JP2015090912A - Reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing temperature rise of a coil on the side not in contact with a heat dissipation material, in a reactor.SOLUTION: In a reactor 2, one side face of a coil 4 wound around a core 3 is in contact with a heat dissipation material 5. The interval D2 between the inner peripheral surface 4a of the coil 4 on the side in contact with a heat dissipation material 5 and the outer peripheral surface 3a of the core 3, is narrower than the interval D1 on the opposite side of the heat dissipation material 5 across the central axis of the coil 4. With such a structure, the flux density is biased close to the heat dissipation material, and it is high on the side close to the heat dissipation material, and low on the side remote therefrom. Consequently, the calorific value of the coil is biased close to the heat dissipation material, and heating of the coil is suppressed at a part remote from the heat dissipation material.

Description

  The technology disclosed in this specification 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 heat sink may be attached to the reactor for cooling. Note that the heat radiating material may be a cooler in which a refrigerant flows, or may be a simple heat radiating plate (or a heat radiating sheet). In the latter case, the housing for fixing the reactor (the housing of the electronic device including the reactor) may function as a heat sink. For example, Patent Document 1 proposes that a heat radiating sheet is provided between the housing and the coil, and the heat of the coil is diffused to the housing through the heat radiating sheet.

JP2013-118208A

  As for the reactor in patent document 1, the heat radiating material is attached to one side (coil outer peripheral surface) of a coil. In such a reactor, there is a difference in heat dissipation efficiency between a portion of the coil close to the heat dissipation material and a portion far from the heat dissipation material. Naturally, the part away from the heat radiating material has lower heat radiating efficiency than the part close to the heat radiating material, and may become high temperature. This specification provides the technique which suppresses the heat_generation | fever of the coil in the side far from a heat-transfer material.

  Generally, the higher the magnetic flux density, the greater the amount of heat generated. This is because the magnetic flux leaking from the core and penetrating the coil winding increases, and the eddy current generated by the magnetic flux increases. In addition, the influence is large when there is a gap in the core inside the coil. Therefore, the technology disclosed in this specification increases the magnetic flux density in the vicinity of the coil at a portion close to the heat dissipation material, and instead reduces the magnetic flux density in the vicinity of the coil at a location far from the heat dissipation material. Suppresses coil heat generation.

  The reactor disclosed in this specification is a reactor in which one side surface of a coil wound around the core is in contact with the heat radiating material, and the inner peripheral surface of the coil and the outer peripheral surface of the core on the side in contact with the heat radiating material. Is narrower than the above-mentioned distance on the opposite side of the heat dissipating material across the central axis of the coil. In other words, the central axis of the core is biased toward the heat dissipation material with respect to the central axis of the coil. Therefore, the distribution of the magnetic flux density is also biased toward the heat radiating material, and the magnetic flux density is high on the side close to the heat radiating material and low on the side far from the heat radiating material. Accordingly, the amount of heat generated by the coil is biased toward the heat radiating material, and the coil heat generation at a portion far from the heat radiating material is suppressed.

  According to the technology disclosed in this specification, heat generation on the outer peripheral surface of the coil that is not in contact with the heat dissipation sheet can be suppressed. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a top view of the reactor of an Example. It is a typical side view of the reactor of an Example. It is sectional drawing of the reactor of the Example in the III-III line of FIG.

  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 a direct current of a battery, further converts it into an alternating current and supplies it to a motor in an electric vehicle. As shown in FIG. 1, the reactor 2 includes an annular core 3 described later and a coil 4 wound around the core 3. As shown in FIG. 2, the reactor 2 is attached to the housing 6 of the power control unit with the heat dissipating material 5 interposed therebetween. Here, the housing 6 serves as a cooler that dissipates the heat of the reactor 2. Heat generated from the reactor 2 is transmitted to the housing 6 by the heat radiating material 5. In each drawing, it should be noted that the housing 6 depicts only a portion attached to the reactor 2. A description of the power control unit and the voltage converter circuit is omitted. Further, the X axis direction coincides with the winding axis direction of the coil 4.

  The core 3 has an annular shape that is partially parallel. Bobbins 7 cover each of the parallel portions. The bobbin 7 includes two cylindrical core covers 8 that cover the parallel portions of the core 3, and two flange portions 9 that connect the two core covers 8. The flange portion 9 is connected to both ends of the cylindrical core cover 8 so that the two core covers 8 are parallel to each other. Two parallel portions of the core 3 are located inside the core cover 8. The core 3 is made of ferromagnetic iron, and the bobbin 7 is made of insulating resin. Further, as well represented in FIG. 3, the cross-sectional shape of the core 3 is a rectangle.

  The coil 4 is formed by winding a conducting wire 12 around the core cover 8. The two coils 4 are arranged in parallel. Although the reactor 2 geometrically has two coils 4, these coils 4 are constituted by a single conducting wire 12. That is, it corresponds electrically to one coil. In this embodiment, the conducting wire 12 is a flat wire, and the coil 4 is made by edgewise winding in which the wide surface of the flat wire is wound in the coil axial direction. The coil 4 has a quadrangular prism shape, and the outer peripheral surface is constituted by four planes. As will be described below, the heat dissipation material 5 is in close contact with one of the four planes of the outer peripheral surface of the coil 4.

