Magnetic circuit structure

Abstract

Because the first and second windings are also wrapped around the outer surface of the core, it is difficult to efficiently dissipate heat from the outer surface of the core. [Solution] A common mode choke coil 10, which is an example of a magnetic circuit structure, comprises a pair of cylindrical cores 20, 20 having through holes 22 formed therein, and a first winding 51 and a second winding 52 that are inserted through each through hole 22 and wound around the pair of cylindrical cores 20, 20 when the pair of cylindrical cores 20, 20 are arranged side by side. The common mode choke coil 10 comprises a metal block 30 having a cylindrical housing space S formed therein for housing each of the arranged cylindrical cores 20, an inner circumferential surface 35 that covers the outer circumferential surface 23 of each cylindrical core 20 and forms the housing space S of the block 30, and a heat dissipation sheet 40 that is in contact with the outer circumferential surface 23 of the cylindrical core 20 and is disposed between the inner circumferential surface 35 and the outer circumferential surface 23.

Description

Technical Field

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[0001] The present invention relates to a magnetic circuit structure having a core and a first winding and a second winding wound around the core.

Background Art

[0002] Conventionally, a magnetic circuit structure in which a first winding and a second winding are wound around a cylindrical core (iron core) has been proposed. The first winding and the second winding are electromagnetically coupled by the core. The magnetic circuit structure is used, for example, in a common mode choke coil or the like. As an example of this type of technology, Patent Document 1 proposes a magnetic circuit structure in which a portion of the core other than the portion around which the first winding and the second winding are wound is covered with a conductive cover.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, due to the current flowing through the first winding and the second winding, magnetic flux is generated in the core and the core generates heat. Since the first winding and the second winding are also wound around the outer peripheral surface of the core, it is difficult to efficiently dissipate heat from the core from the outer peripheral surface of the core having a large surface area.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a magnetic circuit structure capable of efficiently dissipating heat from the outer peripheral surface of the core.

Means for Solving the Problems

[0006] In view of the above problems, the magnetic circuit structure according to the present invention is characterized by comprising: a pair of cylindrical cores having through holes formed therein; a first winding and a second winding inserted through each of the through holes and wound around the pair of cylindrical cores when the pair of cylindrical cores are arranged side by side; a metal block having a cylindrical housing space formed therein for housing each of the arranged cylindrical cores; and a heat dissipation sheet disposed between the inner circumferential surface and the outer circumferential surface so as to contact the inner circumferential surface and the outer circumferential surface of the cylindrical core, which cover the outer circumferential surface of each of the cylindrical cores and form the housing space of the block.

[0007] According to the present invention, the first and second windings are inserted through through holes in each cylindrical core when the pair of cylindrical cores are arranged side by side, and are wound around the pair of cylindrical cores so as to span them. As a result, the first and second windings are not positioned on the outer circumferential surfaces of the pair of cylindrical cores. Therefore, the heat dissipation sheet can be placed in close contact with the outer circumferential surface of each cylindrical core without any gaps being formed by windings or the like, and the outer circumferential surface of the cylindrical core can be covered with the heat dissipation sheet. This heat dissipation sheet is positioned between the inner circumferential surface that forms the housing space of the block and the outer circumferential surface of the cylindrical core, and is in contact with both the inner and outer circumferential surfaces. As a result, the heat generated from the core by the current flowing through the first and second windings can be efficiently dissipated from the heat dissipation sheet positioned on the outer circumferential surface of the core to the metal block.

[0008] In a more preferred embodiment, the block is composed of divided bodies, the cylindrical housing space of which is divided in half along the axial direction, the divided bodies are connected to each other via fastening members, and the heat dissipation sheet is sandwiched between the divided bodies in a compressed and deformed state by fastening the fastening members.

[0009] In this embodiment, the heat dissipation sheet is compressed and deformed by the fastening of the fastening members and sandwiched between the divided parts. As a result, the heat dissipation sheet can be brought into close contact with the inner circumferential surface that forms the housing space of the block and the outer circumferential surface of the cylindrical core, thereby preventing the formation of gaps between the heat dissipation sheet and the inner and outer circumferential surfaces.

