Patent Publication Number: US-2015085532-A1

Title: Reactor and power conversion device

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2013-198966 filed on Sep. 25, 2013 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a reactor and a power conversion device. 
     2. Description of Related Art 
     There has been known a configuration of a reactor in which a coil is formed in a specific shape, a case serving as a heat dissipation path is provided, and an outer peripheral surface of the coil partially makes contact with the case so as to increase a heat dissipation property (see Japanese Patent Application Publication No. 2012-039099 (JP 2012-039099 A), for example). 
     Further, in a power conversion device including a primary side circuit, and a secondary side circuit magnetically coupled with the primary side circuit via a transformer, such a circuit has been known that two reactors magnetically coupled with each other are provided in the primary side circuit and the secondary side circuit (see Japanese Patent Application Publication No. 2011-193713 (JP 2011-193713 A), for example). In the meantime, the reactor described in JP 2012-039099 A is a single reactor, and two lead parts formed in both ends of the coil are placed not on the same side in an axial direction, but on opposite sides in the axial direction. 
     In a case where such a configuration is applied to each of the two reactors magnetically coupled with each other as described in JP 2011-193713 A and the two reactors are formed coaxially, an amount of heat generation is increased on facing-surface sides of the two reactors. That is, respective magnetic fluxes concentrate on the facing-surface sides of the two reactors, thereby resulting in that eddy current is easy to occur on respective facing surfaces of the coils, which may increase the amount of heat generation. 
     SUMMARY OF THE INVENTION 
     The present invention provides a reactor and a power conversion device each of which is able to diffuse heat efficiently or to reduce heat generation while two coils are wound coaxially. 
     A reactor according to a first aspect of the present invention includes: a magnetic core that defines a predetermined axis; a first coil that is wound around the predetermined axis; and a second coil that is wound around the predetermined axis and is placed opposed to the first coil, wherein a first lead part and a second lead part formed in both ends of the first coil are placed on that side of the first coil which is opposed to the second coil. 
     A reactor according to a second aspect of the present invention includes: a magnetic core that defines a predetermined axis; a first coil that is wound around the predetermined axis; and a second coil that is wound around the predetermined axis alternately with the first coil in a direction of the predetermined axis. 
     A power conversion device according to a third aspect of the present invention includes: a primary side circuit provided with a first reactor including a first magnetic core that defines a first predetermined axis, a first coil that is wound around the first predetermined axis, and a second coil that is wound around the first predetermined axis and is placed opposed to the first coil, the first coil includes a first lead part and a second lead part formed in both ends of the first coil, the first lead part and the second lead part are placed on that side of the first coil which is opposed to the second coil; and a secondary side circuit that is magnetically coupled with the primary side circuit via a transformer and is provided with a second reactor that includes a second magnetic core defining a second predetermined axis, a third coil that is wound around the second predetermined axis, and a fourth coil that is wound around the second predetermined axis and is placed opposed to the third coil, the third coil includes a third lead part and a fourth lead part that are formed in both ends of the third coil, the third lead part and the fourth lead part are placed on that side of the third coil which is opposed to the fourth coil. 
     A power conversion device according to a fourth aspect of the present invention includes: a primary side circuit provided with a first reactor device including a first magnetic core defining a first predetermined axis, a first coil wound around the first predetermined axis, and a second coil wound around the first predetermined axis alternately with the first coil in a direction of the first predetermined axis; and a secondary side circuit that is magnetically coupled with the primary side circuit via a transformer and is provided with a second reactor that includes a second magnetic core that defines a second predetermined axis, a third coil that is wound around the second predetermined axis, and a fourth coil that is wound around the second predetermined axis alternately with the third coil in a direction of the second predetermined axis. 
     According to the above aspects, it is possible to obtain a reactor device and a power conversion device each of which is able to diffuse heat efficiently or to reduce heat generation while two coils are wound coaxially. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a block diagram illustrating a configuration of a power conversion device according to one embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating a reactor device according to one embodiment (Embodiment 1); 
         FIG. 3  is a view schematically illustrating a first coil and a second coil in the reactor device; 
         FIG. 4A  is a view diagrammatically illustrating a state where the first coil and the second coil are wound around a magnetic core as an example of winding of the first coil and the second coil; 
         FIG. 4B  is a view diagrammatically illustrating a state where the first coil and the second coil are wound around the magnetic core as the example of the winding of the first coil and the second coil; 
         FIGS. 5A  to C are views illustrating other examples of the winding of the first coil and the second coil; 
         FIGS. 6A ,  6 B are views each schematically illustrating a first coil and a second coil in a comparative example; 
         FIG. 7  is an explanatory view of a reason why heat generation increases in a facing portion between the first coil and the second coil; 
         FIG. 8  is a top view diagrammatically illustrating a reactor device according to Embodiment 2 of the present invention; 
         FIG. 9  is a sectional view illustrating a reactor device according to Embodiment 3 of the present invention; 
         FIG. 10  is a view schematically illustrating a first coil and a second coil in the reactor device; 
         FIG. 11  is a view schematically illustrating a state of magnetic fluxes caused in the reactor device; and 
         FIG. 12  is a sectional view diagrammatically illustrating a reactor device according to Embodiment 4 of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The following describes each embodiment in detail with reference to the attached drawings. 
