Coil assembly

Abstract

A coil assembly (100, 101, 102) comprises a plurality of coil layers (S1, S2, S11, S12, S21, S22) laminated in a lamination direction, the coil layers each having a plurality of planar coils (1 to 8, 1 to 10, 1 to 12) wound in a planar direction intersecting the lamination direction and connected in parallel to each other. The plurality of coil layers constitute a plurality of coil parts (a to d, a to e) each composed of at least one planar coil, the plurality of coil parts being connected in parallel to each other. At least some of the plurality of coil layers include a first-pitch strand group in which the pitch between adjacent strands is a first pitch, and a second-pitch strand group in which the pitch between adjacent strands is a second pitch greater than the first pitch. The first-pitch strand group is positioned further outside in the width direction of the coil width of the coil layer than the second-pitch strand group.

Description

Coil Assembly CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-5765, filed on January 18, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a coil assembly.

[0003] Conventionally, coil assemblies including multiple coil layers each having a planar coil have been used. When such a coil assembly is used with a magnetic body such as a magnetic sheet, the self-inductance of each planar coil varies depending on the distance from the magnetic body. As a result, in a configuration in which multiple coil sections, each consisting of one or multiple planar coils connected in series, are connected in parallel, differences in impedance may occur between the coil sections. Such differences in impedance can cause current concentration in some coil sections, resulting in increased losses. Therefore, a technology has been proposed to suppress differences in impedance between coil sections by increasing the line length of the planar coil in coil layers that are farther away from the magnetic body (see Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2019-186303

[0005] In the coil assembly described above, the mutual inductance between the coil parts affects the impedance of each coil part. However, the above-described technique of adjusting the line length of the planar coil according to the distance from the magnetic body does not take into consideration the mutual inductance between the coil parts, and there is still a risk of the above-described difference in impedance between the coil parts.

[0006] This problem is not limited to configurations that use a magnetic material together with a coil assembly, but can also occur in configurations that do not use a magnetic material. For example, it can also occur in a coil assembly having a configuration in which planar coils included in different coil layers are connected in series to form a single coil section, and multiple such coil sections are connected in parallel. For this reason, a technology that can further suppress current bias between coil sections is desired.

[0007] The present disclosure can be realized in the following forms.

[0008] According to one aspect of the present disclosure, there is provided a coil assembly comprising a plurality of coil layers stacked in a stacking direction, each having a plurality of planar coils wound in a planar direction intersecting the stacking direction and connected in parallel, the plurality of coil layers comprising a plurality of coil sections each formed by at least one of the planar coils and connected in parallel, at least some of the plurality of coil layers including a first pitch wire set in which adjacent wires are spaced apart at a first pitch and a second pitch wire set in which adjacent wires are spaced apart at a second pitch larger than the first pitch, the first pitch wire set being located outward in the coil width direction of the coil layer than the second pitch wire set.

[0009] In this coil assembly, at least some of the coil layers include first-pitch wire sets in which adjacent wires are spaced a first pitch apart, and second-pitch wire sets in which adjacent wires are spaced a second pitch apart that is larger than the first pitch, and the first-pitch wire sets are located outward in the width direction from the second-pitch wire sets. This reduces the mutual inductance between the coil portions located inside in the width direction compared to the mutual inductance between the coil portions located outside in the width direction, thereby preventing a difference in impedance between the coil portions located inside in the width direction and the coil portions located outside in the width direction, and preventing current bias between the coil portions.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an exploded plan view showing a schematic configuration of a coil assembly according to one embodiment of the present disclosure, Fig. 2 is a block diagram showing a schematic configuration of a contactless power supply system to which the coil assembly of the first embodiment is applied, Fig. 3 is an explanatory diagram showing an equivalent circuit of the coil assembly of the first embodiment, Fig. 4 is a partial cross-sectional view of the coil assembly of the first embodiment, Fig. 5 is an explanatory diagram for explaining the impedance of each coil portion in the coil assembly of the first embodiment, Fig. 6 is a partial cross-sectional view of the coil assembly of Comparative Example 1, and Fig. 7 is an explanatory diagram for explaining the impedance of each coil portion in the coil assembly of Example 1 and Comparative Example 1. FIG. 8 is an explanatory diagram showing the results of numerical analysis of various parameters related to the impedance of the coil assembly of the second embodiment, FIG. 9 is an explanatory diagram showing the equivalent circuit of the coil assembly of the second embodiment, FIG. 10 is a partial cross-sectional view of the coil assembly of Comparative Example 2, FIG. 11 is an explanatory diagram showing the results of numerical analysis of various parameters related to the impedance of the coil assemblies of Example 2 and Comparative Example 2, FIG. 12 is an exploded plan view showing the general configuration of the coil assembly of the third embodiment, and FIG. 13 is a partial cross-sectional view of the coil assembly of the third embodiment.

[0011] A. First Embodiment: A1. Overall Configuration: As shown in FIG. 1 , a coil assembly 100 of this embodiment includes a first coil layer S1 and a second coil layer S2. The coil assembly 100 as a whole forms a coil (inductor). In this embodiment, the coil assembly 100 is used in a contactless power transfer system 500 shown in FIG. 2. A detailed configuration of the coil assembly 100 will be described later. The contactless power transfer system 500 is a system for supplying power supplied from a power supply device 300 to a load device 300A electrically connected to the power receiving device 200A by contactlessly transmitting power from a power transmitting device 200 to a power receiving device 200A.

