Abstract:
The disclosed reactor has a case and a cylindrical molded coil assembly which is disposed inside of the case and which is formed by covering a coil with a resin, wherein the coil assembly is sealed by an iron powder mixed resin to which iron powder has been admixed. The reactor has a pillar provided as a single body with the case, and one or multiple ring-shaped core members. The ring-shaped core members are disposed outside the outer surface of the pillar such that the pillar is inserted inside the inner surface of said ring-shaped core members, and the assembly coil is disposed outside the outer surface of the ring-shaped core members such that the ring-shaped core members are inserted inside the inner surface of said coil assembly. The ring-shaped core members are sealed by means of the aforementioned iron powder-mixed resin.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a 371 national phase application of PCT/JP2010/060561 filed on Jun. 22, 2010, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a reactor used for example in a booster circuit of a motor drive device, and a method of manufacturing the reactor. 
       BACKGROUND OF THE INVENTION 
       [0003]    Reactors are known that are used in booster circuits of motor drive devices of electric vehicles or hybrid electric vehicles. The reactor changes voltage using inductive reactance and is made with a core and a coil. The reactor is used as a part integrated in a switching circuit, and it is repeatedly switched on and off, storing energy in the coil when switched on and creating a counter electromotive force when switched off, thereby outputting a high voltage. 
         [0004]    Patent Document 1 discloses a technique for a reactor comprising a coil molded with an iron-resin composite containing iron powder. With this reactor, the iron-resin composite used for molding the coil functions as the core. 
       RELATED ART DOCUMENTS 
     Patent Documents 
       [0005]    Patent Document 1: JP 2006-352021A 
       SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention  
       [0006]    However, with the technique of Patent Document 1, the iron content of the iron-resin composite is low so that the core has a low magnetic permeability. To achieve a necessary inductance, the volume of the iron-resin composite needs to be made large to increase the cross-sectional area of the core. This results in a large outer shape of the reactor. 
         [0007]    One possibility is to adjust the number of windings of the coil and the volume of the iron-resin composite to adjust the inductance. However, when the reactor is to be mounted within a limited area of, for example, a booster circuit of a motor drive device, there are limitations on the number of windings of the coil or the volume of the iron-resin composite, because of which there may be a case where the inductance cannot be adjusted to a necessary level. This means that the reactor cannot be provided with characteristics that keep the inductance changes sufficiently small irrespective of large current changes, i.e., stable DC superimposition characteristics showing a substantially constant (flat) inductance within the range of current being used. That is, the reactor has poor performance. 
         [0008]    The material cost of the iron-resin composite is high, and the composite requires a long time to set. Therefore, a large amount of filling iron-resin composite leads to a higher production cost of the reactor. 
         [0009]    Moreover, the coil is prone to come off of a predetermined position unless the coil is retained by some means when the inside of the case is filled with the iron-resin composite as in the technique of Patent Document 1, which causes a reduction in the productivity of the reactor. 
         [0010]    Accordingly, the present invention has been made to solve the above problems and has a purpose to provide a reactor and a reactor manufacturing method enabling to reduce the size of the outer shape of the reactor and to enhance the performance of the reactor. 
       Means of Solving the Problems 
       [0011]    One aspect of the present invention to solve the above problems is a reactor having a case and a cylindrical coil assembly stored in the case and formed to have a coil covered with resin, an iron-resin composite containing iron powder for sealing the coil assembly, wherein the reactor comprises a pillar integrally formed with the case and one or a plurality of ring-shaped core members, the ring-shaped core member or members are provided outside an outer peripheral surface of the pillar such that the pillar is inserted inside an inner peripheral surface of the ring-shaped core member or members, the coil assembly is provided outside an outer peripheral surface of the ring-shaped core member or members such that the ring-shaped core member or members are inserted inside an inner peripheral surface of the coil assembly, the ring-shaped core member or members are sealed with the iron-resin composite, the reactor includes a bobbin having an opening formed with an end surface and a side wall extending vertically from a peripheral edge of the end surface, the bobbin is provided inside an inner peripheral surface of the coil assembly so as to cover the ring-shaped core member or members, the bobbin has a flange on an opening end portion of the bobbin, and an axial end face of the coil assembly is in contact with the flange. 
         [0012]    According to this aspect, in addition to the iron-resin composite sealing the coil assembly, the reactor comprises the ring-shaped core member(s), so that magnetic property is enhanced. Thereby, large inductance can be obtained even if the volume of the resin core formed by the iron-resin composite is small. This leads to reduction in size of the outer shape of the reactor. Further, the pillar integrally formed with the case is inserted inside the inner peripheral surface of the ring-shaped core member(s), so that the ring-shaped core member(s) can be easily mounted on the case as aligning relative positions of the case and the ring-shaped core member(s) in the axial direction, thus enhancing the productivity of the reactor. 
         [0013]    The ring-shaped core member(s) is sealed with the iron-resin composite, thus preventing corrosion and cracks of the ring-shaped core member(s). 