       FIG. 1  is a block diagram illustrating a configuration of a power conversion device  10  according to one embodiment. The power conversion device  10  may be used, for example, in a system which is provided in a vehicle such as an automobile and which supplies electricity to each load in the vehicle. 
     The power conversion device  10  includes, as a primary side port, a first input-output port  60   a  to which a primary-side high-voltage load  61   a  is connected, and a second input-output port  60   c  to which a primary-side low-voltage load  61   c  and a primary-side low-voltage power supply  62   c  are connected, for example. The primary-side low-voltage power supply  62   c  supplies electric power to the primary-side low-voltage load  61   c  that works at the same voltage system (for example, 12-V system) as the primary-side low-voltage power supply  62   c . Further, the primary-side low-voltage power supply  62   c  supplies electric power boosted by a primary-side conversion circuit  20  provided in the power conversion device  10 , to the primary-side high-voltage load  61   a  that works at a voltage system (for example, 48-V system higher than the 12-V system) different from that of the primary-side low-voltage power supply  62   c . A concrete example of the primary-side low-voltage power supply  62   c  includes a secondary battery such as a lead battery. The power conversion device  10  includes, as a secondary side port, a third input-output port  60   b  to which a secondary-side high-voltage load  61   b  and a secondary-side high-voltage power supply  62   b  are connected, and a fourth input-output port  60   d  to which a secondary-side low-voltage load  61   d  is connected, for example. 
     The power conversion device  10  is a power converter circuit which includes four input-output ports described above and which has a function to perform power conversion between two input-output ports selected from among the four input-output ports. 
     Port electric powers Pa, Pc, Pb, Pd are respective input/output electric powers (input electric power or output electric power) of the first input-output port  60   a , the second input-output port  60   c , a third input-output port  60   b , and a fourth input-output port  60   d . Port voltages Va, Vc, Vb, Vd are respective input/output voltages (input voltage or output voltage) of the first input-output port  60   a , the second input-output port  60   c , the third input-output port  60   b , and the fourth input-output port  60   d . Port currents Ia, Ic, Ib, Id are respective input/output currents (input current or output current) of the first input-output port  60   a , the second input-output port  60   c , the third input-output port  60   b , and the fourth input-output port  60   d.    
     The power conversion device  10  includes a capacitor C 1  provided in the first input-output port  60   a , a capacitor C 3  provided in the second input-output port  60   c , a capacitor C 2  provided in the third input-output port  60   b , and a capacitor C 4  provided in the fourth input-output port  60   d . Concrete examples of the capacitors C 1 , C 2 , C 3 , C 4  include a film capacitor, an aluminum electrolytic capacitor, a ceramic capacitor, a solid polymer capacitor, and the like. 
     The capacitor C 1  is inserted between a high-voltage-side terminal  613  of the first input-output port  60   a  and a low-voltage-side terminal  614  of the first input-output port  60   a  and the second input-output port  60   c . The capacitor C 3  is inserted between a high-voltage-side terminal  616  of the second input-output port  60   c  and the low-voltage-side terminal  614  of the first input-output port  60   a  and the second input-output port  60   c . The capacitor C 2  is inserted between a high-voltage-side terminal  618  of the third input-output port  60   b  and a low-voltage-side terminal  620  of the third input-output port  60   b  and the fourth input-output port  60   d . The capacitor C 4  is inserted between a high-voltage-side terminal  622  of the fourth input-output port  60   d  and the low-voltage-side terminal  620  of the third input-output port  60   b  and the fourth input-output port  60   d.    
     The power conversion device  10  is a power converter circuit constituted by the primary-side conversion circuit  20  and a secondary-side conversion circuit  30 . Note that the primary-side conversion circuit  20  and the secondary-side conversion circuit  30  are connected to each other via a primary-side magnetic coupling reactor  204  and a secondary-side magnetic coupling reactor  304 , and are magnetically coupled with each other via a transformer  400  (a center-tap transformer). 
     The primary-side conversion circuit  20  is a primary side circuit including a primary-side full bridge circuit  200 , the first input-output port  60   a , and the second input-output port  60   c . The primary-side full bridge circuit  200  is a primary-side power converting portion constituted by a primary side coil  202  of the transformer  400 , the primary-side magnetic coupling reactor  204 , a primary-side first upper arm U 1 , a primary-side first lower arm /U 1 , a primary-side second upper arm V 1 , and a primary-side second lower arm /V 1 . Here, the primary-side first upper arm U 1 , the primary-side first lower arm /U 1 , the primary-side second upper arm V 1 , and the primary-side second lower arm /V 1  are each a switching element including an N-channel MOSFET, and a body diode, which is a parasitic element of the MOSFET, for example. A diode may be additionally connected in parallel to the MOSFET. 
