Reactor and reactor manufacturing method

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.

CROSS-REFERENCE TO RELATED APPLICATIONS

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

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

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.

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.

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Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

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.

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.

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.

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.

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

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.

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.

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).

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.

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.

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.

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.

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.

In the above aspect, preferably, the bobbin has an opening on at least one of the end surface and the side wall.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

In the above aspect, preferably, the bobbin has an opening on at least one of the end surface and the side wall.

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.

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.

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.

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.

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.

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

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.

DETAILED DESCRIPTION

Embodiments of the present invention will be hereinafter described in detail with reference to the accompanying drawings.

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.

Therefore, the structure of the drive control system will be described first, after which the reactor according to this embodiment will be described.

First, the drive control system will be described referring toFIG. 1andFIG. 2.

FIG. 1is a schematic diagram illustrating one example of a drive control system configuration including the reactor according to this embodiment.FIG. 2is a circuit diagram illustrating major parts of PCU inFIG. 1.

A drive control system1is formed by a PCU (Power Control Unit)10, a motor generator12, a battery14, a terminal base16, a housing18, a reduction gear20, a differential gear22, drive shaft receiving parts24, and others as shown inFIG. 1.

The converter46is connected between the battery14and the inverter48electrically in parallel with the inverter48. The inverter48is connected to the motor generator12via the output lines52U,52V, and52W.

The battery14is, for example, a secondary battery such as a nickel metal hydride or lithium ion battery. The battery14supplies a direct current to the converter46and is charged by the direct current flowing from the converter46.

The converter46is made up of power transistors Q1and Q2, diodes D1and D2, and the reactor101to be described later in more detail. The power transistors Q1and Q2are connected in series between power supply lines PL2and PL3and supply control signals from the controller50to a base. The diodes D1and D2are each connected between collector and emitter terminals of the power transistors Q1and Q2so that the current flows from the emitter terminals to the collector terminals of the respective power transistors Q1and Q2.

The reactor101is arranged to have one end connected to a power supply line PL1that connects to a positive electrode of the battery14and the other end connected to a connection point between the power transistors Q1and Q2.

The converter46boosts the DC voltage of the battery14by the reactor101and supplies the boosted DC voltage to the power supply line PL2. The converter46charges the battery14with the direct current received from the inverter48at a lowered voltage.

The inverter48is formed by a U-phase arm54U, a V-phase arm54V, and a W-phase arm54W. The respective phase arms54U,54V, and54W are connected in parallel between the power supply lines PL2and PL3. The U-phase arm54U is formed by series-connected power transistors Q3and Q4, the V-phase arm54V is formed by series-connected power transistors Q5and Q6, and the W-phase arm54W is formed by series-connected power transistors Q7and Q8. The diodes D3to D8are each connected between the collector and emitter terminals of the power transistors Q3to Q8so that the current flows from the emitter terminals to the collector terminals of the respective power transistors Q3to Q8. The connection points between the respective pairs of power transistors Q3to Q8at the respective phase arms54U,54V, and54W are connected to the opposite side of the neutral point of the U-phase, V-phase, and W-phase of the motor generator12, respectively, via the output lines52U,52V, and52W.

The inverter48converts a direct current flowing in the power supply line PL2into an alternating current based on a control signal from the controller50and outputs the alternating current to the motor generator12. The inverter48rectifies the alternating current generated by the motor generator12and converts the alternating current into a direct current, and supplies the converted direct current to the power supply line PL2.

The capacitor C1is connected between the power supply lines PL1and PL3and smoothes the voltage level of the power supply line PL1. The capacitor C2is connected between the power supply lines PL2and PL3and smoothes the voltage level of the power supply line PL2.

The controller50calculates the coil voltages at the U-phase, V-phase, and W-phase of the motor generator12based on the rotation angle of a rotor of the motor generator12, motor torque commands, current values at the U-phase, V-phase, and W-phase of the motor generator12, and an input voltage of the inverter48. The controller50generates a PWM (Pulse Width Modulation) signal for switching on and off the power transistors Q3to Q8based on the calculation results and outputs the signal to the inverter48.

Also, in order to optimize the input voltage of the inverter48, the controller50calculates the duty ratio between the power transistors Q1and Q2based on the motor torque commands mentioned above and the motor rpm, generates a PWM signal for switching on and off the power transistors Q1and Q2based on the calculation results, and outputs the signal to the converter46.

