Power inductor and method for manufacturing the same

Abstract

To improve the heat dissipation performance and ease of installation of power inductors. [Solution] A method for manufacturing a power inductor 1 integrally molded by injection molding, wherein the coil 2 and the middle leg core 31 are integrated to form a primary molded product A by primary injection molding forming The system includes a step of integrating a primary molded product A, a first outer leg core 32, a second outer leg core 33, a first connecting core 34, a second connecting core 35, and a pair of insulating ceramic plates 4 to form a rectangular parallelepiped power inductor 1.

Description

Technical Field

[0001] The present invention relates to a power inductor integrally formed by injection molding and a method for manufacturing the same.

Background Art

[0002] With the electrification of automobiles, power inductors (reactors) are becoming increasingly important in applications such as large-power charging circuits for batteries and power conversion circuits from batteries to motor drives. Such in-vehicle power inductors operate with high-frequency large currents, so they require a heat dissipation structure with low thermal resistance to the heat sink while maintaining insulation between the coil and the core or heat sink, and a durability structure that can withstand vehicle vibrations, shocks, heat, etc. for a long time. In recent years, integral molding with PPS (polyphenylene sulfide) resin or the like has become the mainstream as an in-vehicle power inductor that meets such requirements (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, such power inductors have room for improvement in terms of heat dissipation performance and installation properties.

Means for Solving the Problems

[0005] The present invention was created in view of the above circumstances and with the aim of solving these problems, and the invention of claim 1 is a power inductor integrally molded by injection molding, comprising an edgewise coil made by winding a flat wire at a right angle, having a pair of planes parallel to each other and a pair of sides parallel to each other, wherein at least one of the pair of planes functions as a heat dissipation surface, a middle leg core inserted through the hollow part of the coil, a first outer leg core arranged in parallel with the middle leg core and along one of the sides of the coil, and a second outer leg core arranged in parallel with the middle leg core and along the other side of the coil. The power inductor is characterized by comprising: a first connecting core that connects one end of the middle leg core, the first outer leg core, and the second outer leg core; a second connecting core that connects the other ends of the middle leg core, the first outer leg core, and the second outer leg core; an insulating ceramic plate arranged along the heat dissipation surface; a primary molded resin part formed by primary injection molding, which integrates the coil and the middle leg core to form a primary molded product; and a secondary molded resin part formed by secondary injection molding, which integrates the primary molded product, the first outer leg core, the second outer leg core, the first connecting core, the second connecting core, and the insulating ceramic plate to form a rectangular parallelepiped power inductor. Furthermore, the invention of claim 2 is a method for manufacturing a power inductor integrally molded by injection molding, wherein the power inductor is composed of an edgewise coil made by winding a flat wire at a right angle, and has a pair of heat dissipation surfaces and a pair of sides parallel to each other, with at least one of the pair of planes functioning as a heat dissipation surface, a middle leg core inserted through the hollow portion of the coil, a first outer leg core arranged in parallel with the middle leg core and along one of the sides of the coil, a second outer leg core arranged in parallel with the middle leg core and along the other side of the coil, and the middle leg core, the first outer The power inductor comprises a first connecting core that connects one end of the leg core and the second outer leg core, a second connecting core that connects the other ends of the middle leg core, the first outer leg core and the second outer leg core, and an insulating ceramic plate arranged along the heat dissipation surface, and the method for manufacturing the power inductor is characterized by comprising: a primary injection molding step of integrating the coil and the middle leg core to form a primary molded product, and a secondary injection molding step of integrating the primary molded product, the first outer leg core, the second outer leg core, the first connecting core, the second connecting core and the insulating ceramic plate to form the power inductor in the shape of a rectangular parallelepiped. Furthermore, the invention of claim 3 is a method for manufacturing a power inductor as described in claim 2, characterized in that in the primary injection molding step, injection molding is performed while pressing at least one of the planes so that the thickness between the pair of planes of the coil becomes a predetermined thickness. Furthermore, the invention of claim 4 is a method for manufacturing a power inductor as described in claim 2, characterized in that in the secondary injection molding step, injection molding is performed while pressing the first outer leg core, the second outer leg core, the first connecting core, the second connecting core, and the insulating ceramic plate toward the primary molded product. Furthermore, the invention of claim 5 is a method for manufacturing a power inductor as described in claim 2, further comprising a coil lead bending step of bending one of a pair of coil lead wires drawn from the primary molded product so that it is drawn in the same direction as the other coil lead wire, and in the secondary injection molding step, injection molding is performed while pressing in a portion of the bent coil lead wire to embed it in resin. [Effects of the Invention]