         [0014]    Further, the volume of the iron-resin composite can be reduced by the volume of the ring-shaped core member(s), so that time to fill and set the iron-resin composite is shortened. Since the amount of the iron-resin composite to be used is thus reduced, material cost can be reduced. Accordingly, manufacturing cost can be reduced. 
         [0015]    Further, the axial end face of the coil assembly is in contact with the flange of the bobbin, so that the axially relative positions of the bobbin and the coil assembly are decided. Therefore, the coil assembly can be placed at a predetermined position while the iron-resin composite is filled and set in the case. 
         [0016]    Also, own weight of the coil assembly acts on the ring-shaped core member(s) via the bobbin. Thereby, float and misalignment of the ring-shaped core member(s) can be prevented and the ring-shaped core member(s) can be placed at a predetermined position while the iron-resin composite is filled and set in the case. 
         [0017]    In the above aspect, preferably, the reactor includes a seat formed between the pillar and the case, the seat having a larger diameter than that of the pillar, and an axial end face of the ring-shaped core member or members is in contact with the seat. 
         [0018]    According to this aspect, the axial end face of the ring-shaped core member(s) is in contact with the seat, so that the axially relative positions of the case and the ring-shaped core member(s) are decided. Therefore, the ring-shaped core member(s) can be placed at a predetermined position without increasing number of components. 
         [0019]    In the above aspect, preferably, the bobbin has an opening on at least one of the end surface and the side wall. 
         [0020]    According to this aspect, when the iron-resin composite is filled inside the case, the iron-resin composite can be certainly filled in the surroundings of the ring-shaped core member(s) since the iron-resin composite flows inside an inner peripheral surface of the bobbin from the opening thereof. 
         [0021]    In a case that a non-magnetic gap plate is provided between the adjacent ring-shaped core members, the ring-shaped core members and the gap plate are securely bonded by the iron-resin composite flowing inside the inner peripheral surface of the bobbin from the opening thereof. 
         [0022]    In the above aspect, preferably, the reactor has a non-magnetic gap plate formed into a ring-like shape, and the gap plate is provided in between the adjacent ring-shaped core members. 
         [0023]    According to this aspect, inductance can be adjusted by varying thickness and number of the gap plates, so that stable DC superimposition characteristics can be obtained as the inductance is almost at a fixed value (flat) within the used current range. Thereby, performance of the reactor is enhanced. 
         [0024]    In the above aspect, preferably, the gap plate has a slit extending from an inner peripheral surface to an outer peripheral surface of an axial end face of the gap plate. 
         [0025]    According to this aspect, the iron-resin composite filled inside the case flows into a space between the ring-shaped core members and the gap plate via the slit, so that the ring-shaped core members and the gap plate are securely bonded. 
         [0026]    Another aspect of the present invention to solve the above problem is a method of manufacturing a reactor including a case and a cylindrical coil assembly stored inside the case and formed to have a coil covered with resin, an iron-resin composite containing iron powder for sealing the coil assembly, wherein the reactor comprises a pillar integrally formed with the case and one or a plurality of ring-shaped core member or members, the method includes the steps of: placing the ring-shaped core member or members outside an outer peripheral surface of the pillar such that the pillar is inserted inside an inner peripheral surface of the ring-shaped core member or members; covering the ring-shaped core member or members inside an inner peripheral surface of the coil assembly with a bobbin having an opening formed with an end surface and a side wall extending vertically from a peripheral edge of the end surface; placing the coil assembly outside an outer peripheral surface of the bobbin such that the bobbin is inserted inside an inner peripheral surface of the coil assembly; bringing an axial end face of the coil assembly into contact with a flange formed on an opening end portion of the bobbin, and sealing the ring-shaped core member or members with the iron-resin composite. 
         [0027]    According to this aspect, the pillar integrally formed with the case is inserted inside the inner peripheral surface of the ring-shaped core member(s), thereby the ring-shaped core member(s) can be easily mounted on the case as aligning the relative positions of the case and the ring-shaped core member(s) in the radial direction. Thereby, the productivity of the reactor is enhanced. 
         [0028]    Further, the axial end face of the coil assembly is brought into contact with the flange of the bobbin, so that the axially relative positions of the bobbin and the coil assembly are decided. Therefore, the coil assembly can be placed at a predetermined position while the iron-resin composite is filled and set in the case. 
         [0029]    Also, own weight of the coil assembly acts on the ring-shaped core member(s) via the bobbin. Thereby, float and misalignment of the ring-shaped core member can be prevented and the ring-shaped core member(s) can be placed at a predetermined position while the iron-resin composite is filled and set in the case. 
         [0030]    In the above aspect, preferably, the method comprises the step of bringing a seat into contact with an axial end face of the ring-shaped core member or members, the seat being formed between the pillar and the case and having a larger diameter than that of the pillar. 