Further, the controller50controls the switching operation of the power transistors Q1to Q8in the converter46and the inverter48for converting the alternating current generated by the motor generator12into a direct current to charge the battery14.

In the PCU10configured as described above, the converter46boosts the voltage of the battery14based on the control signal of the controller50and applies the boosted voltage to the power supply line PL2. The capacitor C1smoothes the voltage applied to the power supply line PL2and the inverter48converts the DC voltage smoothed by the capacitor C1into an AC voltage and outputs the voltage to the motor generator12.

On the other hand, the inverter48converts the AC voltage generated through regeneration using the motor generator12into a DC voltage and outputs the voltage to the power supply line PL2. The capacitor C2smoothes the voltage applied to the power supply line PL2and the converter46charges the battery14with the DC voltage smoothed by the capacitor C2at a lowered voltage level.

Next, the reactor according to the present embodiment will be described.

<Description of the Structure of the Reactor>

FIG. 3is an external perspective view of the reactor101of Embodiment 1,FIG. 4is a cross sectional view taken along a line A-A inFIG. 3.FIG. 5is an explanatory view explaining how various components configuring the reactor101of this embodiment are mounted on a case110. Note that, in the following description, a “radial direction” shall refer to the X direction inFIG. 4, while an “axial direction” shall refer to the Y-direction inFIG. 4.

The reactor102according to Embodiment 2 to be described later has the same outer shape as the reactor101of this embodiment as shown inFIG. 3. As shown inFIGS. 3 and 4, the reactor101of this embodiment includes the case110, pressed powder core members112, gap plates114, a bobbin116, a coil assembly118, a resin core120, and so on.

The case110is made by casting from aluminum. The case110is formed in an open-end box-like shape with a circular bottom part122and a side wall124provided extending vertically from a peripheral edge of the bottom part122as shown inFIG. 5. At a central portion in an inner face123of the bottom part122is provided with a pillar126via a seat128. The pillar126may be either of solid cylindrical shape or hollow cylindrical shape. The pillar126is thus formed integrally with the case110, with the seat128provided at a base portion of the pillar126. An upper face130of the seat128, which is the surface on which the pillar126is provided, has a larger diameter than that of the pillar126. As shown inFIG. 4, an end face129on a lower side in an axial direction (the bottom part122side of the case110) of a pressed powder core member112A is in contact with the seat128.

The pressed powder core member112is 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 member112has a through hole132extending in the axial direction radially inside an inner peripheral surface131thereof. The pressed powder core member112is provided radially outside an outer peripheral surface133of the pillar126such that the pillar126is inserted into the through hole132. The pressed powder core member112is sealed with an iron-resin composite that forms the resin core120. In this embodiment, there are four pressed powder core members112, which are denoted at112A to112D in the drawings. The pressed powder core members112are provided such as to be spaced apart a certain distance from each other in the axial direction by means of gap plates114interposed between the adjacent pressed powder core members112. The pressed powder core members112A to112D are one example of the “ring-shaped core member” of the present invention.

The gap plate114is a plate formed of a non-magnetic material and formed into a circular ring-like shape. The gap plate114has a through hole134extending in the axial direction radially inside an inner peripheral surface135thereof. To give one example, the gap plate114may be made of alumina ceramics. In this embodiment, there are three gap plates114, which are denoted at114A,114B, and114C in the drawings. The inductance of the reactor101can be adjusted by adjusting the thickness of the gap plates114A to114C. The inductance of the reactor101can also be adjusted by adjusting the numbers of the pressed powder core members112and the gap plates114.

The pressed powder core members112and the gap plates114are provided alternately in the axial direction radially outside the outer peripheral surface133of the pillar126such that the pillar126integral with the case110is inserted into the through holes132of the pressed powder core members112A to112D and the through holes134of the gap plates114A to114C. More specifically, the pressed powder core member112A, gap plate114A, pressed powder core member112B, gap plate114B, pressed powder core member112C, gap plate114C, and pressed powder core member112D are provided in this order from the bottom part122side of the case110. In this manner, the pressed powder core member112A located closest to the bottom part122of the case110is disposed upon the upper face130of the seat128. The plurality of pressed powder core members112A to112D are stacked upon one another with the gap plates114A to114C interposed in between in this manner to form a tubular center core136, which is disposed upon the upper face130of the seat128.

