JP2014154757A - Reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which prevents a periphery of a heat radiation sheet 9 from being torn in a reactor 2 attached to a cooler through the flexible heat radiation sheet 9.SOLUTION: A reactor 2 disclosed by the specification includes: a coil 3; a resin cover 5; and a heat radiation sheet 9. A side surface of the coil 3, which is arranged in parallel with a coil axis line, contacts with a housing 8 (a cooler) sandwiching the heat radiation sheet 9. The resin cover 5 encloses the coil 3 when viewed in a direction perpendicular to the housing 8. An end surface of the resin cover 5, which faces the housing 8, presses the heat radiation sheet 9 against the housing 8 at a periphery of the side surface of the coil 3.

Description

  The present invention relates to a reactor. A reactor is a passive element using a coil, and is sometimes called an inductor.

  The reactor is used for power factor improvement, harmonic current suppression (direct current smoothing), and the like. The reactor may also be used in a circuit that boosts a DC voltage.

  A reactor is sometimes used for an electronic device of an electric vehicle. Since an electric vehicle uses a motor as a driving force, a drive circuit is often provided with a reactor. Since an electric vehicle uses a high-power motor of several tens of kilowatts, a reactor used for its drive circuit also has a large capacity. Therefore, the amount of heat generated by the reactor is large. In the present specification, the “electric vehicle” includes a hybrid vehicle including an engine together with a motor, and a fuel cell vehicle.

  A cooler may be attached to the reactor for cooling. The cooler may be of a type in which a refrigerant flows inside, or may be a simple heat sink. In the latter case, the casing that fixes the reactor (the casing of the electronic device including the reactor) may function as a heat sink. For example, Patent Document 1 proposes that a coil that is entirely covered with a resin is brought into contact with the casing, and the heat of the coil is diffused to the casing through the resin.

  Several techniques using a heat-dissipating sheet having higher heat conductivity than resin have been proposed. According to the technique of Patent Document 2, the reactor is attached to the housing wall with a heat dissipation sheet sandwiched between the side surface of the coil and the housing wall. Resin is filled around the reactor inside the housing, and the reactor is sealed with resin including the heat dissipation sheet. That is, the heat of the reactor is diffused to the casing through the heat dissipation sheet. Moreover, according to the technique of patent document 3, the side surface of a coil and the side surface of a core are fixed to a housing | casing wall with a heat dissipation adhesive. In this technique, the heat of the coil is diffused through the adhesive to the housing. Furthermore, in the technique of Patent Document 4, the entire reactor is covered with resin, and a heat radiation layer having a higher heat transfer coefficient than other portions is formed on the resin side surface facing the housing wall. The reactor coil faces the housing wall with the heat dissipation layer interposed therebetween, and the heat of the coil diffuses into the housing via the heat dissipation layer. In addition, as for the technique of patent documents 1-4, all use a housing | casing as a heat sink of a reactor.

JP 2011-249427 A JP2012-124401A JP 2009-231495 A JP 2012-209333 A

  Some recent heat dissipation sheets are made of a material having high flexibility and low tensile strength. For example, a silicon-based heat dissipation sheet called Sarcon (registered trademark) has a high thermal conductivity of 17 W / mK, but a tensile strength of about 1 to 10 [MPa]. Here, the tensile strength is represented by the magnitude of the stress required to break. Incidentally, the tensile strength of natural rubber is about 1 to 20 [MPa]. On the other hand, in order to improve heat transfer, it is necessary to strongly press the coil to the cooler with the heat dissipation sheet interposed therebetween. Furthermore, in order to improve heat dissipation, the size of the heat dissipation sheet must be wider than the lower surface of the coil facing the cooler so that the entire one side surface of the coil facing the cooler is in contact with the heat dissipation sheet. I must. Here, the “lower surface” is a name for convenience of explanation, and it should be noted that the reactor does not necessarily have to be in contact with the heat dissipation sheet on the lower side in the vertical direction. If the size of the heat radiating sheet is made larger than that of the lower surface of the coil, the portion of the heat radiating sheet that protrudes from the lower surface of the coil is torn off, and there is a risk of becoming a foreign object that can move freely inside the casing where the coil is installed. In particular, in an in-vehicle electronic device, since vibration is large, there is a possibility that a foreign object moves in the housing due to vibration and comes into contact with another device. This specification provides a technique for preventing the peripheral edge of a heat dissipation sheet from being torn when a heat dissipation sheet having a low tensile strength is used.