[0012] As shown in FIG. 2, the contactless power supply system 500 includes a resonant circuit 150 including the coil assembly 100, a power transmitting device 200 including the resonant circuit 150, a power transmitting output circuit 210, a power receiving side coil assembly 100A, a resonant circuit 150A including the power receiving side coil assembly 100A, a power receiving device 200A including the resonant circuit 150A, and a rectifier circuit 210A.

[0013] The resonant circuit 150 has a configuration in which an inductor formed by the coil assembly 100 and a capacitor (not shown) are connected in series. The power transmitting device 200 includes the resonant circuit 150, and uses power supplied from the power transmitting output circuit 210 to supply power to the power receiving device 200A in a wireless manner.

[0014] The power transmission output circuit 210 includes an inverter circuit and a filter circuit (not shown), converts the DC power supplied from the power supply device 300 into AC power of a predetermined operating frequency, and also removes noise components from the AC power before supplying it to the power transmission device 200.

[0015] The coil assembly 100 includes a magnetic body 110 and a shield member 112. The magnetic body 110 is a thin plate-shaped member made of a magnetic material, and in this embodiment, is made of ferrite. As shown in FIG. 2 , the magnetic body 110 and the shield member 112 are disposed on the opposite side of the coil assembly 100 from the side facing the power receiving side coil assembly 100A. The magnetic body 110 more efficiently directs the magnetic flux generated in the coil assembly 100 toward the power receiving side coil assembly 100A, increasing the magnetic flux penetrating the power receiving side coil assembly 100A.

[0016] The shield member 112 is a plate-shaped member made of aluminum or an aluminum alloy. The shield member 112 has a shielding function to prevent magnetic flux generated in the coil assembly 100 from escaping to the outside. The shield member 112 also dissipates heat generated in the coil assembly 100. Note that the shield member 112 may be made of copper or other metal plates instead of aluminum or an aluminum alloy. Other detailed configurations of the coil assembly 100 will be described later. Note that the coil assembly 100 does not necessarily have to include the magnetic body 110 and the shield member 112.

[0017] The power receiving side coil assembly 100A is an inductor that constitutes part of the resonant circuit 150A included in the power receiving device 200A. The configuration of the power receiving side coil assembly 100A is the same as the configuration of the coil assembly 100, which will be described in detail later. Like the coil assembly 100, the power receiving side coil assembly 100A includes a power receiving side magnetic body 110A and a shielding member 112A. The power receiving side magnetic body 110A has the same configuration as the magnetic body 110 described above. Furthermore, the shielding member 112A has the same configuration as the shielding member 112 described above.

[0018] The power receiving device 200A includes a resonant circuit 150A in which an inductor formed by the power receiving side coil assembly 100A and a capacitor (not shown) are connected in series. While power is being supplied to the power transmitting device 200, the resonant circuit 150 in the power transmitting device 200 resonates at a predetermined operating frequency, generating a magnetic flux. This magnetic flux penetrates the power receiving side coil assembly 100A of the power receiving device 200A, and this magnetic flux generates an induced electromotive force in the power receiving device 200A, thereby transmitting and receiving power. The rectifier circuit 210A includes a bridge circuit and a smoothing capacitor (not shown), and converts AC power output from the power receiving device 200A into DC power and supplies it to the load device 300A.

[0019] The contactless power supply system 500 having the above-described configuration may be used, for example, by disposing the power transmission output circuit 210 and the power transmitting device 200 underground or on the ground surface, and mounting the power receiving device 200A, the rectifier circuit 210A, and the load device 300A on a mobile body such as an electric vehicle, to supply power to the moving mobile body. In such a configuration, the load device 300A corresponds to a battery, a motor, or the like mounted on the mobile body.

[0020] A2. Detailed Configuration of Coil Assembly 100: In the coil assembly 100, the two coil layers S1 and S2 shown in FIG. 1 are stacked along the Z axis. Specifically, the first coil layer S1 and the second coil layer S2 are stacked in the +Z direction in that order. In other words, the Z direction corresponds to the "stacking direction" in this disclosure. Note that FIG. 1 depicts mutually orthogonal X, Y, and Z axes, and these X, Y, and Z axes correspond to the X, Y, and Z axes in other drawings. Also, the direction from the power transmitting device 200 toward the power receiving device 200A shown in FIG. 2 corresponds to the +Z direction. Note that the magnetic body 110 and the shielding member 112 are omitted from FIG. 1.

[0021] Each coil layer S1, S2 includes a plurality of planar coils made of wire wound in the XY plane. In this embodiment, the wire is made of copper foil. The number of planar coils included in each coil layer S1, S2 is four, i.e., an even number. Each coil layer S1, S2 includes an insulator such as prepreg sandwiched between coil patterns of planar coils made of copper foil. The planar coil located on the outermost side (surface side) of the coil assembly 100 in the Z direction may be covered with, for example, solder resist.

[0022] The first coil layer S1 includes a first planar coil 1, a second planar coil 2, a third planar coil 3, and a fourth planar coil 4. The second coil layer S2 includes a fifth planar coil 5, a sixth planar coil 6, a seventh planar coil 7, and an eighth planar coil 8. Each of the planar coils 1 to 8 has one turn. Note that the number of turns in each of the planar coils 1 to 8 is not limited to one and may be any number.

[0023] Coil assembly 100 has four through-hole vias v1, v2, v3, and v4 formed through each of coil layers S1 and S2. Fourth planar coil 4 and fifth planar coil 5 each have one end connected to through-hole via v1. Third planar coil 3 and sixth planar coil 6 each have one end connected to through-hole via v2. Second planar coil 2 and seventh planar coil 7 each have one end connected to through-hole via v3. First planar coil 1 and eighth planar coil 8 each have one end connected to through-hole via v4.