The bobbin116is formed in an open-end box-like shape with a circular end surface138and a side wall140extending vertically from a peripheral edge of the end surface138(extending downward inFIG. 4). At an opening end portion, the bobbin116is formed with a flange142of annular shape. Herein, an end face141in the axial direction of the coil assembly118is in contact with the flange142. The bobbin116may be preferably made of resin with thermal resistance and high electric insulation, such as polyphenylene sulfide resin (PPS).

The bobbin116is provided radially inside an inner peripheral surface160of the coil assembly118so as to cover the center core136from an end face144side on an upper side of the pressed powder core member112D. An inner side surface146of the end surface138of the bobbin116is in contact with the end face144of the pressed powder core member112D located uppermost of the center core136. Further, the inner peripheral surface148of the bobbin116has a larger diameter than that of the pressed powder core members112A to112D. Thereby, there is a space created between the inner peripheral surface148of the bobbin116and outer peripheral surfaces150of the pressed powder core members112A to112D, and the iron-resin composite is filled in this space.

The coil assembly118is formed of cylindrical shape and includes an edgewise coil152and a resin film154. The edgewise coil152is covered by the resin film154except for end portions156and158that will form electrode terminals. Thus, the edgewise coil152is insulated from outside except for the end portions156and158. The resin forming the resin film154should preferably be a thermosetting resin having high heat resistance such as an epoxy resin. The coil assembly118is sealed with the iron-resin composite forming the resin core120. This coil assembly118is provided radially outside the outer peripheral surfaces150of the pressed powder core members112A to112D such that the pressed powder core members112A to112D are inserted radially inside the inner peripheral surface160of the coil assembly118.

The coil assembly118is assembled to the bobbin116such that the bobbin116is inserted radially inside the inner peripheral surface160. Thus, the relative positions of the bobbin116and the coil assembly118in the radial direction are determined. Further, the pressed powder core members112A to112D, the bobbin116, and the coil assembly118are coaxially placed with ease as guided by the pillar126. Herein, the coaxial placement of the pressed powder core members112A to112D, the bobbin116, and the coil assembly118means that each center axis of the pressed powder core members112A to112D, the bobbin116, and the coil assembly118is linearly located on the same position.

The resin core120which is formed of the iron-resin composite filled and set in the case110, seals the pressed powder core members112A to112D, the bobbin116, and the coil assembly118. The resin core120is also provided in the space between the inner peripheral surface148of the bobbin116and the outer peripheral surfaces150of the pressed powder core members112A to112D. 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.

The reactor101of this embodiment includes the resin core120formed by filling up the iron-resin composite in the case110and the pressed powder core members112A to112D having a high magnetic permeability at the center core136. Therefore, the reactor101of this embodiment can provide a large inductance despite the small volume of the resin core120due to the magnetic properties being improved while the reactor101maintains the characteristics that the resin core120allows high freedom of outer shape designing. Accordingly, the reactor101of this embodiment can have a smaller outer shape.

Furthermore, the pillar126is inserted in the through holes132of the pressed powder core members112A to112D and the through holes134of the gap plates114A to114C, so that the pressed powder core members112A to112D and the gap plates114A to114C can be easily mounted on the case110as adjusting the radially relative positions of the case110and the pressed powder core members112A to112D and the positions of the case110and the gap plates114A to114C. Thus, the productivity of the reactor101is enhanced.

Moreover, since the pressed powder core members112A to112D are entirely sealed with the rigid resin core120, the pressed powder core members112A to112D are protected from corrosion and prevented from cracks.

The volume of the resin core120is reduced by the volumes of the pressed powder core members112A to112D, so that the time required for filling and setting the iron-resin composite to form the resin core120is 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.

The end face129of the pressed powder core member112A is in contact with the seat128, and the pressed powder core members112B to112D and the gap plates114A to114C are placed above this pressed powder core member112A, thus determining the axially relative positions of the case110, the pressed powder core members112A to112D, and the gap plates114A to114C. Therefore, the pressed powder core members112A to112D can be placed at predetermined positions without increasing number of components.

