are high-B core pieces 4H. In other words, the first end core portion 35a and the second end core portion 35b are formed by powder compacts. 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 interchangeable. That is, the first end core pieces 45a and the second end core pieces 45b may be low B core pieces 4L formed by a composite material molding. 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 number of low B core pieces 4L and the number of high B core pieces 4H be at least two, it is easy to finely set the magnetic characteristics of the entire magnetic core 3.

[0078] (Magnetic Core Ratio BS) The magnetic core 3 has a ratio BS of 0.5 or greater and 1.0 or less. This 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 31 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 35 and the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core portions 33. A ratio BS of 0.5 or greater and 1.0 or less can delay magnetic saturation in the middle core portion, improving inductance at high currents. Therefore, by including the magnetic core 3, the reactor 1 can achieve high inductance even at high currents. The ratio BS may further be 0.5 or greater and 0.9 or less, 0.6 or greater and 0.9 or less, or 0.6 or greater 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] As shown in FIG. 4 , 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. 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. As shown in FIG. 5 , 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. The cross-sectional area Se is the area of ​​the cross section 35x of one end core portion 35. In this example, 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 ​​the portion corresponding to the 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 portions 31, the height Hs of the side core portions 33, and the height He of the end core portions 35 are substantially equal. Also, the width Ws of the side core portions 33 and the width We of the end core portions 35 are substantially equal. Unlike this example, the height Hm of the middle core portions 31, the height Hs of the side core portions 33, and the height He of the end core portions 35 may be different.

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

[0084] Unlike the present example, for example, the first middle core portion 31a and the second middle core portion 31b of the middle core portion 31 may be formed 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 a low-B core piece 4L. In this case, the volume BSm of the middle core portion 31 is calculated as follows: The ratios of the first middle core portion 31a and the second middle core portion 31b are 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, the length of the middle core portion 31 here 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 a 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 a 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 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 calculated 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 formed 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 of the first side core portion 331 is calculated, and the product BSs2 of the saturation magnetic flux density Bs2 and the cross-sectional area Sm of the second side core portion 332 is calculated. 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 then regarded as the product BSs of the side core portion 33.

[0087] Furthermore, unlike this example, if, for example, 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: A product BSs1 of the saturation magnetic flux density Bs and the cross-sectional area Ss1 in the first side core portion 331 and a 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 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 formed of materials with different saturation magnetic flux densities. That is, 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 BSea of ​​the saturation magnetic flux density Bea and the cross-sectional area Se of the first end core portion 35a is calculated, and the product BSeb of the saturation magnetic flux density Beb and the cross-sectional area Se of the second end core portion 35b is calculated. The average of the product BSea of ​​the first end core portion 35a and the product BSeb of the second end core portion 35b is then considered to be the product BSe of the end core portion 35.

[0090] Furthermore, unlike this example, if, for example, 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 can be 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. The average of the product BSea of ​​the first end core portion 35a and the product BSeb of the second end core portion 35b is then regarded as the product BSe of the end core portion 35.

[0091] [Modifications] The arrangement of the core pieces 4 that make up the magnetic core 3 can be modified as appropriate. Modifications of the magnetic core 3 will be described with reference to Figures 6 to 8. The following description will focus on differences from the configuration of the magnetic core 3 of this example shown in Figure 3. In Figures 6 to 8, the boundaries between the core pieces 4 are indicated by solid lines, and the boundaries between each core portion of one core piece 4 are indicated by two-dot chain lines. Figures 6 to 8 also show the coil 2.

[0092] (Variation 1) <Second Arrangement> The configuration of the magnetic core 3 shown in FIG. 6 illustrates a second arrangement. In the magnetic core 3 shown in FIG. 6, the middle core portion 31 includes 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 disposed 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 aligned 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 as appropriate. In the example shown in FIG. 6, a gap portion 31g is disposed 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 disposed between the third middle core portion 31c and the first middle core portion 31a. Furthermore, gaps 31g may be disposed both 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 gaps 31g may be omitted.