         [0031]    According to this aspect, the axial end face of the ring-shaped core member(s) is brought into contact with the seat, so that the axially relative positions of the case and the ring-shaped core member(s) are decided. Therefore, the ring-shaped core member(s) can be placed at a predetermined position without increasing number of components. 
         [0032]    In the above aspect, preferably, the bobbin has an opening on at least one of the end surface and the side wall. 
         [0033]    According to this aspect, when the iron-resin composite is filled inside the case, the iron-resin composite can be certainly filled in the surroundings of the ring-shaped core member(s) since the iron-resin composite flows inside the inner peripheral surface of the bobbin from the opening thereof. 
         [0034]    In a case that a non-magnetic gap plate is provided between the adjacent ring-shaped core members, the ring-shaped core members and the gap plate are securely bonded by the iron-resin composite flowing inside the inner peripheral surface of the bobbin from the opening thereof. 
         [0035]    In the above aspect, preferably, a non-magnetic gap plate formed into a ring-like shape is provided between the adjacent ring-shaped core members. 
         [0036]    According to this aspect, inductance can be adjusted by varying thickness and number of the gap plates, so that stable DC superimposition characteristics can be obtained as the inductance is almost at a fixed value (flat) within the used current range. Thereby, performance of the reactor is enhanced. 
         [0037]    In the above aspect, preferably, the gap plate has a slit extending from an inner peripheral surface to an outer peripheral surface on an axial end face of the gap plate. 
         [0038]    According to this aspect, the iron-resin composite filled inside the case flows into the space between the ring-shaped core members and the gap plate via the slit, so that the ring-shaped core members and the gap plate are securely bonded. 
       Effects of the Invention 
       [0039]    Reactor and reactor manufacturing method according to the present invention enable size reduction of the outer shape of the reactor and enhance the performance of the reactor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]      FIG. 1  is a schematic diagram showing one example of a drive control system configuration including a reactor according to a present embodiment; 
           [0041]      FIG. 2  is a circuit diagram showing major parts of PCU in  FIG. 1 ; 
           [0042]      FIG. 3  is an external perspective view of the reactor according to first and second embodiments; 
           [0043]      FIG. 4  is a sectional view taken along a line A-A in  FIG. 3 ; 
           [0044]      FIG. 5  is an explanatory view explaining how various components configuring the reactor are assembled in a case according to the first embodiment; 
           [0045]      FIG. 6  is an explanatory view showing a state after various components configuring the reactor are assembled in the case and before the case is filled with iron-resin composite; 
           [0046]      FIG. 7  is a view showing another embodiment in which the numbers of pressed powder core members and gap plates are changed; and 
           [0047]      FIG. 8  is an explanatory view showing how various components configuring the reactor are assembled in the case in the second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0048]    Embodiments of the present invention will be hereinafter described in detail with reference to the accompanying drawings. 
         [0049]    The reactor according to this embodiment is mounted in a drive control system of a hybrid electric vehicle for the purpose of boosting a battery voltage to a level applied to a motor generator. 
         [0050]    Therefore, the structure of the drive control system will be described first, after which the reactor according to this embodiment will be described. 
         [0051]    First, the drive control system will be described referring to  FIG. 1  and  FIG. 2 . 
         [0052]      FIG. 1  is a schematic diagram illustrating one example of a drive control system configuration including the reactor according to this embodiment.  FIG. 2  is a circuit diagram illustrating major parts of PCU in  FIG. 1 . 
         [0053]    A drive control system  1  is formed by a PCU (Power Control Unit)  10 , a motor generator  12 , a battery  14 , a terminal base  16 , a housing  18 , a reduction gear  20 , a differential gear  22 , drive shaft receiving parts  24 , and others as shown in  FIG. 1 . 
         [0054]    The PCU  10  includes a converter  46 , an inverter  48 , a controller  50 , capacitors C 1  and C 2 , and output lines  52 U,  52 V, and  52 W as shown in  FIG. 2 . 
         [0055]    The converter  46  is connected between the battery  14  and the inverter  48  electrically in parallel with the inverter  48 . The inverter  48  is connected to the motor generator  12  via the output lines  52 U,  52 V, and  52 W. 
         [0056]    The battery  14  is, for example, a secondary battery such as a nickel metal hydride or lithium ion battery. The battery  14  supplies a direct current to the converter  46  and is charged by the direct current flowing from the converter  46 . 
         [0057]    The converter  46  is made up of power transistors Q 1  and Q 2 , diodes D 1  and D 2 , and the reactor  101  to be described later in more detail. The power transistors Q 1  and Q 2  are connected in series between power supply lines PL 2  and PL 3  and supply control signals from the controller  50  to a base. The diodes D 1  and D 2  are each connected between collector and emitter terminals of the power transistors Q 1  and Q 2  so that the current flows from the emitter terminals to the collector terminals of the respective power transistors Q 1  and Q 2 . 
         [0058]    The reactor  101  is arranged to have one end connected to a power supply line PL 1  that connects to a positive electrode of the battery  14  and the other end connected to a connection point between the power transistors Q 1  and Q 2 . 
