Patent Application
20240161962
The present disclosure relates to a core piece, a reactor, a converter, and a power conversion device.
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-056130 filed in Japan on Mar. 29, 2021, the entire content of which is hereby incorporated by reference.
A reactor disclosed in Patent Document 1 includes a coil and a magnetic core. The magnetic core is configured by combining a plurality of core pieces. Some core pieces are constituted by a molded hardened body. A molded hardened body is a molded body of a composite material obtained by dispersing a soft magnetic powder in a resin.
A core piece according to an aspect of the present disclosure is a core piece constituted by a molded body of a composite material in which a soft magnetic powder is dispersed in a resin, the core piece including: a middle core portion configured to be arranged inside a coil; and an end core portion configured to face an end face of the coil, wherein the middle core portion includes a hole portion or a groove portion extending in an axial direction of the coil, and in a lateral cross-section of the middle core portion, a radius of a first inscribed circle is less than or equal to 0.6 times a radius of a reference inscribed circle, the lateral cross-section being a cross-section of the middle core portion passing through the hole portion or the groove portion along a plane orthogonal to the axial direction of the coil, the first inscribed circle being a largest inscribed circle between an outline of the hole portion or the groove portion in the lateral cross-section and a peripheral outline of the middle core portion in the lateral cross-section, the reference inscribed circle being a largest inscribed circle in a first virtual outline, and the first virtual outline being a smallest quadrilateral circumscribing the lateral cross-section.
A reactor according to an aspect of the present disclosure includes: a coil; and a magnetic core, wherein the coil includes one winding portion, the magnetic core is a compound body that is a combination of a first core piece and a second core piece, and at least either the first core piece or the second core piece is the core piece according to an aspect of the present disclosure.
A converter according to an aspect of the present disclosure includes the reactor according to an aspect of the present disclosure.
A power conversion device according to an aspect of the present disclosure includes the converter according to an aspect of the present disclosure.
A composite material molded body is manufactured as follows. A raw material for the composite material molded body is poured into a mold. The raw material is a fluid material in which a soft magnetic powder is dispersed in an unsolidified resin. The raw material resin is then solidified.
In the manufacturing process, the solidification rate of the surface of the core piece in contact with the mold is faster than the solidification rate of the interior of the core piece. A void is formed inside the core piece if there is a large difference between the solidification rate at the fastest solidifying location and the solidification rate at the slowest solidifying location.
When a reactor is used, the reactor itself vibrates. Also, depending on the location where the reactor is installed, there are cases where the reactor vibrates due to the transmission of external vibration to the reactor. There is concern that a void may become a starting point of cracking caused by vibration.
One object of the present disclosure is to provide a core piece having fewer voids. Another object of the present disclosure is to provide a reactor in which a crack is less likely to be formed in a core piece due to vibration. Another object of the present disclosure is to provide a converter that includes such a reactor, and a power conversion device that includes such a converter.
A core piece of the present disclosure has fewer voids.
In the reactor of the present disclosure, a crack is less likely to be formed in the core piece due to vibration.
The converter according to an aspect of the present disclosure and the power conversion device according to an aspect of the present disclosure have stable performance.
First, embodiments of the present disclosure will be listed and described.
(1) A core piece according to an aspect of the present disclosure is a core piece constituted by a molded body of a composite material in which a soft magnetic powder is dispersed in a resin, the core piece including: a middle core portion configured to be arranged inside a coil; and an end core portion configured to face an end face of the coil, wherein the middle core portion includes a hole portion or a groove portion extending in an axial direction of the coil, and in a lateral cross-section of the middle core portion, a radius of a first inscribed circle is less than or equal to 0.6 times a radius of a reference inscribed circle, the lateral cross-section being a cross-section of the middle core portion passing through the hole portion or the groove portion along a plane orthogonal to the axial direction of the coil, the first inscribed circle being a largest inscribed circle between an outline of the hole portion or the groove portion in the lateral cross-section and a peripheral outline of the middle core portion in the lateral cross-section, the reference inscribed circle being a largest inscribed circle in a first virtual outline, and the first virtual outline being a smallest quadrilateral circumscribing the lateral cross-section.
In general, in a core piece constituted by a composite material molded body, the difference between the solidification rate at the fastest solidifying location and the solidification rate at the slowest solidifying location in the manufacturing process is likely to be higher in the middle core portion of the core piece than in other portions of the core piece. If the difference between the solidification rates is high, a void is likely to be formed as described above. In other words, a void is likely to be formed in the middle core portion.
In the middle core portion of the core piece, the radius of the first inscribed circle is less than or equal to 0.6 times the radius of the reference inscribed circle, and therefore the difference between the solidification rates is low, and a void is less likely to be formed. The core piece therefore has few voids, thus making it easier to construct a reactor in which a crack is less likely to be formed in the middle core portion due to vibration.
(2) In the core piece according to an aspect, an inner area of the hole portion or the groove portion in the lateral cross-section may be less than or equal to 10% of an area of a second virtual outline, the second virtual outline being a smallest shape enclosing the lateral cross-section.
The difference between the solidification rates in the middle core portion of the core piece is small, thus making it easier to suppress a decrease in the magnetic path area of the middle core portion and an increase in the size of the middle core portion.
(3) In the core piece according to an aspect, the hole portion or the groove portion may overlap a center of gravity of the first virtual outline.
If there are no hole portions and no groove portions, the solidification rate is likely to be slowest at the center of gravity of the first virtual outline. Due to the hole portion or the groove portion being provided in the core piece so as to overlap the center of gravity of the first virtual outline, the solidification rate at the slowest solidifying location is faster than the solidification rate at the slowest solidifying location in the case where no hole portion or groove portion is provided. For this reason, it is easier to reduce the difference between the solidification rates in the middle core portion of the core piece.
