JP7205315B2 - reactor unit - Google Patents

Description

This specification discloses a reactor unit comprising two air-core coils.

2. Description of the Related Art There is known an electric vehicle in which the voltage of DC power supplied by a battery is boosted by a boost converter, and the boosted DC power is controlled by an inverter to drive a driving motor. The boost converter has a reactor. A reactor used in a boost converter requires a large inductance, and is made by winding a coil around an iron core.

In order to reduce the manufacturing cost of the reactor, it is advantageous to use an air-core reactor that does not use an iron core. However, the air-core reactor cannot obtain a large inductance, and a large current ripple occurs during operation of the boost converter, which may adversely affect batteries, capacitors, and the like. A large current ripple can cause overheating of batteries and capacitors, or a large current ripple can be a source of electromagnetic noise.

Patent Literature 1 discloses a technique for suppressing current ripple. In this technique, two boost converters are connected in parallel, and the switching elements connected to each reactance are turned on and off in different phases. According to this technique, since the current ripple can be suppressed, the inductance required for the reactor can be reduced and an air-core coil can be used.

JP 2017-143656 A

The technology described above enables the use of an air-core coil, thereby reducing the manufacturing cost of the reactor. However, two air-core coils are required, and compared to the case of using one iron-core coil, for example, when the volume for accommodating two air-core coils is one iron-core coil, If the device becomes larger than the volume, or if the amount of low-resistance metal (typically copper) required to form two air-core coils is one iron-core coil. may exceed the amount used. The present invention discloses a technology capable of reducing the volume of the device, reducing the amount of resources used, and preventing overheating of the air-core coils when two air-core coils are used.

In the technology disclosed in this specification, two air-core coils are unitized. In the reactor unit, two air-core coils are arranged in a positional relationship that satisfies the following relationship. (1) The winding axes of the two air-core coils are the same. (2) The direction of magnetic flux generated when two air-core coils are energized is opposite between one air-core coil and the other air-core coil.

Each air-core coil is housed in a metal case, and a metal plate forming part of the metal case is interposed between one air-core coil and the other air-core coil.

According to the above, the magnetic flux generated in one air-core coil and the magnetic flux generated in the other air-core coil cancel each other out, so that the DC magnetic flux propagating around can be reduced. Moreover, since it is housed in a metal case, it is possible to prevent AC magnetic flux from propagating around. Moreover, it can be efficiently cooled through the metal case, and is less likely to overheat.

FIG. 4 is a schematic exploded perspective view of the reactor unit of the embodiment (illustration of the lower heat transfer plate and the lower case lid is omitted). It is a figure explaining a winding direction typically. FIG. 3 is a diagram of two air-core coils that are not magnetically coupled (FIG. 3(1)) and two air-core coils that are magnetically coupled (FIG. 3(2)). 4 is a graph illustrating total volume and total resource usage; 1 is a circuit diagram of an example of a circuit in which two air-core coils are used; FIG. 4 is a graph showing temporal changes in the value of current flowing through an air-core coil;

FIG. 5 shows a power supply circuit that boosts the direct current supplied by the battery 20 with a boost converter and supplies the direct current to the high-voltage circuit 30 that operates on the boosted direct current. FIG. 5 shows a form using two boost converters 22A, 22B in parallel. The boost converters 22A and 22B have the same internal structure, and the suffixes A and B are omitted from the common description. The boost converter 22 includes a switch element 24 that turns on and off the current flowing through the coil (coil 6 in the case of 22A, coil 14 in the case of 22B), and a switch element 26 that is connected to a higher voltage side than that. there is A freewheeling diode is connected to each switch element. Note that the circuit of the boost converter itself is known, and detailed description thereof will be omitted. Also, in FIG. 5, components such as capacitors are omitted.

The switches 24A and 24B are turned on and off at different timings (phases). FIG. 6 shows the currents flowing through the coils 6 and 14 when the switches 24A and 24B are turned on and off 180 degrees out of phase. Each current repeats an increase period and a decrease period, but when one coil is in an increase period, the other coil is in a decrease period, and the total current value does not change with time. When the two coils 6 and 14 are connected in parallel, even if the inductance of each coil is small, the current ripple can be kept small and the generation of electromagnetic noise can be suppressed. An air-core coil can be used for each coil.

(1) of FIG. 3 shows a case where the air-core coils are arranged side by side, and shows a case where there is no substantial magnetic coupling between the air-core coils. In this case, the total volume of the two air-core coils is C1 (see FIG. 4), and the amount of copper required for the electric wire used as the coil is D1 (see FIG. 4), both of which are insufficient.

FIG. 1 schematically shows an exploded perspective view of a reactor unit of an embodiment that solves the above problem. The coils 6 and 14 are the same and can be used as the coil 6 or as the coil 14 by reversing the front and back. Reference numeral 10 in the figure denotes a metal case, which has an intermediate plate 10a inside and is divided into an upper chamber and a lower chamber.