[0024] First coil layer S1 has a connection terminal t1 in its central portion. Second coil layer S2 has a connection terminal t2 in its central portion. The other ends of first planar coil 1, second planar coil 2, third planar coil 3, and fourth planar coil 4 are connected to connection terminal t1. The other ends of fifth planar coil 5, sixth planar coil 6, seventh planar coil 7, and eighth planar coil 8 are connected to connection terminal t2. Connection terminal t1 and connection terminal t2 are exposed on the −Z direction end surface and the +Z direction end surface of coil assembly 100, and are connected to power transmission device 200 via a capacitor (not shown).

[0025] As shown in FIG. 3 , the first planar coil 1 and the eighth planar coil 8 are connected in series to form coil portion a. Similarly, the second planar coil 2 and the seventh planar coil 7 are connected in series to form coil portion b, the third planar coil 3 and the sixth planar coil 6 are connected in series to form coil portion c, and the fourth planar coil 4 and the fifth planar coil 5 are connected in series to form coil portion d. These four coil portions a to d are connected in parallel to each other. Hereinafter, the current flowing through coil portion a will be referred to as current Ia. Similarly, the current flowing through coil portion b will be referred to as Ib, the current flowing through coil portion c as Ic, and the current flowing through coil portion d as Id. Connecting the four coil portions a to d in parallel in this way allows each wire to be thin, suppressing the generation of eddy currents and improving power transmission efficiency. Note that magnetic body 110 and shield member 112 are omitted from FIG. 3 .

[0026] 4 shows a cross section taken along line IV-IV in FIG. 1. As shown in FIG. 4, among the wires adjacent to each other in the direction along the X-Y plane (hereinafter referred to as the "planar direction") in the first coil layer S1, the wire pair of the first planar coil 1 and the second planar coil 2, which are two wire pairs located on the outer side of the coil width of the first coil layer S1, and the wire pair of the third planar coil 3 and the fourth planar coil 4, are both arranged so that the pitch between the wires is a first pitch p1. That is, the wire pair of the first planar coil 1 and the second planar coil 2, and the wire pair of the third planar coil 3 and the fourth planar coil 4 each correspond to a "first pitch wire pair" in the present disclosure. The "pitch between wires" refers to the distance in the planar direction between the center of each wire in the width direction and the center of the adjacent wire in the width direction. Furthermore, "coil width" refers to the overall width of the wire group constituting one turn, more specifically, the distance between the inner end of the wire that is located on the innermost side in the planar direction and the outer end of the wire that is located on the outermost side in the planar direction among the wire group constituting one turn. Furthermore, "outside in the width direction" refers to the region of the wire group constituting one turn that is farther away from the center position of the coil width, or in this embodiment, the region that is farther away from the center position Ct1.

[0027] On the other hand, among the wires adjacent in the planar direction in the first coil layer S1, the two wire pairs located on the inner side of the coil width of the first coil layer S1—in this embodiment, the two wire pairs closest to the center position Ct1 of the coil width, that is, the wire pair of the second planar coil 2 and the wire pair of the third planar coil 3—are arranged so that the pitch between the wires is the second pitch p2. That is, the wire pair of the second planar coil 2 and the wire pair of the third planar coil 3 corresponds to the “second pitch wire pair” in this disclosure. “Inner side in the width direction” refers to the region of the wire group constituting one turn that is closer to the center position of the coil width, and in this embodiment, the region that is closer to the center position Ct1. As described above, in this embodiment, the first pitch wire pair is located on the outer side of the coil width of the first coil layer S1 than the second pitch wire pair. The effects achieved by having such a positional relationship between the first pitch wire pair and the second pitch wire pair will be described later.

[0028] The wire groups constituting the second coil layer S2 also have the same positional relationship as those in the first coil layer S1. That is, among the wires adjacent in the planar direction in the second coil layer S2, the wire pairs of the fifth planar coil 5 and the sixth planar coil 6, which are two wire pairs located on the outer side of the coil width of the second coil layer S2, and the wire pairs of the seventh planar coil 7 and the eighth planar coil 8, are both arranged with a first pitch p1 between the wires and correspond to first-pitch wire pairs. On the other hand, the wire pairs of the sixth planar coil 6 and the seventh planar coil 7, which are two wire pairs located on the inner side of the coil width of the second coil layer S2, are arranged with a second pitch p2 between the wires and correspond to second-pitch wire pairs. Note that the center positions Ct1 of the coil widths of the coil layers S1 and S2 coincide with each other.

[0029] The second pitch p2 is larger than the first pitch p1. The spacing between the wires constituting the second pitch wire set is larger than the spacing between the wires constituting the first pitch wire set. The "spacing between wires" refers to the width of the space formed between two adjacent wire sets. The reason for this configuration will be explained with reference to Figures 3 and 5.

[0030] The equivalent circuit shown in Figure 3 is represented by equations 1-a, 1-b, 1-c, and 1-d shown in the top row of Figure 5. In each of equations 1-a to 1-d, V is the terminal voltage of coil sections a to d, Ra to Rd are the resistances of each coil section a to d, La to Ld are the self-inductances of each coil section a to d, Mxy (x = a to d, y = a to d) are the mutual inductances between coil section x and coil section y, and ω is the angular frequency. Note that Ia to Id are the currents flowing through each coil section a to d, as described above.