  As shown in FIGS. 2 and 3, the heat dissipation material 5 is disposed between the coil 4 and the housing 6. The heat dissipating material 5 is a rubber-like sheet based on silicon, and has high thermal conductivity and high flexibility. An example of the heat dissipation material 5 is a Sarcon (registered trademark) sheet. The flexibility of the heat dissipating material 5 is about 20 to 100 Hs in terms of rubber hardness (JIS A). The upper surface of the heat dissipating material 5 is in contact with the coil 4 so as to cover the entire lower surface of the coil 4. The lower surface of the heat dissipation material 5 is in contact with the bottom surface of the housing 6.

  Support members 13 are attached to the four locations outside the flange portion 9 of the bobbin 7. Bolt holes are formed in the support member 13. The bobbin 7 is attached to the housing 6 with a bolt 14 through the support member 13. Due to the tightening force of the bolts 14, the heat dissipating material 5 is in close contact with the lower surface of the coil 4 and the bottom surface of the housing 6. Further, due to the flexibility of the heat radiating material 5, the heat radiating material 5 is also in close contact with the depression between the adjacent wound conductors of the coil 4. Therefore, heat conduction from the coil 4 to the housing 6 is promoted.

  The positional relationship between the core 3 and the coil 4 will be described. As shown in FIG. 3, the distance between the outer peripheral surface 3 a of the core 3 and the inner peripheral surface 4 a of the coil 4 is different between the side where the heat radiating material 5 of the coil 4 is in contact and the opposite side. The distance D2 on the side where the heat dissipating material 5 is in contact is narrower than the distance D1 on the opposite side across the winding axis of the coil 4. In other words, the central axis C1 in the cross-sectional shape of the core 3 is biased toward the side where the heat dissipating material 5 is disposed, rather than the central axis C2 in the cross-sectional shape of the coil 4. In FIG. 3, symbols D1 and D2 indicating the distance are given only to the left coil in the drawing, and symbols C1 and C2 showing the central axis are given only to the right coil in the drawing. Same arrangement. That is, as shown in FIG. 3, the two cores 3 arranged in parallel are similarly biased toward the side where the heat dissipating material 5 is disposed.

  Most of the magnetic flux density generated by the coil 4 passes through the inside of the core 3. Therefore, according to such a configuration, the distribution of the magnetic flux density inside the coil 4 is biased toward the heat radiating material 5, and the magnetic flux on the side where the heat radiating material 5 of the coil 4 is in contact (the side where the distance D <b> 2 is located). The density increases, and the magnetic flux density on the side opposite to the side on which the heat dissipating material 5 is in contact (the side on which the distance D1 is located) decreases. The amount of heat generated by the coil 4 depends on the magnitude of the magnetic flux density generated in the vicinity. Therefore, in the coil 4, the amount of heat generation increases on the side where the heat radiating material 5 is in contact with and decreases on the opposite side as compared with the configuration in which the coil and the core are arranged coaxially. Therefore, the upper surface of the coil 4 (the side far from the heat dissipating material 5) is less likely to generate heat than the lower surface of the coil 4 (the side close to the heat dissipating material 5). On the other hand, the lower surface of the coil 4 has a small distance D2, and therefore the amount of heat generated is higher than that of the other side surface of the coil 4. However, since the lower surface of the coil 4 is in contact with the heat radiating material 5, the heat generated here is efficiently transmitted to the housing 6 through the heat radiating material 5. Since the housing 6 has a function as a cooler, the heat transferred from the heat radiating material 5 is cooled by the housing 6. Therefore, the temperature of the coil 4 as a whole is prevented from partially rising.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. In the above-described embodiment, the cross-sectional shape of the coil 4 and the core 3 is preferably a substantially square shape, but may be other polygonal shapes or circular shapes. In addition, a refrigerant passage through which the refrigerant passes may be provided inside the housing 6. With this configuration, the efficiency of cooling the coil 4 can be further increased.

  Although not shown, the core 3 has a gap inside the coil 4. The gap is a gap that the core has in the axial direction. Note that the gap may be filled with an insulating material instead of a space. Around the gap, the magnetic flux lines are curved outward in the radial direction of the core 3 (outside of the core in a direction perpendicular to the central axis of the core). Therefore, the magnetic flux lines penetrating the winding of the coil 4 increase around the gap. The amount of magnetic flux lines penetrating the winding of the coil 4 increases as the distance between the coil 4 and the core 3 (the distance indicated by symbols D1 and D2 in FIG. 3) is closer. Magnetic field lines passing through the windings of the coil 4 generate eddy currents in the windings. The eddy current causes a loss of the coil, and the loss becomes heat energy to cause the coil to generate heat. The technology of the embodiment in which the distance D1 between the inner peripheral surface of the coil and the outer peripheral surface of the core on the side far from the heat sink 5 is wider than the distance D2 on the side close to the heat sink 5 is particularly suitable for a reactor in which the core has a gap inside the coil. It is valid.

  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: Core 3a: Outer peripheral surface 4: Coil 4a: Inner peripheral surface 5: Heat dissipating material 6: Housing 7: Bobbin 8: Core cover 9: Flange part 12: Conductor 13: Support member 14: Bolt C1: Core 3 Center axis C2: coil 4 center axis D1: distance between the inner peripheral surface of the coil 4 and the outer peripheral surface of the core 3 (the far side from the heat dissipation material)
D2: Distance between the inner peripheral surface of the coil 4 and the outer peripheral surface of the core 3 (side closer to the heat dissipation material)

Claims (1)

  A side surface of the coil wound around the core is a reactor that is in contact with the heat radiating material, and an interval between the inner peripheral surface of the coil and the outer peripheral surface of the core on the side in contact with the heat radiating material is A reactor that is narrower than the distance on the opposite side of the heat radiating material across the central axis of the reactor.

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