     The primary-side full bridge circuit  200  includes a primary-side positive electrode bus  298  connected to the high-voltage-side terminal  613  of the first input-output port  60   a , and a primary-side negative electrode bus  299  connected to the low-voltage-side terminal  614  of the first input-output port  60   a  and the second input-output port  60   c.    
     A primary-side first arm circuit  207  that connects the primary-side first upper arm U 1  to the primary-side first lower arm /U 1  in series is attached between the primary-side positive electrode bus  298  and the primary-side negative electrode bus  299 . The primary-side first arm circuit  207  is a primary-side first power converter circuit portion (a primary-side U-phase power converter circuit portion) that can perform a power conversion operation according to ON/OFF switching operations of the primary-side first upper arm U 1  and the primary-side first lower arm /U 1 . Further, a primary-side second arm circuit  211  that connects the primary-side second upper arm V 1  to the primary-side second lower arm /V 1  in series is attached between the primary-side positive electrode bus  298  and the primary-side negative electrode bus  299  in parallel to the primary-side first arm circuit  207 . The primary-side second arm circuit  211  is a primary-side second power converter circuit portion (a primary-side V-phase power converter circuit portion) that can perform a power conversion operation according to ON/OFF switching operations of the primary-side second upper arm V 1  and the primary-side second lower arm /V 1 . 
     A bridge portion that connects a middle point  207   m  of the primary-side first arm circuit  207  to a middle point  211   m  of the primary-side second arm circuit  211  is provided with the primary side coil  202  and the primary-side magnetic coupling reactor  204 . A connection relationship in the bridge portion is described below more specifically. One end of a primary-side first reactor  204   a  of the primary-side magnetic coupling reactor  204  is connected to the middle point  207   m  of the primary-side first arm circuit  207 . Then, one end of the primary side coil  202  is connected to the other end of the primary-side first reactor  204   a . Further, one end of a primary-side second reactor  204   b  of the primary-side magnetic coupling reactor  204  is connected to the other end of the primary side coil  202 . Furthermore, the other end of the primary-side second reactor  204   b  is connected to the middle point  211   m  of the primary-side second arm circuit  211 . Note that the primary-side magnetic coupling reactor  204  is constituted by the primary-side first reactor  204   a , and the primary-side second reactor  204   b  magnetically coupled with the primary-side first reactor  204   a  with a coupling coefficient k 1 . 
     The middle point  207   m  is a primary-side first middle node between the primary-side first upper arm U 1  and the primary-side first lower arm /U 1 , and the middle point  211   m  is a primary-side second middle node between the primary-side second upper arm V 1  and the primary-side second lower arm /V 1 . 
     The first input-output port  60   a  is a port provided between the primary-side positive electrode bus  298  and the primary-side negative electrode bus  299 . The first input-output port  60   a  is constituted by the terminal  613  and the terminal  614 . The second input-output port  60   c  is a port provided between the primary-side negative electrode bus  299  and a center tap  202   m  of the primary side coil  202 . The second input-output port  60   c  is constituted by the terminal  614  and the terminal  616 . 
     The center tap  202   m  is connected to the high-voltage-side terminal  616  of the second input-output port  60   c . The center tap  202   m  is a middle connecting point between a primary-side first winding  202   a  and a primary-side second winding  202   b  provided in the primary side coil  202 . 
     The secondary-side conversion circuit  30  is a secondary side circuit constituted by a secondary-side full bridge circuit  300 , the third input-output port  60   b , and the fourth input-output port  60   d . The secondary-side full bridge circuit  300  is a secondary-side power converting portion including a secondary side coil  302  of the transformer  400 , the secondary-side magnetic coupling reactor  304 , a secondary-side first upper arm U 2 , a secondary-side first lower arm /U 2 , a secondary-side second upper arm V 2 , and a secondary-side second lower arm /V 2 . Here, the secondary-side first upper arm U 2 , the secondary-side first lower arm /U 2 , the secondary-side second upper arm V 2 , and the secondary-side second lower arm /V 2  are each a switching element including an N-channel MOSFET, and a body diode, which is a parasitic element of the MOSFET, for example. 
     The secondary-side full bridge circuit  300  includes a secondary-side positive electrode bus  398  connected to the high-voltage-side terminal  618  of the third input-output port  60   b , and a secondary-side negative electrode bus  399  connected to the low-voltage-side terminal  620  of the third input-output port  60   b  and the fourth input-output port  60   d.    