[0031] In the four coil sections a to d connected in parallel, when there is no current imbalance, Ia = Ib = Ic = Id. Therefore, equations 1-a to 1-d can be transformed into equations 2-a to 2-d in the second row. Here, by replacing the "sum of self-inductance and mutual inductance" in equations 2-a to 2-d with Sa, Sb, Sc, and Sd (hereinafter referred to as "inductance parameters") as in equations 3-a to 3-d in the third row, equations 4-a to 4-d in the fourth row are obtained. In an ideal state where there is no current imbalance in the four coil sections a to d, the left sides of equations 4-a to 4-d are all equal, "V / Ia." In this way, to achieve a state where there is no current imbalance, it is sufficient for the resistances to satisfy Ra = Rb = Rc = Rd, and the inductance parameters to satisfy Sa = Sb = Sc = Sd.

[0032] In this embodiment, the resistors Ra to Rd are made of wires of the same thickness in each of the coil sections a to d, and the wire lengths of the coil sections a to d are equal to each other. Specifically, as shown in FIG. 1 , the coil section a is configured by connecting in series the first planar coil 1 wound radially outward in the first coil layer S1 and the eighth planar coil 8 wound radially inward in the second coil layer S2. On the other hand, the coil section d is configured by connecting in series the fourth planar coil 4 wound radially inward in the first coil layer S1 and the fifth planar coil 5 wound radially outward in the second coil layer S2. By configuring the coil sections a and d in this manner, the wire lengths of the coil sections a and d are made equal to each other.

[0033] Similarly, coil portion b is configured by connecting in series second planar coil 2 wound radially outward in first coil layer S1 with seventh planar coil 7 wound radially inward in second coil layer S2. On the other hand, coil portion c is configured by connecting in series third planar coil 3 wound radially inward in first coil layer S1 with sixth planar coil 6 wound radially outward in second coil layer S2. By configuring coil portions b and c in this manner, the wire path lengths of coil portions b and c are made equal. Note that the wire path lengths of coil portions a and d are configured to be equal to the wire path lengths of coil portions b and c.

[0034] In this embodiment, the self-inductances La to Ld of the inductance parameters Sa to Sd are made uniform by using the same wire diameter and winding the same number of turns in each of the coil sections a to d. However, the mutual inductance between two coil sections that are closer to each other is greater than the mutual inductance between two coil sections that are farther apart. More specifically, the distance between coil section b and coil section c is smaller than the distance between coil section a and coil section d. That is, the mutual inductance Mbc between coil section b and coil section c is greater than the mutual inductance Mad between coil section a and coil section d. Therefore, the inductance parameters Sb and Sc that include a larger mutual inductance Mbc in their formulas are greater than the inductance parameters Sa and Sd that include a smaller mutual inductance Mad in their formulas. In this way, differences can occur among the inductance parameters Sa to Sd.

[0035] Therefore, in this embodiment, the above-described pitch differences cause differences in mutual inductance Mxy (x = a to d, y = a to d), and these differences suppress the differences in the above-described inductance parameters Sa to Sd. Specifically, in first coil layer S1, second pitch p2 between the wires of second planar coil 2 and the wires of third planar coil 3 is made larger than first pitch p1 between the wires of first planar coil 1 and the wires of second planar coil 2 and between the wires of third planar coil 3 and the wires of fourth planar coil 4, thereby reducing mutual inductance Mbc and suppressing the differences in inductance parameters Sa to Sd. This suppresses differences in impedance among coil portions a to d and reduces losses due to current concentration in specific coil portions.

[0036] Similarly, in second coil layer S2, the second pitch p2 between the wires of sixth planar coil 6 and seventh planar coil 7 is made larger than the first pitch p1 between the wires of fifth planar coil 5 and sixth planar coil 6 and the first pitch p1 between the wires of seventh planar coil 7 and eighth planar coil 8, thereby reducing mutual inductance Mbc and suppressing differences in inductance parameters Sa to Sd. This suppresses differences in impedance among coil portions a to d in second coil layer S2 as well, thereby suppressing losses due to current concentration in specific coil portions.

[0037] In the coil assembly 100 of this embodiment, the first pitch p1 and the second pitch p2 are adjusted so that the inductance parameters Sa to Sd, i.e., the sums of the self-inductance and the mutual inductance, are equal to each other. Note that the phrase "the sums of the self-inductance and the mutual inductance are equal to each other" does not necessarily mean that the sums are exactly equal, but has a broader meaning that also includes cases where the relationship between the sums of the self-inductance and the mutual inductance can reduce the difference in inductance parameters between the coil sections a to d compared to a configuration in which the first pitch p1 and the second pitch p2 are equal to each other.

[0038] A3. Examples: The coil assembly 100 of the first embodiment shown in Fig. 4 was numerically analyzed as Example 1, and the coil assembly 900 of Comparative Example 1 shown in Fig. 6 was also numerically analyzed. Then, as shown in Fig. 7, the mutual inductance Mbc and inductance parameters Sa to Sd of these coil assemblies 100 and 900 were numerically analyzed to confirm their effects.

[0039] In Example 1 shown in FIG. 4, the distance from the central axis Cu1 (an axis extending parallel to the Z axis from the center position when viewed in the Z direction) of each coil layer S1, S2 to the central position Ct1 was 20 mm (millimeters). The wire thickness was 300 μm (micrometers), and the wire width was 300 μm. The coil width was 6 mm. As shown in FIG. 7, the first pitch p1 was 0.9 mm, and the second pitch p2 was 4.5 mm.