[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 that constitutes 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 that constitutes 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 that constitutes the third middle core portion 31c. 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 that constitutes the second side core portion 332.

[0094] As shown in FIG. 6 , the middle core portion 31 is composed of a portion of the first end core piece 45a, a portion 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. In other words, the first middle core portion 31a and the first end core portion 35a are formed by an integrally molded powder compact. The second middle core portion 31b and the second end core portion 35b are formed by 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. In other words, the third middle core portion 31c is formed by a composite material compact. The third middle core portion 31c is formed by 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 formed by a composite material compact.

[0095] The high B core pieces 4H and the low B core pieces 4L may be interchanged. That is, 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] 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 low B core pieces 4L and two or more high B core pieces 4H, it is easy to finely set the magnetic characteristics of the entire magnetic core 3.

[0097] (Variation 2) <Third Arrangement> The configuration of the magnetic core 3 shown in FIG. 7 illustrates a third arrangement. The magnetic core 3 shown in FIG. 7 is composed of E-shaped low-B core pieces 4L and E-shaped high-B core pieces 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, each having a first portion 331a, 332a and a second portion 331b, 332b. The first portion 331a and the second portion 331b of the first side core portion 331 are aligned in series along the X-axis. The first portion 332a and the second portion 332b of the second side core portion 332 are aligned in series along the X-axis. The first portions 331a, 332a are coupled to the first end core portion 35a. The second portions 331b, 332b are coupled to the second end core portion 35b. The lengths of the first portions 331a, 332a and the second portions 331b, 332b can be set as appropriate. In the example shown in Figure 7, the first portions 331a, 332a and the second portions 331b, 332b are in contact with each other. Unlike the example shown in Figure 7, there may be gaps between the first portions 331a, 332a and the second portions 331b, 332b.

[0098] 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 formed by an integrally molded body of a composite material. 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. In other words, 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 formed by 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 remainder 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 remainder 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 remainder of the second side core portion 332.

[0099] When the first portions 331a, 332a and the second portions 331b, 332b are formed 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 of the first side core portion 331 is calculated, and the product BSs2 of the saturation magnetic flux density Bs2 and the cross-sectional area Sm of the second side core portion 332 is 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 obtain 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 obtain 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 also 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 331.

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

[0101] In the example shown in Figure 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. In other words, 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 formed by an integrally molded composite material compact. 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. In other words, the second middle core portion 31b and the second end core portion 35b are formed by an integrally molded powder compact. In the example shown in Figure 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 remainder of the middle core portion 31.

[0102] The shapes of the high B core pieces 4H and the low B core pieces 4L may be interchanged. That is, the high B core pieces 4H may be E-shaped core pieces 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 pieces 4L may be T-shaped core pieces 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 there is one low B core piece 4L and one high B core piece 4H, the number of core pieces 4 is small, and the magnetic core 3 is easy to manufacture.

[0104] <Converter / Power Conversion Apparatus> The reactor 1 of the embodiment can be used in applications that satisfy the following energization conditions. The energization conditions include, for example, a maximum DC current of approximately 100 A to 1000 A, an average voltage of approximately 100 V to 1000 V, and an operating frequency of approximately 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 apparatus that includes this 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 plug may also be provided.