(4) In the core piece according to an aspect, the middle core portion may include the hole portion, and an outline shape of the hole portion may be a circular shape or a polygonal shape.
A void is less likely to be formed in the core piece having the hole portion with the outline shape described above. Moreover, the core piece having the hole portion with the outline shape described above can be molded more easily.
(5) In the core piece according to an aspect, the middle core portion may include the groove portion, and the lateral cross-section may be H-shaped or U-shaped or constituted by two parallel I-shaped portions.
A void is less likely to be formed in the core piece whose lateral cross-section is shaped as described above. Moreover, the core piece whose lateral cross-section is shaped as described above can be molded more easily.
(6) In the core piece according to an aspect, the hole portion or the groove portion may extend continuously from an end face of the middle core portion to an outward face of the end core portion.
The above-described core piece is suitable for a reactor that includes a later-described molded resin portion. The reason for this is that the hole portion can be used as a channel for the supply of the raw material for the molded resin portion during the formation process for the molded resin portion.
(7) In the core piece according to an aspect, the hole portion or the groove portion may extend continuously from an end face of the middle core portion to an intermediate position in the end core portion, or extends continuously from an outward face of the end core portion to an intermediate position in the middle core portion, and in a vertical cross-section of the core piece, a radius of a second inscribed circle may be less than or equal to 0.6 times the radius of the reference inscribed circle, the vertical cross-section being a cross-section of the core piece passing through the hole portion or the groove portion along a plane orthogonal to a side view direction of the core piece, and the second inscribed circle being a largest inscribed circle in contact with the end face of the middle core portion and either a bottom portion of the hole portion or an end portion of the groove portion in the vertical cross-section, or a largest inscribed circle in contact with the outward face of the end core portion and either the bottom portion of the hole portion or the end portion of the groove portion in the vertical cross-section.
In the above-described core piece, the radius of the second inscribed circle is less than or equal to 0.6 times the radius of the reference inscribed circle, and therefore a void is less likely to be formed, and a crack is less likely to be formed due to vibration.
(8) In the core piece according to an aspect, the hole portion or the groove portion may extend continuously from an end face of the middle core portion to an intermediate position in the end core portion, or extends continuously from an outward face of the end core portion to an intermediate position in the middle core portion, and in a horizontal cross-section of the core piece, a radius of a third inscribed circle may be less than or equal to 0.6 times the radius of the reference inscribed circle, the horizontal cross-section being a cross-section of the core piece passing through the hole portion or the groove portion along a plane orthogonal to a plan view direction of the core piece, and the third inscribed circle being a largest inscribed circle in contact with the end face of the middle core portion and either a bottom portion of the hole portion or an end portion of the groove portion in the horizontal cross-section, or a largest inscribed circle in contact with the outward face of the end core portion and either the bottom portion of the hole portion or the end portion of the groove portion in the horizontal cross-section.
In the core piece, the radius of the third inscribed circle is less than or equal to 0.6 times the radius of the reference inscribed circle, and therefore a void is less likely to be formed, and a crack is less likely to be formed due to vibration.
(9) A reactor according to an aspect of the present disclosure includes: a coil; and a magnetic core, wherein the coil includes one winding portion, the magnetic core is a compound body that is a combination of a first core piece and a second core piece, and at least either the first core piece or the second core piece is the core piece according to any one of aspects (1) to (8).
Due to the reactor including the above-described core piece, a crack is less likely to be formed in the core piece due to vibration.
(10) A converter according to an aspect of the present disclosure includes the reactor according to aspect (9).
Due to including the above-described reactor, the converter has stable performance.
(11) A power conversion device according to an aspect of the present disclosure includes the converter according to aspect (10).
Due to including the above-described converter, the power conversion device has stable performance.
Details of embodiments of the present disclosure will be described below with reference to the drawings. Like reference numerals in the drawings indicate elements having like names.
[Reactor]
A reactor 1 of the first embodiment will be described below with reference to
[Coil]
The coil 2 includes one hollow winding portion 21, as shown in
The winding portion 21 may have a polygonal tubular shape or a circular tubular shape. A rectangular tubular shape may also be a square tubular shape. The winding portion 21 of the present embodiment has a square tubular shape, as shown in
The winding portion 21 is configured by winding a single coil wire into a spiral without a joint. A known coil wire can be used for the coil wire. A covered flat wire is used as the coil wire of the present embodiment. The conductor wire of the covered flat wire is constituted by a copper flat wire. The insulating coating of the covered flat wire is made of enamel. The winding portion 21 is constituted by an edgewise coil obtained by winding the covered flat wire edgewise.
In the present embodiment, a first end portion 21a and a second end portion 21b of the winding portion 21 are drawn circumferentially outward from the winding portion 21 at one end and the other end, respectively, in the axial direction of the winding portion 21. Although not shown, the insulating coating is stripped from the first end portion 21a and the second end portion 21b of the winding portion 21 to expose the conductor wire. In the present embodiment, the exposed portions of the conductor wire are drawn out of a later-described molded resin portion 4 and are connected to terminal members. The terminal members are not shown. An external device is connected to the coil 2 via the terminal members. The external device is not shown. The external device is a power source that supplies electrical power to the coil 2, for example.