[0006] According to the invention of claim 1 or 2, a power inductor in the shape of a rectangular parallelepiped with excellent installability can be integrally molded by two injection molding processes. Furthermore, since the power inductor of the present invention has a coil heat dissipation surface that can be cooled via an insulating ceramic plate, it can exhibit excellent heat dissipation performance while ensuring insulation. Furthermore, according to the invention of claim 3, in the primary injection molding step, injection molding is performed while pressing at least one of the planes so that the thickness between the pair of planes of the coil becomes a predetermined thickness. As a result, the flatness and parallelism of the coil planes can be improved, and the degree of contact between the coil plane (coil heat dissipation surface) and the heat sink can be increased, thereby improving the cooling efficiency of the power inductor. Furthermore, according to the invention of claim 4, in the secondary injection molding step, the first outer leg core, the second outer leg core, the first connecting core, the second connecting core, and the insulating ceramic plate are pressed toward the primary molded product while injection molding is performed, so that the cores are tightly fixed together without any gaps, and a decrease in magnetic performance due to gaps between the cores can be prevented. In addition, since the heat dissipation surface of the coil and the insulating ceramic plate can be tightly fixed together, a decrease in heat dissipation performance due to gaps can also be prevented. Furthermore, according to the invention of claim 5, the invention further includes a coil lead bending step in which one of the pair of coil lead wires drawn from the primary molded product is bent so that it is drawn in the same direction as the other coil lead wire. This facilitates the electrical connection of the coil lead wires and further improves the ease of installation of the power inductor. In addition, in the secondary injection molding step, the injection molding is performed while pressing in a portion of the bent coil lead wire and embedding it in the resin, thereby improving the insulation of the coil lead wires. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of a power inductor according to one embodiment of the present invention. [Figure 2] This is a perspective view showing the components of a power inductor. [Figure 3] This is an explanatory diagram of the primary injection molding step. [Figure 4] This is a perspective view of the primary molded product. [Figure 5] This is a perspective view showing the components of a secondary injection molding process. [Figure 6] This is an explanatory diagram of the secondary injection molding step. [Figure 7] This is a perspective view showing the secondary molded resin part. [Figure 8] This is a perspective view showing a modified version of the mid-leg core. [Figure 9] This is a perspective view showing a power inductor of the second embodiment. [Figure 10] This is a perspective view showing a power inductor of the third embodiment. [Modes for carrying out the invention]

[0008] [Power Inductor] Embodiments of the present invention will be described below with reference to the drawings. In Figures 1 to 7, 1 is a power inductor integrally molded by injection molding (insert molding) of an insulating resin material such as PPS resin, and the power inductor 1 comprises a coil 2, a core body 3, two insulating ceramic plates 4, a primary molded resin part 5, and a secondary molded resin part 6.

[0009] Coil 2 is composed of an edgewise coil made by winding a flat rectangular wire at a right angle. Coil 2 has a roughly rectangular cylindrical shape, and its outer surface has a pair of parallel heat dissipation surfaces 2a and a pair of parallel side surfaces 2b. Coil 2 also includes a first coil lead wire 2c drawn out from one end in the direction of the coil's central axis along the direction of the coil's central axis, and a second coil lead wire 2d drawn out from the other end in the direction of the coil's central axis along the direction of the coil's central axis. The second coil lead wire 2d is formed to be longer than the first coil lead wire 2c and is bent so as to be drawn out in the same direction as the first coil lead wire 2c.

[0010] The core body 3 is composed of a combination of a middle leg core 31, a first outer leg core 32, a second outer leg core 33, a first connecting core 34, and a second connecting core 35.

[0011] The central leg core 31 is inserted through the hollow portion of the coil 2. The vertical cross-sectional shape of each core 31-35 in the direction of magnetic flux passage is rectangular, but it may also be oval or elliptical. Furthermore, in order to promote the fluidity of the resin in primary injection molding, it is desirable that the central leg core 31 has multiple grooves 31a arranged in parallel along the direction of magnetic flux passage (coil insertion direction) on both its front and back surfaces.

[0012] The first outer leg core 32 is arranged along one side surface 2b of the coil 2 so as to be parallel to the middle leg core 31. The second outer leg core 33 is arranged along the other side surface 2b of the coil 2 so as to be parallel to the middle leg core 31. The first connecting core 34 is arranged to connect one end portions of the middle leg core 31, the first outer leg core 32, and the second outer leg core 33 to each other. The second connecting core 35 is arranged to connect the other end portions of the middle leg core 31, the first outer leg core 32, and the second outer leg core 33 to each other. Note that grooves 34a and 35a for drawing out the coil lead wires 2c and 2d are formed in the first connecting core 34 and the second connecting core 35.