     A secondary-side first arm circuit  307  that connects the secondary-side first upper arm U 2  to the secondary-side first lower arm /U 2  in series is attached between the secondary-side positive electrode bus  398  and the secondary-side negative electrode bus  399 . The secondary-side first arm circuit  307  is a secondary-side first power converter circuit portion (a secondary-side U-phase power converter circuit portion) that can perform a power conversion operation according to ON/OFF switching operations of the secondary-side first upper arm U 2  and the secondary-side first lower arm /U 2 . Further, a secondary-side second arm circuit  311  that connects the secondary-side second upper arm V 2  to the secondary-side second lower arm /V 2  in series is attached between the secondary-side positive electrode bus  398  and the secondary-side negative electrode bus  399  in parallel to the secondary-side first arm circuit  307 . The secondary-side second arm circuit  311  is a secondary-side second power converter circuit portion (a secondary-side V-phase power converter circuit portion) that can perform a power conversion operation according to ON/OFF switching operations of the secondary-side second upper arm V 2  and the secondary-side second lower arm /V 2 . 
     A bridge portion that connects a middle point  307   m  of the secondary-side first arm circuit  307  to a middle point  311   m  of the secondary-side second arm circuit  311  is provided with the secondary side coil  302  and the secondary-side magnetic coupling reactor  304 . A connection relationship in the bridge portion is described below more specifically. One end of a secondary-side first reactor  304   a  of the secondary-side magnetic coupling reactor  304  is connected to the middle point  307   m  of the secondary-side first arm circuit  307 . Then, one end of the secondary side coil  302  is connected to the other end of the secondary-side first reactor  304   a . Further, one end of a secondary-side second reactor  304   b  of the secondary-side magnetic coupling reactor  304  is connected to the other end of the secondary side coil  302 . Furthermore, the other end of the secondary-side second reactor  304   b  is connected to the middle point  311   m  of the secondary-side second arm circuit  311 . Note that the secondary-side magnetic coupling reactor  304  is constituted by the secondary-side first reactor  304   a , and the secondary-side second reactor  304   b  magnetically coupled with the secondary-side first reactor  304   a  with a coupling coefficient k 2 . 
     The middle point  307   m  is a secondary-side first middle node between the secondary-side first upper arm U 2  and the secondary-side first lower arm /U 2 , and the middle point  311   m  is a secondary-side second middle node between the secondary-side second upper arm V 2  and the secondary-side second lower arm /V 2 . 
     The third input-output port  60   b  is a port provided between the secondary-side positive electrode bus  398  and the secondary-side negative electrode bus  399 . The third input-output port  60   b  is constituted by the terminal  618  and the terminal  620 . The fourth input-output port  60   d  is a port provided between the secondary-side negative electrode bus  399  and a center tap  302   m  of the secondary side coil  302 . The fourth input-output port  60   d  is constituted by the terminal  620  and the terminal  622 . 
     The center tap  302   m  is connected to the high-voltage-side terminal  622  of the fourth input-output port  60   d . The center tap  302   m  is a middle connecting point between a secondary-side first winding  302   a  and a secondary-side second winding  302   b  provided in the secondary side coil  302 . 
     Here, the following describes a buck-boost function of the primary-side conversion circuit  20 . In regard to the second input-output port  60   c  and the first input-output port  60   a , the terminal  616  of the second input-output port  60   c  is connected to the middle point  207   m  of the primary-side first arm circuit  207  via the primary-side first winding  202   a  and the primary-side first reactor  204   a  connected in series to the primary-side first winding  202   a . Since both ends of the primary-side first arm circuit  207  are connected to the first input-output port  60   a , a buck-boost circuit is attached between the terminal  616  of the second input-output port  60   c  and the first input-output port  60   a.    
     Further, the terminal  616  of the second input-output port  60   c  is connected to the middle point  211   m  of the primary-side second arm circuit  211  via the primary-side second winding  202   b  and the primary-side second reactor  204   b  connected in series to the primary-side second winding  202   b . Moreover, since both ends of the primary-side second arm circuit  211  are connected to the first input-output port  60   a , a buck-boost circuit is attached in parallel between the terminal  616  of the second input-output port  60   c  and the first input-output port  60   a . Note that the secondary-side conversion circuit  30  is a circuit having generally the same configuration as the primary-side conversion circuit  20 , and therefore, two buck-boost circuits are connected in parallel to each other between the terminal  622  of the fourth input-output port  60   d  and the third input-output port  60   b . Accordingly, the secondary-side conversion circuit  30  has a buck-boost function similarly to the primary-side conversion circuit  20 . 
     Next will be described a reactor device. The reactor device described below can be preferably used in the power conversion device  10 . For example, the reactor device may be used as the primary-side magnetic coupling reactor  204 , or may be used as the secondary-side magnetic coupling reactor  304 . The following description deals with a case where the reactor device constitutes the primary-side magnetic coupling reactor  204 , for example. 
       FIG. 2  is a perspective view illustrating a reactor device  70 A according to one embodiment (Embodiment 1). 
     The reactor device  70 A includes a magnetic core  72 , a first coil  80 , and a second coil  90 . 