[Magnetic Core]
As shown in
(Middle Core Portion)
The middle core portion 31 has a portion located inside the winding portion 21. The middle core portion 31 has a shape corresponding to the inner peripheral shape of the winding portion 21, for example. In the present embodiment, the middle core portion 31 is shaped as a quadrangular prism as shown in
The length of the middle core portion 31 along the first direction D1 is substantially equivalent to the length of the winding portion 21 along the axial direction, as shown in
In the present embodiment, the length of the middle core portion 31 along the first direction D1 is shorter than the length of the first side core portion 321 along the first direction D1 and the length of the second side core portion 322 along the first direction D1. The length of the first side core portion 321 along the first direction D1 is a sum length L21f+L21s, that is to say the sum of a length L21f of a first side core portion 321f along the first direction D1 and a length L21s of a first side core portion 321s along the first direction D1, which will be described later. The length of the second side core portion 322 along the first direction D1 is a sum length L22f+L22s, that is to say the sum of a length L22f of the second side core portion 322f along the first direction D1 and a length L22s of the second side core portion 322s along the first direction D1, which will be described later.
As an alternative to the present embodiment, the length of the middle core portion 31 along the first direction D1 may be equivalent to the length of the first side core portion 321 along the first direction D1 and the length of the second side core portion 322 along the first direction D1.
There are cases where the middle core portion 31 is constituted by two core portions, namely the first middle core portion 31f and the second middle core portion 31s, as in the case where the combination of the first core piece 3f and the second core piece 3s is of the E-E type as in the present embodiment, or of the E-T type or the F-F type, which will be described later, for example. Although not shown, the middle core portion 31 may be constituted by one core portion, namely the first middle core portion 31f, as in the case where the aforementioned combination is of the E-I type, the E-U type, the T-U type, or the F-L type, for example.
(First Side Core Portion and Second Side Core Portion)
As shown in
The length of the first side core portion 321 (L21f+L21s) and the length of the second side core portion 322 (L22f+L22s) are longer than the length of the winding portion 21 along the axial direction, as shown in
There are cases where the first side core portion 321 is constituted by two core portions, namely the first side core portion 321f and the first side core portion 321s, as in the case where the combination of the first core piece 3f and the second core piece 3s is of the E-E type as in the present embodiment, or of the E-U type, which will be described later, for example. Although not shown, the first side core portion 321 may be constituted by one core portion, namely the first side core portion 321f, as in the case where the aforementioned combination is of the E-T type, the E-I type, the T-U type, the F-F type, or the F-L type, for example. There are cases where the second side core portion 322 is constituted by two core portions, namely the second side core portion 322f and the second side core portion 322s, as in the case where the aforementioned combination is of the E-E type or the E-U type, for example. Although not shown, the second side core portion 322 may be constituted by one core portion, namely the second side core portion 322f, as in the case where the aforementioned combination is of the E-T type, the E-I type, the T-U type, the F-F type, or the F-L type, for example.
In the present embodiment, the sum of the cross-sectional area of the first side core portion 321 and the cross-sectional area of the second side core portion 322 is the same as the cross-sectional area of the middle core portion 31. In the present embodiment, the middle core portion 31, the first side core portion 321, and the second side core portion 322 have the same length along the third direction D3. In other words, the sum of the length of the first side core portion 321 along the second direction D2 and the length of the second side core portion 322 along the second direction D2 corresponds to the length of the middle core portion 31 along the second direction D2. The length of the first side core portion 321 along the second direction D2 and the length of the second side core portion 322 along the second direction D2 are 0.5 times the length of the middle core portion 31 along the second direction D2. The lengths of the first side core portion 321 and the second side core portion 322 along the third direction D3 are greater than or equal to the length of the middle core portion 31 along the second direction D2.
(First End Core Portion and Second End Core Portion)
The first end core portion 33f faces a first end face of the winding portion 21. The second end core portion 33s faces a second end face of the winding portion 21. Here, “faces” means that an inward face 33i of the first end core portion 33f and the first end face of the winding portion 21 face each other. This also means that the inward face of the second end core portion 33s and the second end face of the winding portion 21 face each other. In the present embodiment, the shape of the first end core portion 33f and the shape of the second end core portion 33s are thin prismatic shapes, as shown in
The length of the first end core portion 33f along the second direction D2 is longer than the length of the winding portion 21 along the second direction D2. In the present embodiment, the length of the first end core portion 33f along the third direction D3 is shorter than the length of the winding portion 21 along the third direction D3, as shown in
(First Core Piece and Second Core Piece)
Various combinations of the first core piece 3f and the second core piece 3s can be obtained by appropriately selecting the shapes of the first core piece 3f and the second core piece 3s. The shape of the first core piece 3f and the shape of the second core piece 3s may be asymmetrical as in the present embodiment, or, unlike the present embodiment, may be symmetrical. Here, “asymmetrical” means having different shapes. Also, “symmetrical” means having the same shape and size.
The first core piece 3f and the second core piece 3s are divided in the first direction D1 as shown in
A gap portion 3g, which will be described later, may be provided between the first core piece 3f and the second core piece 3s, or the gap portion 3g may not be provided.
The E-shaped first core piece 3f of the present embodiment includes the first middle core portion 31f, the first side core portion 321f, the second side core portion 322f, and the first end core portion 33f. The first middle core portion 31f constitutes a portion of the middle core portion 31. The first side core portion 321f constitutes a portion of the first side core portion 321. The second side core portion 322f constitutes a portion of the second side core portion 322. The first core piece 3f is a molded body in which the first middle core portion 31f, the first side core portion 321f, the second side core portion 322f, and the first end core portion 33f are integrated with each other.
The first end core portion 33f has an inward face 33i and an outward face 33o. The inward face 33i is the face that faces the first end face of the winding portion 21 as described above. The outward face 33o is the face provided on the side opposite to the inward face 33i in the first direction D1. The outer peripheral faces of the first middle core portion 31f, the first side core portion 321f, and the second side core portion 322f are connected to the inward face 33i. The first side core portion 321f and the second side core portion 322f are provided at respective ends of the first end core portion 33f in the second direction D2. The first middle core portion 31f is provided at the center of the first end core portion 33f in the second direction D2.