         [0059]    The converter  46  boosts the DC voltage of the battery  14  by the reactor  101  and supplies the boosted DC voltage to the power supply line PL 2 . The converter  46  charges the battery  14  with the direct current received from the inverter  48  at a lowered voltage. 
         [0060]    The inverter  48  is formed by a U-phase arm  54 U, a V-phase arm  54 V, and a W-phase arm  54 W. The respective phase arms  54 U,  54 V, and  54 W are connected in parallel between the power supply lines PL 2  and PL 3 . The U-phase arm  54 U is formed by series-connected power transistors Q 3  and Q 4 , the V-phase arm  54 V is formed by series-connected power transistors Q 5  and Q 6 , and the W-phase arm  54 W is formed by series-connected power transistors Q 7  and Q 8 . The diodes D 3  to D 8  are each connected between the collector and emitter terminals of the power transistors Q 3  to Q 8  so that the current flows from the emitter terminals to the collector terminals of the respective power transistors Q 3  to Q 8 . The connection points between the respective pairs of power transistors Q 3  to Q 8  at the respective phase arms  54 U,  54 V, and  54 W are connected to the opposite side of the neutral point of the U-phase, V-phase, and W-phase of the motor generator  12 , respectively, via the output lines  52 U,  52 V, and  52 W. 
         [0061]    The inverter  48  converts a direct current flowing in the power supply line PL 2  into an alternating current based on a control signal from the controller  50  and outputs the alternating current to the motor generator  12 . The inverter  48  rectifies the alternating current generated by the motor generator  12  and converts the alternating current into a direct current, and supplies the converted direct current to the power supply line PL 2 . 
         [0062]    The capacitor C 1  is connected between the power supply lines PL 1  and PL 3  and smoothes the voltage level of the power supply line PL 1 . The capacitor C 2  is connected between the power supply lines PL 2  and PL 3  and smoothes the voltage level of the power supply line PL 2 . 
         [0063]    The controller  50  calculates the coil voltages at the U-phase, V-phase, and W-phase of the motor generator  12  based on the rotation angle of a rotor of the motor generator  12 , motor torque commands, current values at the U-phase, V-phase, and W-phase of the motor generator  12 , and an input voltage of the inverter  48 . The controller  50  generates a PWM (Pulse Width Modulation) signal for switching on and off the power transistors Q 3  to Q 8  based on the calculation results and outputs the signal to the inverter  48 . 
         [0064]    Also, in order to optimize the input voltage of the inverter  48 , the controller  50  calculates the duty ratio between the power transistors Q 1  and Q 2  based on the motor torque commands mentioned above and the motor rpm, generates a PWM signal for switching on and off the power transistors Q 1  and Q 2  based on the calculation results, and outputs the signal to the converter  46 . 
         [0065]    Further, the controller  50  controls the switching operation of the power transistors Q 1  to Q 8  in the converter  46  and the inverter  48  for converting the alternating current generated by the motor generator  12  into a direct current to charge the battery  14 . 
         [0066]    In the PCU  10  configured as described above, the converter  46  boosts the voltage of the battery  14  based on the control signal of the controller  50  and applies the boosted voltage to the power supply line PL 2 . The capacitor C 1  smoothes the voltage applied to the power supply line PL 2  and the inverter  48  converts the DC voltage smoothed by the capacitor C 1  into an AC voltage and outputs the voltage to the motor generator  12 . 
         [0067]    On the other hand, the inverter  48  converts the AC voltage generated through regeneration using the motor generator  12  into a DC voltage and outputs the voltage to the power supply line PL 2 . The capacitor C 2  smoothes the voltage applied to the power supply line PL 2  and the converter  46  charges the battery  14  with the DC voltage smoothed by the capacitor C 2  at a lowered voltage level. 
       Embodiment 1 
       [0068]    Next, the reactor according to the present embodiment will be described. 
         [0069]    &lt;Description of the Structure of the Reactor&gt; 
         [0070]      FIG. 3  is an external perspective view of the reactor  101  of Embodiment 1,  FIG. 4  is a cross sectional view taken along a line A-A in  FIG. 3 .  FIG. 5  is an explanatory view explaining how various components configuring the reactor  101  of this embodiment are mounted on a case  110 . Note that, in the following description, a “radial direction” shall refer to the X direction in  FIG. 4 , while an “axial direction” shall refer to the Y-direction in  FIG. 4 . 
         [0071]    The reactor  102  according to Embodiment 2 to be described later has the same outer shape as the reactor  101  of this embodiment as shown in  FIG. 3 . As shown in  FIGS. 3 and 4 , the reactor  101  of this embodiment includes the case  110 , pressed powder core members  112 , gap plates  114 , a bobbin  116 , a coil assembly  118 , a resin core  120 , and so on. 
