Reactor
Provided is a reactor having a small size. A reactor 1 α includes a coil 2 α and a magnetic core 3α in which the coil 2α is disposed. The magnetic core 3α includes an internal core portion 3 i that is inserted through the coil 2α and a couple core portion 3 o that covers the outer periphery of the coil 2α , and these core portions form a closed magnetic path. The reactor 1 α satisfies 1<(B 1 /B 2 ) and 0.17×(B 1 /B 2 )+0.42≦(S 1 ×B 1 )/(S 2 ×B 2 )≦0.50×(B 1 /B 2 )+0.62, where S 1 is the cross-sectional area of the internal core portion, B 1 is the saturation magnetic flux density of the internal core portion, S 2 is the cross-sectional area of the couple core portion, B 2 is the saturation magnetic flux density of the couple core portion, (B 1 /B 2 ) is the saturation magnetic flux density ratio between the core portions, and (S 1 ×B 1 )/(S 2 ×B 2 ) is the magnetic flux ratio between the core portions. The cross-sectional area of the internal core portion 3 i can be reduced because 1<(B 1 /B 2 ) is satisfied, and the size of the reactor 1 α can be reduced because (S 1 ×B 1 )/(S 2 ×B 2 ) is adjusted to be in a specific range.
1. A reactor comprising a coil and a magnetic core, the coil being formed by winding a wire, the magnetic core including an internal core portion that is inserted through the coil and a couple core portion that covers at least a part of an outer periphery of the coil, the core portions forming a closed magnetic path,
wherein 1<(B 1 /B 2 ) and 0.17×(B 1 /B 2 )+0.42≦(S 1 ×B 1 )/(S 2 ×B 2 )≦0.50×(B 1 /B 2 )+0.62 are satisfied,
where S 1 is a cross-sectional area of the internal core portion, B 1 is a saturation magnetic flux density of the internal core portion, S 2 is a cross-sectional area of the couple core portion, B 2 is a saturation magnetic flux density of the couple core portion, (B 1 /B 2 ) is a saturation magnetic flux density ratio between the core portions, and (S 1 ×B 1 )/(S 2 ×B 2 ) is a magnetic flux ratio between the core portions.
2. The reactor according to claim 1 , wherein the couple core portion has a magnetic permeability lower than that of the internal core portion, and the couple core portion is made from a mixture of a magnetic material and a resin, and
wherein the internal core portion and the couple core portion are integrated with each other through the resin.
3. The reactor according to claim 1 , wherein the number of the coils formed by winding the wire is one.
4. The reactor according to claim 1 , wherein the internal core portion is made from a powder molded product, and
wherein the couple core portion is made from a mixture of an iron-based material and a resin.
5. The reactor according to claim 1 , further comprising an internal resin portion that is made from an insulating resin, that covers a surface of the coil, and that retains a shape of the coil.
6. The reactor according to claim 1 , wherein the wire has a flat shape with a cross section having an aspect ratio that is equal to or higher than 5, and
wherein the number of turns of the coil is in the range of 30 to 60.
7. The reactor according to claim 1 , wherein a flatness 3×L 1 /(L 1 +L 2 +L 3 ) of the smallest rectangular parallelepiped that is capable of containing an assembly including the coil and the magnetic core is equal to or larger than 0.5, where L 1 , L 2 , and L 3 are dimensions of the rectangular parallelepiped in ascending order of length.
8. The reactor according to claim 1 , wherein the saturation magnetic flux density B 1 of the internal core portion satisfies 1.6 T≦B 1 and 1.2×B 2 ≦B 1 .
9. The reactor according to claim 1 , wherein a magnetic permeability of the internal core portion is in the range of 50 to 1000, and
wherein a magnetic permeability of the couple core portion is in the range of 5 to 50.
10. The reactor according to claim 1 , further comprising an external resin portion that covers at least a part of an outer periphery of an assembly including the coil and the magnetic core.
11. The reactor according to claim 1 , further comprising a case that contains an assembly including the coil and the magnetic core,
wherein the couple core portion is made from a mixture of a magnetic material and a resin, and
wherein the coil and the internal core portion are sealed in the case by the resin included in the couple core portion.
12. The reactor according to claim 1 , wherein the couple core portion includes an attachment portion for fixing the reactor to a mount object.
13. The reactor according to claim 5 , wherein the internal core portion is retained by the internal resin portion so as to be integrated with the coil.
14. The reactor according to claim 1 , wherein the internal core portion is made from a laminated structure of magnetic steel plates.
15. The reactor according to claim 1 , wherein (B 1 /B 2 )≧1.5.