Patent Application
20220093321
The present invention relates to a coil apparatus including a coil, and a power converter.
To provide a smaller and higher-power-density power converter, it is effective to use planar coil apparatuses that are easily cooled by heat dissipation to a housing or the like, as coil apparatuses such as a transformer and a reactor that occupy large areas in a power converter. A planer coil apparatus is also referred to as a low-profile coil apparatus. In a planar coil apparatus, magnetic paths are formed by a combination of an E-shaped core and an I-shaped core, a combination of an E-shaped core and an E-shaped core, or the like.
A coil apparatus needs to be precisely adjusted in gap length that is the length of a gap between cores, to obtain a desired inductance value. The gap length is sometimes adjusted by fixing cores to each other with a gap sheet sandwiched between polished surfaces of the cores. It is known that, in this case, variations in the dimensions of the gap sheet or variations in the precision of polishing of the cores result in variations in inductance value. The longer gap length the coil apparatus has, the larger the leakage flux. When the leakage flux becomes larger, the magnetic flux causes eddy currents to flow in a coil constituting the coil apparatus, increasing loss in the coil.
Patent Literature 1 discloses a coil apparatus with a combination of an I-shaped core and an E-shaped core, in which gaps are formed between the I-shaped core and the E-shaped core using a bobbin that holds a coil. According to the technique of Patent Literature 1, the gap length can be set with high precision without using a gap sheet. In the coil apparatus of Patent Literature 1, the gaps are distributed among the legs of the E-shaped core to suppress leakage of flux per gap.
Patent Literature 1: Japanese Patent Application Laid-open No. 2005-79546
According to the technique of Patent Literature 1, which is a conventional technique, the number of gaps provided in a magnetic path is limited to up to two. Thus, the conventional technique, in which leakage flux is insufficiently suppressed, has a problem that it is difficult to reduce loss in a coil.
The present invention has been made in view of the above, and its object is to provide a coil apparatus that allows a reduction in loss in a coil.
To solve the above problems and achieve the object a coil apparatus according to the present invention includes: a coil; a first core component including a leg around which the coil is wound; and a second core component that includes a plurality of core segments arranged in a row with gaps between the core segments, and is connected to the leg to form a magnetic path together with the first core component.
The coil apparatus according to the present invention has the effect of allowing a reduction in loss in a coil.
Hereinafter, a coil apparatus and a power converter according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments are not intended to limit this invention.
The power converter 100 includes a full-bridge circuit 110, a resonance coil 120, a transformer 130, a secondary-side rectifier circuit 140, and a smoothing circuit 150. The high DC voltage supplied to the input terminals 101 and 102 is input to the full-bridge circuit 110. The full-bridge circuit 110 includes switching elements 111, 112, 113, and 114. Each of the switching elements 111, 112, 113, and 114 is a metal-oxide semiconductor field-effect transistor (MOSFET), an insulated-gate bipolar transistor (IGBT), or the like. The full-bridge circuit 110 operates to generate an AC voltage from the DC voltage by the switching elements 111, 112, 113, and 114. The AC component generated on the input side by the operation of the full-bridge circuit 110 is mainly absorbed by an input capacitor 103. This reduces the occurrence of noise in input lines.
The resonance coil 120 and a primary coil 131 of the transformer 130 are connected in series. The AC voltage generated by the full-bridge circuit 110 is applied to the resonance coil 120 and the primary coil 131. The resonance coil 120 resonates with capacitance components produced by MOSFETs or external capacitors connected in parallel with the switching elements 111, 112, 113, and 114, respectively, to control the losses of the switching elements 111, 112, 113, and 114. In this operation, the resonance coil 120 is required to have accuracy in inductance value, that is, small variations in inductance value.
When the AC voltage is applied to the primary coil 131, an AC voltage depending on the turn ratio of the transformer 130 is generated in secondary coils 132 and 133 of the transformer 130. The AC voltage generated in the secondary coils 132 and 133 is input to the secondary-side rectifier circuit 140. The AC voltage input to the secondary-side rectifier circuit 140 is rectified by rectifier elements 141 and 142 represented by Schottky barrier diodes. Consequently, at a center tap that is a point of connection between the secondary coil 132 and the secondary coil 133, an AC voltage full-wave rectified relative to ground potential is generated.
The smoothing circuit 150 includes a smoothing coil 151 and an output capacitor 152. The AC voltage generated by the transformer 130 is smoothed by the smoothing circuit 150, so that a desired flat DC voltage is generated between the output terminal 191 and the output terminal 192. The smoothing coil 151 used here is required to have good DC superposition characteristics in addition to accuracy in inductance value. The output terminal 192 that is a negative terminal of the output terminals 191 and 192 is not distinctly provided. A metal housing that is a structure serving as grounds (GNDs) 161, 162, and 163 has its function.
A metal housing 160 is a housing of the power converter 100. The metal housing 160 is a structure serving as the GNDs 161, 162, and 163 and also serves as a cooler. The input terminals 101 and 102, the input capacitor 103, a control circuit of the switching elements 111, 112, 113, and 114, and a drive circuit are mounted on a printed-circuit board 170.
The resonance coil 120 is required to have small variations in inductance value to adjust resonance frequency. As a core constituting the resonance coil 120, a core in which an E-shaped core and an E-shaped core are combined, or a core having a toroidal shape is typically used. As a soft magnetic material to form a magnetic path, a dust core material such as pure iron or an Fe—Si alloy is used. In the first embodiment, the core constituting the resonance coil 120 is a planar core, and is a ferrite core of Mn—Zn or the like provided with a plurality of gaps. The resonance coil 120, which is provided with the plurality of gaps, can achieve higher performance and can control a height from an installation base as compared with the above-mentioned conventional technique.