Further, the inner side surface146of the end surface138of the bobbin116is in contact with the end face144of the pressed powder core member112D placed uppermost of the center core136, so that the axially relative positions of the pressed powder core members112A to112D, the gap plates114A to114C, and the bobbin116are decided. As a result, the bobbin116can be placed at a predetermined position.

The end face141of the coil assembly118is in contact with the flange142of the bobbin116, so that the axially relative positions of the bobbin116and the coil assembly118are decided. Therefore, the coil assembly118can be placed at a predetermined position while the iron-resin composite is filled and set in the case110.

Further, own weight of the coil assembly118acts on the pressed powder core members112A to112D via the bobbin116. Thereby, the pressed powder core members112A to112D can be prevented from float and misalignment and placed at predetermined positions while the iron-resin composite is filled and set in the case110.

With the non-magnetic gap plates114inserted between the adjacent pressed powder core members112, the distance between the adjacent pressed powder core members112can be maintained. Therefore, the magnetic performance is improved, as magnetic flux density saturation is prevented when a large current is applied to the coil.

Also, since the inductance can be readily adjusted by adjusting the thickness or number of the pressed powder core members112and the gap plates114, 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 reactor101.

<Description of the Reactor Manufacturing Method>

FIG. 5is an explanatory view explaining how various components configuring the reactor101of this embodiment are assembled into the case110, as mentioned above.FIG. 6is an explanatory view showing a state after various components configuring the reactor101of this embodiment have been assembled into the case110and before the case is filled with the iron-resin composite.

The reactor101of this embodiment is manufactured as follows. First, as shown inFIG. 5, the pressed powder core members112A to112D and the gap plates114A to114C are alternately disposed with the pillar126integral with the case110being inserted into the through holes132and134of the pressed powder core members112A to112D and the gap plates114A to114C. More specifically, the pressed powder core member112A, gap plate114A, pressed powder core member112B, gap plate114B, pressed powder core member112C, gap plate114C, and pressed powder core member112D are disposed in this order from a side of the bottom part122of the case110.

Thus the cylindrical center core136is formed by the plurality of pressed powder core members112A to112D stacked upon one another with the gap plates114A to114C interposed in between. At this time, the center core136is disposed upon the upper face130of the seat128. More particularly, the pressed powder core member112A, which is the one located closest to the bottom part122of the case110, of the pressed powder core members112A to112D forming the center core136is disposed upon the upper face130of the seat128, so that the end face129of the pressed powder core member112A comes into contact with the upper face130of the seat128. The pressed powder core member112A located closest to the bottom part122of the case110is formed to have an inner peripheral surface131with an inside diameter being smaller than an outside diameter of the upper face130of the seat128. Thereby the pressed powder core member112A can be reliably placed on the upper face130of the seat128.

This arrangement in which the pressed powder core member112A, which is the one located closest to the bottom part122of the case110of the pressed powder core members112A to112D forming the center core136, is disposed upon the upper face130of the seat128, determines the axially relative positions of the pressed powder core members112A to112D and the gap plates114A to114C forming the case110and the center core136. Also, the radially relative positions of the case110and the pressed powder core members112A to112D can be adjusted within the size range of the gap between the outer peripheral surface133of the pillar126and the inner peripheral surface131of the pressed powder core members112A to112D, thereby the pressed powder core members112A to112D can be placed at predetermined positions. Also, the radially relative positions of the case110and the gap plates114A to114C can be adjusted within the size range of the gap between the outer peripheral surface133of the pillar126and the inner peripheral surface135of the gap plates114A to114C, thereby the gap plates114A to114C can be placed at predetermined positions. Using the pillar126and the seat128integral with the case110in this manner enables disposing the pressed powder core members112A to112D and the gap plates114A to114C at predetermined positions without increasing the number of components.

Then, as shown inFIG. 5, the bobbin116is placed so as to cover the center core136. At this time, the inner side surface146of the end surface138of the bobbin116comes to contact with the end face144of the pressed powder core member112D located uppermost of the center core136. Incidentally, a space is provided between the inner peripheral surface148of the bobbin116and the outer peripheral surface150of the pressed powder core members112A to112D.

