JP7832046B2 - Coil device - Google Patents

Description

This invention relates to a coil device.

As a technique for improving the heat dissipation of coil devices, for example, the technique shown in Patent Document 1 is known. The coil device described in Patent Document 1 has an upper core and a lower core arranged vertically, and a case that houses the upper core and the lower core. The bottom plate of the case is fixed to a base equipped with a cooling mechanism, and by transferring heat from the upper core and the lower core to the base via the bottom plate of the case, heat from the upper core and the lower core can be dissipated.

In this type of coil device, the upper and lower cores are sometimes housed inside a case with a strong bond between them. However, as in the coil device described in Patent Document 1, if only the lower core is in contact with the bottom plate of the case, a difference in heat dissipation occurs between the upper and lower cores, resulting in a temperature difference between them. As a result, this temperature difference causes displacement in the upper core, and the lower core follows suit, placing excessive stress on the lower core, which may lead to cracks in a portion of it.

Japanese Patent Publication No. 2014-36194

This invention has been made in view of the above circumstances, and its objective is to provide a coil device capable of effectively preventing core damage.

To achieve the above objective, the coil device according to the present invention is
A first core and a second core are arranged along the first axial direction and joined to each other via a bonding resin,
On the opposite side of the joint between the first core and the second core, a plate-shaped member is provided that contacts the second core along a plane perpendicular to the first axial direction,
The Young's modulus of the bonding resin is 90 MPa or less.

The coil device according to the present invention comprises a first core and a second core arranged along a first axial direction and joined to each other via a bonding resin, and a plate-shaped member that contacts the second core along a plane perpendicular to the first axial direction, on the opposite side of the joint between the first and second cores. Therefore, when the plate-shaped member is fixed directly or indirectly to a cooling mechanism, for example, the second core in contact with the plate-shaped member is cooled more efficiently than the first core, and a temperature difference is generated between the first and second cores. As a result, the temperature of the first core becomes higher than that of the second core, and the displacement of the first core becomes greater than that of the second core. Even in this state, in the coil device according to the present invention, the Young's modulus of the bonding resin that joins the first and second cores is 90 MPa or less, and the bonding resin is flexible, so the first and second cores are mechanically joined relatively weakly, and the effect of the displacement of the first core does not easily affect the second core. Therefore, it is possible to avoid the second core being displaced in accordance with the displacement of the first core, thereby preventing excessive stress on the second core and effectively preventing cracks from forming in a part of it. Thus, the coil device according to the present invention can realize a coil device that effectively prevents core damage.

Furthermore, the first core and the second core are thermally connected via a bonding resin, and the heat from the first core is efficiently transferred to the plate-like member through the second core. Therefore, the heat dissipation performance of both the first and second cores can be maintained at a good level.

Preferably, the glass transition temperature of the bonding resin is 0°C or lower. With this configuration, the bonding resin remains in a soft, rubbery state even at relatively low temperatures (e.g., 0°C to room temperature). Therefore, by bonding the first core and the second core with such a bonding resin, the first and second cores are mechanically bonded relatively weakly, effectively preventing core damage even if a temperature difference occurs between the first and second cores.

The plate-like member may constitute part of the case that houses the first and second cores. This configuration allows heat from the first and second cores to be dissipated through various parts of the case, thereby further enhancing the heat dissipation performance of the coil device.

Preferably, the inside of the case is filled with potting resin. This configuration allows heat from the first core, second core, etc., to be transferred to the case via the potting resin, thereby effectively dissipating this heat.

Preferably, the upper surface of the potting resin filling the inside of the case is located above the joint between the first core and the second core. With this configuration, at least a portion of both the first core and the second core is covered with potting resin inside the case, allowing heat from the first and second cores to be effectively dissipated through the potting resin.

The Young's modulus of the potting resin may be 10 MPa or less.

Preferably, the Young's modulus of the bonding resin is greater than that of the potting resin. This configuration allows for effective prevention of core damage, as described above, while simultaneously bonding the first core and the second core with good bonding strength via the bonding resin.

At least one of the first core and the second core has a pair of side legs and a middle leg formed between each of the pair of outer legs. At the positions of the pair of outer legs, the first core and the second core are joined via the bonding resin, while at the positions of the middle leg, the first core and the second core are not joined via the bonding resin, and a gap may be formed between the first core and the second core. With this configuration, for example, the inductance characteristics of the coil device can be adjusted according to the width of the gap.

The first core and the second core may be combined to form an EE core, EI core, UU core, or UI core. Since the E core or U core has at least an outer leg portion, by configuring at least one of the first core and the second core as an E core or U core, the first core and the second core can be joined at the position of the outer leg portion via a bonding resin.

Figure 1A is a perspective view of a coil device according to the first embodiment of the present invention. Figure 1B is a perspective view showing the coil device shown in Figure 1A with the case removed. Figure 2 is an exploded perspective view of the coil device shown in Figure 1A. Figure 3 is a perspective view of the bobbin shown in Figure 2. Figure 4 is a perspective view of the bobbin, bobbin cover, and cap member shown in Figure 2. Figure 5 is a perspective view showing the state when the bobbin cover is attached to the bobbin shown in Figure 2. Figure 6 is a perspective view showing the state when the second wire is wound around the bobbin cover shown in Figure 5. Figure 7A is a cross-sectional view of the coil device along the VIIA-VIIA line shown in Figure 1A. Figure 7B is a cross-sectional view of the coil device along the VIIB-VIIB line shown in Figure 1A. Figure 8 is a perspective view of a coil device according to a second embodiment of the present invention. Figure 9 is a cross-sectional view showing a modified example of the case shown in Figure 7A. Figure 10 is a cross-sectional view showing a modified example of the core shown in Figure 7A. Figure 11 is a cross-sectional view showing another modified example of the case shown in Figure 7A. Figure 12A shows the simulation results of the stress distribution applied to the core assembly when the Young's modulus of the bonding resin is set to 90 MPa. Figure 12B shows the simulation results of the stress distribution applied to the core assembly when the Young's modulus of the bonding resin is set to 2 MPa. Figure 13A shows the simulation results of the displacement of the core assembly when the Young's modulus of the bonding resin is set to 90 MPa. Figure 13B shows the simulation results of the displacement of the core assembly when the Young's modulus of the bonding resin is set to 2 MPa.

The present invention will be described below based on the embodiments shown in the drawings.

The coil device 10 according to the first embodiment of the present invention, shown in Figures 1A and 1B of the first embodiment, is used, for example, as a transformer and in an in-vehicle power supply circuit. The coil device 10 has a core assembly 40 and a case 60 in which at least a part of the core assembly 40 is housed. Details of the core assembly 40 and the case 60 will be described later.

As shown in Figure 2, the coil device 10 includes a core assembly 40 and a case 60, as well as a bobbin 20, a partition cover 50, a heat dissipation cover (top plate) 70, cap members 80a and 80b, and bobbin covers 90a and 90b (Figure 4). The configuration of each of these members will be described below. In the drawings, the X-axis coincides with the direction in which the first cores 40a, 40a are aligned. The Y-axis coincides with the direction in which the first base 25a and the second base 25b of the bobbin 20 are aligned. The Z-axis corresponds to the height (thickness) of the transformer 10 and is parallel to the winding shafts of the coil sections 31 and 32, which will be described later.