     The magnetic core  72  may be made of any magnetic material (e.g., a material including iron oxide, such as ferrite). In the example illustrated in  FIG. 2 , the magnetic core  72  includes two magnetic core elements  72   a ,  72   b . The magnetic core elements  72   a ,  72   b  are E-type cores, and are placed opposed to each other in a state where two slots  72   c ,  72   d  are defined. In such a configuration, the same components can be used as the magnetic core elements  72   a ,  72   b . Note that the magnetic core  72  may be formed in combination of an E-type core and an I-type core (that is, an EI-type core). Further, the magnetic core  72  may be a punched core or may be a laminated core. 
     A first coil  80  and a second coil  90  are placed coaxially around a predetermined axis. In the example illustrated in  FIG. 2 , the first coil  80  and the second coil  90  are wound around a central leg  73  of the magnetic core  72  so as to pass through two slots  72   c ,  72   d . In this case, the central leg  73  defines a predetermined axis I (see  FIG. 3 ). The first coil  80  and the second coil  90  are typically made of the same material. Each of the first coil  80  and the second coil  90  is preferably formed of that square wire having a rectangular section which can handle a larger current as compared with a thin circular wire having a circular section, as illustrated in  FIG. 2 . However, each of the first coil  80  and the second coil  90  may be formed of a thin circular wire having a circular section. 
       FIG. 3  is a view schematically illustrating the first coil  80  and the second coil  90  in the reactor device  70 A.  FIG. 3  is a perspective view schematically illustrating only the first coil  80  and the second coil  90  taken out of the reactor device  70 A illustrated in  FIG. 2 . 
     Since the first coil  80  and the second coil  90  are placed coaxially around the predetermined axis I as described above, they are opposed to each other in a direction (X-direction) of the predetermined axis I. In the following description, for descriptive purposes, those respective sides of the first coil  80  and the second coil  90  on which the first coil  80  and the second coil  90  are opposed to each other in the direction of the predetermined axis I are each referred to as a “facing side,” and opposite sides to the facing sides in the first coil  80  and the second coil  90  are each referred to as a “non-facing side.” For example, in  FIG. 3 , an X2 side of the first coil  80  in the direction of the predetermined axis I is a “facing side,” and an X1 side thereof is a “non-facing side.” 
     The first coil  80  includes a first lead part  81  and a second lead part  82 . Lengths of the first lead part  81  and the second lead part  82  are optional. The first lead part  81  and the second lead part  82  serve as terminals, and are connected to other components (elements of an electric circuit). For example, in a case where the first coil  80  constitutes the primary-side first reactor  204   a , the first lead part  81  and the second lead part  82  may be connected to the middle point  207   m  of the primary-side first arm circuit  207  and one end of the primary-side first winding  202   a , respectively. 
     The first lead part  81  and the second lead part  82  of the first coil  80  are placed on the facing side of the first coil  80 . That is, the first lead part  81  and the second lead part  82  are both placed on the facing side. Note that as far as the first lead part  81  and the second lead part  82  are placed on the facing side, they may be drawn in any direction on the facing side. For example, in the example of  FIG. 3 , the first lead part  81  and the second lead part  82  are drawn toward a Z1 side in a Z-direction. However, the first lead part  81  may be drawn toward the Z1 side in the Z-direction, and the second lead part  82  may be drawn toward a Z2 side in the Z-direction, for example. 
     The second coil  90  includes a third lead part  91  and a fourth lead part  92 . Lengths of the third lead part  91  and the fourth lead part  92  are optional. The third lead part  91  and the fourth lead part  92  serve as terminals, and are connected to other components (elements of an electric circuit). For example, in a case where the second coil  90  constitutes the primary-side second reactor  204   b , the third lead part  91  and the fourth lead part  92  may be connected to the middle point  211   m  of the primary-side second arm circuit  211  and one end of the primary-side second winding  202   b , respectively. 
     The third lead part  91  and the fourth lead part  92  of the second coil  90  are placed on the facing side of the second coil  90 . That is, the third lead part  91  and the fourth lead part  92  are both placed on the facing side. Note that as far as the third lead part  91  and the fourth lead part  92  are placed on the facing side, they may be drawn in any direction on the facing side. For example, in the example of  FIG. 3 , the third lead part  91  and the fourth lead part  92  are drawn toward the Z1 side in the Z-direction. However, the third lead part  91  may be drawn toward the Z1 side in the Z-direction, and the fourth lead part  92  may be drawn toward the Z2 side in the Z-direction, for example. 
       FIGS. 4A ,  4 B are views illustrating one example of winding of the first coil  80  and the second coil  90 .  FIG. 4A  diagrammatically illustrates a state where the first coil  80  and the second coil  90  are wound around the magnetic core  72 .  FIG. 4B  diagrammatically illustrates the first coil  80  and the second coil  90  taken out of the reactor device  70 A.  FIGS. 4A ,  4 B illustrate the first coil  80  and the second coil  90  in a top view (a view along the Z-direction of  FIG. 3 ). In  FIGS. 4A ,  4 B, P indicates a facing-side plane between the first coil  80  and the second coil  90 . Herein, only winding of the second coil  90  (and its related configuration) is described as a typical example, but the first coil  80  may be wound in the same manner. Note that, in  FIGS. 4A ,  4 B, dotted-line parts of the first coil  80  and the second coil  90  indicate parts wound on their back sides. 