Next, the coil assembly118is disposed radially outside the outer peripheral surface149of the bobbin116such that the bobbin116is inserted radially inside the inner peripheral surface160of the coil assembly118. At this time, the end face141of the coil assembly118comes to contact with the flange142of the bobbin116.

Next, the iron-resin composite in a molten state is poured into the case110and the case110is 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 core120. Thereby, the center core136, the bobbin116, and the coil assembly118are sealed with the resin core120.

The reactor101is manufactured as described above.

According to the method of manufacturing the reactor101in this embodiment, the pillar126is inserted in the through holes132and134of the pressed powder core members112A to112D and the gap plates114A to114C, so that the pressed powder core members112A to112D and the gap plates114A to114C can be easily mounted on the case110, as adjusting the radially relative positions of the case110and the pressed powder core members112A to112D and the radially relative positions of the case110and the gap plates114A to114C. Thus the productivity of the reactor101is enhanced.

The end face129of the pressed powder core member112A is brought into contact with the seat128and the pressed powder core members112B to112D are placed above the pressed powder core member112A, so that the axially relative positions of the case110and the pressed powder core members112A to112D are decided. Therefore, the pressed powder core members112A to112D can be placed at predetermined positions without increasing number of components.

Further, the inner side surface146of the end surface138of the bobbin116is brought into contact with the end face144of the pressed powder core member112D placed uppermost of the center core136, so that the axially relative positions of the pressed powder core members112A to112D, the gap plates114A to114C, and the bobbin116are decided. Therefore, the bobbin116can be placed at a predetermined position.

The end face141of the coil assembly118is brought into contact with the flange142of the bobbin116, so that the axially relative positions of the bobbin116and the coil assembly118are decided. Therefore, the coil assembly118can be placed at a predetermined position while the iron-resin composite is filled and set in the case110.

Further, own weight of the coil assembly118acts on the pressed powder core members112A to112D via the bobbin116. Thereby, float and misalignment of the pressed powder core members112A to112D can be prevented and the pressed powder core members112A to112D can be placed at predetermined positions while the iron-resin composite is filled and set in the case110.

Since the non-magnetic ring-shaped gap plates114are provided between the adjacent pressed powder core members112, inductance can be adjusted by varying thickness or number of the gap plates114. 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 reactor101.

Moreover, the iron-resin composite in a molten state poured into the case110after 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 members112A to112D and the gap plates114A to114C together with adhesive can be omitted.

The numbers of the pressed powder core members112and the gap plates114are not limited to particular ones. There could be an example where two pressed powder core members112and one gap plate114are provided, as shown inFIG. 7.

FIG. 8is an explanatory view showing how various components configuring the reactor102are assembled in the case110in Embodiment 2. The outer shape of the reactor102in Embodiment 2 is similar to that of Embodiment 1 as shown inFIG. 3. InFIG. 8, the pressed powder core members112are 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.

The reactor102in Embodiment 2 has the different configuration from the reactor101in Embodiment 1 that the bobbin116is formed with an opening162on the end surface138in the axial direction and openings164on a side wall140. According to an example shown inFIG. 8, the opening162of circular shape is formed at a center portion of the end surface138, and four openings164are formed along an outer periphery of the end surface138. However, position and shape of the openings162and164are not limited to the ones shown inFIG. 8. An opening may be provided on either one of the end surface138or the side wall140.

According to the reactor102in Embodiment 2, when the iron-resin composite in a molten state is filled inside the case110after various components are mounted, the iron-resin composite flows radially inside the inner peripheral surface148of the bobbin116from the openings162and164. Thus, the pressed powder core members112and the gap plates114are securely bonded by setting the flowing iron-resin composite.

Also as shown inFIG. 8, the gap plates114have slits170radially extending from inner peripheral surfaces166to outer peripheral surfaces168on axial end faces159. Thereby, the iron-resin composite flowing radially inside the inner peripheral surface148of the bobbin116further flows into the space between the pressed powder core members112and the gap plates114via the slits170. Accordingly, the pressed powder core members112and the gap plates114are further securely bonded by setting the iron-resin composite flowing into the space between the pressed powder core members112and the gap plates114via the slits170.

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.

The plurality of pressed core members112are provided in the above examples. Alternately, a reactor provided with a single pressed core member112may be adopted.

REFERENCE SIGNS LIST