JP2009239207A - Reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactor that is compact and has excelling heat discharge properties. <P>SOLUTION: The reactor 1 comprises a core 2 having a coil-wound portion 2c, and a coil 3 disposed on the coil-wound portion 2c. A heat discharge layer 4 is disposed on a coil installation surface 3i of the coil 3, located at a cooling base B side where the reactor 1 is installed. The discharge layer 4 has a coil contact surface side 4c, contacting the coil 3 which is constituted of a carbon nanotube layer (CNT layer) 4a, and has a plate (CE plate) 4e of an insulating organic material, such as ceramics, on the cooling base B side of the CNT layer 4a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reactor used for components of a DC-DC converter of a hybrid vehicle or an electric vehicle. In particular, the present invention relates to a reactor that is small and has excellent heat dissipation performance.

  Conventionally, a reactor including a core made of a magnetic material and a coil disposed on the core is known. A typical reactor structure includes a structure in which a reactor is accommodated in an aluminum case having an opening, and the reactor is sealed by injecting resin into the case. This case is attached to a cooling base (cooler) for cooling a coil and a core that generate heat when the reactor is driven (see, for example, Patent Document 1).

  In addition, a technique for producing so-called vertically aligned carbon nanotubes in which a plurality of carbon nanotubes are erected on the substrate surface is being established. Carbon nanotubes have excellent properties such as thermal conductivity, electrical conductivity, and mechanical strength, and are expected as a new material (see, for example, Non-Patent Document 1).

Japanese Patent Laying-Open No. 2007-129146 (FIG. 5) "Understanding! Technical explanation-Carbon nanotube related project", [online], NEDO Technology Development Organization, [Search March 10, 2008], Internet <URL: http://app2.infoc.nedo.go.jp /kaisetsu/nan/na05/na05_p.html>

  However, with a conventional reactor, it is difficult to further improve the heat dissipation performance.

  In recent years, reactors used for components of DC-DC converters such as hybrid vehicles are required to have higher frequencies and higher currents, and in order to cool coils and cores that generate more heat, the reactor's heat dissipation performance is improved. There is a need for further improvement. Moreover, it is preferable to omit the case in order to reduce the size and weight of the reactor.

  Patent Document 1 discloses a configuration in which the case is omitted and a silicone resin sheet is disposed between the coil and the cooler. However, the thermal conductivity of the silicone resin described in Patent Document 1 is 3 W. / m · K or less, and with this configuration, it is difficult to achieve the required heat dissipation performance.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a reactor that is small in size and excellent in heat dissipation performance.

  The reactor of this invention is equipped with the core which has a coil winding part, and the coil arrange | positioned at a coil winding part. A heat dissipation layer is disposed on the coil installation surface of the coil located on the cooling base side to which the reactor is attached, and the heat dissipation layer is composed of a carbon nanotube layer on the coil contact surface side in contact with the coil. A layer of an insulating inorganic material is provided on the cooling base side of the layer.

  In the reactor according to the present invention, the coil contact surface side of the heat dissipation layer disposed between the coil and the cooling base is composed of a layer of carbon nanotubes having thermal conductivity comparable to that of diamond. On the cooling base side, an inorganic material plate generally having a higher thermal conductivity than the silicone resin is provided. Therefore, the heat of the coil, which is likely to become high temperature, can be efficiently transferred to the carbon nanotube layer in contact with the coil, the inorganic material plate, and the cooling base in this order to dissipate heat. Moreover, since the reactor of this invention is not accommodated in a case but attached directly to a cooling base, a case can be abbreviate | omitted and it can implement | achieve size reduction and weight reduction.

  It is assumed that the insulating inorganic material plate in the present invention is made of a material having high thermal conductivity. Specifically, it is preferable that the thermal conductivity α is made of a material of more than 3 W / m · K, particularly 20 W / m · K or more, more particularly 30 W / m · K or more. Further, since the heat dissipation layer is disposed in the vicinity of the coil, it is preferable that the whole is made of a nonmagnetic material in consideration of magnetic characteristics. Examples of the material having the above characteristics include nonmagnetic insulating inorganic materials. The insulating inorganic material plate is located on the cooling base side of the carbon nanotube layer in contact with the coil, and has a function of ensuring insulation between the cooling base and the coil. Further, the heat dissipation layer may be composed of a carbon nanotube layer and an insulating inorganic material plate, and may further include a conductive inorganic material layer on the cooling base side of the insulating inorganic material plate.