     As illustrated in  FIGS. 4A ,  4 B (also see  FIG. 3 ), the second coil  90  includes a winding part  93  in addition to the third lead part  91  and the fourth lead part  92 . 
     The winding part  93  is a part wound around the predetermined axis I, and serves as a body portion that substantially implements a magnetic flux forming function of the first coil  80 . The third lead part  91  and the fourth lead part  92  are formed in both ends of the winding part  93 . Note that the number of windings of the winding part  93  is optional. 
     The winding part  93  includes a single-layer winding part  93   a  wound in a single layer, and an intersecting part  94 . The intersecting part  94  passes on an inner side or an outer side (the inner side is a side closer to the predetermined axis I in a radial direction around the predetermined axis I) of the single-layer winding part  93   a , and intersects with the single-layer winding part  93   a . In the example illustrated in  FIGS. 4A ,  4 B (and  FIG. 3 ), the intersecting part  94  passes on the outer side of the single-layer winding part  93   a . Note that the intersecting part  94  may be formed outside the slots  72   c ,  72   d  of the magnetic core  72  in consideration of limited spaces of the slots  72   c ,  72   d  of the magnetic core  72 . 
     The intersecting part  94  is formed so that the third lead part  91  and the fourth lead part  92  are both placed on the facing side as described above. In the example illustrated in  FIGS. 4A ,  4 B, the second coil  90  is configured such that the single-layer winding part  93   a  (a part other than the intersecting part  94 ) of the winding part  93  is formed by three turns from the third lead part  91 , and the intersecting part  94  is formed so as to return toward the facing side from the non-facing side. At this time, the intersecting part  94  is provided so as to extend toward the facing side across the outer side of the single-layer winding part  93   a . Hereby, the fourth lead part  92  can be formed on the facing side. 
       FIGS. 5A to 5C  are views illustrating other examples of the winding of the first coil  80  and the second coil  90 . In the following description, only the winding of the second coil  90  (and its related configuration) is described as a typical example, but the first coil  80  may be wound in the same manner. 
     In the example illustrated in  FIG. 5A , the second coil  90  is wound in two turns. Similarly to the above, the intersecting part  94  passes on the outer side of the single-layer winding part  93   a  and extends toward the facing side. Hereby, the fourth lead part  92  can be formed on the facing side. 
     In the example illustrated in  FIG. 5B , the second coil  90  is wound in four turns. Similarly to the above, the intersecting part  94  passes on the outer side of the single-layer winding part  93   a  and extends toward the facing side. Hereby, the fourth lead part  92  can be formed on the facing side. Thus, the number of windings of the second coil  90  is optional. 
     In the example illustrated in  FIG. 5C , the second coil  90  is wound in four turns. In the example illustrated in  FIG. 5C , the intersecting part  94  includes a first intersecting part  94   a  and a second intersecting part  94   b . The first intersecting part  94   a  extends toward the facing side from the non-facing side only by one turn, and the second intersecting part  94   b  extends toward the non-facing side only by three turns. Hereby, the fourth lead part  92  can be formed on the facing side. Thus, the intersecting part  94  may be constituted by a plurality of intersecting parts. 
       FIGS. 6A ,  6 B are views each schematically illustrating a first coil  80 ′ and a second coil  90 ′ in a comparative example.  FIG. 6A  is a view illustrated in comparison with  FIG. 3 .  FIG. 6B  is a view illustrated in comparison with  FIG. 4B . In the comparative example, the first coil  80 ′ includes a first lead part  81 ′ on a non-facing side thereof, and includes a second lead part  82 ′ on a facing side thereof. Further, the second coil  90 ′ includes a third lead part  91 ′ on a non-facing side thereof, and includes a fourth lead part  92 ′ on a facing side thereof. 
       FIG. 7  is an explanatory view of a reason why heat generation increases in a facing portion between the first coil  80  and the second coil  90 , and is a sectional view diagrammatically illustrating a left half of the reactor device  70 A (a left half with respect to the predetermined axis I in the Y-direction) when the reactor device  70 A is cut on a surface perpendicular to the Z-direction of  FIG. 2 . 
     In the present embodiment, since the first coil  80  and the second coil  90  are placed coaxially around the predetermined axis I as described above end surfaces of the first coil  80  and the second coil  90  on their facing sides are opposed to each other. When a current is applied to the first coil  80  and the second coil  90 , respective magnetic fluxes M 1 , M 2  are formed as diagrammatically illustrated in  FIG. 7 . The magnetic fluxes M 1 , M 2  concentrate on between the end surfaces of the first coil  80  and the second coil  90  on their facing sides. Because of this, eddy current is easy to occur in the end surfaces of the first coil  80  and the second coil  90  on their facing sides, which causes such a problem that an amount of heat generation increases. 