[0010] In a more preferred embodiment, an insulating guide member is attached to the end face of the block surface, including the opening edge in which the housing space is formed, so as to guide the first winding and the second winding so that the first winding and the second winding do not come into contact with the end face of the block.

[0011] According to this embodiment, since the first winding and the second winding are guided by the guide member so as not to contact the surface of the block, it is possible to avoid the first winding and the second winding contacting the end face of the block.

[0012] In a more preferred embodiment, the first winding and the second winding are twisted together in pairs.

[0013] According to this embodiment, since the first winding and the second winding are twisted together in pairs, noise generated in the first winding and the second winding can be reduced.

[0014] In a more preferred embodiment, the magnetic circuit structure is a common-mode choke coil, and the block is electrically connected to ground.

[0015] In this embodiment, the magnetic circuit structure is a common-mode choke coil, and the heat dissipation sheet electrically insulates the cylindrical core and the metal block. Furthermore, since the cylindrical core and the metal block each act as electrodes and the heat dissipation sheet acts as a dielectric, the portion from the cylindrical core to the metal block functions as a first capacitor. Furthermore, since the first and second windings act as electrodes, and the resin material covering the wires of the first and second windings, as well as the space between the first and second windings and the cylindrical core, acts as a dielectric, the portion from the first and second windings to the cylindrical core functions as a second capacitor. In this case, the cylindrical core is at a floating potential. That is, the first and second capacitors are connected in series between the metal block and the first and second windings. The first and second capacitors formed in this way function like the Y capacitor of a common-mode choke coil, and thus can suppress common-mode noise. [Effects of the Invention]

[0016] According to the present invention, heat can be efficiently dissipated from the outer surface of the core. [Brief explanation of the drawing]

[0017] [Figure 1] This is a block diagram of an inverter device equipped with a magnetic circuit structure according to an embodiment of the present invention as a common mode choke coil. [Figure 2] Figure 1 is a schematic perspective view of a common mode choke coil. [Figure 3] Figure 2 shows an exploded perspective view of the common mode choke coil, excluding the first and second windings. [Figure 4] Figure 2 shows a schematic cross-sectional view of a common mode choke coil along line AA. [Figure 5] (a) is a cross-sectional view of the common mode choke coil shown in Figure 4, taken along the arrow BB, and (b) is a cross-sectional view of the common mode choke coil shown in Figure 4, taken along the arrow CC. [Figure 6] (a) is a cross-sectional view taken along the D-D line of the common-mode choke coil shown in FIG. 5, and (b) is a cross-sectional view related to a modified example of the common-mode choke coil shown in FIG. 5. [Figure 7] (a) is a diagram for explaining the potential state of the common-mode choke coil shown in FIG. 1, and (b) is a block diagram for explaining the function of the common-mode choke coil in the inverter device shown in FIG. 1.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the magnetic circuit structure according to the present invention will be described with reference to FIGS. 1 to 7. FIG. 1 is a block diagram of an inverter device 100 including the magnetic circuit structure according to the embodiment of the present invention as a common-mode choke coil 10.

[0019] In the present embodiment, as the magnetic circuit structure, the common-mode choke coil 10 is exemplified, and as will be described later, the first winding 51 and the second winding 52 are wound so as to pass through the cylindrical core 20. However, instead of using the common-mode choke coil 10 as the magnetic circuit structure, the magnetic circuit structure can be made to function as a transformer by using the first winding 51 as the primary-side winding and the second winding 52 as the secondary-side winding.