         [0072]    The case  110  is made by casting from aluminum. The case  110  is formed in an open-end box-like shape with a circular bottom part  122  and a side wall  124  provided extending vertically from a peripheral edge of the bottom part  122  as shown in  FIG. 5 . At a central portion in an inner face  123  of the bottom part  122  is provided with a pillar  126  via a seat  128 . The pillar  126  may be either of solid cylindrical shape or hollow cylindrical shape. The pillar  126  is thus formed integrally with the case  110 , with the seat  128  provided at a base portion of the pillar  126 . An upper face  130  of the seat  128 , which is the surface on which the pillar  126  is provided, has a larger diameter than that of the pillar  126 . As shown in  FIG. 4 , an end face  129  on a lower side in an axial direction (the bottom part  122  side of the case  110 ) of a pressed powder core member  112 A is in contact with the seat  128 , 
         [0073]    The pressed powder core member  112  is a high density magnetic composite (HDMC) made by press-forming magnetic powder with a high density, and formed into a circular ring-like shape. The pressed powder core member  112  has a through hole  132  extending in the axial direction radially inside an inner peripheral surface  131  thereof. The pressed powder core member  112  is provided radially outside an outer peripheral surface  133  of the pillar  126  such that the pillar  126  is inserted into the through hole  132 . The pressed powder core member  112  is sealed with an iron-resin composite that forms the resin core  120 . In this embodiment, there are four pressed powder core members  112 , which are denoted at  112 A to  112 D in the drawings. The pressed powder core members  112  are provided such as to be spaced apart a certain distance from each other in the axial direction by means of gap plates  114  interposed between the adjacent pressed powder core members  112 . The pressed powder core members  112 A to  112 D are one example of the “ring-shaped core member” of the present invention. 
         [0074]    The gap plate  114  is a plate formed of a non-magnetic material and formed into a circular ring-like shape. The gap plate  114  has a through hole  134  extending in the axial direction radially inside an inner peripheral surface  135  thereof. To give one example, the gap plate  114  may be made of alumina ceramics. In this embodiment, there are three gap plates  114 , which are denoted at  114 A,  114 B, and  114 C in the drawings. The inductance of the reactor  101  can be adjusted by adjusting the thickness of the gap plates  114 A to  114 C. The inductance of the reactor  101  can also be adjusted by adjusting the numbers of the pressed powder core members  112  and the gap plates  114 . 
         [0075]    The pressed powder core members  112  and the gap plates  114  are provided alternately in the axial direction radially outside the outer peripheral surface  133  of the pillar  126  such that the pillar  126  integral with the case  110  is inserted into the through holes  132  of the pressed powder core members  112 A to  112 D and the through holes  134  of the gap plates  114 A to  114 C. More specifically, the pressed powder core member  112 A, gap plate  114 A, pressed powder core member  112 B, gap plate  114 B, pressed powder core member  112 C, gap plate  114 C, and pressed powder core member  112 D are provided in this order from the bottom part  122  side of the case  110 . In this manner, the pressed powder core member  112 A located closest to the bottom part  122  of the case  110  is disposed upon the upper face  130  of the seat  128 . The plurality of pressed powder core members  112 A to  112 D are stacked upon one another with the gap plates  114 A to  114 C interposed in between in this manner to form a tubular center core  136 , which is disposed upon the upper face  130  of the seat  128 . 
         [0076]    The bobbin  116  is formed in an open-end box-like shape with a circular end surface  138  and a side wall  140  extending vertically from a peripheral edge of the end surface  138  (extending downward in  FIG. 4 ). At an opening end portion, the bobbin  116  is formed with a flange  142  of annular shape. Herein, an end face  141  in the axial direction of the coil assembly  118  is in contact with the flange  142 . The bobbin  116  may be preferably made of resin with thermal resistance and high electric insulation, such as polyphenylene sulfide resin (PPS). 
         [0077]    The bobbin  116  is provided radially inside an inner peripheral surface  160  of the coil assembly  118  so as to cover the center core  136  from an end face  144  side on an upper side of the pressed powder core member  112 D. An inner side surface  146  of the end surface  138  of the bobbin  116  is in contact with the end face  144  of the pressed powder core member  112 D located uppermost of the center core  136 . Further, the inner peripheral surface  148  of the bobbin  116  has a larger diameter than that of the pressed powder core members  112 A to  112 D. Thereby, there is a space created between the inner peripheral surface  148  of the bobbin  116  and outer peripheral surfaces  150  of the pressed powder core members  112 A to  112 D, and the iron-resin composite is filled in this space. 
         [0078]    The coil assembly  118  is formed of cylindrical shape and includes an edgewise coil  152  and a resin film  154 . The edgewise coil  152  is covered by the resin film  154  except for end portions  156  and  158  that will form electrode terminals. Thus, the edgewise coil  152  is insulated from outside except for the end portions  156  and  158 . The resin forming the resin film  154  should preferably be a thermosetting resin having high heat resistance such as an epoxy resin. The coil assembly  118  is sealed with the iron-resin composite forming the resin core  120 . This coil assembly  118  is provided radially outside the outer peripheral surfaces  150  of the pressed powder core members  112 A to  112 D such that the pressed powder core members  112 A to  112 D are inserted radially inside the inner peripheral surface  160  of the coil assembly  118 . 