[0040] The thickness of the magnetic body 110 and the thickness of the shield member 112 were each 1 mm. The magnetic body 110 was made of ferrite. The planar coils constituting each of the coil layers S1 and S2, the magnetic body 110, and the shield member 112 each had a circular shape in plan view. The radius of the magnetic body 110 and the radius of the shield member 112 were each 30 mm. A current of 1 A was passed through the coil assembly 100 having the above configuration at a frequency of 85 kHz.

[0041] On the other hand, the coil assembly 900 of Comparative Example 1 differs from the coil assembly 100 of Example 1 in that the first pitch p1 and the second pitch p2 are both 1.9 mm, but the other configurations are the same.

[0042] As shown in Figure 7, by making the second pitch p2 larger than the first pitch p1, the mutual inductance Mbc is reduced. This allows the inductance parameters Sb and Sc to be smaller, thereby suppressing the differences between the inductance parameters Sa to Sd. As a result, the differences between the currents Ia to Id are reduced, and the AC resistance R of the coil assembly 100 in Example 1 is kept lower than that in Comparative Example 1.

[0043] The coil assembly 100 of the first embodiment described above includes a first pitch wire set in which the pitch between adjacent wires is a first pitch p1, and a second pitch wire set in which the pitch between adjacent wires is a second pitch p2 that is larger than the first pitch p1, and the first pitch wire set is located outward in the width direction from the second pitch wire set. This makes it possible to reduce the mutual inductance between the coil portions located inside in the width direction compared to the mutual inductance between the coil portions located outside in the width direction, thereby suppressing the occurrence of an impedance difference between the coil portions located inside in the width direction and the coil portions located outside in the width direction and suppressing current bias between the coil portions.

[0044] In addition, in each coil section a to d, the planar coil wound radially inward and the planar coil wound radially outward are connected in series, thereby suppressing differences in the wire path length between the coil sections and suppressing differences in impedance between the coil sections.

[0045] Furthermore, the number of planar coils constituting each of the coil layers S1 and S2 is "4," i.e., an even number, and the second pitch wire set is composed of the wire set of the two wires closest to the center position of the coil width, wires 2 and 3. Therefore, in a coil assembly having a coil layer composed of an even number of planar coils, it is possible to suppress current bias between the coil portions.

[0046] Furthermore, the sum of the self-inductance and the mutual inductance is equal among the coil sections a to d, so that the occurrence of differences in impedance among the coil sections a to d can be suppressed.

[0047] B. Second Embodiment: A coil assembly 101 of the second embodiment shown in Figure 8 differs from the coil assembly 100 of the first embodiment in that the number of planar coils constituting each coil layer is "5", i.e., an odd number, but the other configurations are similar. In the coil assembly 101, the same components as those in the coil assembly 100 are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0048] B1. Detailed Configuration of Coil Assembly 101: FIG. 8 shows a cross section of coil assembly 101 at a position similar to the cross section IV-IV in FIG. 1 . As shown in FIG. 8 , coil assembly 101 includes a first coil layer S11 and a second coil layer S12 stacked on top of each other. First coil layer S11 includes a first planar coil 1, a second planar coil 2, a third planar coil 3, a fourth planar coil 4, and a fifth planar coil 5. Second coil layer S12 includes a sixth planar coil 6, a seventh planar coil 7, an eighth planar coil 8, a ninth planar coil 9, and a tenth planar coil 10. Each of planar coils 1 to 10 has one turn. Note that the number of turns in each of planar coils 1 to 10 is not limited to one and may be any number.

[0049] In each of the coil layers S11 and S12, the center position Ct2 of the coil width is the same. In this embodiment, the third planar coil 3 of the first coil layer S11 and the eighth planar coil 8 of the second coil layer S12 are both located at the center position Ct2.

[0050] As shown in FIG. 9 , in this embodiment, first planar coil 1 and tenth planar coil 10 are connected in series to form coil portion a. Similarly, second planar coil 2 and ninth planar coil 9 are connected in series to form coil portion b, third planar coil 3 and eighth planar coil 8 are connected in series to form coil portion c, fourth planar coil 4 and seventh planar coil 7 are connected in series to form coil portion d, and fifth planar coil 5 and sixth planar coil 6 are connected in series to form coil portion e. These five coil portions a to e of the fifth planar coil are connected in parallel to each other. Hereinafter, the current flowing through coil portion a will be referred to as current Ia, the current flowing through coil portion b as Ib, the current flowing through coil portion c as Ic, the current flowing through coil portion d as Id, and the current flowing through coil portion e as Ie.

[0051] In the present embodiment, in the first coil layer S11, two wire pairs located on the outer side of the coil width of the first coil layer S11, that is, the wire pair of the first planar coil 1 and the wire pair of the second planar coil 2, and the wire pair of the fourth planar coil 4 and the wire pair of the fifth planar coil 5, are arranged so that the pitch between the wires is a first pitch p1 and correspond to first pitch wire pairs. Similarly, in the second coil layer S12, two wire pairs located on the outer side of the second coil layer S12 in the width direction, that is, the wire pair of the sixth planar coil 6 and the wire pair of the seventh planar coil 7, and the wire pair of the ninth planar coil 9 and the tenth planar coil 10, are arranged so that the pitch between the wires is a first pitch p1 and correspond to first pitch wire pairs.