As described above, the second core piece 3s of the present embodiment, which is E-shaped and asymmetric with the first core piece 3f, includes the second middle core portion 31s, the first side core portion 321s, the second side core portion 322s, and the second end core portion 33s. The second middle core portion 31s constitutes the remaining portion of the middle core portion 31. The first side core portion 321s constitutes the remaining portion of the first side core portion 321. The second side core portion 322s constitutes the remaining portion of the second side core portion 322. The second core piece 3s is a molded body in which the second middle core portion 31s, the first side core portion 321s, the second side core portion 322s, and the second end core portion 33s are integrated with each other. The positions and connections of the core portions in the second core piece 3s are the same as the positions and connections of the core portions in the first core piece 3f described above.
The first core piece 3f and the second core piece 3s are combined such that the end face of the first side core portion 321f and the end face of the first side core portion 321s are in contact with each other, and furthermore the end face of the second side core portion 322f and the end face of the second side core portion 322s are in contact with each other. A gap is provided between an end face 311e of the first middle core portion 31f and an end face 312e of the second middle core portion 31s. The length of this gap along the first direction D1 corresponds to a length Lg of the gap portion 3g along the first direction D1.
As an alternative to the present embodiment, the first core piece 3f and the second core piece 3s may be combined such that a gap is provided between the end face of the first side core portion 321f and the end face of the first side core portion 321s, and furthermore a gap is provided between the end face of the second side core portion 322f and the end face of the second side core portion 322s. If the length of the middle core portion 31 along the first direction D1 is shorter than the length of the first side core portion 321 along the first direction D1, a gap is also provided between the end face 311e of the first middle core portion 31f and the end face 312e of the second middle core portion 31s. In this case, the distance between the end face 311e and the end face 312e is larger than the distance between the end face of the first side core portion 321f and the end face of the first side core portion 321s, and also the distance between the end face of the second side core portion 322f and the end face of the second side core portion 322s. It is preferable that the first core piece 3f and the second core piece 3s are combined with each other using the molded resin portion 4, which will be described later.
<Hole Portion>
Out of the first core piece 3f and the second core piece 3s, the core piece that is constituted by a composite material molded body has a hole portion 34 as shown in
As shown in
The outline shape, size, and location of the hole portion 34 in the lateral cross-section of the first middle core portion 31f can be selected as appropriate such that a radius r1 of a first inscribed circle C1 is less than or equal to 0.6 times a radius r0 of a reference inscribed circle C0. The first inscribed circle C1 of the present embodiment is the largest inscribed circle between the peripheral outline of the first middle core portion 31f and the outline of the hole portion 34 in the lateral cross-section of the first middle core portion 31f. The reference inscribed circle C0 is the largest inscribed circle in a first virtual outline V1. The first virtual outline V1 is the smallest quadrilateral that circumscribes the lateral cross-section of the first middle core portion 31f. Although the first virtual outline V1 in
In the first middle core portion 31f in which the radius r1 is less than or equal to 0.6 times the radius r0, a void is less likely to be formed during the manufacturing process for the first core piece 3f. This is because in the first middle core portion 31f in which the radius r1 satisfies less than or equal to 0.6 times the radius r0, the difference between the solidification rate at the fastest solidifying location and the solidification rate at the slowest solidifying location in the manufacturing process is small. For this reason, a crack is less likely to be formed in the first middle core portion 31f due to vibration. The radius r1 may also be less than or equal to 0.55 times the radius r0, and particularly less than or equal to 0.5 times the radius r0. The radius r1 may be greater than or equal to 0.44 times the radius r0, for example. When the radius r1 is greater than or equal to 0.44 times the radius r0, the magnetic path area of the first middle core portion 31f is not excessively small, thus making it easier to suppress deterioration of a magnetic characteristic of the first core piece 3f. Thus, the radius r1 may be 0.44 to 0.6 times the radius r0 inclusive, more preferably 0.44 to 0.55 times the radius r0 inclusive, and particularly 0.44 to 0.5 times the radius r0 inclusive.
The outline shape of the hole portion 34 in the lateral cross-section of the first middle core portion 31f is circular or polygonal, for example. A circular shape includes the perfect circle shown in
The size of the hole portion 34 in the lateral cross-section of the first middle core portion 31f, that is to say an inner area S1 of the hole portion 34, may be less than or equal to 10% of an area S2 of the second virtual outline V2. The inner region of the hole portion 34 is the region surrounded by the outline of the hole portion 34. The second virtual outline V2 is the smallest shape that encloses the lateral cross-section of the first middle core portion 31f. In the present embodiment, the lateral cross-section of the first middle core portion 31f has a rectangular shape, and therefore the second virtual outline V2 has the same shape and size as the first virtual outline V1. If the lateral cross-section of the first middle core portion 31f has a circular shape unlike the present embodiment, for example, the second virtual outline V2 is circular and has a different shape and size from the first virtual outline V1.
According to the first core piece 3f whose area S1 is less than or equal to 10% of the area S2, it is possible to suppress the formation of a void in the first middle core portion 31f during the manufacturing process for the first core piece 3f. Also, according to the first core piece 3f, it is possible to more easily suppress a decrease in the magnetic path area of the first middle core portion 31f and an increase in the size of the first middle core portion 31f. The area S1 may also be less than or equal to 7% of the area S2, and particularly less than or equal to 5% of the area S2. The area S1 may be greater than or equal to 1% of the area S2. In the first core piece 3f whose area S1 is greater than or equal to 1% of the area S2, a void is less likely to be formed in the first core piece 3f during the manufacturing process for the first core piece 3f. Thus, the area S1 may be 1% to 10% of the area S2 inclusive, furthermore 1% to 7% of the area S2 inclusive, and particularly 2% to 5% of the area S2 inclusive.