The transformer 130 is a planar transformer. The primary coil 131 and the secondary coil 132 are a coil unit included in the transformer 130. The transformer 130 includes: an E-shaped core; an I-shaped core; a printed-circuit board on which the primary coil 131 is formed; and a printed-circuit board on which the secondary coil 132 is formed. There are no gaps in a magnetic path formed by the E-shaped core and the I-shaped core. In the secondary-side rectifier circuit 140, the rectifier element 141 and the rectifier element 142 are installed in one package.
The smoothing coil 151 requires a highly accurate inductance value and DC superposition characteristics. As a core constituting the smoothing coil 151, a core in which an E-shaped core and an E-shaped core are combined, or a core having a toroidal shape is typically used, similarly as the case of resonance coil 120. As a soft magnetic material to form a magnetic path, a dust core material such as pure iron or an Fe—Si alloy is used. In the first embodiment, the core constituting the smoothing coil 151 is a planar core, and is a ferrite core of Mn—Zn or the like provided with a plurality of gaps. The smoothing coil 151, which is provided with the plurality of gaps, can achieve higher performance and can control a height from an installation base as compared with the above-mentioned conventional technique. The coil constituting the smoothing coil 151 is formed on a printed-circuit board.
In
The following describes the configuration of the resonance coil 120 and the configuration of the smoothing coil 151 included in the power converter 100. The resonance coil 120 and the smoothing coil 151 are coil apparatuses included in the power converter 100.
A coil apparatus 12 according to the first embodiment includes a base core 7 that is a first core component, a core module 11 that is a second core component, and a coil unit 6. The core module 11 includes: a plurality of core segments 1, 2, and 3 arranged in a row with gaps between them; divider plates 4 that are plates disposed between the core segments 1, 2, and 3; and a case 5 in which the core segments 1, 2, and 3 and the divider plates 4 are accommodated. The core module 11 is an I-shaped core.
The base core 7 is an E-shaped core with three legs. Outer legs 7e are legs formed at both ends of the base core 7 in the X-axis direction. The center leg 7f is a leg formed at the center of the base core 7 in the X-axis direction. The core module 11 is connected to the center leg 7f and the two outer legs 7e so that the base core 7 and the core module 11 form two magnetic paths 9 that are both closed magnetic paths.
The coil unit 6 is configured using a double-layer printed-circuit board made of Flame Retardant Type 4 (FR-4). A wound winding wire pattern is printed on each side of the printed-circuit board. To reduce the current density of current flowing through the coil unit 6, a four-layer printed-circuit board may be used as the coil unit 6 to have a plurality of separate current paths. The coil unit 6 may be configured using an FR-5 base material or a ceramic base material to increase heat resistance. Instead of using a printed-circuit board, the coil unit 6 may use a copper plate or an aluminum plate having a thickness of about 0.5 mm to 2 mm. An opening is provided in the center of the coil unit 6. The coil unit 6 is installed in the coil apparatus 12 with the center leg 7f passed through the opening. Thus, a coil that is the winding wire patterns printed on the printed-circuit board becomes a state being wound around the center leg 7f.
The area of the ZX plane of the core segments 1 parallel to the Z axis and the X axis is equal to the area of the ZX plane of the outer legs 7e. The area of the YZ plane of the core segments 1 parallel to the Y axis and the Z axis is equal to the area of the ZX plane of the outer legs 7e. The area of the ZX plane of the core segments 1 may be larger than the area of the ZX plane of the outer legs 7e. The area of the YZ plane of the core segments 1 may be larger than the area of the ZX plane of the outer legs 7e.
The area of the ZX plane of the core segment 2 is equal to the area of the ZX plane of the center leg 7f. The area of the YZ plane of the core segment 2 is equal to the area of the ZX plane of the outer legs 7e. The area of the ZX plane of the core segment 2 may be larger than the area of the ZX plane of the center leg 7f. The area of the YZ plane of the core segment 2 may be larger than the area of the ZX plane of the outer legs 7e.
The height of the core segments 3 in the Y-axis direction is the same as the height of the core segments 1 in the Y-axis direction. The depth of the core segments 3 in the Z-axis direction is the same as the depth of the core segments 1 in the Z-axis direction. Here, dimensional differences of about ±3% between the core segments 3 and the core segments 1 due to dimensional tolerances at the time of manufacturing are ignored. The height of the core segments 3 and the height of the core segments 1 being the same includes the case where there are dimensional differences of about ±3%. The depth of the core segments 3 and the depth of the core segments 1 being the same includes the case where there are dimensional differences of about ±3%. The thickness of the core segments 3 in the X-axis direction is smaller than the thickness of the core segments 1 in the X-axis direction. A soft magnetic material is used as the material of the cores, which are the core segments 1, the core segment 2, the core segments 3, and the base core 7. As the soft magnetic material, an Mn—Zn or Ni—Zn ferrite core material, and a dust core material such as pure iron, an Fe—Si alloy, an Fe—Si—Al alloy, an Ni—Fe alloy, or an Ni—Fe—Mo alloy are used. The cores may be coated with a powder resin for insulation.
