Core device and method for manufacturing the same

Abstract

We provide technology that can be useful in the manufacturing process. [Solution] The core device applied to the DC-DC converter 100 comprises two core members 130, 140 that form a core corresponding to a coil when assembled in a direction along the coil axis without providing a gap between their mating surfaces, a core clip 160 that is assembled to surround the outside of the core, including at least two points where the mating surfaces of the two core members 130, 140 intersect on their outer surfaces, and capable of holding the two core members 130, 140 pressed against each other in a direction along the coil axis, and a core cover 150 provided between the core clip 160 and the core, covering the outer surfaces of the two core members 130, 140, including at least one point where the mating surfaces intersect.

Description

Technical Field

[0001] The present invention relates to a core device applicable to, for example, transformers, reactors, etc., and a method for manufacturing the same.

Background Art

[0002] As prior art related to this type of core device, etc., for example, a core of a transformer, a choke coil, etc. is known to be constituted by a core member and a core combination member (see, for example, Patent Document 1).

[0003] In this prior art, a pair of core members are installed in a form of sandwiching from both the front and back sides of a substrate on which a coil pattern portion is formed, and further, the pair of core members are sandwiched and combined from both the front and back sides by a core combination member. The core combination member has a substantially U-shaped configuration having a base portion and leg portions respectively formed upright at both end positions thereof, and the tips of each leg portion are bent inwardly facing each other to form claw portions. And the pair of core members are configured to be sandwiched and combined from both the front and back sides by the claw portions and the base portion of the core combination member.

[0004] According to the configuration of the prior art, even after a pair of core members are installed on the substrate, the pair of core members are always sandwiched by the core combination member. Therefore, for example, when a gap is not intentionally provided between the mating surfaces of the pair of core members, it is considered possible to prevent the coil characteristics (inductance value) from deteriorating due to the inadvertent formation of a gap or misalignment between the mating surfaces.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The aforementioned prior art incorporates ingenuity into the detailed shape of the core assembly components, aiming to achieve a good fit with the core components after assembly. However, the prior art is so focused on improving the condition of the product after assembly that it lacks consideration for the manufacturing process.

[0007] Therefore, the present invention provides a technology that can be useful in the manufacturing process. [Means for solving the problem]

[0008] To solve the above problems, the present invention employs the following solutions. Note that the parenthetical statements and other references in the following description are merely examples, and the present invention is not limited thereto.

[0009] [Invention of the device] The present invention provides a coil device. This coil device comprises two core members and a core clip. The two core members are combined in the direction of the coil's axis (coil center) to form a gapless type core, and the two core members are held in a state where they are pressed against each other by the core clip.

[0010] As a result, in the completed core device, the good characteristics of a gapless type core can be maintained by holding the two core components with core clips. However, these are known technical means specific to the completed state and do not contribute to the manufacturing process on their own.

[0011] Therefore, the inventors of the present invention focused on the need for technical means that would contribute to the manufacturing process and conceived the core device of the present invention through research and development. As a result, the coil device of the present invention adopts a configuration that includes a core cover. This core cover is provided between the core clip and the core (two core members in an assembled state). The core cover covers the outer surfaces of the two core members, and the area that covers the outer surfaces includes at least one point where the mating surfaces of the two core members intersect.

[0012] This solves the following problems in the manufacturing process. [Premise] In other words, a core clip capable of holding two core members pressed together is attached in a manner that surrounds the outside of the combined core members. To achieve this function, the core clip is made of a material (such as a leaf spring) capable of generating elastic force (restoring force due to elastic deformation). In the free state before attachment, the inner dimension of one of the parts surrounding the two core members of such a core clip must be set smaller than the outer dimension of the combined core members. When attaching the core clip during the manufacturing process, the core clip must be elastically deformed at some point to expand the inner dimension of the part surrounding the two core members. This allows the core clip to be attached in a manner that surrounds the outside of the two core members. After attachment, the core clip exerts elastic force (restoring force), making it possible to hold the two core members pressed together as described above.