The position at which the hole portion 34 is formed in the lateral cross-section of the first middle core portion 31f may be a position overlapping the center of gravity of the first virtual outline V1. The center of gravity of the first virtual outline V1 is the intersection of the diagonal lines of the first virtual outline V1. The state in which the hole portion 34 overlaps the center of gravity of the first virtual outline V1 refers to a state in which the outline of the hole portion 34 encloses the center of gravity of the first virtual outline V1. If the hole portion 34 is not provided, the solidification rate is likely to be the slowest at the location of the center of gravity of the first virtual outline V1. Due to the hole portion 34 being provided so as to overlap the center of gravity of the first virtual outline V1, the solidification rate at the slowest solidifying location in the case of having the hole portion 34 is faster than the solidification rate at the slowest solidifying location in the case of not having the hole portion 34. For this reason, the difference between the solidification rate at the fastest solidifying location and the solidification rate at the slowest solidifying location in the first middle core portion 31f is likely to be small. Also, due to the hole portion 34 being provided so as to overlap the center of gravity of the first virtual outline V1, the distance between the outer peripheral surface of the first middle core portion 31f and the outline of the hole portion 34 is likely to be uniform along the circumferential direction of the hole portion 34. In particular, the hole portion 34 may be provided such that the center of gravity of the region surrounded by the outline of the hole portion 34 coincides with the center of gravity of the first virtual outline V1.
In
As shown in
The hole portion 34, which is a through hole, is continuous from the end face 311e of the first middle core portion 31f to the outward face 33o of the first end core portion 33f. In other words, the openings of the hole portion 34 are respectively connected to the end face 311e and the outward face 33o. In the case where the reactor 1 includes the later-described molded resin portion 4, the hole portion 34 can be used as a channel for the supply of the raw material for the molded resin portion 4 from the outside of the first core piece 3f through the space between the end face 311e and the end face 312e during the formation process for the molded resin portion 4. Note that the hole portion 34 may be a blind hole as in a second embodiment described later with reference to
<Other Aspects>
In the case where the first core piece 3f has the first side core portion 321f and the second side core portion 322f as in the present embodiment, a radius r4 of a fourth inscribed circle C4 and a radius r5 of a fifth inscribed circle C5 are less than or equal to 0.6 times the radius r0 of the above-described reference inscribed circle C0. The fourth inscribed circle C4 is the largest inscribed circle within the peripheral outline of the lateral cross-section of the first side core portion 321f. The fifth inscribed circle C5 is the largest inscribed circle within the peripheral outline of the lateral cross-section of the second side core portion 322f. As described above, in the present embodiment, the lengths of the first side core portion 321f and the second side core portion 322f along the second direction D2 are 0.5 times the length of the first middle core portion 31f along the second direction D2. Also, the lengths of the first side core portion 321f and the second side core portion 322f along the third direction D3 are greater than or equal to the length of the first middle core portion 31f along the second direction D2. In other words, the radius r4 and the radius r5 are 0.5 times the radius r0. Also, as shown in
(Materials)
At least either the first core piece 3f or the second core piece 3s is constituted by a composite material molded body. The first core piece 3f and the second core piece 3s may be constituted by different materials, or may be constituted by the same material. Being constituted by different materials includes not only the case in which the materials of the individual constituent elements of the core portions are different, but also the case in which the content ratios of constituent elements are different even though the individual constituent elements are constituted by the same material. For example, even in the case where the first core piece 3f and the second core piece 3s are constituted by a composite material molded body, if at least either the soft magnetic powder or the resin constituting the composite material include different materials, or if the materials constituting the soft magnetic powder and the resin are the same but the content ratios of the materials constituting the soft magnetic powder and the resin are different, the materials are considered to be different from each other. As described above, in the present embodiment, the first core piece 3f is constituted by a composite material molded body, and the second core piece 3s is constituted by a powder compact.
The composite material molded body is obtained by dispersing a soft magnetic powder in resin. The first core piece 3f constituted by a composite material molded body is manufactured as described below. A core corresponding to the hole portion 34 described above is placed inside a mold. The raw material for the composite material molded body is then poured into the mold. The raw material is a fluid material, which includes a soft magnetic powder dispersed in an unsolidified resin. The raw material resin is then solidified.
The soft magnetic particles constituting the soft magnetic powder are particles of a soft magnetic metal, coated particles that are particles of a soft magnetic metal coated with an insulating coating, or particles of a soft magnetic non-metal. Examples of soft magnetic metals include pure iron and an iron-based alloy. Examples of iron-based alloys include Fe—Si alloy and Fe—Ni alloy. The insulating coating is made of phosphate, for example. One example of a soft magnetic non-metal is ferrite.
The resin of the composite material is a thermosetting resin or a thermoplastic resin, for example. Examples of thermosetting resins include epoxy resins, phenol resins, silicone resins, and urethane resins. Examples of thermoplastic resins include polyphenylene sulfide resins, polyamide resins, liquid crystal polymers, polyimide resins, and fluorine resins. Examples of polyamide resins include nylon 6, nylon 66, and nylon 9T.
The composite material molded body may contain a ceramic filler. Examples of ceramic fillers include alumina and silica.
The content of the soft magnetic powder in the molded body of the composite material is 20% by volume or more and 80% by volume or less, for example. The content of the resin in the composite material molded body is 20% by volume or more and 80% by volume or less, for example. These content ratios are values when the composite material is 100% by volume, for example.