For a ferrite core made of a ferrite core material and a dust core made of a dust core material, a powder material is molded by a press and then fired by heat treatment. The material molded by the press shrinks during heat treatment. Thus, the dimensional accuracy decreases as the core size increases. A large core has a longer firing time and a larger loss in a coil than a small core. Two types of ferrite core materials, a general-purpose ferrite core material and a low-loss ferrite core material, are generally known. The low-loss ferrite core material shows tendencies such as a deterioration in dimensional accuracy and an increase in loss more conspicuously. Therefore, a low-loss, large core is more difficult to control firing temperature and tends to have a large loss in the coil, and thus requires a large amount of manufacturing know-how.
The core segments 1, 2, and 3 are each smaller than a one-piece core when the second core component is formed as the one-piece core, and thus are easier to fire than the one-piece core. Further, the core segments 1, 2, and 3 can reduce loss in the coil unit 6 as compared with the one-piece core. By the use of the core segments 1, 2, and 3 in the core module 11, the core module 11 can be increased in dimensional accuracy and can be reduced in firing time. Either the general-purpose ferrite core material or the low-loss ferrite core material may be used for the core segments 1, 2, and 3. Since both the general-purpose ferrite core material and the low-loss ferrite core material can be used, the number of procurement sources from which the material of the core segments 1, 2, and 3 can be procured increases. Consequently, the procurement of components for manufacturing the core module 11 can be stabilized, and procurement cost can be reduced. Further, the core module 11 can be reduced in loss in the coil unit 6 and improved in quality.
In
The core module 11 may use core segments having a smaller width in the X-axis direction than the core segments 3.
As the core segments 3b, a low-loss ferrite core used in a small planar transformer can be used. Such a ferrite core is distributed in large quantities in the market, and thus is low-cost and easy to procure. The core module 11, in which the core segments 3b are used, can be stabilized in component procurement and reduced in cost.
The core module 11 may be changed in the dimensions of the core segments 1, 2, and 3 from those illustrated in
Next, the case 5 and the divider plates 4 illustrated in
The case 5 has an I shape that allows the plurality of core segments 1, 2, and 3 to be aligned in the X-axis direction. The divider plates 4 divide the interior of the case 5 to form, with the case 5, spaces in which the core segments 1, 2, and 3 are disposed separately. The divider plates 4 may be of any size as long as they fit in the case 5. The area of the YZ plane of the divider plates 4 is equal to the area of the case 5 in the Y- and Z-directions or about half the area of the case 5 in the Y- and Z-directions. Gaps are formed in the magnetic paths 9 by the divider plates 4 and the case 5. In the following description, the gaps formed in the magnetic paths 9 may be referred to as core gaps.
The length of each core gap in the direction of the magnetic paths 9 is set so that the sum total gap length agrees with a length determined by design. The sum total gap length is the length of the core gaps in the direction of the magnetic paths 9 that is the sum of the lengths of all the core gaps provided at the base core 7 and the core module 11. Core gaps with the Y-axis direction as the length direction are formed between the core module 11 and the outer legs 7e and between the core module 11 and the center leg 7f. Core gaps with the X-axis direction as the length direction are formed in the core module 11.
The relative magnetic permeability of a ferrite core is about 1500 to 4000. The sum total length of the core gaps is set to about 1 mm to 30 mm. The sum total length of the core gaps is adjusted so that a desired inductance value is obtained. Magnetic flux leaking from the core gaps can interlink with the coil unit 6 disposed adjacent to the core gaps, inducing eddy currents in the coil unit 6. Eddy currents flowing through the coil unit 6 cause loss in the coil unit 6. Leakage flux is reduced by reducing length per core gap. Specifically, the length of each core gap is desirably 1 mm or less. The divider plates 4 and the case 5 use a thin-walled material that can provide core gaps of such a length.
A non-magnetic material such as a resin is used as the material of the divider plates 4 and the case 5. Among resins, a liquid crystal polymer (LCP) or the like is suitable as the material of the divider plates 4 and the case 5. The LCP can form a thin wall of about 0.5 mm, has good dimensional accuracy, and is suitable for processing of complicated shapes, and thus is suitable as the material of the divider plates 4 and the case 5. The LCP has excellent heat resistance. Even when the core temperature reaches a high temperature of about 120 degrees Celsius, the LCP does not cause changes such as softening. Since the divider plates 4 and the case 5 are thin-walled, the amount of the material used in the processing of the divider plates 4 and the case 5 is reduced accordingly. Consequently, even when the LCP, which is expensive among resins, is used, the core module 11 can prevent an increase in cost. As a resin, other than the LCP, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene (PP), polyphenylene sulfide (PPS), or the like may be used.
Injection molding is used as a method for processing the divider plates 4 and the case 5. Injection molding is excellent in cost and dimensional accuracy, and is also suitable for processing of complicated shapes. As a method for processing the divider plates 4 and the case 5, extrusion molding, compression molding, or additional processing by a 3D printer may be used.
Of the case 5, portions between the core segments 1 and the outer legs 7e and a portion between the core segment 2 and the center leg 7f are portions to form core gaps, and thus are desirably thin-walled. On the other hand, the other portions of the case 5 are not portions to form core gaps, and thus do not need to be thin-walled. Portions of the case 5 other than portions to form core gaps may be formed with a thickness that can secure the strength of the case 5.
The core module 11 only needs to be able to provide a desired gap length, and the case 5 need not be provided with the divider plates 4.
In the first embodiment, the core module 11, in which the core segments 1, 2, and 3 are disposed in the case 5, holds the core segments 1, 2, and 3 together by the case 5. Therefore, an increase in the number of core segments 1, 2, and 3 provided in the core module 11 rarely leads to a deterioration in the productivity of the core module 11. In the core module 11, the core segments 1, 2, and 3 are inserted into the spaces into which the interior of the case 5 is divided, to be held. No adhesive is used to hold the core segments 1, 2, and 3. Thus, the core module 11 can eliminate the concern that cracks may occur in the core segments 1, 2, and 3 due to the difference in the coefficient of linear expansion between the core segments 1, 2, and 3 and an adhesive.