The upper chamber accommodates the upper central heat transfer plate 8 , the coil 6 , and the upper heat transfer plate 4 , and is sealed with the upper cover 2 . In FIG. 1, for clarity of illustration, a lower central heat transfer plate (same as the upper central heat transfer plate 8), a lower surface side heat transfer plate (same as the upper surface side heat transfer plate 4), and a lower cover (same as upper cover 2) is omitted. The lower chamber accommodates the lower central heat transfer plate, the coil 14 and the lower heat transfer plate, and is sealed with a lower cover. The coils 6 and 14 are copper flat wires (the cross section of which has a flat rectangular shape) wound around the Z-axis, and the flat surfaces of the flat wires are parallel to the Z-axis. . The height of the coils 6 and 14 in the Z-axis direction is equal to the width of the rectangular copper wire in the Z-axis direction, and the coils 6 and 14 have a flat disc shape as a whole. A terminal 6a of the coil 6 passes through the hole 4a of the upper heat transfer plate 4 and extends from the opening 2a of the lid 2 to the outside of the case. The terminal 6b extends out of the case through an opening 10b of the case 10, the terminal 14a extends out of the case through an opening in the lower lid, and the terminal 14b extends out of the case through an opening 10c. An insulating bush (not shown) insulates between the opening and the terminal.

FIG. 2(1) shows a plan view of the coil 6. FIG. The illustration is simplified to show the direction of winding. When a current flows from point a to point b, a magnetic flux is generated toward the back of the paper. (2) indicates the winding direction and current flow direction of the coil 14. When a current flows from point a to point b, a magnetic flux is generated toward the front side of the paper. Points a in FIGS. (1) and (2) correspond to points a in FIG. 5, and the same applies to points b. As is apparent from FIGS. 2(1) and 2(2), the coils 6 and 14 are placed in a relationship in which the directions of the magnetic fluxes generated when energized are opposite to each other. There is a relationship in which mutual magnetic fluxes cancel each other out.

FIG. 2(3) shows the case where the winding directions of the coils 6 and 14 are the same. In this case, if wiring is performed so that point a in FIGS. 2(1) and 2(3) becomes point a in FIG. 5 and point b becomes point b in FIG.

The coils 6 and 14 of this embodiment are formed by winding a flat wire having a rectangular cross section flatwise, and can be wound without gaps, so that the coil volume can be reduced. In addition, since the flat coils are stacked in two stages as a whole, the dead space can be small, and as shown in FIG. can be Additionally, the amount of copper required to form the coil can be reduced to D2. Since C1>C2 and D1>D2, the advantage of unitization can be obtained.

Metal plates are in contact with both sides of each flat coil. Since there is no iron core, the outer shape of the coil is simple, and the flat surface of the flat coil can be uniformly in contact with the metal case. The flat coil can be efficiently cooled from both sides. In addition, the coil can be accommodated in the metal case without difficulty, and the case can play the role of maintaining the external shape of the coil. It is not necessary to cover the periphery of the coil with mold resin to protect it as in the conventional art. A metal case can replace the resin mold. In addition, the windings of the coil are coated with an insulating coating, so that the coil does not short-circuit with the metal case.

According to the coils of the reactor unit of this embodiment, each coil is housed in a metal case, which can prevent an AC magnetic field from leaking out of the case. Moreover, since the magnetic fluxes of the two coils cancel each other out, the DC magnetic field leaking out of the case is also reduced. Note that the intermediate plate 10a of the case 10 may be provided with a through hole. The center of the coil is hollow, and even if a hole is formed in the portion of the intermediate plate 10a facing the hollow portion, the cooling performance does not deteriorate. The outer surface of the case 10 is closed, and even if a through hole is formed in the intermediate plate, noise and the like will not leak out.

Although specific examples of the present invention have been described in detail above, 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 in the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims as of the filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

2: lid 4: heat transfer plate 6: air core coil 8: heat transfer plate 14: air core coil 20: battery 22: boost converter 30: high voltage circuit

Claims (1)

A reactor unit used in two boost converters connected in parallel,
Each said boost converter comprises:
two switch elements connected in series;
An air-core coil having an a-end and a b-end, the a-end being connected to the input end of the boost converter and also being connected to the a-end of the air-core coil of the other boost converter, and the b-end being an air-core coil connected to the midpoint of the series connection of the two switch elements;
and
The reactor unit includes the air-core coils of the two boost converters,
The two air-core coils are wound in such a relationship that the winding axes of the air-core coils match and the direction from the end a to the end b is opposite when viewed from one end of the winding axis. has been
Each air-core coil is housed in a metal case,
A reactor unit, wherein a metal plate forming the metal case is interposed between one air-core coil and the other air-core coil.

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