[0013] The two insulating ceramic plates 4 are arranged along a pair of heat dissipation surfaces 2a of the coil 2. The insulating ceramic plates 4 ensure insulation between the heat dissipation surface 2a of the coil 2 and a heat sink (not shown), and closely adhere the heat dissipation surface 2a of the coil 2 and the heat sink with low thermal resistance.

[0014] The primary molded resin part 5 is formed by primary injection molding, and integrates the coil 2 and the middle leg core 31 to form a primary molded product A. Specifically, as shown in FIG. 4, in primary injection molding, the primary molded resin part 5 is filled between the inner peripheral surface of the coil 2 and the outer peripheral surface of the middle leg core 31, and integrates the coil 2 and the middle leg core 31 while insulating the coil 2 and the middle leg core 31.

[0015] The secondary molded resin part 6 is formed by secondary injection molding, and integrates the primary molded product A, the first outer leg core 32, the second outer leg core 33, the first connecting core 34, the second connecting core 35, and the two insulating ceramic plates 4 to form a rectangular parallelepiped-shaped power inductor 1.

[0016] [Manufacturing Method of Power Inductor] Next, the manufacturing method of the power inductor 1 will be described with reference to FIGS. 3 to 7. However, in the drawings, only the main part of the primary molding die 7 is shown, and the illustration of the secondary molding die is omitted.

[0017] The method for manufacturing the power inductor 1 includes a primary injection molding step of integrating the coil 2 and the middle leg core 31 to form a primary molded product A; a coil lead wire bending step of bending one of a pair of coil lead wires 2c and 2d drawn from the primary molded product A so that it is drawn in the same direction as the other coil lead wire 2c; and a secondary injection molding step of integrating the primary molded product A, the first outer leg core 32, the second outer leg core 33, the first connecting core 34, the second connecting core 35, and two insulating ceramic plates 4 to form a rectangular parallelepiped power inductor 1.

[0018] According to this method for manufacturing the power inductor 1, a rectangular parallelepiped power inductor 1 with excellent installation properties can be formed by two injection molding processes. Furthermore, since the power inductor 1 has a pair of coil heat dissipation surfaces 2a that can be cooled via an insulating ceramic plate 4, it can exhibit excellent heat dissipation performance while ensuring insulation. The following describes specific examples of each step in the manufacturing method of the power inductor 1.

[0019] As shown in Figure 3, the primary injection molding step is performed by placing the coil 2 and the middle leg core 31 in the primary molding die 7, then closing the primary molding die 7 and injecting resin between the coil 2 and the middle leg core 31. At this time, in the primary injection molding step of this embodiment, injection molding is performed while pressing at least one of the heat dissipation surfaces 2a so that the thickness between the pair of heat dissipation surfaces 2a of the coil 2 (thickness after molding) becomes a predetermined thickness W. This improves the flatness and parallelism of the heat dissipation surfaces 2a of the coil 2, and increases the degree of contact between the heat dissipation surfaces 2a of the coil 2 and the heat sink.

[0020] To explain in more detail, as shown in Figure 3, the primary molding die 7 includes at least a fixed die 71 having a first surface 71a for positioning one end face of the middle leg core 31 and a second surface 71b for positioning one heat dissipation surface 2a of the coil 2, a first movable die 72 that sandwiches the coil 2 between itself and the second surface 71b of the fixed die 71, and a second movable die 73 that sandwiches the middle leg core 31 between itself and the first surface 71a of the fixed die 71.

[0021] In the primary injection molding step, as shown in Figure 3, the coil 2 and the middle leg core 31 are placed vertically in the primary molding die 7. Then, the first movable die 72 and the second movable die 73 are moved to position the coil 2 and the middle leg core 31. Furthermore, the first movable die 72 applies pressure to press down on the heat dissipation surface 2a of the coil 2, and is ultimately moved to the final position shown in Figure 3.