  The technology disclosed in this specification is directed to a reactor attached to a cooler via a flexible heat dissipation sheet. Here, the flexible heat dissipation sheet is a sheet having a tensile strength of about 20 [MPa] or less. Such a sheet may be torn off when the center portion is pressed while leaving the periphery. In the reactor disclosed in this specification, the side surface parallel to the coil axis is orthogonal to the coil that is indirectly in contact with one surface of the cooler with the heat dissipation sheet interposed therebetween, and the side surface (side surface parallel to the coil axis) of the reactor. A resin cover is provided that surrounds the coil when viewed from the direction of the coil. In other words, the direction orthogonal to the side surface parallel to the coil axis is the direction orthogonal to one surface of the cooler (reactor mounting surface). Hereinafter, for convenience of explanation, the coil side surface facing the cooler may be referred to as a coil lower surface. The size of the heat dissipation sheet is larger than the lower surface of the coil. That is, when viewed from the direction orthogonal to the reactor mounting surface of the cooler (the direction orthogonal to the lower surface of the coil), the heat dissipation sheet spreads outside the lower surface of the coil. And the end surface facing the reactor mounting surface of the resin cover presses the heat radiation sheet against the cooler around the lower surface of the coil. That is, in the reactor disclosed in this specification, the resin cover that covers the periphery of the coil presses the periphery of the heat dissipation sheet against the cooler around the coil. Thus, the peripheral edge of the heat dissipation sheet is prevented from being torn off. The reactor is fixed to the cooler through a resin cover.

  In the reactor disclosed in this specification, it is preferable that a recess is provided between the periphery of the coil and the end surface of the resin cover as viewed from the reactor mounting surface side. By providing such a depression, the deformed portion of the heat dissipation sheet enters into the depression due to the pressure between the cooler and the lower surface of the coil. The heat dissipation sheet that has entered the recess comes into contact with the side surface that is curved (bent) from the lower surface at the edge of the lower surface of the coil, further enhancing the coil cooling effect.

  In a vehicle-mounted reactor, a coil formed in a substantially quadrangular prism shape may be used. When the technology disclosed in this specification is applied to the reactor of such a coil, it is preferable that one side surface of the rectangular column coil is opposed to the reactor mounting surface of the cooler with the heat dissipation sheet interposed therebetween. Heat can be diffused to the cooler through the heat dissipation sheet on the entire side surface of the quadrangular column.

  Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a three-plane figure of the reactor of an Example. (A) shows a plan view, (B) shows a side view, and (C) shows a front view. Sectional drawing in the II-II line | wire of FIG. 1 is shown. FIG. 3 is a view before assembly in the cross section of FIG. 2. Sectional drawing in the IV-IV line of FIG. 1 is shown. The figure before an assembly in the section of Drawing 4 is shown.

  The reactor 2 of an Example is demonstrated with reference to drawings. Reactor 2 is a component of a voltage converter circuit built in a power control unit that boosts DC power of a battery, converts it into AC, and supplies it to a motor in an electric vehicle. The reactor 2 is attached to the housing 8 of the power control unit. In the figure, only a part of the housing 8, that is, the surface on which the reactor 2 is attached (reactor attachment surface) is depicted. The partial housing 8 also serves as a wall of the coolant channel through which the coolant passes, and the housing itself also serves as a cooler for the heating element including the reactor 2.

  FIG. 1 shows a three-sided view of the reactor 2. 1A, 1B, and 1C show a plan view, a side view, and a front view of the reactor 2, respectively. The main components of the reactor 2 are an annular core 4, a series of coils 3, and a resin cover 5. Since the core 4 and the coil 3 are covered with the resin cover 5, the core 4 and the coil 3 are drawn with broken lines in FIG.

  The annular core 4 is made of a magnetic material such as ferrite. The core 4 may be composed of a single ring or may be divided into a plurality of parts. For example, the core 4 may be composed of a pair of U-shaped parts and an I-shaped part disposed between a pair of U-shaped parts whose end faces are opposed to each other. The annular core 4 has parallel parts, and the coils 3 are wound around the parallel parts. The two coils are made of one winding, and 3a corresponds to the connecting portion. In the figure, the lead portion of the coil 3 (the lead wire of the coil end portion) is not shown. The entire coil 3 is formed in a substantially quadrangular prism.