[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 approximately 200 V or more and 300 V or less, to approximately 400 V or more and 700 V or less, when the vehicle 1200 is running, and supplies power to the inverter 1120. During regeneration, the converter 1110 reduces 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, and when regenerating, it 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 the elements on and off. The conversion of the input voltage here refers to boosting and bucking the voltage. 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 hinders changes in current flowing through the circuit, and has the function of smoothing 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 converter 1110, vehicle 1200 also includes a power supply converter 1150 connected to main battery 1210, and an auxiliary power supply converter 1160 connected to main battery 1210 and sub-battery 1230, which serves as a power source for auxiliary equipment 1240, and converts the high voltage of main battery 1210 to low voltage. Converter 1110 typically performs DC-DC conversion, while power supply converter 1150 and auxiliary power supply converter 1160 perform AC-DC conversion. Some power supply converters 1150 perform DC-DC conversion. Reactors for power supply converter 1150 and auxiliary power supply converter 1160 may have the same configuration as reactor 1 of the embodiment, but may be modified in size or shape as appropriate. Furthermore, reactor 1 of the embodiment may also be used for a converter that converts input power and that only boosts or only bucks the voltage.

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

[0110] Test example 1 used a magnetic core 3 having the configuration shown in Fig. 3. The first middle core piece 41a and the second middle core piece 41b constituting the middle core portion 31 were low-B core pieces 4L formed by a composite material molding. The first side core piece 431 and the second side core piece 432 constituting the side core portion 33 were low-B core pieces 4L formed by a composite material molding. The first end core piece 45a and the second end core piece 45b constituting the end core portion 35 were high-B core pieces 4H formed 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 BS ratio was 1.2 to 0.4. The magnetic core No. 1-0, which was designed so that the BS ratio was 1.2, was used as the reference. The configuration of the reference magnetic core is shown below.

[0112] (Dimensions of magnetic core) Length L of magnetic core: 77 mm Width W of magnetic core: 82 mm Height H of magnetic core: 30 mm As shown in Figure 1, length L is the dimension in the X direction. 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 part Lm: 47 mm - Width of middle core part Wm: 30 mm - Length of gap part: 1.5 mm - Length of side core part Ls: 47 mm - Width of side core part Ws: 15 mm - Length of end core part Le: 82 mm - Width of end core part We: 15 mm The height of each core part is 30 mm.

[0114] (Materials of the core pieces that make up each core section) Middle core section: Composite material compact Side core section: Composite material compact End core section: 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] Models No. 1-1 to No. 1-5 are models in which the BS ratio of the magnetic core was adjusted by reducing the width of each of the side core portions and end core portions 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 portion, 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 portion.

[0116]

[0117] The inductance and loss were analyzed for reactor models No. 1-0 to No. 1-5. To analyze the inductance and loss, JMAG-Designer 22.0 manufactured by JSOL Corporation, a commercially available electromagnetic field analysis software, was used to perform a magnetic field transient response analysis.

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

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

[0120]

[0121] As shown in Table 2, No. 1-1 to No. 1-4 have improved inductance at 250 A and 300 A compared to No. 1-0. In other words, models designed with a magnetic core having a BS ratio of 0.5 or greater and 1.0 or less have high inductance at high currents. In particular, No. 1-2 and No. 1-3 have higher inductance at 250 A and 300 A than No. 1-1. Furthermore, No. 1-1 to No. 1-4 have lower 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, the high B core pieces 4H and low B core pieces 4L were interchanged in the magnetic core 3 having the configuration shown in Figure 3. The first middle core pieces 41a and second middle core pieces 41b constituting the middle core portion 31 were high B core pieces 4H formed by powder compacts. The first side core pieces 431 and second side core pieces 432 constituting the side core portion 33 were high B core pieces 4H formed by powder compacts. The first end core pieces 45a and second end core pieces 45b constituting the end core portion 35 were low B core pieces 4L formed by composite material compacts.

[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 BS ratio was 1.2 to 0.4. The magnetic core No. 2-0, which was designed so that the BS ratio was 1.2, was used as the reference. The configuration of the reference magnetic core is shown below.

[0124] (Dimensions of the magnetic core) Length of the magnetic core L: 89 mm Width of the magnetic core W: 94 mm Height of the magnetic core H: 30 mm

[0125] (Dimensions of each core part) - Length of middle core part Lm: 47 mm - Width of middle core part Wm: 30 mm - Length of gap part: 1.5 mm - Length of side core part Ls: 47 mm - Width of side core part Ws: 21 mm - Length of end core part Le: 94 mm - Width of end core part We: 21 mm The height of each core part is 30 mm.