[0022] The thickness W1 of the coil 2 in its natural state (before primary molding) is slightly greater than the target thickness W after primary injection molding. Therefore, as shown in Figure 4, the shape of the coil 2 deforms slightly in the width direction (direction between the side surfaces 2b) and expands compared to before primary injection molding due to the pressing of the first movable mold 72. Subsequently, when PPS resin at a high temperature (for example, around 300°C) is poured into the gap between the coil 2 and the central leg core 31, the coil 2 and the coating on the coil 2 are instantaneously heated by the resin temperature and become slightly softer. As the resin solidifies, the shape of the coil 2 also solidifies, creating a pair of heat dissipation surfaces 2a with high flatness and parallelism.

[0023] In the primary injection molding step and immediately thereafter, the coil lead wires 2c and 2d are drawn linearly along the coil central axis. In the coil lead wire bending step, one of the pair of coil lead wires 2c and 2d drawn from the primary molded product A, the coil lead wire 2d, is bent so that it is drawn in the same direction as the other coil lead wire 2c. For example, as shown in Figure 6, one coil lead wire 2d is bent at multiple locations (e.g., four locations) in the second injection molding step so that it wraps around the outer circumference of the first connecting core 34, the first outer leg core 32, and the second connecting core 35 to the vicinity of the other coil lead wire 2c.

[0024] In the secondary injection molding step, as shown in Figures 5 and 6, the primary molded product A, the first outer leg core 32, the second outer leg core 33, the first connecting core 34, the second connecting core 35, and the two insulating ceramic plates 4 are placed in a secondary molding die (not shown), and then the secondary molding die is closed and PPS resin is injected. This secondary injection molding step is performed while pushing the first outer leg core 32, the second outer leg core 33, the first connecting core 34, the second connecting core 35, and the two insulating ceramic plates 4 toward the primary molded product A.

[0025] This secondary injection molding step ensures that the cores 31-35 are tightly and securely fixed together without any gaps, preventing a decrease in magnetic performance due to gaps between the cores 31-35. Furthermore, since the heat dissipation surface 2a of the coil 2 and the insulating ceramic plate 4 are tightly fixed together, a decrease in heat dissipation performance due to gaps is also prevented. The two insulating ceramic plates 4 are pre-attached to the heat dissipation surface 2a of the primary molded product A (coil 2) via adhesive, and then tightly fixed to the heat dissipation surface 2a by secondary injection molding using PPS resin.

[0026] Furthermore, in the secondary injection molding step, as shown in Figure 6, injection molding is performed while pressing multiple points of one of the bent coil lead wires 2d into the outer circumference of the cores 32, 34, and 35, thereby embedding the base of one of the coil lead wires 2d in resin. This improves the insulation properties of the coil lead wire 2d.

[0027] As shown in Figure 7, the secondary injection molding step forms a rectangular parallelepiped power inductor 1, which is surrounded by a secondary molded resin part 6 or an insulating ceramic plate 4. Round holes 6a and 6b are formed on the sides of the power inductor 1, which are the marks left by pressing in the cores 32-35 and the coil lead wires 2d. The necessary insulation distance (distance from the heat sink or metal chassis) is ensured between these round holes 6a and 6b and the heat dissipation surface of the power inductor 1 (the mounting surface of the insulating ceramic plate 4), but the insulation may be improved by filling the round holes 6a and 6b with insulating material. Furthermore, the insulation of the coil lead wires 2d can be changed by selecting the coating material of the coil winding (enamel coating, PEEK, fluororesin (e.g., Teflon®)), etc.).

[0028] [Differentiation] Next, a modified example of the power inductor 1 will be described with reference to Figure 8. However, for components common to the previously described embodiment, the same reference numerals as in the previously described embodiment may be used, and the description of the previously described embodiment may be referred to.

[0029] The mid-leg core 31 in the embodiment described above does not have a gap, but as shown in Figure 8, a mid-leg core 31B with a gap may be used to adjust the characteristics of the power inductor 1. Such a mid-leg core 31 can be composed of, for example, a plurality of divided cores 31b divided in the direction of magnetic flux passage and gap spacers 31c connecting the divided cores 31b.

[0030] It should be noted that the present invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the claims.

[0031] For example, in the embodiment described above, PPS resin was used as an example of the resin material used for integral molding of the power inductor 1, but the resin material used is not limited to PPS resin, and may be PBT, nylon, or other resins.

[0032] Furthermore, in the embodiment described above, the two planes of the coil 2 are used as heat dissipation surfaces 2a, and an insulating ceramic plate 4 is arranged along each heat dissipation surface 2a to realize an insulating heat dissipation structure. However, the heat dissipation surface 2a may be either one of the two planes of the coil 2.

[0033] Furthermore, the insulating ceramic plate 4 may be used not only to insulate the coil 2, but also to insulate the core body 3.