         [0079]    The coil assembly  118  is assembled to the bobbin  116  such that the bobbin  116  is inserted radially inside the inner peripheral surface  160 . Thus, the relative positions of the bobbin  116  and the coil assembly  118  in the radial direction are determined. Further, the pressed powder core members  112 A to  112 D, the bobbin  116 , and the coil assembly  118  are coaxially placed with ease as guided by the pillar  126 . Herein, the coaxial placement of the pressed powder core members  112 A to  112 D, the bobbin  116 , and the coil assembly  118  means that each center axis of the pressed powder core members  112 A to  112 D, the bobbin  116 , and the coil assembly  118  is linearly located on the same position. 
         [0080]    The resin core  120  which is formed of the iron-resin composite filled and set in the case  110 , seals the pressed powder core members  112 A to  112 D, the bobbin  116 , and the coil assembly  118 . The resin core  120  is also provided in the space between the inner peripheral surface  148  of the bobbin  116  and the outer peripheral surfaces  150  of the pressed powder core members  112 A to  112 D. The iron-resin composite may be preferably a thermosetting resin having high thermal resistance and high thermal conductivity such as an epoxy resin mixed with iron powder. 
         [0081]    The reactor  101  of this embodiment includes the resin core  120  formed by filling up the iron-resin composite in the case  110  and the pressed powder core members  112 A to  112 D having a high magnetic permeability at the center core  136 . Therefore, the reactor  101  of this embodiment can provide a large inductance despite the small volume of the resin core  120  due to the magnetic properties being improved while the reactor  101  maintains the characteristics that the resin core  120  allows high freedom of outer shape designing. Accordingly, the reactor  101  of this embodiment can have a smaller outer shape. 
         [0082]    Furthermore, the pillar  126  is inserted in the through holes  132  of the pressed powder core members  112 A to  112 D and the through holes  134  of the gap plates  114 A to  114 C, so that the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C can be easily mounted on the case  110  as adjusting the radially relative positions of the case  110  and the pressed powder core members  112 A to  112 D and the positions of the case  110  and the gap plates  114 A to  114 C. Thus, the productivity of the reactor  101  is enhanced. 
         [0083]    Moreover, since the pressed powder core members  112 A to  112 D are entirely sealed with the rigid resin core  120 , the pressed powder core members  112 A to  112 D are protected from corrosion and prevented from cracks. 
         [0084]    The volume of the resin core  120  is reduced by the volumes of the pressed powder core members  112 A to  112 D, so that the time required for filling and setting the iron-resin composite to form the resin core  120  is shortened. Also, the amount of use of the iron-resin composite can be reduced, so that the material cost can be reduced. Accordingly, the production cost can be reduced. 
         [0085]    The end face  129  of the pressed powder core member  112 A is in contact with the seat  128 , and the pressed powder core members  112 B to  112 D and the gap plates  114 A to  114 C are placed above this pressed powder core member  112 A, thus determining the axially relative positions of the case  110 , the pressed powder core members  112 A to  112 D, and the gap plates  114 A to  114 C. Therefore, the pressed powder core members  112 A to  112 D can be placed at predetermined positions without increasing number of components. 
         [0086]    Further, the inner side surface  146  of the end surface  138  of the bobbin  116  is in contact with the end face  144  of the pressed powder core member  112 D placed uppermost of the center core  136 , so that the axially relative positions of the pressed powder core members  112 A to  112 D, the gap plates  114 A to  114 C, and the bobbin  116  are decided. As a result, the bobbin  116  can be placed at a predetermined position. 
         [0087]    The end face  141  of the coil assembly  118  is in contact with the flange  142  of the bobbin  116 , so that the axially relative positions of the bobbin  116  and the coil assembly  118  are decided. Therefore, the coil assembly  118  can be placed at a predetermined position while the iron-resin composite is filled and set in the case  110 . 
         [0088]    Further, own weight of the coil assembly  118  acts on the pressed powder core members  112 A to  112 D via the bobbin  116 . Thereby, the pressed powder core members  112 A to  112 D can be prevented from float and misalignment and placed at predetermined positions while the iron-resin composite is filled and set in the case  110 . 
         [0089]    With the non-magnetic gap plates  114  inserted between the adjacent pressed powder core members  112 , the distance between the adjacent pressed powder core members  112  can be maintained. Therefore, the magnetic performance is improved, as magnetic flux density saturation is prevented when a large current is applied to the coil. 
         [0090]    Also, since the inductance can be readily adjusted by adjusting the thickness or number of the pressed powder core members  112  and the gap plates  114 , stable DC superimposition characteristics can be achieved, with the inductance being substantially constant (flat) within the range of current being used, leading to improved performance of the reactor  101 . 