As shown in Figure 3, the bobbin 20 has a bobbin substrate 21. The bobbin substrate 21 is a substantially elliptical flat plate and forms the bottom of the bobbin 20. Leg portions 22, 22 are formed at each end of the bobbin substrate 21 in the Y-axis direction. The leg portions 22 protrude downward from the bobbin substrate 21 and serve to support the bobbin 20. A concave portion 22a is formed on the bottom surface of the leg portions 22, and the block 102 shown in Figure 2 can be arranged inside the concave portion 22a in the manner shown in Figure 5. The block 102 is made of a block-shaped material with thermal conductivity, and is made of, for example, metal.

A first hollow cylindrical portion 23 is integrally molded in the approximate center of the bobbin substrate 21, extending upward. The first hollow cylindrical portion 23 has a cylindrical shape, and a first wire 37 (Figure 4) is wound around its outer surface. A separation plate fixing portion 28 is formed on the inner surface of the first hollow cylindrical portion 23. A pair of separation plate fixing portions 28 are formed on the inner surface of the first hollow cylindrical portion 23, but only one is shown in the drawing. As shown in Figure 2, a separation plate portion 106, which has a substantially flat shape, is fixed to the separation plate fixing portion 28 so as to be positioned approximately perpendicular to the bobbin substrate 21. The separation plate portion 106 is made of a metal material such as aluminum.

The separation plate fixing portion 28 extends in the Z-axis direction and is positioned between the intermediate leg portions 46a, 46a of the two first cores 40a, 40a facing each other in the X-axis direction, and between the intermediate leg portions 46b, 46b of the second cores 40b, 40b. The separation plate fixing portion 28 is designed to prevent the intermediate leg portions 46a, 46a (and intermediate leg portions 46b, 46b) facing each other in the X-axis direction from contacting each other within a predetermined gap inside the first hollow cylindrical portion 23. The separation plate portion 106 fixed to the separation plate fixing portion 28 has a similar function.

A bobbin upper flange portion 24 is formed on the upper part of the first hollow cylindrical portion 23. The bobbin upper flange portion 24 is integrally molded to the upper end of the first hollow cylindrical portion 23 and protrudes radially in a direction parallel to the XY plane. A base 25a is integrally formed on one end of the bobbin upper flange portion 24 in the Y-axis direction, and a base 25b is integrally formed on the other end. Since bases 25a and 25b have similar configurations, the configuration of base 25b will be omitted below.

The base 25a has a bottom surface 250. The bottom surface 250 constitutes the bottom surface of the base 25a and has an elongated shape in the X-axis direction. An insulating wall 251 and outer walls 252a to 252c are formed around the bottom surface 250, surrounding it. The insulating wall 251 and outer walls 252a to 252c are formed to protrude upward.

The insulating wall 251 is formed at the boundary between the bottom surface 250 and the bobbin upper flange 24. The insulating wall 251 prevents the base portions 44a and 44b from contacting the second lead portion 38a of the second wire 38, which passes through the inside of the base 25a, when the first cores 40a, 40a shown in Figure 2 are attached to the bobbin 20.

The outer walls 252a to 252c are formed to face the insulating wall 251 in the Y-axis direction. The outer wall 252a is integrally formed with the insulating wall 251, and a portion of the outer wall 252a extends along one end of the bottom surface 250 in the X-axis direction. The other end of the bottom surface 250 in the X-axis direction is open to allow the second lead portions 38a and 38b of the second wire 38, as shown in Figure 2, to be pulled out. In the base 25b, the other end of the bottom surface 250 in the X-axis direction is open to allow the first lead portions 37a and 37b of the first wire 37 to be pulled out.

Outer walls 252a and 252b are formed adjacent to each other in the X-axis direction, with the outer wall notch 253a in between. Outer walls 252b and 252c are formed adjacent to each other in the X-axis direction, with the outer wall notch 253b in between. The bottom surface 250 has a bottom surface notch 254a formed so as to be continuous with the outer wall notch 253a in the Y-axis direction, and a bottom surface notch 254b formed so as to be continuous with the outer wall notch 253b in the Y-axis direction.

A partition wall 255 is formed between the insulating wall 251 and the outer wall 252c. The partition wall 255 is positioned approximately parallel to the insulating wall 251 and the outer wall 252c, and extends along the X-axis direction.

A first insertion passage 256a is formed on one side of the partition wall 255 in the Y-axis direction. The first insertion passage 256a is for inserting the second lead portion 38b of the second wire 38 shown in Figure 2. The first insertion passage 256a extends in the X-axis direction from the position where the bottom notch 254a is formed, along the outer walls 252b and 252c, straddling the bottom notch 254b. In the base 25b, the first lead portion 37a of the first wire 37 shown in Figure 2 is inserted through the first insertion passage 256a.

A second insertion passage 256b is formed on the other side of the partition wall 255 in the Y-axis direction. The first insertion passage 256b is for inserting the second lead portion 38a of the second wire 38 shown in Figure 2. The second insertion passage 256b extends along the partition wall 255 in the X-axis direction from the position where the bottom notch 254b is formed. The extension directions of the second insertion passage 256b and the first insertion passage 256a are approximately parallel. In the base 25b, the first lead portion 37b of the first wire 37 shown in Figure 2 is inserted through the second insertion passage 256b.

An engaging projection 257a is formed on one outer surface of the insulating wall 251 in the X-axis direction, and an engaging projection 257b is formed on the outer surface on the other side. The engaging projections 257a and 257b are for engaging with the engaging recesses 82a and 82b formed on the cap member 80a, which will be described later. In the base 25b, the engaging projections 257a and 257b engage with the engaging recesses 82a and 82b of the cap member 80b.

Multiple positioning protrusions 26 are formed on the outer circumferential surface of the first hollow cylindrical portion 23 at predetermined intervals along the circumferential direction of the first hollow cylindrical portion 23. Each positioning protrusion 26 is formed at the lower end of the outer circumferential surface of the first hollow cylindrical portion 23 and protrudes radially outward from that surface. The positioning protrusions 26 are provided to position the bobbin covers 90a and 90b (Figure 4) that are attached to their outer circumference. When the bobbin covers 90a and 90b are attached to the bobbin 20, it is possible to position the inner circumferential surface of the second hollow cylindrical portion 91 of the bobbin covers 90a and 90b at a distance from the outer circumferential surface of the first hollow cylindrical portion 23 by the radial protrusion length of the positioning protrusions 26.

A first wire fixing portion 27 is formed on the outer circumferential surface of the first hollow cylindrical portion 23. The first wire fixing portion 27 is formed at a position approximately the width of one wire of the first wire 37, spaced upward from the positioning projection 26. The first wire fixing portion 27 protrudes radially outward from the outer circumferential surface of the first hollow cylindrical portion 23. While the shape of the first wire fixing portion 27 is a thin plate shape, its shape is not particularly limited, and various shapes with protrusions can be adopted. The first lead portion 37b of the first wire 37 can be hooked onto and fixed to the first wire fixing portion 27. Furthermore, the first wire 37 can be inserted through the gap in the Z-axis direction between the first wire fixing portion 27 and the positioning projection 26, allowing the first wire 37 to be wound around the lower end of the first hollow cylindrical portion 23 in the circumferential direction.