The powder compact is obtained by subjecting a soft magnetic powder to compression molding. Compared with a composite material, the powder compact can have a higher percentage of the soft magnetic powder in the core piece. For this reason, it is easy to improve a magnetic characteristic of the powder compact. Examples of magnetic characteristics include saturation magnetic flux density and relative magnetic permeability. Also, a powder compact includes a smaller amount of resin and a larger amount of soft magnetic powder than a molded body of composite material, and therefore has excellent heat dissipation. The magnetic powder content in the powder compact is 85% by volume or more and 99.99% by volume or less, for example. This content ratio is a value when the powder compact is 100% by volume.
The content of the soft magnetic powder in the powder compact or the composite material molded body is considered to be equivalent to the ratio of the area of the soft magnetic powder to the area of the lateral cross-section of the molded body. The content of the soft magnetic powder in the molded body is determined as follows. A cross-section of the molded body is observed with an SEM (Scanning Electron Microscope) to obtain an observation image. The magnification of the SEM is set from 200 to 500 times. Also, ten or more observation images are acquired. The total cross-sectional area is 0.1 cm2 or more. One observation image may be acquired for each cross-section, or a plurality of observation images may be acquired for each cross-section. Image processing is performed on each acquired observation image to extract the outlines of particles. One example of the image processing is binarization processing. The area ratio of the soft magnetic particles is calculated for each observation image, and the average value of the area ratios is obtained. The average value is considered to be the content ratio of the soft magnetic powder.
(Size)
In the present embodiment, the sizes of the first core piece 3f and the second core piece 3s are different from each other. As an alternative to the present embodiment, the size of the first core piece 3f and the size of the second core piece 3s may be the same.
In the present embodiment, there is a portion in which the lengths of the core portions of the first core piece 3f along the first direction D1 are different from the lengths of the core portions of the second core piece 3s along the first direction D1. Specifically, the length L1f of the first middle core portion 31f is longer than the length L1s of the second middle core portion 31s. The length L21f of the first side core portion 321f is longer than the length L21s of the first side core portion 321s. The length L22f of the second side core portion 322f is longer than the length L22s of the second side core portion 322s. The length L3s of the second end core portion 33s is shorter than the length L3f of the first end core portion 33f. As an alternative to the present embodiment, the length L3s and the length L3f may be the same.
Among the length L1f of the first middle core portion 31f, the length L21f of the first side core portion 321f, and the length L22f of the second side core portion 322f, at least one of the lengths may be different, or all of the lengths may be the same. Among the length L1s of the second middle core portion 31s, the length L21s of the first side core portion 321s, and the length L22s of the second side core portion 322s, at least one of the lengths may be different, or all of the lengths may be the same. In the present embodiment, the length L21f and the length L22f are the same, and are longer than the length L1f. Also, the length L21s and the length L22s are the same, and are longer than the length L1s.
(Gap Portion)
The gap portion 3g is constituted by a member made of a material having a smaller relative magnetic permeability than the first core piece 3f and the second core piece 3s. In the present embodiment, the gap portion 3g is constituted by a portion of the molded resin portion 4, which will be described later. As an alternative to the present embodiment, the gap portion 3g may be an air gap. The gap portion 3g may be arranged inside the winding portion 21 as in the present embodiment. The gap portion 3g of the present embodiment is provided between the first middle core portion 31f and the second middle core portion 31s. If the gap portion 3g is provided inside the winding portion 21, eddy current loss in the winding portion 21 caused by the entrance of leakage magnetic flux into the winding portion 21 can be reduced more easily than in the case of being provided outside the winding portion 21.
[Molded Resin Portion]
The reactor 1 may further include the molded resin portion 4 as shown in
The molded resin portion 4 of the present embodiment covers the outer surface of an assembly of the coil 2 and the magnetic core 3. The molded resin portion 4 protects the assembly from the external environment. Moreover, the coil 2 and the magnetic core 3 are integrated by the molded resin portion 4. The molded resin portion 4 of the present embodiment is located between the coil 2 and the magnetic core 3, between the first middle core portion 31f and the second middle core portion 31s, and inside the hole portion 34. The portion of the molded resin portion 4 provided between the first middle core portion 31f and the second middle core portion 31s constitutes the gap portion 3g. The resin of the molded resin portion 4 is the same as the resin of the composite material described above. The resin of the molded resin portion 4 may contain a ceramic filler, similarly to the composite material.
[Other Aspects]
Although not shown, the reactor 1 may include at least any of a case, an adhesive layer, and a holding member, for example. The case houses the assembly of the coil 2 and the magnetic core 3. The assembly in the case may be embedded in a sealing resin portion. An adhesive layer fixes the assembly to a mounting surface, fixes the assembly to an inner bottom surface of the case, and fixes the case to a mounting surface, for example. A holding member is provided between the coil 2 and the magnetic core 3 and ensures insulation between the coil 2 and the magnetic core 3.
[Actions and Effects]
In the reactor 1 of the present embodiment, a crack is less likely to be formed in the first core piece 3f due to vibration. The reason is as follows. In the first middle core portion 31f in which the radius r1 of the first inscribed circle C1 is less than or equal to 0.6 times the radius r0 of the reference inscribed circle C0, the difference between the solidification rate at the fastest solidifying location and the solidification rate at the slowest solidifying location in the manufacturing process is small. For this reason, a void is less likely to be formed in the first middle core portion 31f. Also, the radius r4 of the fourth inscribed circle C4 and the fifth inscribed circle C5 are 0.5 times the radius r0 of the reference inscribed circle C0, and therefore a void is less likely to be formed in the first side core portion 321f and the second side core portion 322f. Moreover, the radius r6 of the sixth inscribed circle C6 is 0.5 times the radius r0 of the reference inscribed circle C0, and therefore a void is less likely to be formed in the first end core portion 33f as well. Therefore, the first core piece 3f has few or substantially no voids that act as starting points for the formation of a crack.