[0020] In this embodiment, as shown in FIG. 1, the inverter device 100 includes a semiconductor switching element 6 such as a high-voltage FET (field effect transistor). The semiconductor switching element 6 is driven by a gate drive circuit 5 which is a driver. The voltage from the DC power supply is boosted by a DC-DC converter 2, and the boosted voltage is input to the gate drive circuit 5 as a gate drive voltage. On the other hand, the PWM optical transmission unit 3 transmits an optical signal (pulse signal) to the optical reception unit 4 via an optical fiber, and the gate drive circuit 5 controls the waveform of the gate drive voltage using the optical signal (pulse signal) received by the optical reception unit 4 as a control signal. The common mode choke coil 10 is arranged between the DC power supply and the DC-DC converter 2. The common mode choke coil 10 functions as a filter for cutting the noise of the voltage waveform input from the DC power supply to the DC-DC converter 2.

[0021] Note that in this embodiment, the potential of the high-potential side terminal of the DC power supply is, for example, 24V, and the potential of the low-potential side terminal of the DC power supply is, for example, the ground potential. That is, the DC power supply outputs a DC voltage with a potential difference of 24V.

[0022] Also, in this embodiment, one end of the first winding 51 is connected to the high-potential side terminal of the DC power supply shown in FIG. 1, and the other end of the first winding 51 is connected to the high-potential side terminal of the DC-DC converter 2. Also, one end of the second winding 52 is connected to the low-potential side terminal of the DC power supply shown in FIG. 1, and the other end of the second winding 52 is connected to the low-potential side terminal of the DC-DC converter 2.

[0023] The potential difference between the high-potential side terminal and the low-potential side terminal of the DC-DC converter 2 is also 24V as exemplified above. However, since an alternating current flows through the first winding 51 and the second winding 52, the potentials of the high-potential side terminal and the low-potential side terminal of the DC-DC converter 2 can be at a higher potential than the potentials of the high-potential side terminal and the low-potential side terminal of the DC power supply.

[0024] As shown in Figures 2 to 6, the common mode choke coil 10 comprises a pair of cylindrical cores 20, 20 and a first winding 51 and a second winding 52 wound around the pair of cylindrical cores 20, 20. The pair of cylindrical cores 20, 20, along with a heat dissipation sheet 40 (described later), are housed in a metal block 30 made of aluminum or copper.

[0025] As shown in Figure 3, the cylindrical core 20 is a toroidal core, which is a molded body (e.g., a compacted magnetic core) formed from a soft magnetic material such as ferrite (iron). The cylindrical core 20 has cylindrical through holes 22 through which the first winding 51 and the second winding 52 are inserted. In this embodiment, each cylindrical core 20 is composed of divided cores 21 which are divided into multiple (e.g., three) sections in a direction intersecting the axial direction, but it may also be composed as a single core.

[0026] The first winding 51 and the second winding 52 are twisted together in pairs, forming a so-called twisted pair cable. These first and second windings 51 and 52 are inserted through the through-holes 22 of a pair of cylindrical cores 20, which are arranged side-by-side, and are wound around the pair of cylindrical cores 20, 20. In this embodiment, the first and second windings 51 and 52 are wound around the pair of cylindrical cores 20, 20 in the same winding direction and for the same number of turns (approximately 2 times in this embodiment, as shown in Figure 4). As a result, the first and second windings 51 and 52 function as windings constituting the common mode choke coil 10. Of course, the number of turns of the first and second windings 51 and 52 around the pair of cylindrical cores 20, 20 is not limited to approximately 2.

[0027] In this embodiment, the first winding 51 and the second winding 52 are made of wires coated with a resin material. In this embodiment, the wires are copper wires, and the resin material coating the wires is an insulating material, and examples of insulating resins include fluororesin, polyvinyl chloride, and nylon. The resin material is not particularly limited as long as it has the necessary pressure resistance for the first winding 51 and the second winding 52 (for example, pressure resistance of several hundred volts) and can ensure the flexibility of the first winding 51 and the second winding 52. Since the first winding 51 and the second winding 52 are made of wires coated with a resin material, it is possible to prevent the first winding 51 and the second winding 52 from directly contacting the block 30.

[0028] The block 30 has a tetrahedral (or rectangular parallelepiped in this embodiment) external shape, and the block 30 has a cylindrical housing space S (see, for example, Figures 3 and 4) that accommodates each of the parallel cylindrical cores 20. The housing space S is a space that penetrates the block 30, and circular opening edges 34 (see, for example, Figure 2) corresponding to the shape of the housing space S are formed on the end faces 30a on both sides of the block 30.