As shown in Figure 5, a fitting groove 29 is formed on the bottom surface of the base 25a. The fitting groove 29 is formed approximately in the center of the base 25a in the X-axis direction and extends along the Y-axis direction. The fitting groove 29 is a groove of a predetermined depth, and the upper end of the cover partition portion 94a (Figure 4) of the bobbin cover 90a can be fitted into it. In the case of base 25b, the upper end of the cover partition portion 94b of the bobbin cover 90b is fitted into the fitting groove 29.

As shown in Figure 4, the first wire 37 is wound around the outer circumferential surface of the first hollow cylindrical portion 23. More specifically, the first wire 37 is wound in multiple turns above the first wire fixing portion 27 on the outer circumferential surface of the first hollow cylindrical portion 23, and in one turn below the first wire fixing portion 27 (at the lower end of the first hollow cylindrical portion 23). This forms a first coil portion 31 on the outer circumferential surface of the first hollow cylindrical portion 23, where the first wire 37 is wound. Note that the winding method for the first wire 37 can include aligned winding or α-winding.

The first lead portion 37b of the first wire 37 is raised from a position below the first wire fixing portion 27 toward the base 25b. More specifically, the first lead portion 37b is raised upward while being hooked onto the first wire fixing portion 27, and guided from the outside to the inside of the base 25b in the Y-axis direction via the outer wall notch portion 253b. The first lead portion 37b is then guided further inward in the Y-axis direction of the base 25b via the bottom notch portion 254b, and is pulled out outward in the X-axis direction while being inserted through the inside of the second insertion passage 256b, in a state where it is bent approximately perpendicularly toward the positive X-axis direction.

On the other hand, the first lead portion 37a is raised from the upper end of the outer circumferential surface of the first hollow cylindrical portion 23 toward the base 25b. More specifically, the first lead portion 37a is guided from the outside to the inside in the Y-axis direction of the base 25b via the outer notch 253a. The first lead portion 37a is then guided further inward in the Y-axis direction of the base 25b via the bottom notch 254a, and is pulled out outward in the X-axis direction while passing through the interior of the first insertion passage 256a, in a state where it is bent approximately perpendicularly toward the positive X-axis direction.

The bobbin covers 90a and 90b are attached to the bobbin 20 with the first wire 37 wound around the outer surface of the first hollow cylindrical portion 23. Each of the bobbin covers 90a and 90b is made of a split body, and they are configured to be combined. In the following, regarding the overlapping configurations of the bobbin covers 90a and 90b, only the bobbin cover 90a will be described, and the description of the bobbin cover 90b will be omitted.

The bobbin cover 90a has a second hollow cylindrical portion 91. The second hollow cylindrical portion 91 is made of a split body, and when the second hollow cylindrical portion 91 of bobbin cover 90a and the second hollow cylindrical portion 91 of bobbin cover 90b are combined, a cylindrical body is formed. The outer circumferential surface of the second hollow cylindrical portion 91 allows for winding of the second wire 38.

A cover partition portion 94a is formed on the outer circumferential surface of the second hollow cylindrical portion 91. The cover partition portion 94a is formed at the upper end of the second hollow cylindrical portion 91 and protrudes radially outward from the outer circumferential surface of the second hollow cylindrical portion 91. The cover partition portion 94a has a predetermined length in the Z-axis direction, and its upper end is fitted into the fitting groove 29 of the base 25a in the manner shown in Figure 5.

A pair of upper cover flanges 92a, 92a are formed on the upper part of the second hollow cylindrical portion 91. One upper cover flange 92a is formed on one side of the cover partition portion 94a, and the other upper cover flange 92a is formed on the other side of the cover partition portion 94a. The upper cover flanges 92a, 92a are integrally molded to the upper end of the second hollow cylindrical portion 91 and protrude radially in a direction parallel to the XY plane.

A lead insertion passage 95 is formed between the cover partition 94a and the upper flange 92a formed on one side of the cover, and a lead insertion passage 96 is formed between the cover partition 94a and the upper flange 92a formed on the other side of the cover. The second lead portion 38a of the second wire 38 can be inserted through the lead insertion passage 95, and the second lead portion 38b of the second wire 38 can be inserted through the lead insertion passage 96.

Multiple upward projections 97 are formed on the upper surface of the upper flange portion 92a of the cover. As shown in Figure 5, these upward projections 97 are intended to create a gap between the upper flange portion 92a of the cover and the bottom surface of the base 25a of the bobbin 20 (or the bottom surface of the upper flange portion 24 of the bobbin) when the bobbin covers 90a and 90b are fixed to the bobbin 20.

As shown in Figure 4, each end of the pair of upper flange portions 92a, 92a of the cover is formed with a pair of engaging portions 98, 98. The engaging portions 98, 98 are each formed as either convex or concave portions and are configured to engage with the engaging portions 98, 98 formed at both ends of the upper flange portion 92b of the bobbin cover 90b.

A lower flange portion 93 is formed at the lower part of the second hollow cylindrical portion 91. The lower flange portion 93 is integrally molded with the lower end of the second hollow cylindrical portion 91 and protrudes radially in a direction parallel to the XY plane.

As shown in Figure 5, a second wire fixing portion 99 is formed on the outer circumferential surface of the second hollow cylindrical portion 91. The second wire fixing portion 99 is formed at a position approximately the width of one wire of the second wire 38, above the lower flange portion 93 of the cover. The second wire fixing portion 99 protrudes outward from the outer circumferential surface of the second hollow cylindrical portion 91. While the shape of the second wire fixing portion 99 is a thin plate shape, its shape is not particularly limited, and various shapes with protrusions can be adopted.

The second wire fixing portion 99 has the same function as the first wire fixing portion 27 (Figure 4) formed on the outer circumferential surface of the first hollow cylindrical portion 23. That is, the second lead portion 38b of the second wire 38 can be hooked onto and fixed to the second wire fixing portion 99. The second wire 38 can be inserted through the gap between the second wire fixing portion 99 and the lower flange portion 93 of the cover, allowing the second wire 38 to be wound around the lower end of the second hollow cylindrical portion 91 in the circumferential direction.

As shown in Figure 4, the configuration of the upper flange portion 92b and the cover partition portion 94b in the bobbin cover 90b differs from the configuration of the upper flange portions 92a, 92a and the cover partition portion 94a in the bobbin cover 90a. More specifically, the upper flange portion 92b is formed continuously along the outer circumference of the upper part of the second hollow cylindrical portion 91.

The cover partition portion 94b is formed to protrude upward from the upper surface of the cover's upper flange portion 92b. The cover partition portion 94b has a predetermined length in the Y-axis direction, and its upper end is fitted into the fitting groove 29 of the base 25b.