[Reactor]
A reactor according to a second embodiment will be described below with reference to
<Hole Portion>
The hole portion 34 shown in
The length of the hole portion 34 along the first direction D1 may be selected such that at least either a radius r2 of a second inscribed circle or a radius r3 of a third inscribed circle C3 is less than or equal to 0.6 times the radius r0 of the reference inscribed circle C0 described above. Although not shown, the second inscribed circle is the largest inscribed circle in contact with a first surface and the bottom portion 341 of the hole portion 34 in a vertical cross-section of the first core piece 3f. The third inscribed circle C3 is the largest inscribed circle in contact with the first surface and the bottom portion 341 of the hole portion 34 in the horizontal cross-section of the first middle core portion 31f shown in
A reactor according to a third embodiment will be described below with reference to
<Groove Portion>
As shown in
There may be one or a plurality of groove portions 35. In the present embodiment, two groove portions 35 are provided. In the present embodiment, the two groove portions 35 are aligned with each other on the same straight line extending in the third direction D3 in the lateral cross-section of the first middle core portion 31f. The lateral cross-section of the first middle core portion 31f is H-shaped due to the two groove portions 35. As an alternative to the present embodiment, the two groove portions 35 may be aligned on the same straight line extending in the second direction D2 in the lateral cross-section of the first middle core portion 31f.
The depth of the groove portions 35 can be appropriately selected in accordance with the number of groove portions 35. The depth of each of the groove portions 35 is the length from the opening of the groove portion 35 to a bottom portion 351 of the groove portion 35 shown in
The outline shape of the groove portion 35 in the lateral cross-section of the first middle core portion 31f is U-shaped, for example.
The inner area S1 of the interior of the groove portion 35 may be less than or equal to 10% of an area S2 of the second virtual outline V2. The inner region of the groove portion 35 is the region surrounded by the outline of the groove portion 35 and the second virtual outline V2. In the case where a plurality of groove portions 35 are provided as in the present embodiment, the area S1 is the sum of the inner areas of the groove portions 35. The preferred range of the inner area S1 of the groove portions 35 is the same as the preferred range of the area S1 of interior of the hole portion 34 described above. Similarly to the first virtual outline V1, the second virtual outline V2 includes straight lines that extend across the openings of the groove portions 35 rather than extending along the inward faces of the groove portions 35. Note that in the case where the lateral cross-sectional shape of the first middle core portion 31f is circular, the second virtual outline V2 includes curves that extend across the openings of the groove portions 35.
As shown in
The first core piece 3f constituted by a composite material molded body is manufactured as described below. Protrusions corresponding to the groove portions 35 described above are provided on the inner peripheral surface of a mold. The raw material for the composite material molded body is poured into the mold, and the raw material resin is solidified.
In the reactor of the present embodiment, similarly to the first embodiment, a void is less likely to be formed in the first middle core portion 31f, the first side core portion 321f, the second side core portion 322f, and the first end core portion 33f, and thus a crack is less likely to be formed in the first core piece 3f due to vibration.
A reactor according to a fourth embodiment will be described below with reference to
<Groove Portion>
As shown in
A reactor according to a fifth embodiment will be described below with reference to
<Groove Portion>
As shown in
As shown in
The length of the groove portion 35 along the first direction D1 may be selected such that at least either the second inscribed circle C2 or the third inscribed circle C3 is less than or equal to 0.6 times the radius r0 of the reference inscribed circle C0 described above. The second inscribed circle C2 is the largest inscribed circle in contact with a first surface and the end portion 352 of the groove portion 35 in the vertical cross-section of the first core piece 3f shown in
[Converter and Power Conversion Device]
The reactor 1 according to any of the first to fifth embodiments can be used for an application in which the following power conduction conditions are satisfied. Examples of the power conduction conditions include the maximum DC current, the average voltage, and the operating frequency. The maximum DC current is about 100 A or more and 1000 A or less. The average voltage is about 100 V or more and 1000 V or less. The operating frequency is about 5 kHz or more and 100 kHz or less. The reactor 1 according to any of the first to fifth embodiments can be typically used as a component of a converter for installation in a vehicle 1200 shown in
The vehicle 1200 includes a main battery 1210, a power conversion device 1100, and a motor 1220, as shown in
The power conversion device 1100 includes a converter 1110 and an inverter 1120. The converter 1110 is connected to the main battery 1210. The inverter 1120 performs conversion between direct current and alternating current. The inverter 1120 is connected to the converter 1110. During traveling of the vehicle 1200, the converter 1110 shown in this example steps up the input voltage from the main battery 1210 from approximately 200 V to 300 V to approximately 400 V to 700 V, and supplies the stepped-up power to the inverter 1120. During regeneration, the converter 1110 steps down the input voltage that is output from the motor 1220 via the inverter 1120 to a DC voltage suitable for the main battery 1210, and charges the main battery 1210 with the DC voltage. The input voltage is a DC voltage. During traveling of the vehicle 1200, the inverter 1120 converts the direct current boosted by the converter 1110 into a predetermined alternating current, and supplies the alternating current to the motor 1220, and during regeneration, the inverter 1120 converts the alternating current output from the motor 1220 into direct current, and outputs the direct current to the converter 1110.