Ceramics can be suitably used as the insulating inorganic material. Specifically, silicon nitride (Si ₃ N ₄ ): α = about 20 to 150 W / m · K, alumina (Al ₂ O ₃ ): α = about 20 to 30 W / m · K, aluminum nitride (AlN): α = 200 to 250 W / m · K, boron nitride (BN): α = 50 to 65 W / m · K, and silicon carbide (SiC): at least selected from α = 50 to 130 W / m · K One kind is mentioned. That is, the insulating inorganic material plate may be composed of one kind of material, or a plurality of kinds of materials may be laminated to partially differ in thermal conductivity. Of the ceramics, silicon nitride is preferable in that it has high thermal conductivity and is superior in bending strength to alumina, aluminum nitride, and silicon carbide.

  The insulating inorganic material plate can be composed of the ceramic plate material, and can be easily obtained in various sizes and shapes by, for example, producing by a powder sintering method. Commercial products may be used.

  Carbon nanotubes have anisotropy in thermal conductivity and exhibit extremely high thermal conductivity in the length direction (axial direction). Therefore, the carbon nanotube layer in the present invention is preferably composed of a plurality of carbon nanotubes oriented in a direction perpendicular to the plate surface of the insulating inorganic material. The term “orientation in the vertical direction” as used herein does not need to be oriented in a completely vertical direction with respect to the plate surface, but includes cases in which the carbon nanotubes are oriented in a substantially vertical direction. And may be inclined within a range of 5 ° or less.

  In addition, since the plurality of carbon nanotubes are oriented in a direction perpendicular to the plate surface of the insulating inorganic material, when the heat dissipation layer is arranged in the coil, the carbon nanotubes enter the recesses on the coil surface, and the coil and the heat dissipation layer A gap formed between them can be filled with a carbon nanotube layer. Therefore, the adhesion between the carbon nanotube layer (heat dissipation layer) and the coil is increased, and the contact area between the heat dissipation layer and the coil is increased. As a result, the contact thermal resistance between the coil and the heat dissipation layer can be reduced, and the heat dissipation of the reactor is achieved. The performance can be further improved. Carbon nanotubes have supple elasticity and are not easily damaged.

  The carbon nanotube layer is preferably 0.5 mm or more, and by setting the carbon nanotube layer to 0.5 mm or more, a gap generated between the coil and the heat dissipation layer can be reliably filled.

  For the formation of the carbon nanotube layer, a chemical vapor deposition method (CVD method) can be suitably used, and it is preferable to form the carbon nanotube layer directly on the plate surface of the insulating inorganic material.

  In the reactor of the present invention, a heat dissipation layer is arranged on the coil installation surface of the coil located on the cooling base side, and this heat dissipation layer is on the coil contact surface side on the carbon nanotube layer and on the cooling base side of the carbon nanotube layer. By providing an insulating inorganic material plate, the heat dissipation performance is excellent. Further, by omitting the case, it is small and lightweight.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. Moreover, the same code | symbol is attached | subjected to the same member in the figure.

(Embodiment 1)
1 is a perspective view of a reactor according to the present invention, FIG. 2 is a right side view of the reactor according to the present invention attached to a cooling base, and FIG. 3 is a plan view of a core provided in the reactor according to the present invention. In FIG. 2, the cooling base is shown in cross section (the same applies to FIG. 5 described later).

  The reactor 1 is directly attached to a cooling base B in which a refrigerant circulation path (not shown) is formed, and includes a core 2 made of a magnetic material, a coil 3 disposed in the core 2, a coil 3 and a cooling base. The heat dissipating layer 4 disposed between B and the main component is used.