As shown in Figure 6, the second wire 38 is wound around the outer circumferential surface of the second hollow cylindrical portion 91 of the bobbin covers 90a and 90b. More specifically, the second wire 38 is wound in multiple turns above the second wire fixing portion 99 on the outer circumferential surface of the second hollow cylindrical portion 91, and in one turn below the second wire fixing portion 99 (at the lower end of the second hollow cylindrical portion 91). This forms a second coil portion 32 on the outer circumferential surface of the second hollow cylindrical portion 91, which is formed by the winding of the second wire 38.

The second lead portion 38b of the second wire 38 is raised from a position below the second wire fixing portion 99 toward the base 25a. More specifically, the second lead portion 38b is raised upward while being hooked onto the second wire fixing portion 99, and guided from the outside to the inside of the base 25a in the Y-axis direction via the outer wall notch portion 253a. The second lead portion 38b is then guided further inward in the Y-axis direction of the base 25a via the bottom notch portion 254a, and is pulled out outward in the X-axis direction while being inserted through the inside of the first insertion passage 256a, in a state where it is bent approximately perpendicularly toward the positive X-axis direction.

On the other hand, the second lead portion 38a is raised from the upper end of the outer circumferential surface of the second hollow cylindrical portion 91 toward the base 25a. More specifically, the second lead portion 38a is guided from the outside to the inside in the Y-axis direction of the base 25a via the outer notch 253b. The second lead portion 38a is then guided further inward in the Y-axis direction of the base 25a via the bottom notch 254b, and is pulled out outward in the X-axis direction while passing through the inside of the second insertion passage 256b, in a state where it is bent approximately perpendicular to the positive X-axis direction.

As shown in Figure 4, the first wire 37 is wound around the outer circumferential surface of the first hollow cylindrical portion 23, and as shown in Figure 6, the second wire 38 is wound around the outer circumferential surface of the second hollow cylindrical portion 91. This forms a double-layered coil section, as shown in Figure 7A, where the first coil section 31 is positioned on the inside and the second coil section 32 is positioned on the outside. Either the first coil section 31 or the second coil section 32 constitutes the primary coil, and the other constitutes the secondary coil.

As shown in Figure 4, a cap member 80a is attached to base 25a, and a cap member 80b is attached to base 25b. Since cap members 80a and 80b have similar configurations, the configuration of cap member 80b will not be described below.

The cap member 80a has a top plate portion 81. A pair of inner side walls 82, 82 and a pair of outer side walls 83, 83 are formed on the sides of the top plate portion 81. The outer side walls 83, 83 are formed at one end of the top plate portion 81 in the Y-axis direction, while the inner side walls 82, 82 are formed at the other end of the top plate portion 81 in the Y-axis direction.

The outer lateral walls 83, 83 of the cap member 80a are arranged to overlap with the outer walls 252a to 252c of the base 25a, and the outer lateral walls 83, 83 of the cap member 80b are arranged to overlap with the outer walls 252a to 252c of the base 25b.

Each of the pair of inner side walls 82, 82 is positioned at a predetermined distance in the X-axis direction. An engaging recess 82a is formed in one inner side wall 82, and an engaging recess 82b is formed in the other inner side wall 82. By engaging the engaging projection 257a shown in Figure 3 with the engaging recess 82a, and engaging the engaging projection 257b with the engaging recess 82b, the cap member 80a can be attached to the base 25a.

As shown in Figure 2, partition covers 50, 50 are positioned on the outside of the bobbin covers 90a, 90b. One partition cover 50 is formed on one side of the bobbin covers 90a, 90b in the X-axis direction, and the other partition cover 50 is formed on the other side of the bobbin covers 90a, 90b in the X-axis direction.

The partition cover 50 has a cover body 52 and a pair of locking pieces 54, 54 formed at both ends of the cover body 52 in the Z-axis direction. The cover body 52 is curved to cover the periphery of the second coil portion 32 formed on the outer circumferential surface of the second hollow cylindrical portion 91, 91 of the bobbin covers 90a, 90b. The locking pieces 54 are bent inward from the cover body 52 in a substantially vertical direction. The pair of locking pieces 54, 54 are attached so as to sandwich the upper cover flanges 92a, 92b formed at the upper ends of the second hollow cylindrical portion 91, 91 of the bobbin covers 90a, 90b and the lower cover flanges 93, 93 formed at the lower ends.

As shown in Figure 7B, insulating covers 103, 103, as shown in Figure 2, are positioned outside the bobbin covers 90a, 90b. The insulating cover 103 has a cover body 104 and a folded portion 105. The cover body 104 is positioned along the inner surface of the side plate 64 of the case 60 (described later), and the folded portion 105 is configured to engage with the upper end of the side plate 64. The insulating cover 103 is intended to prevent the second coil portion 32, formed on the outer circumferential surface of the second hollow cylindrical portion 91 of the bobbin covers 90a, 90b, from contacting the side plate 64.

As shown in Figure 2, terminals 100, 100 are attached to the ends of the first lead portions 37a and 37b of the first wire 37, respectively. The first lead portions 37a and 37b are bundled together with an insulating wire cover 101. Similarly, terminals 100, 100 are attached to the ends of the second lead portions 38a and 38b of the second wire 38, respectively. The second lead portions 38a and 38b are also bundled together with an insulating wire cover 101.

As shown in Figure 7A, the case 60 houses at least a portion of the core assembly 40. In the illustrated example, the case 60 houses a portion of the upper cores 40a, 40a and all of the lower cores 40b, 40b. The base surfaces 440b, 44b of the base portions 44b, 44b are placed on the bottom plate (bottom) 62 of the case 60 and form the mounting surfaces of the lower cores 40b, 40b. The case 60 is made of a plate-like material, such as aluminum, which has high thermal conductivity, and functions as a heat dissipation case.

As shown in Figures 2 and 7A, the case 60 has a bottom plate 62 and side plates 64. The side plates 64 extend upward and are formed on the periphery of the bottom plate 62. More specifically, the side plates 64 are formed on each side of the bottom plate 62, which is substantially rectangular when viewed from above, and have two opposing surfaces parallel to the YZ plane and two opposing surfaces substantially parallel to the XZ plane. A bulge 66 is formed on each of the two surfaces of the side plate 64 substantially parallel to the XZ plane. The bulge 66 consists of a portion that bulges outward in the Y-axis direction, and a recess is formed inside the case 60 at the location where the bulge 66 is formed. A part of the second coil section 32 shown in Figure 6 is arranged inside this recess. The case 60 (for example, the bottom plate 62) is fixed directly or indirectly to a cooling mechanism (not shown).

Two boss portions 68, 68 are formed at the corners of the base plate 62. Openings (e.g., bolt holes) are formed in the boss portions 68, and by fixing fasteners or the like to these openings, the case 60 can be fixed to, for example, a cooling mechanism.

The inside of the case 60 is filled with potting resin 300. The potting resin 300 is a heat-dissipating resin with high thermal conductivity, and is filled between the side of the core assembly 40 and the side plate 64 of the case 60, as well as around the first coil section 31 and around the second coil section 32.

The Young's modulus of the potting resin 300 is preferably 10 MPa or less, and more preferably 0.1 to 10 MPa. As the material constituting the potting resin 300, a silicone resin, urethane resin, epoxy resin, etc., that remains flexible after injection can be used.