[0052] On the other hand, in the first coil layer S11, two wire pairs located on the inner side of the first coil layer S11 in the width direction, that is, the wire pair of the second planar coil 2 and the wire pair of the third planar coil 3, and the wire pair of the third planar coil 3 and the wire pair of the fourth planar coil 4, are each arranged so that the pitch between the wires is the second pitch p2 and correspond to the second pitch wire pairs. Similarly, in the second coil layer S12, two wire pairs located on the inner side of the second coil layer S12 in the width direction, that is, the wire pair of the seventh planar coil 7 and the wire pair of the eighth planar coil 8, and the wire pair of the eighth planar coil 8 and the wire pair of the ninth planar coil 9, are each arranged so that the pitch between the wires is the second pitch p2 and correspond to the second pitch wire pairs.

[0053] B2. Example: The coil assembly 101 of the second embodiment shown in Fig. 8 was numerically analyzed as Example 2, and the coil assembly 901 of Comparative Example 2 shown in Fig. 10 was also numerically analyzed. Then, as shown in Fig. 11, the mutual inductances Mbc, Mcd, Mbd and inductance parameters Sa to Se of these coil assemblies 101 and 901 were numerically analyzed to confirm their effects.

[0054] 11 , in Example 2, the first pitch p1 was 0.6 mm and the second pitch p2 was 2.25 mm. On the other hand, in Comparative Example 2, the first pitch p1 and the second pitch p2 were both 1.425 mm. The other configurations were the same as those used in the numerical analysis of the first embodiment.

[0055] 11, by making the second pitch p2 larger than the first pitch p1, the mutual inductances Mbc, Mcd, and Mbd are smaller. This allows the inductance parameters Sb, Sc, and Sd to be smaller, thereby minimizing the differences in the inductance parameters Sa to Se. As a result, the differences in the currents Ia to Ie are smaller, and the AC resistance R of the coil assembly 101 in Example 2 is kept lower than that in Comparative Example 2.

[0056] In the coil assembly 101 of the second embodiment described above, the number of planar coils constituting each of the coil layers S11 and S12 is "5," i.e., an odd number. In the coil assembly 101 having a coil layer composed of an odd number of planar coils, current bias between the coil portions can be suppressed, as in the first embodiment.

[0057] C. Third Embodiment: A coil assembly 102 of a third embodiment shown in Figures 12 and 13 differs from the coil assembly 100 of the first embodiment in that it includes a housing 120, but is otherwise similar in configuration. In the coil assembly 102, the same components as those in the coil assembly 100 are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0058] 12 , coil assembly 102 includes a first coil layer S21 and a second coil layer S22 stacked on top of each other. First coil layer S21 includes a first planar coil 1, a second planar coil 2, a third planar coil 3, a fourth planar coil 4, a fifth planar coil 5, and a sixth planar coil 6. Second coil layer S12 includes a seventh planar coil 7, an eighth planar coil 8, a ninth planar coil 9, a tenth planar coil 10, an eleventh planar coil 11, and a twelfth planar coil 12. The number of turns in each of planar coils 1 to 12 is 1.5. Note that the number of turns in each of planar coils 1 to 12 is not limited to 1.5 and may be any number.

[0059] Coil assembly 102 has, in its center, four through-hole vias v21, v22, v23, v24, v25, and v26 that penetrate each of coil layers S21 and S22. Sixth planar coil 6 and seventh planar coil 7 each have one end connected to through-hole via v21. Fifth planar coil 5 and eighth planar coil 8 each have one end connected to through-hole via v22. Fourth planar coil 4 and ninth planar coil 9 each have one end connected to through-hole via v23. Third planar coil 3 and tenth planar coil 10 each have one end connected to through-hole via v24. Second planar coil 2 and eleventh planar coil 11 each have one end connected to through-hole via v25. First planar coil 1 and twelfth planar coil 12 each have one end connected to through-hole via v26. In this way, each coil section is formed by connecting two planar coils, each with 1.5 turns, in series, resulting in a total of three turns. In the following description, the first turn of each coil section will be referred to as the "first turn T1," the second turn as the "second turn T2," and the third turn as the "third turn T3." In this embodiment, the "coil width" refers to the overall width of the wire group constituting each turn; more specifically, the distance between the inner end of the wire positioned innermost in the planar direction and the outer end of the wire positioned outermost in the planar direction among the wire groups constituting each turn. Furthermore, the center positions Ct21 of the coil widths of the first turn T1 and the third turn T3 coincide with each other. The center position Ct22 of the coil width of the second turn T2 is the center position Ct22.

[0060] First coil layer S21 includes connection terminal portion t21. Second coil layer S22 includes connection terminal portion t22. The other ends of first planar coil 1, second planar coil 2, third planar coil 3, fourth planar coil 4, fifth planar coil 5, and sixth planar coil 6 are connected to connection terminal portion t21. The other ends of seventh planar coil 7, eighth planar coil 8, ninth planar coil 9, tenth planar coil 10, eleventh planar coil 11, and twelfth planar coil 12 are connected to connection terminal portion t2. Connection terminal portion t21 and connection terminal portion t22 are exposed on the −Z direction end surface and the +Z direction end surface of coil assembly 102 and are connected to power transmission device 200 via a capacitor (not shown).

[0061] 13 shows a cross section taken along line XIII-XIII in FIG. 12 . As shown in FIG. 13 , in this embodiment, the wires of the third planar coil 3 and the wires of the fourth planar coil 4, which are two wire pairs located on the inner side in the width direction in each of the first turn T1 and the second turn T2, are arranged so that the pitch between the wires is the second pitch p2, and correspond to a second pitch wire pair. Similarly, the wires of the ninth planar coil 9 and the wires of the tenth planar coil 10, which are two wire pairs located on the inner side in the width direction in the third turn T3, are arranged so that the pitch between the wires is the second pitch p2, and correspond to a second pitch wire pair. Note that in this embodiment, the “inner side in the width direction” refers to the region closer to the center position Ct21 in the first turn T1 and the third turn T3, and to the region closer to the center position Ct22 in the second turn T2.