     In this regard, in a case of the comparative example illustrated in FIGS.  6 A, 6 B, the first coil  80 ′ and the second coil  90 ′ just include two lead parts (the second lead part  82 ′ and the fourth lead part  92 ′) on their facing sides, so that an amount of heat that can be relieved outside through the lead parts is limited. This may cause a problem with heat concentration (an increase in temperature) in the facing portion between the first coil  80 ′ and the second coil  90 ′. 
     On the other hand, according to the present embodiment, since the first coil  80  and the second coil  90  include four lead parts (the first lead part  81 , the second lead part  82 , the third lead part  91 , and the fourth lead part  92 ) on their facing sides, it is possible to efficiently relieve heat outside through these lead parts. This makes it possible to reduce heat concentration (an increase in temperature) in the facing portion between the first coil  80  and the second coil  90 . 
     Note that, in the examples illustrated in  FIGS. 2 ,  3  and so on, the first lead part  81 , the second lead part  82 , the third lead part  91 , and the fourth lead part  92  are all placed on the facing sides, but only any three of them may be placed on the facing sides. Further, the first lead part  81 , the second lead part  82 , the third lead part  91 , and the fourth lead part  92  are all formed on both sides in the Y-direction, but may be formed on any positions in the Y-direction. 
     Further, in the examples illustrated in  FIGS. 2 ,  3  and so on, the intersecting part  94  extends in a diagonal direction with respect to the X-direction in a state where the intersecting part  94  forms part of the winding part  93 , but may extend in parallel to the X-direction. In this case, the intersecting part  94  extends in parallel to the predetermined axis I. 
       FIG. 8  is a top view diagrammatically illustrating a reactor device  70 B according to another embodiment (Embodiment 2). 
     Embodiment 2 is different from Embodiment 1 mainly in that a magnetic core  72 B has a U-shape. The other configurations of Embodiment 2 may be substantially the same as those in Embodiment 2, so that the same reference signs are attached thereto and description of the other configurations are omitted. 
     The magnetic core  72 B may be formed by placing two U-shaped cores so as to face each other, or may be formed integrally in a ring shape. Further, the magnetic core  72 B may be formed of a single U-shaped core. 
     Similarly to the above, a first coil  80  and a second coil  90  are placed coaxially around a predetermined axis. In the example illustrated in  FIG. 8 , the first coil  80  and the second coil  90  are wound around a one-side central leg  73 B of the magnetic core  72 B so as to pass through a central slot  72   e . In this case, the leg  73 B defines a predetermined axis I. The first coil  80  and the second coil  90  may be wound around the predetermined axis I in a similar manner to the abovementioned Embodiment 1. 
     Even Embodiment 2 yields the effect similar to that of Embodiment 1 described above. That is, since the first coil  80  and the second coil  90  include four lead parts (the first lead part  81 , the second lead part  82 , the third lead part  91 , and the fourth lead part  92 ) on their facing sides, it is possible to efficiently relieve heat outside through these lead parts. This makes it possible to reduce heat concentration (an increase in temperature) in the facing portion between the first coil  80  and the second coil  90 . 
       FIG. 9  is a sectional view illustrating a reactor device  70 C in another embodiment (Embodiment 3). 
     The reactor device  70 C includes a magnetic core  72 , a first coil  800 , and a second coil  900 . The magnetic core  72  may be configured in a similar manner to Embodiment 1. 
     The first coil  800  and the second coil  900  are placed coaxially around a predetermined axis. In the example illustrated in  FIG. 9 , the first coil  800  and the second coil  900  are wound around a central leg  73  of the magnetic core  72  so as to pass through two slots  72   c ,  72   d  of the magnetic core  72 . In this case, the central leg  73  defines a predetermined axis I (see  FIGS. 9 ,  10 ). The first coil  800  and the second coil  900  are typically made of the same material. Each of the first coil  800  and the second coil  900  is preferably formed of that square wire having a rectangular section which can handle a larger current as compared with a thin circular wire having a circular section. However, each of the first coil  800  and the second coil  900  may be formed of a thin circular wire having a circular section. 
       FIG. 10  is a view schematically illustrating the first coil  800  and the second coil  900  in the reactor device  70 C.  FIG. 10  is a perspective view schematically illustrating only the first coil  800  and the second coil  900  taken out of the reactor device  70 C illustrated in  FIG. 9 . 
     The first coil  800  and the second coil  900  are wound in a single layer around the predetermined axis. At this time, the first coil  800  and the second coil  900  are wound alternately in a direction of the predetermined axis (X-direction) as illustrated in  FIG. 10 . 