During the production of the core module 11, the sum total gap length may vary due to the dimensional tolerances of the plurality of core segments 1, 2, and 3, the divider plates 4, and the case 5. Variations in the sum total gap length affect variations in inductance value. Such dimensional tolerances generally have a normal distribution. The core module 11 is provided with the plurality of core segments 1, 2, and 3 and the divider plates 4. It is statistically impossible that all of them have a large error of, for example, ±3σ to ±6σ with respect to average dimensions. As the number of core segments 1, 2, and 3 and the number of divider plates 4 provided in the core module 11 increase, the sum total gap length approaches the sum total gap length when the dimensions are average values. Therefore, the core module 11, in which a core is divided into the plurality of core segments 1, 2, and 3, can reduce variations in the sum total gap length, and can increase the accuracy of the inductance value.
The above content will be quantitatively explained using a core as an example. The dimensions of a core have percentage errors. If an average dimension is 150 mm and the dimensional tolerance of an unpolished core is 1%, the dimensional tolerance is ±1.5 mm. For a 30-mm core segment 3, the 1%-dimensional tolerance is ±0.3 mm. When a 150-mm core is formed using five 30-mm core segments 3, a dimensional tolerance of ±0.3 mm, which is 1% of 30 mm, takes the square root of sum of squares of the five core segments 3. Thus, for the total length of the five core segments 3, the dimensional tolerance can be reduced to ±0.67 mm. This corresponds to 45% of the dimensional tolerance of the 150-mm core, and the dimensional tolerance can be reduced by 55%. Likewise, when a 150-mm core is formed using ten 15-mm core segments 3, the dimensional tolerance of the total length of the ten core segments 3 is ±0.47 mm. This corresponds to 32% of the dimensional tolerance of the 150-mm core, and the dimensional tolerance can be reduced by 68%.
Thus, the coil apparatus 12 can reduce variations in inductance value as the number of divisions of the core forming the magnetic paths 9 is increased. The coil apparatus 12 can eliminate the need for core polishing, which has conventionally been performed to reduce dimensional tolerances, and thus allows a reduction in the processing time of the core module 11 and a reduction in manufacturing cost.
Even if the core segments 1, 2, and 3 are displaced in the X-axis direction in the case 5, the sum total gap length does not change in the core module 11. Thus, even when the core segments 1, 2, and 3 are not fixed to the case 5 by an adhesive or the like, the coil apparatus 12 can reduce variations in inductance value, and can obtain stable electrical characteristics. The displacement of the core segments 1, 2, and 3 in the Z-axis direction hardly affects the inductance value if it is a displacement of about a dimensional tolerance of the case 5.
The coil apparatus 12 can reduce length per core gap as the number of core gaps increases. By shortening the core gaps, the coil apparatus 12 can reduce magnetic flux leaking from the core gaps, and can reduce eddy-current loss in the coil unit 6 disposed adjacent to the core module 11. As a result, the coil apparatus 12 can suppress the amount of heat generation. The power converter 100 can improve power efficiency.
A ferrite core is vulnerable to shock and thus can be chipped or cracked by shock. In the first embodiment, all of the core segments 1, 2, and 3 are accommodated in the case 5, so that the coil apparatus 12 can protect the core segments 1, 2, and 3 from vibration or shock. The coil apparatus 12 can reduce damage to the core segments 1, 2, and 3. If any of the core segments 1, 2, and 3 is chipped and a broken piece is produced, the broken piece having conductivity is kept in the case 5 since the core segments 1, 2, and 3 are disposed in the case 5. Thus, the power converter 100 can prevent a short-circuit failure due to the entry of a broken piece into the printed-circuit board 170 or the switching elements 111, 112, 113, and 114.
A lid may be provided on the top of the case 5.
By the provision of the lid 8 on the case 5c, if any of the core segments 1, 2, and 3 is damaged, the coil apparatus 12 can prevent a broken piece produced by the damage from flying to the outside of the case 5c. Further, by the mechanism for increasing the fitting strength provided to the lid 8 and the case 5c, the core module 11 can increase the strength of fixing the core segments 1, 2, and 3. Consequently, the core module 11 can improve vibration resistance. The lid 8 may be attached to the case 5 illustrated in
A metal plate 160a is a plate material that covers the upper part of the coil apparatus 12. Two metal blocks 160b are columnar structures that support the metal plate 160a on the metal housing 160. The metal blocks 160b are erected at positions adjacent to the coil apparatus 12 in the X-axis direction in the metal housing 160. Screws 10 fix the metal plate 160a and the metal blocks 160b to the metal housing 160. The configuration for installing the coil apparatus 12 includes the metal housing 160, the metal plate 160a, and the metal blocks 160b.
Heat generated in the base core 7 is mainly transferred to the metal housing 160. Heat generated in the core module 11 is mainly transferred to the metal plate 160a. The heat transferred to the metal plate 160a is transferred to the metal housing 160 via the metal blocks 160b. Arrows illustrated in
The metal plate 160a and the metal blocks 160b illustrated in
The metal structure 160c may be provided with radiating fins 166.