[0029] In this embodiment, the block 30 is composed of divided bodies 31 and 32, which divide the cylindrical storage space S in half along the axial direction. As a result, each of the divided bodies 31 and 32 has a semicircular inner surface 35 that forms the storage space S.

[0030] As shown in Figure 2, the divided parts 31 and 32 are connected to each other via fastening members 71, such as long screws, with their respective divided surfaces 38 and 39 facing each other. Specifically, each of the divided parts 31 and 32 has multiple mounting holes 36 (for example, two on each side, a total of four) that are screwed into the fastening members 71, sandwiching a pair of inner circumferential surfaces 35, 35. The divided parts 31 and 32 are connected to each other by screwing the fastening members 71 into each mounting hole 36 and tightening the fastening members 71.

[0031] As shown in Figures 2, 4, and 6(a), insulating guide members 8 are attached to both end faces 30a of the surface of the block 30, including the opening edge 34 where the housing space S is formed, to guide the first winding 51 and the second winding 52 so that they do not come into contact with the end faces 30a of the block 30.

[0032] As shown in Figures 2 and 3, the guide member 8 is fixed to the block 30 (divided body 31) by a fixing member 72 such as a round screw through a screw hole 33 formed in the end face 30a of the divided body 31. The guide member 8 is made of an insulating resin material and comprises a guide cylinder 81 through which the first winding 51 and the second winding 52 are inserted, and a support member 82 extending from the side surface of the guide cylinder 81. A fastening hole 83 is formed in the support member 82, and the guide member 8 can be fixed to the block 30 (divided body 31) by inserting the fixing member 72 through the fastening hole 83 and screwing it into the screw hole 33.

[0033] In this way, the first winding 51 and the second winding 52 are guided by the guide member 8 so as not to contact the end face 30a of the block 30. Therefore, it is possible to avoid the first winding 51 and the second winding 52 contacting the opening edge 34 on the end face 30a of the block 30. In particular, in this embodiment, as shown in Figure 3, the guide cylinder 81 is positioned between a pair of opening edges 34 formed on the end face 30a, and the length L of the guide cylinder 81 is greater than the distance W between the pair of opening edges 34, 34. This makes it easier to avoid the first winding 51 and the second winding 52 contacting the opening edge 34 on the end face 30a of the block 30. As a result, even if the potential of the first winding 51 and the second winding 52 is set to a high potential relative to the block 30, the electrical insulation of the first winding 51 and the second winding 52 can be ensured. In this embodiment, a guide member 8 is provided to guide the first winding 51 and the second winding 52. However, instead of the guide member 8, a clamping mechanism that holds the first winding 51 and the second winding 52 in a predetermined position may be provided.

[0034] Preferably, the dividing surfaces 38 and 39 of the divided bodies 31 and 32 (see, for example, Figures 3 and 5(b)) are coated with a highly thermally conductive grease, such as a silicone-based grease, and metal or ceramic compound particles may be dispersed in this grease. However, when the divided bodies 31 and 32 are connected by fastening members 71 with a heat dissipation sheet 40 sandwiched between them, gaps may be formed between the dividing surfaces 38 and 39. Since these gaps can be filled with grease, it is possible to suppress the loss of thermal conductivity between the divided bodies 31 and 32 due to these gaps. Furthermore, if the grease is electrically conductive, the entire block 30 can be set to the potential of ground by electrically connecting either one of the divided bodies 31 or 32 to ground.

[0035] Through holes 37 are formed at the four corners of the block 30, penetrating the block 30. Fixing devices (not shown) can be inserted through these through holes 37 to fix the block 30 to a heat sink (not shown) or the like. The block 30 is a rectangular parallelepiped, and the surface of the block 30 that contacts the heat sink (the surface 30t on the side into which the fastening member 71 is inserted and the opposite surface 30b) are flat, so the heat dissipated from the block 30 can be efficiently transferred to the heat sink.