The converter 1110 includes a plurality of switching elements 1111, a drive circuit 1112, and a reactor 1115 as shown in
The vehicle 1200 includes a power supply device converter 1150 and an auxiliary power supply converter 1160, in addition to the converter 1110. The power supply device converter 1150 is connected to the main battery 1210. The auxiliary power supply converter 1160 is connected to a sub battery 1230, which serves as a power source for auxiliary devices 1240, and is connected to the main battery 1210. The auxiliary power supply converter 1160 converts high voltage from the main battery 1210 to low voltage, and the converter 1110 typically performs DC-DC conversion. The power supply device converter 1150 and the auxiliary power supply converter 1160 perform AC-DC conversion. Some power supply converters 1150 perform DC-DC conversion. The reactor of the power supply device converter 1150 and the auxiliary power supply converter 1160 has a configuration similar to that of the reactor 1 according to any of the first to fifth embodiments, and the size, shape, and the like of the reactor can be changed appropriately. Also, the reactor 1 according to any of the first to fifth embodiments can be used in a converter that performs conversion on input power but performs only either stepping up or stepping down.
The existence of cracks and voids in various core pieces was examined along with reactor characteristics.
[Samples No. 1 to No. 5]
The core pieces of Samples No. 1 to No. 5 were E-shaped core pieces with hole portions, similarly to the configuration in the first embodiment described with reference to
The hole portion in the core piece of each sample was a through hole. The hole portion extended continuously from the end face of the first middle core portion to the outward face of the first end core portion. The outline shape of the hole portion of each sample was a perfect circle. The diameter of the hole portion was set differently for each sample as shown in Table 1 by changing the diameter of the core. The first virtual outline was a square. The second virtual outline was a square. The length of one side of the first virtual outline was 30 mm Table 1 shows the ratio r1/r0 of the radius r1 of the first inscribed circle to the radius r0 of the reference inscribed circle. Table 1 shows the ratio (S1/S2)×100 of the inner area S1 of the hole portion to the area S2 of the second virtual outline.
[Samples No. 11 to No. 16]
The core pieces of Samples No. 11 to No. 16 are E-shaped core pieces with groove portions, similarly to the third embodiment described with reference to
The lateral cross-sectional shape of the first middle core portion in the core piece of each sample was H-shaped. The groove portions of the core piece of each sample extended continuously from the end face of the first middle core portion to the outward face of the first end core portion. The groove portions were U-shaped. The width and depth of the groove portions were set differently as shown in Table 2 by changing the width and height of the protrusions. The first virtual outline was a square. The second virtual outline was a square. The length of one side of the first virtual outline was 30 mm Table 2 shows the ratio r1/r0 of the radius r1 of the first inscribed circle to the radius r0 of the reference inscribed circle. Table 2 shows the ratio (S1/S2)×100 of the inner area S1 of the groove portion to the area S2 of the second virtual outline.
[Sample No. 17]
The core piece of Sample No. 17 was manufactured similarly to the core piece of Sample No. 16, with the exception that the hole portion and the groove portion were omitted. Due to having neither a hole portion nor a groove portion, the mark “-” is shown in the “groove width”, “groove depth”, and “(S1/S2)×100” columns for Sample No. 17 in Table 2.
[Voids and Cracks]
The core pieces of the samples were evaluated with respect to the presence or absence of voids and cracks. The results are shown in Tables 1 and 2. The meanings of A, B, C, and D shown in Tables 1 and 2 are as follows. Here, “A” means having neither voids nor cracks. Also, “B” means that the ratio of the volume of voids to the volume of the core piece is 1% or less, and no cracks were formed. Furthermore, “C” means that the ratio of the volume of voids to the volume of the core piece is more than 1% and 2% or less, and the ratio of the length of a crack to the length of the cracked portion of the core piece is 10% or less. This length is the length in the second direction D2 or the third direction D3, namely whichever the lengthwise direction of the crack conforms to. For example, if the crack extends along the second direction D2, the ratio of the length of the crack along the second direction D2 to the length of the cracked portion of the core piece along the second direction D2 is 10% or less. Moreover, “D” means that the ratio of the volume of voids to the volume of the core piece is more than 2%, and the ratio of the length of a crack to the length of the cracked portion of the core piece is more than 10%. The volume of voids is a value estimated from the ratio of the measured density of the core piece determined by the Archimedes method to the designed density of the core piece. The designed density refers to the density obtained from the mass and volume of the core piece assuming that neither voids nor cracks have formed.
[Reactor Characteristic]
Reactors of the first embodiment described with reference to
The core pieces of Samples No. 1 to No. 5 had fewer voids and cracks than the core piece of Sample No. 17. The core piece of Sample No. 1 had a small extent of reduction in inductance approximately the same as that of the core piece of Sample No. 17. The core pieces of Sample No. 2 to No. 4 had a relatively small extent of reduction in inductance.
The core pieces of Sample No. 12, Sample No. 13, Sample No. 15, and Sample No. 16 had fewer voids and cracks than the core piece of Sample No. 17. The core piece of Sample No. 12 had a small extent of reduction in inductance approximately the same as that of the core piece of Sample No. 17. The core pieces of Sample No. 13, Sample No. 15, and Sample No. 16 had a relatively small extent of reduction in inductance.
The present invention is not intended to be limited to these examples, but rather is indicated by the scope of the claims, and is intended to include all modifications within the meaning and scope of equivalents of the scope of the claims. For example, in the first to fifth embodiments, the second core piece may be constituted by a laminate body. The laminate body is formed by laminating a plurality of magnetic thin plates. The magnetic thin plates have an insulating coating. The magnetic thin plates are electromagnetic steel plates, for example.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-056130 | Mar 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/010881 | 3/11/2022 | WO |