The metal spring 14 is a metal plate of about 0.1 mm to 1 mm in thickness and has elasticity. The metal spring 14 is fixed to the metal housing 160 by the screws 10a. The metal spring 14 is provided with projections 14a for fixing the position of the core module 11 in the Z-axis direction. The coil apparatus 12 is fixed in a state of being pressed against the metal housing 160 by the elasticity of the metal spring 14. The coil apparatus 12 is limited in displacement in the Z-axis direction by the projections 14a to be fixed in position in the metal housing 160.
A typical example of the case where it is not necessary to transfer the heat of the core module 11 to the metal housing 160 is the case where a low-loss ferrite core is used as the core segments 1a, 2a, and 3a as illustrated in
The coil apparatus 12 may include a base core 7 other than the E-shaped core.
The coil apparatus 12 may include two or more coil units 6.
The circuit configuration of the power converter 100 is not limited to that illustrated in
According to the first embodiment, the core module 11 includes the plurality of core segments 1, 2, and 3 arranged in a row with gaps between them, so that the coil apparatus 12 can easily distribute gaps in the magnetic paths 9. By distributing gaps, the coil apparatus 12 can reduce length per gap, and can reduce leakage flux in the gaps. By the reduction of leakage flux, the coil apparatus 12 can reduce loss in the coil unit 6. Thus, the coil apparatus 12 has the effect of being able to reduce loss in the coil unit 6.
The coil apparatus 12 can use a low-loss ferrite core as the core segments 1, 2, and 3, and thus can further reduce loss in the coil unit 6. As compared with conventional techniques, the coil apparatus 12 can reduce the tolerance of the inductance value during the production of the coil apparatus 12. The coil apparatus 12 can be easily assembled, allowing an improvement in productivity. The coil apparatus 12 eliminates the need for core polishing, allowing a reduction in core procurement cost. A reduction in the production cost of the coil apparatus 12 allows a reduction in the production cost of the power converter 100. The thermal coupling between the coil apparatus 12 and the metal housing 160 allows the power converter 100 to efficiently cool the coil apparatus 12, allowing a reduction in the size of the power converter 100.
The case 5d is the case 5a illustrated in
According to the second embodiment, the coil apparatus 12a can provide the same effects as those of the first embodiment, and is provided with the case 5d or the case 5f to be able to facilitate assembly and prevent a misalignment between the core module 11a and the base core 7.
By the provision of the case 5d or the case 5f in the coil apparatus 12a, the power converter 100 can prevent a misalignment between the core module 11a and the base core 7 when vibration or shock is applied to the power converter 100. The coil apparatus 12a can maintain electrical characteristics by preventing a misalignment between the core module 11a and the base core 7. The power converter 100 can be improved in quality since the electrical characteristics of the coil apparatus 12a can be maintained.
The case 5e is made by adding projections 5i to the case 5c illustrated in
According to the third embodiment, as in the second embodiment, by including the case 5e, the coil apparatus 12b can facilitate assembly and prevent a misalignment between the core module 11b and the base core 7. The coil apparatus 12b, which can be fixed to the metal housing 160 by the case 5e, eliminates the need to additionally provide a configuration for fixing to the metal housing 160. The power converter 100 can have a simpler configuration than when a configuration for the coil apparatus 12b to the metal housing 160 is additionally required. In the coil apparatus 12b with the lid 8, the projections 5i and the fixing portions 5h may be provided to the lid 8 instead of to the case 5e. The projections 5i and the fixing portions 5h may be attached to any of the case 5 illustrated in
In the fourth embodiment, a first core component consists of a plurality of core components that is two base cores 7a and one base core 7b. The base core 7b is disposed in the center of the coil apparatus 12c in the X-axis direction. The base cores 7a are adjacent to the base core 7b in the X-axis direction. Gaps are provided between the base cores 7a and the base core 7b. Thermal coupling between the base cores 7a and 7b and the metal housing 160 is provided as is the case with the base core 7.
By the provision of the gaps between the base cores 7a and the base core 7b, the coil apparatus 12c can provide much more gaps in the magnetic paths 9 than in the case illustrated in
According to the fourth embodiment, by the provision of the base cores 7a and 7b, the coil apparatus 12c can increase the number of gaps provided in the magnetic paths 9. Consequently, the coil apparatus 12c can further reduce loss in the coil unit 6.
In the fifth embodiment, a first core component consists of the four base cores 7a, which are a plurality of core components. The four base cores 7a are formed from core components of one type. The four base cores 7a have the same shape. Here, dimensional differences of about ±3% between the base cores 7a due to dimensional tolerances at the time of manufacturing are ignored. The plurality of base cores 7a having the same shape includes the case where there are dimensional differences of about ±3%. Gaps are provided between the base cores 7a. By the provision of the gaps between the base cores 7a, the coil apparatus 12d can provide much more gaps in the magnetic paths 9 than in the case illustrated in
The size of a core component installed in the power converter 100 increases in proportion to electric power. The upper limit of the size of the core component that can be manufactured is limited by the size of core manufacturing equipment such as a press or a firing machine. If the coil apparatus 12d is provided with the first core component that is a one-piece core component instead of the four base cores 7a, the maximum size of the first core component is determined by the size of the core manufacturing equipment. In the fifth embodiment, in which the first core component is divided into the four base cores 7a, each of the four base cores 7a can be increased in size to the maximum size. Consequently, the size of the first core component provided in the coil apparatus 12d can be up to four times the size of the first core component that is a one-piece core component. Thus, even if core manufacturing equipment larger than existing core manufacturing equipment is not used in the manufacturing of the first core component, the coil apparatus 12d including the first core component up to four times as large as the first core component formed of a one-piece core component can be manufactured.