[0036] The heat dissipation sheet 40 is a sheet material that is heat-dissipating and elastically deformable, and the heat dissipation sheet 40 is, for example, a rubber sheet. In this embodiment, the heat dissipation sheet 40 is insulating. The thermal conductivity of the heat dissipation sheet 40 is preferably in the range of 1.0 W / mK to 3.0 W / mK, and more preferably in the range of 1.8 W / mK to 2.3 W / mK. The dielectric breakdown voltage of the heat dissipation sheet 40 is preferably 1 kV or more in the thickness direction, and this value can be adjusted by the thickness of the heat dissipation sheet 40. In this embodiment, the dielectric breakdown voltage of the heat dissipation sheet 40 is about 20 kV.

[0037] Examples of materials for such a heat dissipation sheet 40 include insulating rubber materials such as silicone rubber. The heat dissipation sheet 40 covers the outer peripheral surface 23 of each cylindrical core 20 and is positioned between the inner peripheral surface 35 and the outer peripheral surface 23 so as to be in contact with the inner peripheral surface 35 that forms the housing space S of the block 30 and the outer peripheral surface 23 of the cylindrical core 20. In this embodiment, the heat dissipation sheet 40 consists of divided sheets 41 and 42 that are positioned on the inner peripheral surface 35 of the housing space formed in each of the divided bodies 31 and 32 that constitute the block 30. The heat dissipation sheet 40 is sandwiched between the divided bodies 31 and 32 in a compressed and deformed state by fastening the fastening member 71.

[0038] Specifically, in this embodiment, the outer diameter of the cylindrical core 20 covered with the heat dissipation sheet 40 is larger than the inner diameter of the housing space S. As a result, when the fastening member 71 is tightened, the divided parts 31 and 32 are pulled together, and the heat dissipation sheet 40 can be compressed and deformed so that it comes into close contact with the inner circumferential surface 35 that forms the housing space S and the outer circumferential surface 23 of the cylindrical core 20.

[0039] According to this embodiment, the first winding 51 and the second winding 52 are inserted through the through holes 22 of each cylindrical core 20 when the pair of cylindrical cores 20 are arranged side by side, and are wound around the pair of cylindrical cores 20, 20 so as to span across them.

[0040] As a result, the first winding 51 and the second winding 52 are not positioned on the outer circumferential surfaces 23 of the pair of cylindrical cores 20, 20. Therefore, gaps formed by the first winding 51 and the second winding 52, etc., along the outer circumferential surface 23 of each cylindrical core 20 are suppressed, and the outer circumferential surface 23 of the cylindrical core 20 can be covered with the heat dissipation sheet 40. This heat dissipation sheet 40 is positioned between the inner circumferential surface 35 that forms the housing space S of the block 30 and the outer circumferential surface 23 of the cylindrical core 20, and is in contact with the inner circumferential surface 35 and the outer circumferential surface 23.

[0041] As a result, the heat generated from the cylindrical core 20 by the current flowing through the first winding 51 and the second winding 52 can be efficiently dissipated from the heat dissipation sheet 40 placed on the outer circumferential surface 23 of the cylindrical core 20 to the metal block 30. In particular, in this embodiment, the heat dissipation sheet 40 is compressed and deformed by the fastening member 71 (specifically, by tightening the fastening member 71) and sandwiched between the divided parts 31 and 32. As a result, the heat dissipation sheet 40 is in close contact with the inner circumferential surface 35 that forms the housing space S of the block and the outer circumferential surface 23 of the cylindrical core 20, so that the formation of a gap between the heat dissipation sheet 40 and the inner circumferential surface 35 and the outer circumferential surface 23 can be suppressed.