The core assembly 40 comprises upper cores 40a, 40a and lower cores 40b, 40b. The core assembly 40 constitutes a so-called vertical core, and the upper cores 40a, 40a and the lower cores 40b, 40b are configured to be combined in the Z-axis direction. The material of each core 40a, 40b may be a metal or a soft magnetic material such as ferrite, but is not particularly limited.

The upper cores 40a, 40a each consist of two divided cores 42a, 42a having the same shape, and are divided by a plane parallel to the YZ plane. When the upper cores 40a, 40a are combined in the X-axis direction, they have an E-shaped cross-section (however, the cross-section is parallel to the XZ plane), forming a so-called E-shaped core. Note that the upper cores 40a, 40a are not limited to E-shaped cores; for example, they may be composed of a U-shaped core (preferably a core with outer legs).

The lower cores 40b, 40b each consist of two divided cores 42b, 42b having the same shape, and are divided by a plane parallel to the YZ plane. When the lower cores 40b, 40b are combined in the X-axis direction, they have an E-shaped cross-section (however, the cross-section is parallel to the XZ plane), forming a so-called E-shaped core. Note that the lower cores 40b, 40b are not limited to an E-shaped core; for example, they may be composed of a U-shaped core (preferably a core with outer legs).

Each of the upper cores 40a, 40a has a base portion 44a extending in the X-axis direction, a middle leg portion 46a protruding in the Z-axis direction from one end of the base portion 44a in the X-axis direction, and an outer leg portion 48a protruding in the Z-axis direction from the other end. The upper cores 40a, 40a are assembled in the X-axis direction at the positions of the middle leg portions 46a, 46a. That is, in this embodiment, the upper cores 40a, 40a are divided at the positions of the middle leg portions 46a, 46a, but not at the positions of the outer leg portions 48a, 48a.

When the upper cores 40a, 40a are assembled in the X-axis direction, the middle leg portions 46a, 46a are positioned between the outer leg portions 48a, 48a of the upper cores 40a, 40a, respectively. The pair of middle leg portions 46a, 46a are inserted into the through-hole of the first hollow cylindrical portion 23 of the bobbin 20 from above in the Z-axis direction. In the following, the surfaces of the base portions 44a, 44a will be referred to as the base surfaces 440a, 440a.

Each of the lower cores 40b, 40b has a base portion 44b extending in the X-axis direction, a middle leg portion 46b projecting in the Z-axis direction from one end of the base portion 44b in the X-axis direction, and an outer leg portion 48b projecting in the Z-axis direction from the other end. The lower cores 40b, 40b are assembled in the X-axis direction at the positions of the middle leg portions 46b, 46b. That is, in this embodiment, the lower cores 40b, 40b are divided at the positions of the middle leg portions 46b, 46b, but not at the positions of the outer leg portions 48b, 48b.

When the lower cores 40b, 40b are assembled in the X-axis direction, the middle legs 46b, 46b are positioned between the outer legs 48b, 48b of the lower cores 40b, 40b. The pair of middle legs 46b, 46b are inserted into the through-hole of the first hollow cylindrical portion 23 of the bobbin 20 from below in the Z-axis direction. In the following, the surfaces of the base portions 44b, 44b will be referred to as the base surfaces 440b, 440b.

The Z-axis ends of the outer legs 48a, 48a of the upper cores 40a, 40a and the outer legs 48b, 48b of the lower cores 40b, 40b abut against each other in the Z-axis direction on the outside of the bobbin 20. The Z-axis ends of the middle legs 46a, 46a of the upper cores 40a, 40a and the middle legs 46b, 46b of the lower cores 40b, 40b abut against each other in the Z-axis direction on the inside of the bobbin 20. The base surfaces 440b, 440b of the lower cores 40b, 40b are in contact with the bottom plate 62 along a plane perpendicular to the Z-axis direction (XY plane) on the opposite side of the joint (butt surface) between the upper cores 40a, 40a and the lower cores 40b, 40b.

As shown in the enlarged view of Figure 7A, the Z-axis ends of the outer legs 48a, 48a of the upper cores 40a, 40a and the outer legs 48b, 48b of the lower cores 40b, 40b are joined to each other via a bonding resin (e.g., adhesive) 200. Similarly, the Z-axis ends of the middle legs 46a, 46a of the upper cores 40a, 40a and the middle legs 46b, 46b of the lower cores 40b, 40b are also joined to each other via the bonding resin 200. Therefore, a thin layer (buffer layer) made of the bonding resin 200 is formed at the joint between the upper cores 40a, 40a and the lower cores 40b, 40b. Note that the upper cores 40a, 40a and the lower cores 40b, 40b are weakly mechanically joined and are not completely integrated via the bonding resin 200, as will be described later.

In a state where the upper cores 40a, 40a and the lower cores 40b, 40b are joined vertically, the dimensions of the core assembly 40 in the X-axis direction are 25 mm or more, the dimensions in the Y-axis direction are 25 mm or more, and the dimensions in the Z-axis direction are 20 mm or more. The present invention exhibits excellent effects in such a relatively large core assembly 40.

The bonding resin 200 is composed of a soft resin, and its Young's modulus is preferably 90 MPa or less, and more preferably 2 to 20 MPa, at 20 to 150°C. Furthermore, the glass transition temperature Tg of the bonding resin 200 is 0°C or less.

By setting the Young's modulus or glass transition temperature Tg of the bonding resin 200 within the above range, the mechanical bond between the upper cores 40a, 40a and the lower cores 40b, 40b can be kept relatively weak, preventing damage to the lower cores 40b, 40b as described later. The bonding resin 200 can be composed of materials such as silicone resin, urethane resin, or epoxy resin, and such resins can maintain a soft state even after injection. The bonding resin 200 may also be a mixture of multiple resins.

The Young's modulus of the bonding resin 200 used to join the Z-axis ends of the outer leg portions 48a, 48a and 48b, 48b may differ from the Young's modulus of the bonding resin 200 used to join the Z-axis ends of the middle leg portions 46a, 46a and 46b, 46b. The Young's modulus of one may be greater than the other.

The thickness of the resin layer (adhesive layer) formed by the bonding resin 200 is preferably 8 to 100 μm, and more preferably 8 to 20 μm. By keeping the thickness of the bonding resin 200 within this range, the degree of mechanical bonding between the upper cores 40a, 40a and the lower cores 40b, 40b can be maintained at a relatively weak level, thereby preventing damage to the lower cores 40b, 40b, as described later.

In the illustrated example, the upper cores 40a, 40a and the lower cores 40b, 40b are joined via bonding resin 200 at the positions of the outer leg portions 48a, 48a and the middle leg portions 46a, 46a. However, they may also be joined via bonding resin 200 only at the positions of the outer leg portions 48a, 48a.

The bonding resin 200 and the potting resin 300 have different Young's moduli; the Young's moduli of the bonding resin 200 are greater than those of the potting resin 300.