[0013] 〔defect〕 However, a problem arises in the manufacturing process. For example, if a method is used in the manufacturing process in which a part of the core clip is elastically deformed while in contact with the outer surface of the core member, the restoring force at that time will act directly on the core member. Normally, the core member (for example, a sintered ferrite powder member) has sufficient surface hardness, and the restoring force of the core clip is unlikely to cause damage to its contact surface. However, if a method is adopted in which a part of the elastically deformed core clip is in contact with the outer surface of the core member and then slid along that outer surface during installation, one of the two core members will be displaced by the restoring force during the sliding process (e.g., its position will shift along the mating surface), causing the mating surfaces to shift from their normal positions, and a part of the mating surface to be exposed to the outside. In this state, if a part of the contact part passes over the point where the mating surfaces of the two core members intersect with the outer surface, the contact part of the core clip will catch on the exposed mating surface, causing defects such as chipping by cutting along the outer surface of the core member. Damage to core components like this (partial cutting, chipping, etc.) can lead to a deterioration in performance after completion.

[0014] [Solution] The above-mentioned problems are resolved by adopting a core cover. Since the core cover is configured to cover the outer surfaces of two core members, including at least one point where the mating surfaces intersect, the area of ​​the outer surface of the core member that comes into contact with a portion of the core clip during the manufacturing process is protected by the core cover. Therefore, the core cover reliably prevents displacement of the core member due to the restoring force of the core clip, prevents the core clip from getting stuck due to misalignment of the mating surfaces, and reliably prevents damage to the core member.

[0015] This makes it possible to prevent defects that may occur during the manufacturing process and to reliably prevent deterioration of characteristics after completion.

[0016] [Form details] The extent to which the core cover covers the outer surface of the core member depends on the shape of the core clip. In other words, the extent to which the core cover covers the outer surface of the core member can be determined by how the core clip surrounds the outer surface of the core when installed. For example, a single core formed by combining two core members forms a magnetic path in the circumferential direction of the magnetic field (magnetic flux) generated by the coil, and the outer surface along this magnetic path becomes the outer surface. Since such a core is formed by combining two core members, there will always be at least two points where the mating surfaces of the two intersect somewhere within the entire range of its outer surface. If the core clip surrounds only one point where the mating surfaces on the outer surface of the core member intersect, then even if a method is used in which the core clip is elastically deformed along the outer surface of the core member during the manufacturing process, the above-mentioned problems may be avoided depending on the direction and position of installation, and in such cases, the function of the core cover may be unnecessary.

[0017] In contrast, if the core clip is attached in a manner that surrounds both points where the mating surfaces on the outer circumferential surface of the core member intersect, then when the core clip is attached while elastically deforming along the outer circumferential surface of the core member during the manufacturing process, a portion of the core clip will inevitably pass through an area that includes at least one of the points where the mating surfaces on the outer circumferential surface of the core member intersect. In this case, the core cover will function effectively.

[0018] This is also related to the shapes of the two core members. For example, consider a case where the two core members are symmetrical in shape, each having a middle leg and a pair of outer legs, and mating surfaces are formed on the end faces of these middle and outer legs. In this case, the outer surface of the combined core will intersect with the mating surfaces formed on the pair of outer legs of the two core members, so it is preferable that the core cover covers the portion of the outer surface of the core members where these mating surfaces intersect.

[0019] [Electronic components using core devices] The core device of the present invention can have several configurations. For example, it has a configuration including a circuit board, a case member, and a filler. On the circuit board, a coil and an electric circuit can be formed using a wiring pattern, and it is assumed that a through hole is formed in the thickness direction at the position of the axis of the coil. At least two core members can be attached to such a circuit board in a combined state through the through hole. In addition, various circuit elements, external connection terminals, etc. can be appropriately mounted on the circuit board.

[0020] When the two core members have a shape with a middle leg portion and a pair of outer leg portions, the two core members can be made into a non-gap type core corresponding to the coil by bringing the mating surfaces of the middle leg portions into close contact with each other through the through hole. In addition, the above core cover and core clip are attached to the two core members.

[0021] The case member together with the circuit board houses the two core members, the core clip, and the core cover inside, thereby constituting a form as an electronic component packaged with these. And the filler is filled inside the case member to seal the periphery of the circuit board, the two core members, the core clip, and the core cover inside the case member. Such a filler can protect the internal components including the electronic circuit inside the case body from the external environment.

[0022] Even when housed inside the case body as described above and when filling (sealing) with a filler is adopted, the two core members are surely held in a proper combined state by the core clip, so that the characteristic change (for example, the change rate of the inductance of the coil with respect to the ambient temperature based on the case of no filling) accompanying the environmental change after filling is minimized.