  As shown in FIG. 3, the core 2 is an annular member having coil winding portions 2c facing each other and forming a closed magnetic path, and includes a magnetic body portion 2m and a gap portion 2g. Here, the magnetic body portion 2m is formed of a compacted body of soft magnetic powder, and includes a rectangular parallelepiped block 2a and a curved block 2b in which a corner portion of the rectangular parallelepiped is curved. The gap 2g is a rectangular plate material made of a nonmagnetic material such as glass epoxy resin or alumina. In addition, here, six rectangular parallelepiped blocks 2a and a pair of curved blocks 2b are prepared, and a pair of rectangular parallelepiped assemblies in which the three rectangular parallelepiped blocks 2a are grouped are produced, and these rectangular parallelepiped assemblies are separated. The annular core 2 is formed by arranging them between the curved blocks 2b and joining them together. Between the rectangular parallelepiped blocks 2a of the core 2, a total of four gap portions 2g are arranged, and each rectangular parallelepiped set becomes a coil winding portion 2c.

  The rectangular parallelepiped block 2a (cuboid assembly) and the curved block 2b are different in height (distance in the vertical direction from the surface of the cooling base B to the upper surface of each block when the reactor 1 is installed on the cooling base B). As shown in FIG. 2, when viewed from the side, the core 2 is H-shaped. Further, in a state where the coil 3 is disposed on the outer periphery of the coil winding portion 2c, the surface of the coil 3 (coil installation surface 3i) located on the cooling base B side protrudes from the surface of the core 2 (core installation surface 2i). So that the height Lh of the curved block 2b (the length in the vertical direction of the curved block 2b when the reactor 1 is installed on the cooling base B) is set, and the core is located on the cooling base B side. The installation surface 2i is in contact with the cooling base B.

  The coil 3 is provided with a first coil 3a and a second coil 3b obtained by edgewise winding a wire having an enamel coating on the surface of a flat copper wire, and after arranging the coil 3a and 3b on the coil winding part 2c, It is formed by welding one edge part of (refer FIG. 1). It is also possible to form a coil with a continuous winding. In this case, the coil is wound from one end side to the other end side of one coil winding portion 2c, folded at the other end side, What is necessary is just to wind a coil | winding continuously toward the one end side from the other end side of the coil winding part 2c. Here, since the coil 3 is not folded, the core length Lc (distance from the end surface of one curved block 2b to the end surface of the other curved block 2b, see FIGS. 2 and 3) is shortened accordingly. can do.

  When the coil 3 is arranged in the coil winding portion 2c (a rectangular parallelepiped set of the rectangular parallelepiped blocks 2a), the rectangular parallelepiped block 2a is covered with the coil 3, and the curved block 2b is exposed from the coil 3.

  An insulator 5 is provided in the assembly of the core 2 and the coil 3. The insulator 5 includes a cylindrical portion (not shown) that covers the outer periphery of the coil winding portion 2c, and a pair of flange portions 5f that come into contact with the respective end surfaces of the coil 3. The tubular portion covers the outer periphery of the coil winding portion 2c by engaging the half-cut square tube pieces. The flange portion 5f is a pair of rectangular frames that are disposed so as to face both end portions of the cylindrical portion and come into contact with each end face of the coil 3. For the insulator 5, a synthetic resin such as polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), or liquid crystal polymer (LCP) can be suitably used.

  In the coil 3, a heat radiation layer 4 is disposed on the coil installation surface 3i located on the cooling base B side.

  The heat dissipation layer 4 is composed of a carbon nanotube layer (hereinafter referred to as a CNT layer) 4a and an insulating inorganic material plate (hereinafter referred to as a CE plate) 4e, and the coil mounting surfaces of both the first coil 3a and the second coil 3b. This is a plate-like member having an area that can cover 3i. The CE plate 4e is made of a silicon nitride (α = 27 W / m · K) plate material. The heat dissipation layer 4 has a coil contact surface 4c that contacts the coil 3 and a base contact surface 4b that contacts the cooling base B. It is preferable to apply grease or the like to the base contact surface 4b of the heat dissipation layer 4 because adhesion with the cooling base B can be improved. Further, if a carbon nanotube layer is also formed on the base contact surface 4b side of the heat dissipation layer 4, the adhesion to the cooling base B can be improved without applying grease or the like.