[0062] On the other hand, in each of the first turn T1 and the second turn T2, two wire pairs located widthwise outside the wire pair of the third planar coil 3 and the fourth planar coil 4, namely, the wire pair of the first planar coil 1 and the second planar coil 2, the wire pair of the second planar coil 2 and the third planar coil 3, the wire pair of the fourth planar coil 4 and the fifth planar coil 5, and the wire pair of the fifth planar coil 5 and the sixth planar coil 6, are arranged so that the pitch between each wire is the first pitch p1, and correspond to the first pitch wire pairs. Similarly, in the third turn T3, the following two wire pairs located widthwise outside the wire pair of the ninth planar coil 9 and the tenth planar coil 10: the wire pair of the seventh planar coil 7 and the eighth planar coil 8, the wire pair of the eighth planar coil 8 and the ninth planar coil 9, the wire pair of the tenth planar coil 10 and the eleventh planar coil 11, and the wire pair of the eleventh planar coil 11 and the twelfth planar coil 12 are arranged with a first pitch p1 between the wires and correspond to the first pitch wire pairs. In this embodiment, the “outside in the widthwise direction” refers to a region farther away from the central position Ct21 in the first turn T1 and the third turn T3, and to a region farther away from the central position Ct22 in the second turn T2.

[0063] Housing 120 has a plurality of support pillars 121 arranged at equal intervals along each of the X-axis and Y-axis directions as shown in Fig. 12 , and a plurality of support pillars 121 extending along the Z-axis as shown in Fig. 13 . Housing 120 houses first coil layer S21 and second coil layer S22. More specifically, first coil layer S21 is housed within housing 120 so that support pillars 121 are located between the wires of third planar coil 3 and the wires of fourth planar coil 4, which are wires constituting the second pitch wire set, in each of first turn T1 and second turn T2. ​​This is because the spacing between the wires constituting the second pitch wire set is larger than the spacing between the wires constituting the first pitch wire set, making it easier to arrange support pillars 121 than between the wires constituting the first pitch wire set. Similarly, the second coil layer S22 is arranged and housed in the third turn T3 such that the support 121 is located between the wires of the ninth planar coil 9 and the wires of the tenth planar coil 10, which are wires that make up the second pitch wire set. Note that the magnetic body 110 and the shield member 112 are not shown in FIGS. 12 and 13 .

[0064] The coil assembly 102 of the third embodiment described above achieves the same effects as those of the first embodiment. In addition, the coil assembly 102 further includes a housing 120 having support posts 121 extending along the stacking direction, and each of the coil layers S21, S22 housed in the housing 120 is arranged so that the support posts 121 are located between the wires that make up the second pitch wire set. This allows the spacing between the multiple support posts 121 in the space within the housing 120 to be reduced compared to an embodiment in which a support post 121 is provided for each turn of the wire group, thereby improving the strength of the housing 120 against external forces applied in a direction parallel to the stacking direction and protecting the coil layers from external forces.

[0065] Furthermore, since the spacing between the wires that make up the second pitch wire set is greater than the spacing between the wires that make up the first pitch wire set, it is easier to arrange the support posts 121 between the wires that make up the second pitch wire set compared to between the wires that make up the first pitch wire set.

[0066] D. Other Embodiments: (D1) In the above embodiment, the pitch between the wires constituting each first pitch wire group in the plurality of first pitch wire groups is the same as each other, i.e., the first pitch p1, but the present disclosure is not limited to this. The pitch between the wires constituting each first pitch wire group may be any pitch smaller than the second pitch p2. This embodiment also achieves the same effects as the above embodiment.

[0067] In the above embodiment, the pitch between the wires constituting each second pitch wire group is the same as the second pitch p2, but the present disclosure is not limited to this. The pitch between the wires constituting each second pitch wire group may be any pitch greater than the first pitch p1. This configuration also achieves the same effects as the above embodiment.

[0068] (D2) In the third embodiment described above, in each of the first turn T1 and the second turn T2, the wire pair of the second planar coil 2 and the third planar coil 3, and the wire pair of the fourth planar coil 4 and the fifth planar coil 5, are configured as a first-pitch wire pair having a first pitch p1. However, the present disclosure is not limited to this. The wire pair of the second planar coil 2 and the third planar coil 3, and the wire pair of the fourth planar coil 4 and the fifth planar coil 5 may be configured as a second-pitch wire pair having a second pitch p2. Similarly, in the third turn T3, the wire pair of the eighth planar coil 8 and the ninth planar coil 9, and the wire pair of the tenth planar coil 10 and the eleventh planar coil 11 may be configured as a second-pitch wire pair having a second pitch p2, rather than as a first-pitch wire pair having a first pitch p1. This configuration also provides the same effects as the above embodiment.

[0069] (D3) In the third embodiment, the support pillars 121 are provided between the wires constituting the second pitch wire set, but the present disclosure is not limited to this. The support pillars 121 may be provided between the wires constituting the first pitch wire set. This configuration also improves the strength of the housing 120 against external forces applied in a direction parallel to the stacking direction, compared to a configuration without the support pillars 121, and can protect the coil layers from external forces.

[0070] (D4) In the above embodiment, each of the multiple coil layers has a first pitch wire set and a second pitch wire set, but the present disclosure is not limited to this. As long as at least some of the multiple coil layers have a first pitch wire set and a second pitch wire set, the pitch between the wires constituting the coil layer in the other coil layers may all be the same. This configuration also makes it possible to suppress current bias compared to a configuration in which the pitch between the wires constituting each coil layer in all of the multiple coil layers is the same.