         [0091]    &lt;Description of the Reactor Manufacturing Method&gt; 
         [0092]      FIG. 5  is an explanatory view explaining how various components configuring the reactor  101  of this embodiment are assembled into the case  110 , as mentioned above.  FIG. 6  is an explanatory view showing a state after various components configuring the reactor  101  of this embodiment have been assembled into the case  110  and before the case is filled with the iron-resin composite. 
         [0093]    The reactor  101  of this embodiment is manufactured as follows. First, as shown in  FIG. 5 , the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C are alternately disposed with the pillar  126  integral with the case  110  being inserted into the through holes  132  and  134  of the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C. More specifically, the pressed powder core member  112 A, gap plate  114 A, pressed powder core member  112 B, gap plate  114 B, pressed powder core member  112 C, gap plate  114 C, and pressed powder core member  112 D are disposed in this order from a side of the bottom part  122  of the case  110 . 
         [0094]    Thus the cylindrical center core  136  is formed by the plurality of pressed powder core members  112 A to  112 D stacked upon one another with the gap plates  114 A to  114 C interposed in between. At this time, the center core  136  is disposed upon the upper face  130  of the seat  128 . More particularly, the pressed powder core member  112 A, which is the one located closest to the bottom part  122  of the case  110 , of the pressed powder core members  112 A to  112 D forming the center core  136  is disposed upon the upper face  130  of the seat  128 , so that the end face  129  of the pressed powder core member  112 A comes into contact with the upper face  130  of the seat  128 . The pressed powder core member  112 A located closest to the bottom part  122  of the case  110  is formed to have an inner peripheral surface  131  with an inside diameter being smaller than an outside diameter of the upper face  130  of the seat  128 . Thereby the pressed powder core member  112 A can be reliably placed on the upper face  130  of the seat  128 . 
         [0095]    This arrangement in which the pressed powder core member  112 A, which is the one located closest to the bottom part  122  of the case  110  of the pressed powder core members  112 A to  112 D forming the center core  136 , is disposed upon the upper face  130  of the seat  128 , determines the axially relative positions of the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C forming the case  110  and the center core  136 . Also, the radially relative positions of the case  110  and the pressed powder core members  112 A to  112 D can be adjusted within the size range of the gap between the outer peripheral surface  133  of the pillar  126  and the inner peripheral surface  131  of the pressed powder core members  112 A to  112 D, thereby the pressed powder core members  112 A to  112 D can be placed at predetermined positions. Also, the radially relative positions of the case  110  and the gap plates  114 A to  114 C can be adjusted within the size range of the gap between the outer peripheral surface  133  of the pillar  126  and the inner peripheral surface  135  of the gap plates  114 A to  114 C, thereby the gap plates  114 A to  114 C can be placed at predetermined positions. Using the pillar  126  and the seat  128  integral with the case  110  in this manner enables disposing the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C at predetermined positions without increasing the number of components. 
         [0096]    Then, as shown in  FIG. 5 , the bobbin  116  is placed so as to cover the center core  136 . At this time, the inner side surface  146  of the end surface  138  of the bobbin  116  comes to contact with the end face  144  of the pressed powder core member  112 D located uppermost of the center core  136 . Incidentally, a space is provided between the inner peripheral surface  148  of the bobbin  116  and the outer peripheral surface  150  of the pressed powder core members  112 A to  112 D. 
         [0097]    Next, the coil assembly  118  is disposed radially outside the outer peripheral surface  149  of the bobbin  116  such that the bobbin  116  is inserted radially inside the inner peripheral surface  160  of the coil assembly  118 . At this time, the end face  141  of the coil assembly  118  comes to contact with the flange  142  of the bobbin  116 . 
         [0098]    Next, the iron-resin composite in a molten state is poured into the case  110  and the case  110  is placed in a heating furnace (not shown) and heated at a predetermined temperature for a predetermined period of time to set the iron-resin composite to form the resin core  120 . Thereby, the center core  136 , the bobbin  116 , and the coil assembly  118  are sealed with the resin core  120 . 
         [0099]    The reactor  101  is manufactured as described above. 
         [0100]    According to the method of manufacturing the reactor  101  in this embodiment, the pillar  126  is inserted in the through holes  132  and  134  of the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C, so that the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C can be easily mounted on the case  110 , as adjusting the radially relative positions of the case  110  and the pressed powder core members  112 A to  112 D and the radially relative positions of the case  110  and the gap plates  114 A to  114 C. Thus the productivity of the reactor  101  is enhanced. 
         [0101]    The end face  129  of the pressed powder core member  112 A is brought into contact with the seat  128  and the pressed powder core members  112 B to  112 D are placed above the pressed powder core member  112 A, so that the axially relative positions of the case  110  and the pressed powder core members  112 A to  112 D are decided. Therefore, the pressed powder core members  112 A to  112 D can be placed at predetermined positions without increasing number of components. 