[0042] As shown in Figure 6(a), in this embodiment, the first winding 51 and the second winding 52 are guided by the guide member 8, thereby preventing the first winding 51 and the second winding 52 from contacting the end face 30a of the block 30, and preventing a short circuit between the first winding 51 and the second winding 52, which can become high voltage, and the block 30 connected to ground. Furthermore, as shown in the modified example in Figure 6(b), the peripheral end 41a of the heat dissipation sheet 40 may protrude from the end face 30a of the block 30. This prevents the first winding 51 and the second winding 52 from contacting the peripheral end 41a and the end face 30a of the block 30.

[0043] In the modified example shown in Figure 6(b), a guide member 8 is provided on the block 30. However, the guide member 8 may be omitted if the heat dissipation sheet 40 prevents the first winding 51 and the second winding 52 from contacting the end face 30a of the block 30. Furthermore, the first winding 51 and the second winding 52 may be secured with resin cable ties to cover them, or they may be gripped by resin clamps attached to external equipment.

[0044] Furthermore, as shown in Figure 7(a), the cylindrical core 20 and the block 30 connected to ground each act as electrodes, and the heat dissipation sheet 40 placed between the cylindrical core 20 and the metal block 30 connected to ground acts as a dielectric. Therefore, the portion from the cylindrical core 20 to the metal block 30 functions as the first capacitor C1.

[0045] Furthermore, the first winding 51 and the second winding 52 act as electrodes, and the resin covering the wires of the first winding 51 and the second winding 52, as well as the space between the first winding 51 and the second winding 52 and the cylindrical core 20, act as dielectrics. Therefore, the portion of the cylindrical core 20 from the first winding 51 and the second winding 52 functions as a second capacitor C2. When the first and second capacitors C1 and C2 function in this way, the cylindrical core 20 becomes stray at a potential of detachment.

[0046] In other words, the first capacitor C1 and the second capacitor C2 are connected in series between the metal block 30 and the high-voltage first winding 51 and second winding 52. Therefore, the first capacitor C1 and the second capacitor C2 are connected in series between the metal block 30 and the first winding 51 and second winding 52. The first and second capacitors C1 and C2 formed in this way function like the Y capacitor 11 of the common mode choke coil 10, as shown in Figure 7(b), and thus can suppress common mode noise. When comparing the capacitances of the first capacitor C1 and the second capacitor C2, the capacitance of the first capacitor C1 is greater than the capacitance of the second capacitor C2, so in effect, the second capacitor C2 functions as the Y capacitor 11.

[0047] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design modifications can be made without departing from the spirit of the invention as described in the claims. [Explanation of Symbols]

[0048] 8: Guide member, 10: Common mode choke coil, 20: Cylindrical core, 22: Through hole, 23: Outer surface, 30: Block, 31, 32: Divided parts, 40: Heat dissipation sheet, 51: First winding, 52: Second winding, S: Housing space

Claims

1. A pair of cylindrical cores with through holes formed therein, With the pair of cylindrical cores arranged side by side, a first winding and a second winding are inserted through each of the through holes and wound around the pair of cylindrical cores so as to span them, A metal block having a cylindrical housing space formed for housing each of the parallel cylindrical cores, A magnetic circuit structure characterized by comprising an inner circumferential surface that covers the outer circumferential surface of each cylindrical core and forms the housing space of the block, and a heat dissipation sheet disposed between the inner circumferential surface and the outer circumferential surface so as to be in contact with the outer circumferential surface of the cylindrical core.

2. The aforementioned block is composed of divided parts, the cylindrical storage space being divided in half along the axial direction. The divided parts are connected to each other via fastening members. The magnetic circuit structure according to claim 1, characterized in that the heat dissipation sheet is sandwiched between the divided parts in a compressed and deformed state by fastening the fastening member.

3. The magnetic circuit structure according to claim 1, characterized in that an insulating guide member is attached to the end face of the surface of the block, including the opening edge in which the housing space is formed, such that the first winding and the second winding do not come into contact with the end face of the block.

4. The magnetic circuit structure according to claim 1, characterized in that the first winding and the second winding are twisted together in pairs.

5. The magnetic circuit structure according to claim 1, characterized in that the magnetic circuit structure is a common mode choke coil, and the block is electrically connected to ground.

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