[0071] (D5) In the above embodiment, all of the multiple coil layers are configured with an odd number of planar coils, or all of the multiple coil layers are configured with an even number of planar coils, but the present disclosure is not limited to this. For example, in a configuration in which the coil assembly has four coil layers, two of the four coil layers may each be configured with an even number of planar coils, and the other two planar coils may each be configured with an odd number of planar coils. This configuration also achieves the same effects as the above embodiment.

[0072] (D6) In the above embodiment, each coil layer is formed by sandwiching an insulator such as prepreg between coil patterns of a planar coil made of copper foil, but the present disclosure is not limited to this. Each coil layer may be formed by winding a Litz wire. This configuration also achieves the same effects as the above embodiment.

[0073] (D7) In each embodiment, the center position of the coil width of each turn in one coil layer coincides with the center position of the coil width of each turn in the other coil layer, but the present disclosure is not limited to this. The center position of the coil width of each turn in one coil layer may be located farther from the central axis of each coil layer than the center position of the coil width of each turn in the other coil layer. This configuration also achieves the same effects as the above embodiments.

[0074] (D8) The coil assemblies 100 to 103 in each embodiment are merely examples and may be modified in various ways. For example, the planar shape (shape when viewed in the Z direction) of each coil layer S1, S2, S11, S12, S21, and S22 does not have to be rectangular as in each embodiment, and may be, for example, circular, elliptical, or rounded rectangle with rounded corners. Furthermore, the number of coil layers is not limited to two and may be any number multiple of the above.

[0075] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in each embodiment corresponding to the technical features in the form described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. (Mode 1) A coil assembly (100, 101, 102) comprising a plurality of coil layers (S1, S2, S11, S12, S21, S22) stacked in a stacking direction, each of the coil layers having a plurality of planar coils (1-8, 1-10, 1-12) wound in a planar direction intersecting the stacking direction and connected in parallel, wherein the plurality of coil layers are a plurality of coil sections (a-d, a-e) each formed of at least one of the planar coils, constituting a plurality of coil sections connected in parallel, at least some of the plurality of coil layers include a first pitch wire set in which a pitch between adjacent wires is a first pitch, and a second pitch wire set in which a pitch between adjacent wires is a second pitch larger than the first pitch, and the first pitch wire set is located outward in the width direction of the coil width of the coil layer than the second pitch wire set. (Mode 2) The coil assembly according to Mode 1, wherein the spacing between the wires constituting the second pitch wire set is greater than the spacing between the wires constituting the first pitch wire set. (Mode 3) The coil assembly according to Mode 2, further comprising a housing (120) for accommodating the plurality of coil layers, the housing having struts (121) extending in the stacking direction, and the plurality of coil layers are arranged such that the struts are located between the wires constituting the second pitch wire set.(Mode 4) The coil assembly according to any one of Modes 1 to 3, wherein each of the coil sections is configured by connecting the planar coils of two or more of the coil layers in series, and the two or more planar coils configuring each of the coil sections include the planar coil wound radially inward in one of the coil layers and the planar coil wound radially outward in another of the coil layers. (Mode 5) The coil assembly according to any one of Modes 1 to 4, wherein the number of planar coils configuring at least some of the coil layers among the plurality of coil layers is an even number, and the second pitch strand set is configured by two strands closest to a center position of the coil width. (Mode 6) The coil assembly according to any one of Modes 1 to 5, wherein the sums of self-inductance and mutual inductance between the coil sections are equal to each other.

Claims

1. A coil assembly (100, 101, 102) comprising a plurality of coil layers (S1, S2, S11, S12, S21, S22) laminated in a lamination direction, the plurality of coil layers each having a plurality of planar coils (1-8, 1-10, 1-12) wound in a planar direction intersecting the lamination direction and connected in parallel to each other, the plurality of coil layers being a plurality of coil portions (a-d, a-e) each constituted by at least one of the planar coils and constituting a plurality of coil portions connected in parallel to each other, at least some of the plurality of coil layers including a first pitch wire set having a first pitch between adjacent strands and a second pitch wire set having a second pitch greater than the first pitch between adjacent strands, the first pitch wire set being located outside the width direction of the coil width of the coil layer relative to the second pitch wire set, the coil assembly.

2. The coil assembly according to claim 1, wherein the distance between the strands constituting the second pitch wire set is greater than the distance between the strands constituting the first pitch wire set, the coil assembly.

3. The coil assembly according to claim 2, further comprising a housing (120) for accommodating the plurality of coil layers, the housing having a support column (121) extending in the lamination direction, the plurality of coil layers being arranged such that the support column is located between the strands constituting the second pitch wire set, the coil assembly.

4. In the coil assembly according to any one of claims 1 to 3, each of the coil portions is constituted by connecting in series the planar coils respectively included in two or more of the coil layers, and the two or more planar coils constituting each of the coil portions include a planar coil wound radially inward in one of the coil layers and a planar coil wound radially outward in another of the coil layers, the coil assembly.

5. The coil assembly according to any one of claims 1 to 3, wherein the number of the planar coils constituting at least a part of the plurality of coil layers is an even number, and the second pitch wire set is composed of two wires closest to the central position of the coil width. Coil assembly.

6. In the coil assembly according to any one of claims 1 to 3, the sum of the self-inductance and the mutual inductance between the coil portions is equal to each other. Coil assembly.

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