         [0102]    Further, the inner side surface  146  of the end surface  138  of the bobbin  116  is brought into contact with the end face  144  of the pressed powder core member  112 D placed uppermost of the center core  136 , so that the axially relative positions of the pressed powder core members  112 A to  112 D, the gap plates  114 A to  114 C, and the bobbin  116  are decided. Therefore, the bobbin  116  can be placed at a predetermined position. 
         [0103]    The end face  141  of the coil assembly  118  is brought into contact with the flange  142  of the bobbin  116 , so that the axially relative positions of the bobbin  116  and the coil assembly  118  are decided. Therefore, the coil assembly  118  can be placed at a predetermined position while the iron-resin composite is filled and set in the case  110 . 
         [0104]    Further, own weight of the coil assembly  118  acts on the pressed powder core members  112 A to  112 D via the bobbin  116 . Thereby, float and misalignment of the pressed powder core members  112 A to  112 D can be prevented and the pressed powder core members  112 A to  112 D can be placed at predetermined positions while the iron-resin composite is filled and set in the case  110 . 
         [0105]    Since the non-magnetic ring-shaped gap plates  114  are provided between the adjacent pressed powder core members  112 , inductance can be adjusted by varying thickness or number of the gap plates  114 . Thereby, stable DC superimposition characteristics can be obtained as the inductance is almost at a fixed value (flat) within the used current range, thus enhancing the performance of the reactor  101 . 
         [0106]    Moreover, the iron-resin composite in a molten state poured into the case  110  after the various components have been placed also takes a role as the adhesive for the various parts, so that a step of bonding the pressed powder core members  112 A to  112 D and the gap plates  114 A to  114 C together with adhesive can be omitted. 
         [0107]    The numbers of the pressed powder core members  112  and the gap plates  114  are not limited to particular ones. There could be an example where two pressed powder core members  112  and one gap plate  114  are provided, as shown in  FIG. 7 . 
       Embodiment 2 
       [0108]      FIG. 8  is an explanatory view showing how various components configuring the reactor  102  are assembled in the case  110  in Embodiment 2. The outer shape of the reactor  102  in Embodiment 2 is similar to that of Embodiment 1 as shown in  FIG. 3 . In  FIG. 8 , the pressed powder core members  112  are not shown for convenience in explanation. Further, same or similar elements as Embodiment 1 will be given the same reference numerals and not described again, and different point will be mainly explained in the following description. 
         [0109]    The reactor  102  in Embodiment 2 has the different configuration from the reactor  101  in Embodiment 1 that the bobbin  116  is formed with an opening  162  on the end surface  138  in the axial direction and openings  164  on a side wall  140 . According to an example shown in  FIG. 8 , the opening  162  of circular shape is formed at a center portion of the end surface  138 , and four openings  164  are formed along an outer periphery of the end surface  138 . However, position and shape of the openings  162  and  164  are not limited to the ones shown in  FIG. 8 . An opening may be provided on either one of the end surface  138  or the side wall  140 . 
         [0110]    According to the reactor  102  in Embodiment 2, when the iron-resin composite in a molten state is filled inside the case  110  after various components are mounted, the iron-resin composite flows radially inside the inner peripheral surface  148  of the bobbin  116  from the openings  162  and  164 . Thus, the pressed powder core members  112  and the gap plates  114  are securely bonded by setting the flowing iron-resin composite. 
         [0111]    Also as shown in  FIG. 8 , the gap plates  114  have slits  170  radially extending from inner peripheral surfaces  166  to outer peripheral surfaces  168  on axial end faces  159 . Thereby, the iron-resin composite flowing radially inside the inner peripheral surface  148  of the bobbin  116  further flows into the space between the pressed powder core members  112  and the gap plates  114  via the slits  170 . Accordingly, the pressed powder core members  112  and the gap plates  114  are further securely bonded by setting the iron-resin composite flowing into the space between the pressed powder core members  112  and the gap plates  114  via the slits  170 . 
         [0112]    The above mentioned embodiments are merely examples, not limiting the invention. The present invention may be embodied in other specific forms without departing from the essential characteristics thereof. 
         [0113]    The plurality of pressed core members  112  are provided in the above examples. Alternately, a reactor provided with a single pressed core member  112  may be adopted. 
       REFERENCE SIGNS LIST 
       [0114]      1  Drive control system 
         [0115]      10  PCU 
         [0116]      12  Motor generator 
         [0117]      14  Battery 
         [0118]      101  Reactor 
         [0119]      102  Reactor 
         [0120]      110  Case 
         [0121]      112  Pressed powder core member 
         [0122]      114  Gap plate 
         [0123]      116  Bobbin 
         [0124]      118  Coil assembly 
         [0125]      120  Resin core 
         [0126]      126  Pillar 
         [0127]      128  Seat 
         [0128]      136  Center core 
         [0129]      142  Flange 
         [0130]      162  Opening 
         [0131]      164  Opening 
         [0132]      170  Slit