The upper surface of the potting resin 300 filled inside the case 60 is located above the joint between the upper cores 40a, 40a and the lower cores 40b, 40b. Since the joint between the upper cores 40a, 40a and the lower cores 40b, 40b is filled with bonding resin 200, the potting resin 300 does not penetrate the joint, but only comes into contact with the bonding resin 200 filled in the joint. Furthermore, from the viewpoint of improving the heat dissipation of the coil device 10, it is preferable that the thermal conductivity of the potting resin 300 is greater than that of the bonding resin 200.

Since the periphery of the outer leg portions 48a, 48a or the middle leg portions 46a, 46a is covered with potting resin 300, the resin layer formed by the joining resin 200 at the joint between the upper core 40a, 40a and the lower core 40b, 40b is surrounded by the potting resin 300.

As shown in Figure 2, a pair of heat dissipation covers 70, 70 are attached to the core assembly 40. Each heat dissipation cover 70 has a top cover 72 and side covers 74. As shown in Figure 1B, the top cover 72 is fixed to the base surface 440a of the base portion 44a, and the side covers 74 are fixed to their respective outer surfaces so as to straddle the outer leg portions 48a and 48b.

In the manufacturing of the coil device 10, first, the components shown in Figure 2 are prepared. Next, as shown in Figure 4, the first wire 37 is wound around the outer circumferential surface of the first hollow cylindrical portion 23 of the bobbin 20 to form the first coil portion 31. Furthermore, from the lower end of the first hollow cylindrical portion 23, the first lead portion 37b of the first wire 37 is hooked onto the first wire fixing portion 27 and pulled out toward the base 25b. At this time, the first lead portion 37b, which has been raised to the base 25b, is pulled out in the Y-axis direction from the outside of the base 25b through the outer wall notch 253b and the bottom notch 254b to the position of the second insertion passage 256b, and then pulled out outward in the X-axis direction through the second insertion passage 256b.

Furthermore, the first lead portion 37a of the first wire 37 is pulled out from the upper end of the first hollow cylindrical portion 23 toward the base 25b. At this time, the first lead portion 37a is pulled out in the Y-axis direction from the outside of the base 25b, through the outer wall notch 253a and the bottom notch 254a, to the position of the first insertion passage 256a, and then pulled out outward in the X-axis direction through the first insertion passage 256a.

Next, as shown in Figure 5, bobbin covers 90a and 90b are attached to the bobbin 20 so as to cover the periphery of the first coil portion 31. Then, as shown in Figure 6, the second wire 38 is wound around the outer circumferential surface of the second hollow cylindrical portion 91 to form the second coil portion 32. Next, from the lower end of the second hollow cylindrical portion 91, the second lead portion 38b of the second wire 38 is hooked onto the second wire fixing portion 99 and pulled out towards the base 25a. At this time, the second lead portion 38b is pulled out in the Y-axis direction from the outside of the base 25a, through the outer wall notch 253a and the bottom notch 254a to the position of the first insertion passage 256a, and then pulled out outward in the X-axis direction through the first insertion passage 256a.

Furthermore, the second lead portion 38a of the second wire 38 is pulled out from the upper end of the second hollow cylindrical portion 91 toward the base 25a. At this time, the second lead portion 38a is pulled out in the Y-axis direction from the outside of the base 25a, through the outer wall notch 253b and the bottom notch 254b, to the position of the second insertion passage 256b, and then pulled out outward in the X-axis direction through the second insertion passage 256b.

Next, the partition covers 50, 50 shown in Figure 2 are attached to the bobbin covers 90a, 90b in the manner shown in Figure 7A, so as to cover the periphery of the second coil section 32, and the separation plate section 106 is attached to the separation plate fixing section 28.

Next, the upper cores 40a, 40a are attached to the bobbin 20 while the middle leg portions 46a, 46a are inserted from above into the through-holes of the first hollow cylindrical portion 23. The lower cores 40b, 40b are attached to the bobbin 20 while the middle leg portions 46b, 46b are inserted from below into the through-holes of the first hollow cylindrical portion 23, thereby forming the core assembly 40.

At this time, bonding resin 200 is applied to the tips of the middle leg portions 46a, 46a and/or the middle leg portions 46b, 46b, and also to the tips of the outer leg portions 48a, 48a and/or the outer leg portions 48b, 48b. As a result, when the upper core 40a, 40a and the lower core 40b, 40b are assembled vertically, the tips of the middle leg portions 46a, 46a and the middle leg portions 46b, 46b are joined to each other via the bonding resin 200, and the tips of the outer leg portions 48a, 48a and the outer leg portions 48b, 48b are joined to each other. The timing of the process of joining the upper core 40a, 40a and the lower core 40b, 40b with the bonding resin 200 may be changed as appropriate.

Before and after this, the cap members 80a and 80b shown in Figure 4 are attached to the bases 25a and 25b, and the heat dissipation covers 70 and 70 shown in Figure 2 are attached to the core assembly 40 in the manner shown in Figure 1B. Furthermore, the blocks 102 and 102 shown in Figure 2 are fixed inside the concave portions 22a and 22a (Figure 5) of the legs 22 and 22 of the bobbin 20.

Next, the bobbin 20, with the core assembly 40 and other components attached, is housed inside the case 60, and the insulating covers 103, 103 are engaged with the upper ends of the side plates 64 of the case 60 in the manner shown in Figure 7B. Then, potting resin 300 is injected into the case 60, filling the gaps between the side of the core assembly 40 and the side plates 64, and around the coil sections 31, 32, with a predetermined amount of potting resin 300. In this way, the coil device 10 shown in Figure 1A is obtained. If necessary, terminals 100 and wire covers 101 are attached to the first lead sections 37a, 37b and the second lead sections 38a, 38b.

As shown in Figure 7A, the coil device 10 according to this embodiment has upper cores 40a, 40a and lower cores 40b, 40b that are joined to each other via a bonding resin 200, and a bottom portion 62 of the case 60 that contacts the base surfaces 440b, 440b of the lower cores 40b, 40b. Therefore, if the bottom portion 62 is directly or indirectly fixed to a cooling mechanism (e.g., a water cooling means), the lower cores 40b, 40b in contact with the bottom portion 62 are cooled more efficiently than the upper cores 40a, 40a, resulting in a temperature difference between the upper cores 40a, 40a and the lower cores 40b, 40b. As a result, the temperature of the upper cores 40a, 40a becomes higher than that of the lower cores 40b, 40b, and the displacement of the upper cores 40a, 40a becomes greater compared to the lower cores 40b, 40b.

Even under these conditions, in the coil device 10 according to this embodiment, the Young's modulus of the bonding resin 200 that joins the upper cores 40a, 40a and the lower cores 40b, 40b is 90 MPa or less, and the bonding resin 200 is flexible. Therefore, the upper cores 40a, 40a and the lower cores 40b, 40b are mechanically joined relatively weakly, and the displacement of the upper cores 40a, 40a does not easily affect the lower cores 40b, 40b. Therefore, it is possible to avoid the displacement of the lower cores 40b, 40b following the displacement of the upper cores 40a, 40a, thereby preventing excessive stress on the lower cores 40b, 40b and effectively preventing cracks from forming in some parts of them. Thus, according to the coil device 10 according to this embodiment, a coil device that can effectively prevent core damage can be realized.