  The core 4 and the coil 3 are covered with a resin cover 5 except for the lower surface of the coil. The resin cover 5 is made of PPS (polyphenylene sulfide) resin. In the plan view of FIG. 1A, that is, when viewed from a direction orthogonal to the housing 8 (reactor mounting surface), the resin cover 5 surrounds the coil 3 and the core 4. The resin cover 5 is formed by placing the assembly of the coil 3 and the core 4 in a mold and injecting resin into the mold. In other words, the resin cover 5 is made to be integrated with the assembly of the coil 3 and the core 4. The resin cover 5 covers the entire coil 3 except for the lower surface of the coil 3. In other words, the lower surface of the coil 3 is exposed from the resin cover 5. Here, the coil 3 is formed in a substantially quadrangular prism, and the lower surface thereof corresponds to one side surface of the quadrangular column.

  As well shown in the plan view of FIG. 1A, ribs 6 are provided at the four corners of the resin cover 5, and the reactor 2 is fixed to the housing 8 with bolts 7 through the ribs 6. .

  As shown in FIGS. 1B and 1C, a heat radiation sheet 9 is disposed between the lower surface of the coil 3 and the housing 8 (reactor mounting surface). In other words, the coil 3 is indirectly in contact with the housing 8 via the heat dissipation sheet 9. The heat dissipating sheet 9 is a rubber-like sheet based on silicon, and has high thermal conductivity and high flexibility. An example of a heat dissipation sheet is a Sircon (registered trademark) sheet. The thermal conductivity of the heat radiating sheet 9 is about 17 W / mk, and the flexibility of the heat radiating sheet 9 is about 20 to 100 [Hs] in terms of rubber hardness (JIS A). By sandwiching a flexible heat dissipation sheet 9 having a high thermal conductivity between the lower surface of the coil 3 and the housing 8, the heat dissipation sheet is also closely attached to a recess between adjacent windings of the coil 3. Heat conduction to is promoted.

  On the other hand, the flexible heat-dissipating sheet does not have a high tensile strength and is approximately 1 to 10 [MPa]. By the way, the Young's modulus of aluminum is 70.3 [GPa] (Giga Pascal), which is different by 3 digits. In order to increase the heat transfer efficiency from the coil 3 to the housing 8, it is necessary to press the lower surface of the coil 3 against the housing 8 with the heat radiating sheet 9 interposed therebetween. There is a possibility that the periphery of the sheet 9 may be cut off. Therefore, in the reactor 2, the heat radiating sheet 9 has a size that extends to the periphery of the coil 3, and the periphery of the heat radiating sheet 9 is pressed by the end surface of the resin cover 5 around the coil 3. Here, the end surface of the resin cover 5 means a resin cover end surface facing the housing 8. By pressing the peripheral edge of the heat dissipation sheet 9 with the end face of the resin cover 5, the edge of the heat dissipation sheet 9 is prevented from being broken.

  The relationship between the heat dissipation sheet 9 and the resin cover 5 will be described in detail with reference to FIGS. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a diagram (pre-assembly diagram) before the assembly of the coil 3, the core 4 and the resin cover 5 is attached to the housing 8 in the cross section of FIG. As well shown in FIG. 3, the resin cover 5 is provided with a recess 5a between the coil 3 and the resin cover end face 5t. When the heat radiating sheet 9 is sandwiched between the resin cover 5 and the housing 8 and pressure is applied, the heat radiating sheet 9 is deformed and the deformed portion 9a enters the recess 5a. As shown well in FIG. 2, the deformed portion 9 a contacts a part of the axial end surface of the coil 3. This further contributes to increasing the heat transfer rate from the coil 3 to the housing 8. It should be noted that the pressure applied to the heat dissipation sheet 9 can be increased by tightening the bolt 7.