  In the heat dissipation layer 4, a CNT layer 4a is formed on the coil contact surface 4c side. The CNT layer 4a is composed of a plurality of carbon nanotubes oriented in the vertical direction and has a thickness of 0.5 mm. Such a vertically aligned CNT layer can be produced, for example, as follows.

  First, using a sputtering method, cobalt serving as a catalyst is vapor-deposited on the surface of a CE plate, and cobalt fine particles are adhered in a certain pattern. Next, this CE plate is placed in a furnace, and ethanol gas is used as argon gas as a carrier gas, and the reaction is performed for a certain period of time at a furnace temperature of 800 ° C. and a furnace pressure of 300 torr (about 40 kPa). This makes it possible to form a CNT layer grown almost perpendicular to the CE plate surface. By adjusting the reaction time, it is possible to change the thickness of the CNT layer to be formed.

  In addition, heat dissipation layer 4 is an adhesive with excellent thermal conductivity so that it does not fall off from coil 3 (specific example, sheet-like thermally conductive epoxy adhesive (α = 5 W / m · K) manufactured by Nagase ChemteX Corporation) ) Is fixed to coil 3. Further, the base contact surface 4b of the heat dissipation layer 4 and the core installation surface 2i are flush with each other.

  Furthermore, the reactor 1 includes a resin coating portion 6 that covers the outer periphery thereof. Here, the resin coating part 6 is an assembly of the core 2 and the coil 3, and after fixing the heat radiation layer 4 to a predetermined location on the outer peripheral surface of the coil 3, it is placed in a mold and casted with epoxy resin. It is formed by molding. However, the base contact surface 4b of the heat dissipation layer 4 and the core installation surface 2i of the core 2 are exposed from the resin coating portion 6, and the end portion of the coil 3 to which a separate wiring is connected also protrudes from the resin coating portion 6. Yes. The resin-coated portion 6 has a rectangular parallelepiped shape, and bolts 7 for fixing the reactor 1 to the cooling base B at respective locations (four corners of the resin-coated portion 6) that cover the curved portions of the curved block 2b of the core 2. A fixing flange portion 6f provided with an insertion hole 6h through which the (fastening member) is inserted is provided. The average thickness of the portion covering the core 2 and the coil 3 of the resin coating portion 6 is 1 to 2 mm. Since the shape of the resin coating portion 6 is not particularly limited, it may be a shape generally along the outer shape of the assembly of the core 2 and the coil 3. The installation location, shape (thickness), and installation number of the fixed flange portion 6f can be selected as appropriate. For example, the fixing flange portion 6f may be provided so as to protrude from the outer surface side of the curved block 2b when viewed from the side, or from the side surface side of the coil 3 when viewed from the front.

  The resin coating 6 is (1) the core 2, the coil 3 and the heat dissipation layer 4 are integrated, (2) the heat dissipation layer 4 is securely fixed to the coil 3, (3) the core 2 is reinforced, (4) There are various effects such as protecting the core 2 and the coil 3 from the external environment and (5) ensuring insulation between members disposed around.

  The reactor 1 is attached to the cooling base B by aligning the insertion hole 6h of the fixing flange portion 6f of the resin coating portion 6 with the screw hole Bh provided in the cooling base B, and screwing and tightening the bolt 7. Since the fixing flange portion 6f is integrally provided on the resin coating portion 6, it can be easily attached to the cooling base B without using a separate fixing member. In addition, the resin flange is near the fixing flange portion 6f in the resin coating portion 6, but the thick portion is limited to the four corners of the outer periphery of the reactor 1, and is fixed because it is thin overall. A decrease in heat dissipation performance due to the presence of the flange portion 6f can be reduced. With this attachment, the heat dissipation layer 4 and the core 2 come into contact with the cooling base B.