Furthermore, according to simulation results conducted by the inventors, as shown in Figure 7A, when the tips of the upper cores 40a, 40a and the lower cores 40b, 40b were joined together with a bonding resin 200 (specifically, silicone resin) having a Young's modulus of 2 MPa, the stress applied to the lower cores 40b, 40b was reduced to less than half, and it was confirmed that crack formation near the base of the outer leg portions 48b, 48b of the base portions 44b, 44b in the lower cores 40b, 40b could be effectively prevented. In addition, it was confirmed that the stress applied to the upper cores 40a, 40a near the base of the outer leg portions 48a, 48a was also reduced, and the displacement of the upper cores 40a, 40a themselves was reduced.

Figure 12A shows the simulation results of the stress distribution applied to the core assembly 40 when the Young's modulus of the bonding resin 200 is 90 MPa. Figure 12B shows the simulation results of the stress distribution applied to the core assembly 40 when the Young's modulus of the bonding resin 200 is 2 MPa. In Figures 12A and 12B, the degree (relative magnitude) of stress applied to the upper cores 40a, 40a and the lower cores 40b, 40b is indicated by shaded lines. Specifically, areas with a smaller density of shaded lines indicate relatively large stresses, while areas with a larger density of shaded lines indicate relatively small stresses.

As is clear from comparing Figures 12A and 12B, reducing the Young's modulus of the bonding resin 200 from 90 MPa to 2 MPa effectively reduces the stress applied to the lower cores 40b, 40b (especially near the bases of the outer legs 48b, 48b in the base portions 44b, 44b). Furthermore, reducing the Young's modulus of the bonding resin 200 from 90 MPa to 2 MPa also effectively reduces the stress applied to the upper cores 40a, 40a. Also, as shown in Figure 12A, when the Young's modulus of the bonding resin 200 is set to 90 MPa, the stress applied to the lower cores 40b, 40b (especially near the bases of the outer legs 48b, 48b in the base portions 44b, 44b) can be made relatively small.

Figure 13A shows the simulation results of the displacement distribution of the core assembly 40 when the Young's modulus of the bonding resin 200 is 90 MPa. Figure 13B shows the core assembly 40 when the Young's modulus of the bonding resin 200 is 2 MPa.
This figure shows the simulation results of the displacement distribution. In Figures 13A and 13B, the degree (relative magnitude) of the displacement of the upper cores 40a, 40a and the lower cores 40b, 40b is indicated by the shaded lines. Specifically, areas with a smaller density of shaded lines indicate relatively larger displacements, while areas with a larger density of shaded lines indicate relatively smaller displacements.

As is clear from comparing Figure 13A and Figure 13B, the displacement of the upper cores 40a, 40a and the lower cores 40b, 40b hardly changes when the Young's modulus of the bonding resin 200 is 90 MPa compared to when the Young's modulus of the bonding resin 200 is 2 MPa. In other words, when the Young's modulus of the bonding resin 200 is set to 90 MPa, the effect of suppressing the displacement of the upper cores 40a, 40a and the lower cores 40b, 40b can be obtained at a level comparable to when the Young's modulus of the bonding resin 200 is 2 MPa.

Furthermore, the upper cores 40a, 40a and the lower cores 40b, 40b are thermally connected via the bonding resin 200. Heat from the upper cores 40a, 40a is efficiently transferred to the bottom plate 62 through the lower cores 40b, 40b, thus maintaining good heat dissipation for both the upper cores 40a, 40a and the lower cores 40b, 40b.

Furthermore, since the glass transition point of the bonding resin 200 is below 0°C, the bonding resin 200 remains in a soft, rubbery state even at relatively low temperatures (e.g., 0°C to room temperature). Therefore, by bonding the upper cores 40a, 40a and the lower cores 40b, 40b with such a bonding resin 200, the upper cores 40a, 40a and the lower cores 40b, 40b are mechanically bonded relatively weakly. Even if a temperature difference occurs between the upper cores 40a, 40a and the lower cores 40b, 40b, damage to these cores can be effectively prevented.

Furthermore, since the bottom portion 62 constitutes part of the case 60 that houses the upper cores 40a, 40a and the lower cores 40b, 40b, heat from the upper cores 40a, 40a and the lower cores 40b, 40b is dissipated through various parts of the case 60, further enhancing the heat dissipation performance of the coil device 10.

Furthermore, since the inside of the case 60 is filled with potting resin 300, heat from the upper cores 40a, 40a and the lower cores 40b, 40b can be transferred to the case 60 via the potting resin 300, allowing for effective heat dissipation.

Furthermore, since the upper surface of the potting resin 300 is located above the joint between the upper cores 40a, 40a and the lower cores 40b, 40b in the case 60, at least a portion of both the upper cores 40a, 40a and the lower cores 40b, 40b are covered by the potting resin 300 inside the case 60. Therefore, heat from the upper cores 40a, 40a and the lower cores 40b, 40b can be effectively dissipated via the potting resin 300.

Furthermore, since the Young's modulus of the potting resin 300 is 10 MPa or less, and the Young's modulus of the bonding resin 200 is greater than that of the potting resin 300, as described above, the upper cores 40a, 40a and the lower cores 40b, 40b can be joined with good bonding strength via the bonding resin 200 while effectively preventing core damage.

The coil device 110 according to the second embodiment of the present invention, shown in Figure 8 of the second embodiment , differs only in the following points, and the other configurations are the same as those of the first embodiment described above, and it provides the same effects. In the drawings, common reference numerals are used for members common to the first embodiment, and the description of overlapping parts is omitted.

As shown in Figure 8, in the coil device 110 of this embodiment, a gap G is formed between the intermediate leg portions 46a, 46a and intermediate leg portions 46b, 46b, and the inside of the gap G is filled with potting resin 300. The width of the gap G in the Z-axis direction is preferably 10 to 100 μm. In this embodiment, the intermediate leg portions 46a, 46a and intermediate leg portions 46b, 46b are not joined via bonding resin 200, and the bonding resin 200 is not filled between the respective tips of the upper core 40a, 40a and the lower core 40b, 40b at the positions of the intermediate leg portions 46a, 46a and intermediate leg portions 46b, 46b.

The middle leg portions 46a, 46a and 46b, 46b are joined via potting resin 300. Note that the inside of the gap G does not necessarily need to be filled with potting resin 300; it may remain hollow.

In this embodiment, the same effects as in the first embodiment can be obtained. In addition, in this embodiment, the inductance characteristics of the coil device 110 can be adjusted according to the Z-axis width of the gap G.

Furthermore, the present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the present invention.

(1) As shown in Figure 9, a plurality (8) of support portions 622 may be integrally formed on the bottom plate 62, and the lower cores 40b, 40b may be placed on these support portions 622. The support portions 622 consist of protrusions (projections) that protrude from the upper surface 620 of the bottom plate 62. Each of the plurality of support portions 622 is formed discretely (locally) on the upper surface 620 of the bottom plate 62 and is in surface or point contact with the base surfaces 440b, 440b of the lower cores 40b, 40b. The support portions 622 support the base surfaces 440b, 440b at a position spaced upward from the upper surface 620 of the bottom plate 62. The upward protrusion length of the support portions 622 is preferably 0.05 to 1.5 mm, and more preferably 0.1 to 1.0 mm. In the illustrated example, the protrusion length of the support portions 622 is smaller than the thickness of the bottom plate 62.