[0023] In addition, the core clip can be provided with the advantageous features associated with the adoption of the filler. That is, the core clip is composed of a plate-shaped elastic member surrounding the outside of the core, and a slit penetrating in the thickness direction is formed in the plate-shaped portion. Such a core clip will have a space between it and the outer surface of the core (between the core cover) in the attached state due to its elastic deformation range. It is preferable that such a space (gap) is surely sealed with a filler inside the case body. The above slit prevents the formation of an air pocket between the core clip and the outer peripheral surface of the core during the process of filling the inside of the case body with the filler (filling in a fluid state). Thereby, the filler can be allowed to enter between the core clip and the outer peripheral surface of the core and be surely sealed.

[0024] 〔Invention of manufacturing method〕 The present invention provides the following manufacturing method. This manufacturing method performs the following respective steps.

[0025] 〔Preparation step〕 In this step, a circuit board having a coil and an electric circuit formed using a wiring pattern and having a through hole formed at least at the position of the axis of the coil is prepared. Various circuit elements, external connection terminals, etc. may be appropriately mounted on the circuit board.

[0026] 〔Assembly step〕 In this step, two core members that form a core corresponding to the coil by being combined in the direction along the axis of the coil through the through hole with respect to the circuit board are assembled in a state where no gap is formed between their mating surfaces. Here, the two core members may be in a temporarily assembled state.

[0027] 〔Arrangement step〕 In this step, a core cover that covers the outer surfaces of the two core members in a range including at least one location where their mating surfaces intersect is arranged with respect to the two core members assembled on the circuit board. The core cover may cover the outer surface including two locations where the mating surfaces of the two core members intersect.

[0028] [Installation process] In this step, core clips are attached to the outside of the two core members to which the core cover is attached. The core clips are assembled in such a way that they surround the outside of the core, including at least two points where the mating surfaces intersect on the outer surfaces of the two core members. This presses the two core members together in a direction along the coil axis, while exerting a holding force that maintains the assembled state on the circuit board.

[0029] In particular, in this process, since the two core components are already assembled to the circuit board in the previous assembly process, the core clip cannot be attached from a position or direction where the circuit board interferes (becomes an obstacle). As a result, if one attempts to attach the core clip from a position or direction where the circuit board does not interfere, a portion of the core clip will inevitably pass through an area that includes at least one point where the mating surfaces of the two core components intersect on their outer surfaces, thus effectively protecting the outer surface with the core cover.

[0030] Therefore, according to the above manufacturing method, in the process of assembling the core clip, the outer surface of the two core members is already covered by the core cover, including one point where the mating surfaces intersect. By attaching the core clip from the outside, even if a part of the core clip comes into contact with the outer surface, that contact point is protected by the core cover. This reliably prevents the occurrence of the above-mentioned defects.

[0031] Furthermore, the above manufacturing method can further simplify the assembly of the core clip. For example, in the core clip assembly process, it is conceivable to attach the core clip to the outside of the two core members while elastically deforming the core clip independently. However, this method requires a first action of gripping the core clip independently, a second action of elastically deforming the core clip gripped in the first action, and a third action of attaching the core clip, which has been elastically deformed in the second action, by covering it from the outside of the two core members.

[0032] In contrast, with the above manufacturing method, the core clip can be elastically deformed through a series of actions, such as bringing the core clip into contact with the two core members from the outside of the core cover and then pressing the core clip through the core cover. Therefore, there is no need to perform actions to grip the core clip individually or actions to elastically deform it based on such actions. This simplifies the work process and improves manufacturing efficiency. The structure of the core device of the present invention makes it possible to realize such a manufacturing method. [Effects of the Invention]

[0033] As described above, the present invention can provide technology that contributes to the manufacturing process. [Brief explanation of the drawing]

[0034] [Figure 1] This is a perspective view of a DC-DC converter 100 to which the core device of one embodiment is applied. [Figure 2] This is a disassembled perspective view of the DC-DC converter 100. [Figure 3] This figure shows an example of the assembly configuration of the core device in one embodiment. [Figure 4] This is a sequential diagram showing the manufacturing process of the core device in order of steps. [Figure 5] This is a sequential diagram showing the manufacturing process of the core device in order of steps. [Figure 6] This is a longitudinal cross-sectional view showing an example of protection configuration during the manufacturing process by the core cover 150. [Figure 7] This is a sequence diagram showing the manufacturing process of the comparative example. [Figure 8] This is a cross-sectional view showing another example of a DC-DC converter 100 to which the core device of this embodiment is applied. [Figure 9] This is a data comparison chart of inductance change rates. [Modes for carrying out the invention]

[0035] Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, a core device applied to a board-mounted transformer (planar transformer) of a DC-DC converter is given as an example, but the present invention is not limited to this.