  The reactor 1 according to the first embodiment described above does not require a case, is small and lightweight, and has a heat dissipation layer 4 having a high thermal conductivity between the coil 3 and the cooling base B. Since the CNT layer 4a is formed on the coil contact surface 4c side of the layer 4, the heat dissipation performance is excellent.

  In the reactor 1, since the base contact surface 4b of the heat dissipation layer 4 and the core installation surface 2i of the core 2 are flush with each other, the heat of the core 2 can also be efficiently transmitted to the cooling base B. Moreover, with this configuration, when the volume of the curved block 2b is constant, the rectangular parallelepiped block 2a and the curved block 2b have the same height (see FIG. 5 of Patent Document 1) in plan view. In this case, the area of the core 2 exposed from the coil 3, that is, the area of the core installation surface 2i can be reduced. Therefore, the core length Lc can be shortened, and the reactor 1 can be further downsized.

(Modification 1-1)
In the first embodiment described above, the resin covering portion 6 is provided with a fixing portion (fixing flange portion 6f) for fixing the reactor 1 to the cooling base B. However, the core 2 itself has an insertion hole through which a bolt is inserted. It may be provided. For example, if a portion that protrudes outward from the curved portion of the curved block 2b is provided and an insertion hole is provided in this protruding portion, the magnetic characteristics of the core 2 are unlikely to be affected. The shape and the number of the protruding portions can be selected as appropriate, and are not particularly limited. Further, the core 2 having such an insertion hole can be easily produced by forming a compacted body. When this protruding portion is also covered with the resin coating portion 6, an insertion hole is also provided in the resin coating portion 6 so as to be continuous with the insertion hole of the core 2.

(Modification 1-2)
In addition, a fixing member may be separately prepared without providing the fixing flange portion 6f in the resin coating portion 6 or the insertion hole in the core 2, and the reactor 1 may be fixed to the cooling base by the fixing member. FIG. 4 is a diagram illustrating a state in which the reactor 1 is attached to the cooling base using the fixing member. The fixing member 8 is composed of a pair of leg portions 8a and a connecting portion 8b that connects the leg portions 8a to each other. The connecting portion 8b that is located on the upper surface of the resin coating portion 6 includes the core 2 and the coil. 3 is to be pressed against the cooling base. Here, two fixing members 8 made of stainless steel are used in pairs. The leg portion 8a is provided with an insertion hole 8h through which a bolt (not shown) is inserted. Further, a portion protruding in the outer surface direction of the curved block 2b is provided at the central portion of the connecting portion 8b, and the protruding portion is bent along the corner portion of the resin coating portion 6. Therefore, it is possible to reliably prevent the reactor 1 from moving in the front / rear, left / right, up / down directions.

  Further, the connecting portion 8b is bent in a bow shape so that the central portion of the connecting portion 8b is in contact with the upper surface of the resin covering portion 6, and the core 2 and the coil 3 are cooled by pressing the resin covering portion 6 by the elasticity of the connecting portion. It is good also as a structure pressed on the base side. According to this configuration, an effect of improving the adhesion between the CNT layer 4a (heat radiation layer 4) and the coil 3 can be expected.

(Embodiment 2)
FIG. 5 is a right side view of the reactor according to another embodiment attached to the cooling base. Reactor 10 also has core 2, coil 3, and heat dissipation layer 4 as main components, and is different from reactor 1 of Embodiment 1 in that it does not have a resin coating portion, and the other points are the same. . Since such a reactor 10 has few constituent members, it is easy to manufacture the reactor.

  The reactor 10 is preferably integrated by fixing the heat dissipation layer 4 to the coil 3 with an adhesive or the like. According to this configuration, for example, even when the reactor 10 is attached to the lower surface of the cooling base B with the heat dissipation layer 4 facing upward, the heat dissipation layer 4 can be prevented from being displaced or dropped, and the installation work of the reactor can be prevented. Easy to do.