As in the fourth embodiment, the metal housing 160 may be provided with the grooves 15 or the ribs 16 for positioning the base cores 7a. This allows the base cores 7a to be positioned to form gaps of a predetermined length between the base cores 7a. Further, the gap length between the base cores 7a can be kept constant.
According to the fifth embodiment, by the provision of the plurality of base cores 7a, the coil apparatus 12d can increase the number of gaps provided in the magnetic paths 9. Consequently, the coil apparatus 12d can further reduce loss in the coil unit 6.
By the bonding of the core segments 1, 2, and 3 to each other, the core segments 1, 2, and 3 are fixed in a core module 11c. Since the core segments 1, 2, and 3 are fixed by the dividers 4b, it is not necessary to provide the case 5 in the coil apparatus 12e for fixing the core segments 1, 2, and 3. In this case, the manufacturing cost of the case 5 and a mold for processing the case 5 are unnecessary, so that the core module 11c can reduce manufacturing cost. Further, the coil apparatus 12e can eliminate gaps between the base core 7 and the core module 11c. The coil apparatus 12e can eliminate leakage flux from between the base core 7 and the core module 11c, and thus can further reduce loss in the coil unit 6.
According to the sixth embodiment, the coil apparatus 12e or 12f, in which the core segments 1, 2, and 3 are bonded to each other, forming gaps between them, eliminates the need for the case 5 for fixing the core segments 1, 2, and 3, and can reduce manufacturing cost. The coil apparatus 12e or 12f can eliminate leakage flux from between the base core 7 and the core module 11c or 11d, and thus can further reduce loss in the coil unit 6.
The ribs 165 are formed on a surface of the metal plate 160d facing the core module 11e. The ribs 165 have a thickness of 1 mm or less in the X-axis direction. The core segments 1, 2, and 3 are stuck between the ribs 165 using an adhesive 4d. The core segments 1, 2, and 3 are positioned by the ribs 165 in the X-axis direction, so that gaps are formed between the core segments 1, 2, and 3.
By the sticking of the core segments 1, 2, and 3 to the metal plate 160d, the core segments 1, 2, and 3 are fixed in the core module 11e. Since the core segments 1, 2, and 3 are fixed by the metal plate 160d, it is not necessary to provide the case 5 in the coil apparatus 12g for fixing the core segments 1, 2, and 3. In this case, the manufacturing cost of the case 5 and a mold for processing the case 5 are unnecessary, and thus the core module 11e can reduce manufacturing cost. Further, the coil apparatus 12g can eliminate gaps between the base core 7 and the core module 11e. The coil apparatus 12g can eliminate leakage flux from between the base core 7 and the core module 11e, and thus can further reduce loss in the coil unit 6.
In general, if metal objects are disposed to block the magnetic paths 9, the electrical characteristics of the coil apparatus 12g will be affected. In the seventh embodiment, the ribs 165 are located in outer edge portions of the annular magnetic paths 9. In the annular magnetic paths 9, magnetic flux passes through the inner side of the center of the magnetic paths 9 in cross section. Thus, the coil apparatus 12g can eliminate the influence of the provision of the ribs 165 that are metal objects in the magnetic paths 9, on the electrical characteristics.
The direction of the magnetic paths 9 in the core module 11e is the X-axis direction, whereas the thickness direction of the adhesive 4d is the Y-axis direction. When the thickness of the adhesive 4d varies, the core segments 1, 2, and 3 vary in position in the Y-axis direction, but do not vary in position in the X-axis direction. Thus, even if the thickness of the adhesive 4d varies, it does not affect the length of the core gaps. Therefore, the coil apparatus 12g can eliminate the influence of variations in the thickness of the adhesive 4d on the inductance value.
Also in the first modification of the seventh embodiment, the coil apparatus 12h can eliminate the influence of the provision of the ribs 165 in the magnetic paths 9 on the electrical characteristics. The coil apparatus 12h can eliminate the influence of variations in the thickness of the adhesive 4d on the inductance value. Further, since there are no core segments 1 and 2 above the legs of the base core 7, the coil apparatus 12h can eliminate variations in the length of gaps above the legs. Consequently, the coil apparatus 12h can further reduce variations in inductance value.
According to the seventh embodiment, by fixing the core segments 1, 2, and 3 to the metal plate 160d, 160e, or 160f provided with the ribs 165, the coil apparatus 12g, 12h, or 12i eliminates the need for the case 5 for fixing the core segments 1, 2, and 3, and can reduce manufacturing cost. The coil apparatus 12g, 12h, or 12i can eliminate leakage flux from between the base core 7 and the core module 11e or 11f, and thus can further reduce loss in the coil unit 6. The coil apparatus 12g, 12h, or 12i can fix the core segments 1, 2, and 3 with the core gaps of a desired length provided between them, and can reduce variations in inductance value.
The coil apparatus 20 includes a core module 21 and the coil unit 6. The core module 21 includes a core segment group that is the plurality of core segments 1c, 2c, and 3c, and a case 22 that holds the core segment group. The core segment group includes two core segments 1c, one core segment 2c, and any number of core segments 3c. Each of the two core segments 1c constitutes an outer leg 26. The core segment 2c constitutes a center leg 25. The core module 21 forms the two magnetic paths 9 that are both closed magnetic paths.