[0034] Furthermore, the routing paths and routing directions of the coil lead wires 2c and 2d are not limited to the embodiments described above. For example, in the embodiments described above, the coil lead wire 2d was routed along the outer circumference of the core body 3, but as shown in Figure 9, the coil lead wire 2d may be routed along the inner circumference of the core body 3. Doing so not only shortens the length of the coil lead wire 2d but also reduces the bending process.

[0035] Furthermore, in the embodiment described above, the coil lead wires 2c and 2d are drawn out in the direction of the coil's central axis, but as shown in Figure 10, the coil lead wires 2c and 2d may be drawn out in a direction perpendicular to the coil's central axis. In this way, the coil lead wires 2c and 2d can be drawn out in the same direction without bending the coil lead wire 2d after primary forming. [Explanation of Symbols]

[0036] 1 Power Inductor 2 coils 2a Heat dissipation surface (flat) 2b side 2c, 2d coil lead wires 3 Core Body 31, 31B Mid-leg core 31a Groove 31b Split Core 31c Gap Spacer 32. First outer leg core 33. Second outer leg core 34. First Linked Core 34a groove 35 Second Linked Core 35a groove 4. Insulating ceramic plate 5 Primary molded resin part 6 Secondary molded resin part 6a, 6b Round holes 7. Primary molding die 71 Fixed mold 71a 1st page 71b 2nd side 72 First movable mold 73. Second movable mold

Claims

1. A power inductor integrally molded by injection molding, The coil is constructed from an edgewise coil made by winding a flat wire at a right angle, and has a pair of planes and a pair of sides that are parallel to each other, with at least one of the pair of planes functioning as a heat dissipation surface. A middle leg core inserted through the hollow portion of the coil, A first outer leg core is arranged in parallel with the middle leg core and along one of the sides of the coil, A second outer leg core is arranged in parallel with the middle leg core and along the other side of the coil, A first connecting core that connects one end each of the middle leg core, the first outer leg core, and the second outer leg core, A second connecting core that connects the other ends of the middle leg core, the first outer leg core, and the second outer leg core, An insulating ceramic plate arranged along the heat dissipation surface, A primary molded resin part formed by primary injection molding, which integrates the coil and the central leg core to form a primary molded product, A power inductor characterized by comprising a secondary molded resin part formed by secondary injection molding, which integrates the primary molded product, the first outer leg core, the second outer leg core, the first connecting core, the second connecting core, and the insulating ceramic plate to form the power inductor in the shape of a rectangular parallelepiped.

2. A method for manufacturing a power inductor integrally formed by injection molding, The aforementioned power inductor is The coil is constructed from an edgewise coil made by winding a flat wire at a right angle, and has a pair of planes and a pair of sides that are parallel to each other, with at least one of the pair of planes functioning as a heat dissipation surface. A middle leg core inserted through the hollow portion of the coil, A first outer leg core is arranged in parallel with the middle leg core and along one of the sides of the coil, A second outer leg core is arranged in parallel with the middle leg core and along the other side of the coil, A first connecting core that connects one end each of the middle leg core, the first outer leg core, and the second outer leg core, A second connecting core that connects the other ends of the middle leg core, the first outer leg core, and the second outer leg core, The system comprises an insulating ceramic plate arranged along the heat dissipation surface, The method for manufacturing the power inductor is as follows: A primary injection molding step in which the coil and the central leg core are integrated to form a primary molded product, A method for manufacturing a power inductor, comprising: a secondary injection molding step of integrating the primary molded product, the first outer leg core, the second outer leg core, the first connecting core, the second connecting core, and the insulating ceramic plate to form the power inductor in the shape of a rectangular parallelepiped.

3. The method for manufacturing a power inductor according to claim 2, characterized in that the injection molding is performed in the primary injection molding step while pressing at least one of the planes of the coil so that the thickness between the pair of planes of the coil becomes a predetermined thickness.

4. The method for manufacturing a power inductor according to claim 2, characterized in that, in the secondary injection molding step, the injection molding is performed while pressing the first outer leg core, the second outer leg core, the first connecting core, the second connecting core, and the insulating ceramic plate toward the primary molded product.

5. The process further includes a coil lead bending step in which one of a pair of coil lead wires drawn from the primary molded product is bent so that it is drawn in the same direction as the other coil lead wire. The method for manufacturing a power inductor according to claim 2, characterized in that, in the secondary injection molding step, injection molding is performed while pressing in a portion of one of the bent coil lead wires and embedding it in resin.

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