     The first coil  800  includes a first lead part  810  on an X1 side in the X-direction, and a second lead part  820  on an X2 side in the X-direction. The first lead part  810  and the second lead part  820  serve as terminals, and are connected to other components (elements of an electric circuit). For example, in a case where the first coil  800  constitutes the primary-side first reactor  204   a , the first lead part  810  and the second lead part  820  may be connected to the middle point  207   m  of the primary-side first arm circuit  207  and one end of the primary-side first winding  202   a , respectively. 
     The second coil  900  includes a third lead part  910  on the X1 side in the X-direction, and a fourth lead part  920  on the X2 side in the X-direction. The third lead part  910  and the fourth lead part  920  serve as terminals, and are connected to other components (elements of an electric circuit). For example, in a case where the second coil  900  constitutes the primary-side second reactor  204   b , the third lead part  910  and the fourth lead part  920  may be connected to the middle point  211   m  of the primary-side second arm circuit  211  and one end of the primary-side second winding  202   b , respectively. 
     Note that, in this example, the first coil  800  and the second coil  900  are wound in the same number of windings, but they may be wound in different numbers of windings. Further, the first lead part  810  and the second lead part  820  are drawn toward a Z1 side in a Z-direction in this example. However, a direction where the first lead part  810  and the second lead part  820  are drawn is optional. For example, the first lead part  810  may be drawn toward the Z1 side in the Z-direction, and the second lead part  820  may be drawn toward a Z2 side in the Z-direction. Similarly, the third lead part  910  and the fourth lead part  920  are drawn toward the Z1 side in the Z-direction. However, the third lead part  910  may be drawn toward the Z1 side in the Z-direction, and the fourth lead part  920  may be drawn toward the Z2 side in the Z-direction, for example. 
       FIG. 11  is a view schematically illustrating a state of magnetic fluxes caused in the reactor device  70 C, and a view corresponding to  FIG. 7  in Embodiment 1 described above. 
     In Embodiment 3, the first coil  800  and the second coil  900  are wound alternately around the predetermined axis I, as described above. When a current is applied to the first coil  800  and the second coil  900 , respective magnetic fluxes M 1 , M 2  are formed as diagrammatically illustrated in  FIG. 11 . However, concentration of the magnetic fluxes M 1 , M 2  is suppressed (see  FIG. 7  as a comparison). That is, in Embodiment 3, the concentration of the magnetic fluxes M 1 , M 2  is suppressed at the time of current application of the first coil  800  and the second coil  900 , thereby reducing an amount of heat generation. Further, heat generation parts are dispersed, thereby making it possible to perform cooling easily. Note that according to CAE (computer-aided engineering) analysis by the inventor(s) of the present invention, it is found that a coil heat generation amount in Embodiment 3 is reduced to about ¼ of a coil heat generation amount in the comparative example illustrated in  FIGS. 6A ,  6 B. 
       FIG. 12  is a sectional view diagrammatically illustrating a reactor device  70 D according to another embodiment (Embodiment 4). Embodiment 4 is different from Embodiment 3 mainly in that a magnetic core  72 B has a U-shape. The other configurations of Embodiment 4 may be substantially the same as those in Embodiment 3, so that the same reference signs are attached thereto and description of the other configurations are omitted. A magnetic core  72 B may be configured in a similar manner to Embodiment 2. 
     The magnetic core  72 B may be formed by placing two U-shaped cores so as to face each other, or may be formed integrally in a ring shape. Further, the magnetic core  72 B may be formed of a single U-shaped core. 
     Similarly to the above, a first coil  800  and a second coil  900  are placed coaxially around a predetermined axis. In the example illustrated in  FIG. 12 , the first coil  800  and the second coil  900  are wound around a one-side central leg  73 B of the magnetic core  72 B so as to pass through a central slot  72   e . In this case, the leg  73 B defines a predetermined axis I. The first coil  800  and the second coil  900  may be wound around the predetermined axis I in a similar manner to the abovementioned Embodiment 3. 
     Even Embodiment 4 yields the effect similar to that of Embodiment 3 described above. That is, concentration of magnetic fluxes is suppressed at the time of current application to the first coil  800  and the second coil  900 , thereby making it possible to reduce a whole amount of heat generation of the first coil  800  and the second coil  900 . 
     Each embodiment has been described above, but this invention is not limited to any specific embodiment, and various modifications and alternations can be made within a scope of Claims. Further, all or some of constituents in the above embodiment can be combined. 
     For example, the reactor devices  70 A,  70 B in the above embodiments are not limited to a magnetic coupling reactor in the power conversion device  10  having a configuration as illustrated herein, but also usable as a magnetic coupling reactor in a power conversion device having a different configuration. Further, the reactor devices  70 A,  70 B in the embodiments can be used as a transformer. 
     Further, in Embodiment 3 and Embodiment 4, the first coil  800  and the second coil  900  are wound in a single layer, but may be configured by a multi-layer winding in which the first coil  800  wand the second coil  900  are wound alternately in each layer.