In the core segment group, a plurality of core segments 3c provided in place of the base core 7 illustrated in
The height of each core segment 1c in the Y-axis direction is larger than the height of each core segment 3c in the Y-axis direction. The height of the core segment 2c in the Y-axis direction is larger than the height of each core segment 3c in the Y-axis direction. The height of each core segment 1c in the Y-axis direction and the height of the core segment 2c in the Y-axis direction are the same. Here, dimensional differences of about ±3% between the core segments 1c and the core segment 2c due to dimensional tolerances at the time of manufacturing are ignored. The height of each core segment 1c and the height of the core segment 2c being the same includes the case where there are dimensional differences of about ±3%.
Each of the core segments 1c, 2c, and 3c is smaller than the base cores 7, 7a, 7b, 7c, and 7d of the first to seventh embodiments, and thus is easy to fire as compared with the base cores 7, 7a, 7b, 7c, and 7d. The core segments 1c, 2c, and 3c can reduce loss in the coil unit 6 as compared with the base cores 7, 7a, 7b, 7c, and 7d. By using the core segments 1c, 2c, and 3c, the core module 21 can increase dimensional accuracy and can shorten firing time.
The coil apparatus 20 can reduce the dimensional tolerances of the core segments 1c, 2c, and 3c, and thus can reduce variations in inductance value. The coil apparatus 20 can eliminate the need for core polishing, which has conventionally been performed to reduce dimensional tolerances, and thus allows a reduction in the processing time of the core module 21 and a reduction in manufacturing cost.
Either the general-purpose ferrite core material or the low-loss ferrite core material may be used for the core segments 1c, 2c, and 3c. Since both the general-purpose ferrite core material and the low-loss ferrite core material can be used, the number of procurement sources from which the material of the core segments 1c, 2c, and 3c can be procured increases. Consequently, the procurement of components for manufacturing the core module 21 can be stabilized, and the procurement cost can be reduced. Further, the core module 21 can be reduced in loss in the coil unit 6 and improved in quality.
When the case 22 is viewed from a position away from the case 22 in the Z-axis direction, the outer edge of the case 22 has a rectangular shape. The case 22 has a three-dimensional shape surrounding a hollow portion 24. Spaces in which the core segments 1c, 2c, and 3c are disposed are provided around the hollow portion 24. The case 22 includes divider plates 23. The divider plates 23 separate adjacent core segments of the core segments 1c, 2c, and 3c from each other in the X-axis direction. The case 22 is a component molded in one piece including the divider plates 23. Since the case 22 is molded in one piece including the divider plates 23, the core module 21 can reduce manufacturing cost. The divider plates 23 may be components formed separately from the case 22.
The case 22 may include the ribs 13 illustrated in
Further, the lid 8 illustrated in
The core segments 1c are passed through portions of the case 22 corresponding to the short sides of the rectangle. The core segment 2c passes through the case 22 and the hollow portion 24 in the center of the case 22 in the X-axis direction. The coil unit 6 is disposed through the hollow portion 24. The coil unit 6 is installed in the coil apparatus 20 in a state the core segment 2c has passed through the opening of the coil unit 6. When the core module 21 is being assembled, the core segment 2c is fitted into the case 22 after the coil unit 6 is disposed in the hollow portion 24. The core segments 1c and the core segments 3c are fitted into the case 22 in any order.
In the core module 21, the magnetic paths 9 are formed by the core segments 1c, 2c, and 3c, so that core gaps between the core segments are provided in the entire magnetic paths 9. Thus, the number of core gaps in the entire magnetic paths 9 is larger than that in the case where core gaps between core segments are provided only in part of the magnetic paths 9. The coil apparatus 20 can reduce length per core gap because it can increase the number of core gaps. By shortening the core gaps, the coil apparatus 20 can reduce magnetic flux leaking from the core gaps, and can reduce eddy-current loss in the coil unit 6.
The core segments 1c, 2c, and 3c constituting the first core component are held with the lower surfaces of the core segments 1c, 2c, and 3c exposed to the outside of the case 22 at the bottom of the case 22. The coil apparatus 20 is installed in the metal housing 160 with the lower surfaces of the core segments 1c, 2c, and 3c in contact with the metal housing 160. Thus, in the coil apparatus 20, some core segments included in the core segment group are disposed to be able to be thermally coupled to the metal housing 160 that is an external structure of the case 22. Heat-conductive grease or a heat dissipation sheet may be sandwiched between the lower surfaces of the core segments 1c, 2c, and 3c and the metal housing 160.
The metal housing 160 has a configuration for fixing the coil apparatus 20 and also serves as a cooler. The coil apparatus 20 is assembled with some core segments included in the core segment group thermally coupled to the metal housing 160. Consequently, the coil apparatus 20 can obtain high heat dissipation by the use of the metal housing 160.
The coil apparatus 20 is fixed to the metal housing 160 when the coil apparatus 20 is assembled. The coil apparatus 20 may be fixed to the metal housing 160 after the assembly of the coil apparatus 20 is completed. Thus, the degree of freedom in the assembly order of the coil apparatus 20 is improved, so that a more efficient assembly order can be selected to manufacture the coil apparatus 20. This allows a reduction in the manufacturing time of the coil apparatus 20.
The core segment group constituting the core module 21 may include the sheet-shaped core segments 3b illustrated in
By the formation of the cutouts 27 in the case 22a, the coil apparatus 20a can improve heat dissipation. By the provision of the cutouts 27, the amount of material used for manufacturing the case 22a can be reduced. The position, shape, and number of the cutouts 27 can be set as desired so as to prevent the core segments 1c, 2c, and 3c in the case 22a from passing through the cutouts 27 and falling off. Further, by the provision of the cutouts 27, it can be visually checked from the outside of the case 22a how the core segments 1c, 2c, and 3c are fitted into the case 22a. Consequently, poor assembly of the core segments 1c, 2c, and 3c can be prevented from being left unnoticed.