[0126] (Materials of the core pieces that make up each core section) Middle core section: powder compact Side core section: powder compact End core section: composite material 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.

[0127] Models No. 2-1 to No. 2-5 are models in which the magnetic core ratio BS was adjusted by reducing the width of each of the side core portions and end core portions 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 portion, 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 portion.

[0128]

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

[0130]

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

[0132] REFERENCE SIGNS LIST 1 Reactor 2 Coil 2a First end 2b Second end 3 Magnetic core 31 Middle core portion 31a First middle core portion 31b Second middle core portion 31c Third middle core portion 31g Gap portion 31x Cross section 33 Side core portion 331 First side core portion 332 Second side core portion 331a, 332a First portion 331b, 332b Second portion 33x Cross section 35 End core portion 35a First end core portion 35b Second end core portion 35x Cross section 4 Core piece 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 REFERENCE SIGNS LIST 1100 Power conversion device, 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 Vehicle 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. A reactor comprising: a coil and a magnetic core composed of a plurality of core pieces, the magnetic core having a shape of θ, the magnetic core comprising: a middle core section arranged inside the coil, side core sections arranged in parallel with the middle core section so as to sandwich the coil, and end core sections arranged to face both ends of the coil, the plurality of core pieces including low B core pieces and high B core pieces, the low B core pieces and the high B core pieces being formed from materials having different saturation magnetic flux densities, the saturation magnetic flux density of the low B core pieces being lower than the saturation magnetic flux density of the high B core pieces, a ratio BS of the magnetic core being 0.5 or more and 1.0 or less, the ratio BS being the ratio of the product BSm of the saturation magnetic flux density Bm and the cross-sectional area Sm in the middle core section to the sum of the product BSe of the saturation magnetic flux density Be and the cross-sectional area Se in the end core sections and the product BSs of the saturation magnetic flux density Bs and the cross-sectional area Ss in the side core sections.

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

3. A reactor according to claim 1 or 2, wherein the high B core pieces are formed by compacting soft magnetic powder.

4. A reactor according to any one of claims 1 to 3, wherein the low B core piece is formed by molding a composite material in which soft magnetic powder is dispersed in resin.

5. A reactor according to any one of claims 1 to 4, wherein the number of the plurality of core pieces is two, and the number of the low B core piece and the number of the high B core piece are each one.

6. The reactor according to claim 5, wherein 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 having a part of the middle core portion, the first end core portion, a part of the first side core portion and a part of the second side core portion, and 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 reactor according to claim 5, wherein 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 having a part of the middle core portion, the first end core portion, the first side core portion, and the second side core portion, and the remaining core piece of the low B core piece and the high B core piece has a T-shape having a remainder of the middle core portion and the second end core portion.

8. A reactor according to any one of claims 1 to 4, 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 has a first middle core portion connected to the first end core portion, a second middle core portion connected to the second end core portion, and a third middle core portion disposed between the first middle core portion and the second middle core portion, the multiple core pieces have 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, and an I-shaped second side core piece constituting the second side core portion, the first end core piece and the second end core piece being either of the low B core pieces or the high B core pieces, 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 reactor according to claim 8, wherein 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 include 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, and 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 of the low B core piece and the high B core piece, and the middle core piece, the first side core piece and the second side core piece are the remaining core pieces of the low B core piece and the high B core piece.

11. The reactor according to any one of claims 1 to 10, wherein the middle core portion has a gap portion.

12. The reactor according to claim 11, wherein the length of the gap is 0.5 mm or more and 3 mm or less.

13. A converter comprising a reactor according to any one of claims 1 to 12.

14. A power conversion device comprising the converter according to claim 13.

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