A gap 624 is formed between the upper surface 620 of the bottom plate 62 and the base surfaces 440b, 440b, and potting resin 300 is filled inside this gap. The base surfaces 440b, 440b are in partial contact with the bottom plate 62 and are partially connected to the bottom plate 62 via the potting resin 300.

The base surfaces 440b, 440b are floating above the upper surface 620 of the bottom plate 62 in positions other than where the support portion 622 is provided, and the entire base surfaces 440b, 440b do not come into contact with the upper surface 620 of the bottom plate 62. Therefore, the contact area between the base surfaces 440b, 440b and the bottom plate 62 can be reduced, thereby reducing the stress on the lower cores 40b, 40b caused by the difference in thermal expansion coefficients between the two, and preventing cracks from forming in the lower cores 40b, 40b (especially near the bases of the outer leg portions 48b, 48b in the base portions 44b, 44b).

Furthermore, at the location where the support portion 622 is provided, heat generated in the core assembly 40, etc., can be transmitted to the bottom plate 62 via the support portion 622, and the heat can be dissipated via the bottom plate 62. At locations other than where the support portion 622 is provided, heat generated in the core assembly 40, etc., can be dissipated via the potting resin 300 filled in the gap 624 and the bottom plate 62.

(2) As shown in Figure 10, a plurality (eight) of contact portions 441 may be integrally formed on the base surfaces 440b, 440b of the lower cores 40b, 40b. Each of the plurality of contact portions 441 consists of a convex portion (projection) that protrudes from the base surfaces 440b, 440b of the base portions 44b, 44b. The shape and size of the contact portions 441 are the same as those of the support portion 622 in the above modified example (1). The contact portions 441 are formed discretely (locally) on the base surfaces 440b, 440b and contact the upper surface 620 of the bottom plate 62 of the case 60 at a position spaced downward from the base surfaces 440b, 440b.

When the lower cores 40b, 40b are placed on the upper surface 620 of the base plate 62, the base portions 44b, 44b locally (partially) contact (join) the base plate 62. The gap 624 between the upper surface 620 of the base plate 62 and the base surfaces 440b, 440b is filled with potting resin 300, so the lower cores 40b, 40b partially contact the base plate 62, and the base surfaces 440b, 440b are partially connected to the base plate 62 via the potting resin 300.

In the example shown in Figure 10, the contact area between the lower cores 40b, 40b and the bottom 62 is reduced, thereby reducing the stress on the lower cores 40b, 40b caused by the difference in thermal expansion coefficients between the two, and preventing cracks from forming in the lower cores 40b, 40b (especially near the base of the outer leg portions 48b, 48b in the base portions 44b, 44b). Furthermore, at locations other than where the contact portions 441 are formed, heat generated in the core assembly 40, etc., can be effectively dissipated via the potting resin 300 and the bottom plate 62. At the locations where the contact portions 441 are formed, the heat can be transmitted to the bottom plate 62 via the contact portions 441 for heat dissipation. As shown in the figure, multiple (eight) contact portions 441 may also be integrally formed on the base surfaces 440a, 440a of the upper cores 40a, 40a.

(3) As shown in Figure 11, a stepped portion 69 may be formed on the bottom plate 62 of the case 60, and the lower cores 40b, 40b may be placed on the upper surface of the stepped portion 69. The stepped portion 69 is formed separately from the bottom plate 62 and constitutes part of the side plate 64. In this case as well, a gap 624 is formed between the base surfaces 440b, 440b and the bottom plate 62, so the contact area between the lower cores 40b, 40b and the bottom 62 is reduced, and the same effects as in the above modifications (1) and (2) can be obtained.

(4) In each of the above embodiments, as shown in Figure 7A, the upper cores 40a, 40a and the lower cores 40b, 40b were housed inside the case 60, but the case 60 is not essential. For example, the upper cores 40a, 40a and the lower cores 40b, 40b may simply be placed on a flat plate made of metal or the like (heat sink). In this case as well, it is preferable that the plate is directly or indirectly fixed to the cooling mechanism.

(5) In each of the above embodiments, the bottom plate 62 and the side plate 64 were both made of metal, but the side plate 64 may be made of, for example, a resin molded body.

(6) In each of the above embodiments, as shown in Figure 2, the core assembly 40 was composed of a combination of E-shaped cores. However, it may also be composed of a combination of U-shaped cores, a combination of an E-shaped core and an I-shaped core, a combination of an E-shaped core and an I-shaped core, or a combination of cores of other shapes. Since E-shaped cores or U-shaped cores are provided with at least outer legs, by composing at least one of the upper cores 40a, 40a and the lower cores 40b, 40b with E-shaped cores or U-shaped cores, the upper cores 40a, 40a and the lower cores 40b, 40b can be joined at the position of the outer legs via a bonding resin.

(7) In each of the above embodiments, as shown in Figure 2, the upper cores 40a, 40a were each composed of segmented cores divided in the X-axis direction, but they may be formed as a single unit. The same applies to the lower cores 40b, 40b.

(8) Although the above embodiments describe examples of applying the present invention to transformers, the present invention may also be applied to other coil devices.

(9) In the second embodiment described above, the gap G may be filled with bonding resin 200 instead of potting resin 300.

10, 110... Coil device 20... Bobbin 31... First coil section 32... Second coil section 40... Core assembly 40a... Upper core 40b... Lower core 42a, 42b... Divided core 44a, 44b... Base section 440a, 440b... Base surface 441... Contact section 46a, 46b... Middle leg section 48a, 48b... Outer leg section 50... Partition cover 60... Case 62... Bottom plate 620... Top surface 622... Support section 624... Gap 64, 264... Side plate 66... Bulging section 68... Boss section 69... Step section 200... Joining resin 300... Potting resin

Claims (4)

A first core and a second core are arranged along the first axial direction and joined to each other via a bonding resin,
On the opposite side of the joint between the first core and the second core, a plate-shaped member is provided that contacts the second core along a plane perpendicular to the first axial direction,
The Young's modulus of the bonding resin is 90 MPa or less.
The glass transition temperature of the bonding resin is 0°C or lower.
The plate-shaped member constitutes a part of the case in which the first core and the second core are housed.
The inside of the aforementioned case is filled with potting resin.
The Young's modulus of the bonding resin is greater than that of the potting resin.
At least one of the first core and the second core has a pair of outer legs and a middle leg formed between each of the pair of outer legs,
A coil device in which the first core and the second core are joined via the bonding resin at all positions of the middle leg portion and the pair of outer leg portions . The coil device according to claim 1 , wherein the upper surface of the potting resin filled inside the case is located above the joint between the first core and the second core. The coil device according to claim 1 or 2 , wherein the Young's modulus of the potting resin is 10 MPa or less. The coil device according to claim 1 or 2, wherein the first core and the second core are combined to form an EE core or an EI core.