  4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a diagram (pre-assembly diagram) before the assembly of the coil 3, the core 4 and the resin cover 5 is attached to the housing 8 in the cross section of FIG. 4, the resin cover 5 is provided with a recess 5b between the coil 3 and the resin cover end surface 5t, as in the cross section of FIG. A recess 5c is also provided between the double coils. When the heat radiating sheet 9 is sandwiched between the resin cover 5 and the housing 8 and pressure is applied, the heat radiating sheet 9 is deformed, the deformed portion 9b enters the dent 5b, and the deformed portion 9c is dent 5c between the two coils. Break into. As shown well in FIG. 4, the deformed portions 9 b and 9 c are in contact with part of the side surface of the coil 3. As can be understood from FIGS. 2 and 4, recesses (5 a, 5 b, 5 c) are provided on the end surface 5 t of the resin cover 5 facing the housing 8 so as to surround the coil 3. The deformation part of the heat dissipation sheet 9 enters. The deformed portion that comes into contact with the coil 3 increases the heat transfer rate from the coil 3 to the housing 8.

  Points to be noted regarding the technology described in the embodiments will be described. One of the advantages of the reactor 2 disclosed in the present specification is as follows. One side surface (coil lower surface) of the substantially square-shaped coil 3 is opposed to the housing 8, and a heat dissipation sheet 9 having a larger area than the one side surface is sandwiched. When viewed from the orthogonal direction of the housing 8, the heat dissipation sheet 9 projects around the coil 3, and the projecting portion is pressed by the end surface 5 t of the resin cover 5. With such a structure, the heat radiating sheet 9 can be brought into contact with the entire surface of one side surface of the coil 3, and the peripheral edge protruding from the coil 3 is not broken even by the pressure between the coil and the housing.

  The resin cover 5 is provided with recesses 9 a to 9 c surrounding the coil 3 on the end surface 5 t facing the housing 8. In plan view, the coil 3 presses the heat dissipation sheet 9 inside the recess, and the end surface 5t of the resin cover presses the heat dissipation sheet 9 outside the recess. When the heat dissipation sheet 9 is strongly pressed, the flexible heat dissipation sheet 9 is deformed between a portion pressed by the coil 3 and a portion pressed by the end face 5t. The deformed portion enters the recesses 9a to 9c. The heat dissipating sheet 9 is brought into contact with not only the side surface of the coil 3 that faces the housing 8 but also another side surface that is curved (bent) from the side surface, thereby increasing the heat transfer efficiency from the coil 3 to the housing 8. When the heat radiating sheet 9 is pressed more strongly, the deformed portions of the heat radiating sheet are filled in the depressions 9a to 9c. If it does so, the heat-transfer efficiency from the coil 3 to the housing | casing 8 will further be improved.

  The technology disclosed in this specification is suitable for a reactor that employs a heat-dissipating sheet that is flexible and not strong against pulling, particularly a heat-dissipating sheet having a tensile strength of 1 to 10 [MPa] or less.

  The reactor 2 of the embodiment has a structure in which two coils 3 are wound around a parallel portion of a ring-shaped core 4. The technique disclosed in this specification is also preferably applied to a reactor in which a single coil is wound around a linear core.

  Reactor 2 is mounted on a power control unit that supplies AC power to a motor in an electric vehicle. The power control unit here is an electronic device provided with a reactor, and the housing 8 also serves as a cooler for the reactor. That is, the housing 8 corresponds to an example of a cooler that cools the reactor. In addition, the technology disclosed in this specification can be expressed as a structure in which the reactor 2 is fixed to the cooler.

  The resin cover 5 does not need to cover all parts except the lower surface of the coil 3. Moreover, what is necessary is just to hold down the thermal radiation sheet 9 in at least one part of the circumference | surroundings of the coil 3 in planar view.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Reactor 3: Coil 4: Core 5: Resin cover 5a, 5b, 5c: Recess 5t: Resin cover end face 6: Rib 8: Housing (cooler)
9: Heat radiation sheet 9a, 9b, 9c: Deformation site

Claims (3)

It is a reactor attached to the cooler via a heat dissipation sheet,
A coil whose side surface parallel to the coil axis is in contact with the cooler with the heat dissipation sheet interposed therebetween;
A resin cover surrounding the coil as seen from the direction orthogonal to the side surface;
With
The end surface facing the cooler of the resin cover is pressing the heat dissipation sheet against the cooler around the side surface of the coil.
A reactor characterized by that.   The reactor according to claim 1, wherein a recess is provided between the periphery of the coil and the end surface of the resin cover when viewed from the cooler side.   The reactor according to claim 1 or 2, wherein the coil is formed in a substantially quadrangular prism shape, and one side surface of the quadrangular column is in contact with a cooler with a heat dissipation sheet interposed therebetween.

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