  In order to fix the reactor 10 to the cooling base B, as described in the modification 1-1 above, a bolt (fastening member, not shown) for fixing the reactor 10 to the cooling base B is inserted into the core 2 itself. An insertion hole (not shown) may be provided, or a separate fixing member may be used. The fixing member includes, for example, a pair of leg portions and a coupling portion that couples the leg portions to each other. The substantially linear coupling portion along the outer peripheral surface of the core or coil is a core or coil. Is configured to be pressed against the cooling base side. The leg is provided with an insertion hole through which the bolt is inserted. Further, as described in Modification 1-2 above, a portion that protrudes toward the outer surface of the curved block 2b is provided at the center of the connecting portion, and this protruding portion is bent along the corner of the curved block 2b. May be.

  Furthermore, the central portion of the connecting portion 8b is curved in a bow shape that bulges downward, the core 2 and the coil 3 are pressed by the elasticity of the connecting portion, and the core 2 and the coil 3 are pressed against the cooling base side. Good. According to this configuration, an effect of improving the adhesion between the CNT layer 4a (heat radiation layer 4) and the coil 3 can be expected. Moreover, when using a fixing member, it is preferable to provide an insulating coating at a place where the fixing member may come into contact with the coil, or to dispose the insulating member between the fixing member and the coil.

(Modification I)
In the first and second embodiments described above, the configuration in which the reactors 1 and 10 are attached to the upper surface of the cooling base has been described. However, the reactor may be attached to the lower surface of the cooling base. Since both reactors 1 and 10 have the heat dissipation layer fixed to the coil, there is no risk of the heat dissipation layer dropping when attaching to the cooling base, and the mounting workability is excellent.

(Modification II)
In the first and second embodiments described above, the heat dissipation layer in which the carbon nanotube layer is formed on the surface of the ceramic plate has been described as an example. In addition, the ceramic layer and the carbon nanotube layer on the surface of the metal plate made of a conductive material. Can be used. Examples of the metal plate include aluminum (α = 236 W / m · K), copper (α = 390 W / m · K), alloys thereof, and austenitic stainless steel (for example, SUS304: α = 16.7 W / m · K). And those made of non-magnetic metal materials. The ceramic layer is formed by preparing a ceramic plate or foil and bonding this plate (foil) to a metal plate, or by depositing a ceramic film on the surface of the metal plate using PVD or CVD. Can be formed.

  Note that the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the gist of the present invention. For example, the core may be composed of a laminate in which silicon steel plates are laminated.

  The reactor of the present invention is small in size and excellent in heat dissipation performance, and can be suitably used for, for example, a component part of a DC-DC converter of a hybrid vehicle or an electric vehicle.

1 is a perspective view of a reactor according to a first embodiment. It is a right view of the reactor which concerns on Embodiment 1. FIG. 3 is a core plan view of the reactor according to Embodiment 1. FIG. It is a figure explaining the state which attached the reactor to the cooling base using the member for fixation. It is a right view of the reactor which concerns on Embodiment 2. FIG.

Explanation of symbols

1,10 reactor
2 core
2m Magnetic part 2g Gap part
2a Rectangular block 2b Curved block 2c Coil winding part
2i Core installation surface
3 coils
3a 1st coil 3b 2nd coil 3i Coil installation surface
4 Heat dissipation layer
4c Coil contact surface 4b Base contact surface
4a Carbon nanotube layer (CNT layer) 4e Insulating inorganic material plate (CE plate)
5 Insulator 5f Buttocks
6 Resin coating
6f Fixed flange 6h Insertion hole
7 volts
8 Fixing member
8a Leg 8b Connection 8h Insertion hole
B Cooling base Bh Screw hole

Claims (2)

A reactor comprising a core having a coil winding part and a coil arranged in the coil winding part,
A heat dissipation layer is arranged on the coil installation surface of the coil located on the cooling base side to which the reactor is attached,
The reactor is characterized in that a coil contact surface side in contact with the coil is formed of a carbon nanotube layer, and the insulating layer is provided on the cooling base side of the carbon nanotube layer.   The reactor according to claim 1, wherein the carbon nanotube layer is composed of a plurality of carbon nanotubes oriented in a direction perpendicular to a surface of the insulating inorganic material plate.

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