In the coil apparatus 20b, a case 22b constituting a core module 21b is not provided with the divider plates 23 for separating the core segments 1c from the core segments 3c. Further, the case 22b is not provided with the divider plates 23 for separating the core segment 2c from the core segments 3c. Each core segment 1c constituting the core module 21b is in contact with each of the two core segments 3c adjacent to the core segment 1c. The core segment 2c constituting the core module 21b is in contact with each of the four core segments 3c adjacent to the core segment 2c.
Edges of the coil unit 6 are susceptible to magnetic flux, and thus loss in the coil unit 6 tends to occur at the edges. As illustrated in
In the example illustrated in
Since the core module 21c does not use the core segment 2c, the number of types of components is reduced as compared with those of the core modules 21, 21a, and 21b described above. By the reduction of the number of types of components constituting the core module 21c, the productivity of the core module 21c can be improved, and the manufacturing cost of the core module 21c can be reduced.
The XY plane of each core segment 3d is rectangular. The long side of the rectangle is longer than the short side of the rectangle, and has a length up to about twice that of the short side. Of the plurality of core segments 3d constituting the core module 21d, core segments 3d constituting the center leg 25 and core segments 3d constituting the outer legs 26 are disposed with their long sides aligned with the Y-axis direction. Of the plurality of core segments 3d constituting the core module 21d, core segments 3d other than the core segments 3d constituting the center leg 25 and the core segments 3d constituting the outer legs 26 are disposed with their long sides aligned with the X-axis direction.
A case 22d is configured so that the core segments 3d whose long-side directions are determined as described above can be disposed therein. By the disposition of the core segments 3d whose long sides are aligned with the Y-axis direction at the center leg 25 and the outer legs 26, spaces in which the coil unit 6 is disposed are provided between the core segments 3d disposed in the upper part of the case 22d and the core segments 3d disposed in the lower part of the case 22d.
The core module 21d is reduced in the number of types of components as compared with the core modules 21, 21a, 21b, and 21c described above. By the reduction of the number of types of components constituting the core module 21d, the productivity of the core module 21d can be improved, and the manufacturing cost of the core module 21d can be reduced.
Core segments 3d disposed in the lower part of the case 22e are disposed in the same manner as the core segments 3d disposed in the lower part of the case 22d in the fourth modification. That is, of the core segments 3d disposed in the lower part of the case 22e, core segments 3d constituting the center leg 25 and core segments 3d constituting the outer legs 26 are disposed with their long sides aligned with the Y-axis direction. Of the core segments 3d disposed in the lower part of the case 22e, core segments 3d other than the core segments 3d constituting the center leg 25 and the core segments 3d constituting the outer legs 26 are disposed with their long sides aligned with the X-axis direction.
The case 22e is configured so that the core segments 3d whose long-side directions are determined as described above can be disposed therein. Of the core segments 3d disposed in the lower part of the case 22e, the core segments 3d constituting the center leg 25 and the core segments 3d constituting the outer legs 26 are disposed with their long sides aligned with the Y-axis direction, so that spaces in which the coil unit 6 is disposed are provided between the core segments 3d disposed in the upper part of the case 22e and the core segments 3d disposed in the lower part of the case 22e. Like the core module 21d in the fourth modification of the eighth embodiment, the core module 21e can reduce the number of types of components constituting the core module 21e. Consequently, the productivity of the core module 21e can be improved, and the manufacturing cost of the core module 21e can be reduced.
By the disposition of the core segments 3d whose long sides are all aligned with the Y-axis direction in the upper part of the case 22e, the cross-sectional area of the magnetic paths 9 in the upper part of the core module 21e is about one to two times larger than that when the core segments 3d whose long sides are aligned with the X-axis direction are disposed. By the reduction of magnetic flux density in the upper part of the core module 21e, the coil apparatus 20e can reduce loss in the coil unit 6 in the core module 21e. The coil apparatus 20e can reduce the amount of heat generation and the density of heat generation in the core module 21e, and can reduce a temperature rise in the core module 21e. Consequently, the coil apparatus 20e eliminates the need to cool the core module 21e by placing the core module 21e in contact with a structure such as the metal plate 160a illustrated in
Further, by the elimination of the need to cool the core module 21e by placing the core module 21e in contact with the structure, the coil apparatus 20e can be fixed using the metal spring 14 illustrated in
As in the second modification of the eighth embodiment, the magnetic paths 9 in the coil apparatuses 20a, 20c, 20d, and 20e according to the first modification of the eighth embodiment and the third to fifth modifications of the eighth embodiment may include at least one point at which adjacent core segments are in contact with each other. This allows the coil apparatuses 20a, 20c, 20d, and 20e to suppress the occurrence of eddy currents in the coil unit 6 to reduce loss in the coil unit 6.
As in the second modification of the eighth embodiment, the magnetic paths 9 in the coil apparatuses 12, 12a, 12b, 12c, 12d, 12g, 12h, and 12i according to the first to fifth embodiments and the seventh embodiment may include at least one point at which adjacent core segments are in contact with each other. This allows the coil apparatuses 12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, and 12i to suppress the occurrence of eddy currents in the coil unit 6 to reduce loss in the coil unit 6.
The configurations described in the above embodiments illustrate an example of the subject matter of the present invention, and can be combined with another known art, and can be partly omitted or changed without departing from the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-030961 | Feb 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/003913 | 2/3/2020 | WO | 00 |