[0036] Figure 1 is a perspective view of a DC-DC converter 100 to which a core device of one embodiment is applied. In Figure 1(A), it is an upper perspective view of the DC-DC converter 100, and in Figure 1(B), it is a lower perspective view thereof. Here, as an example, the width direction (X-axis direction) of the DC-DC converter 100 is defined in the diagonal downward left direction in Figure 1(A), its forward direction (Y-axis direction) is defined in the diagonal downward right direction, and its height direction is defined in the upward direction (Z-axis direction). Furthermore, Figure 1(B) shows the DC-DC converter 100 inverted vertically around the X-axis as shown in Figure 1(A).

[0037] [Configuration overview] To briefly describe the configuration of the DC-DC converter 100, the DC-DC converter 100 includes a case member 110, and a circuit board unit 120 is housed inside this case member 110. The circuit board unit 120 includes a circuit board 122 and connection terminal units 124 and 126, and when the connection terminal units 124 and 126 are mounted on the circuit board 122, their connection terminals (not shown) protrude from the case member 110. In one embodiment, the core device, when mounted on the circuit board unit 120, functions as a core device that constitutes the transformer of the DC-DC converter 100.

[0038] [Internal structure] Figure 2 is an exploded perspective view of the DC-DC converter 100. Figure 2 shows the configuration of the circuit board unit 120 and the core device of one embodiment in more detail. Defining the front-to-back and left-to-right directions for the DC-DC converter 100 as a whole, the Y-axis direction shown in Figure 2 is the front-to-back direction, and the X-axis direction, which is perpendicular to it, is the left-to-right direction. Also, the vertical direction (height direction, thickness direction) of the DC-DC converter 100 is the Z-axis direction.

[0039] The circuit board unit 120 includes a circuit board 122 as described above, on which the above-mentioned connection terminal units 124 and 126 are mounted, as well as a core device according to one embodiment. The core device includes two core members 130 and 140, which form a pair in the vertical direction. The core device also includes a core cover 150 and a core clip 160, of which the core cover 150 is positioned to cover the outer surfaces of the core members 130 and 140. The core clip 160 is further attached from the outside of the core cover 150 so as to surround the outside of the core members 130 and 140 (the outer peripheral surface around the Y axis). A more detailed explanation follows below.

[0040] [Two core components] The two core members 130 and 140 are assembled to the circuit board 122 by sandwiching it from above and below (in the thickness direction), and are combined to form one core (no reference numerals). Such core members 130 and 140 are formed, for example, by sintering ferrite powder. The two core members 130 and 140 constitute an EE-type core as an example, and each has a central leg portion 130a and 140a at the left-right center position, and a pair of outer leg portions 130b and 140b at both ends. The end faces of the central leg portions 130a and 140a and the pair of outer leg portions 130b and 140b of the two core members 130 and 140 are smoothed mating surfaces, and these mating surfaces are tightly pressed together without any gaps to form one core (a no-gap type core).

[0041] [Circuit board] The circuit board 122 has through-holes 122a that penetrate vertically (in the thickness direction), and these through-holes 122a are rectangular in shape, corresponding to the middle leg portions 130a and 140a of the core members 130 and 140. Primary and secondary coils are formed on the circuit board 122 using a wiring pattern (not shown) around the through-holes 122a, and electrical circuits connected to these primary and secondary coils are also formed. For this reason, various circuit components (circuit elements, etc.) 128 that constitute the electrical circuits are also mounted on the circuit board 122. In addition, various circuit elements (not shown) are also mounted on the mounting surface of the circuit board 122.

[0042] Furthermore, the circuit board 122 has notches 122b formed on both the left and right side edges flanking the through hole 122a, and these notches 122b extend from both side edges toward the center. In the combined state of the core members 130 and 140 (mounted on the circuit board 122), the pair of outer legs 130b and 140b are positioned within the left and right notches 122b, respectively. Therefore, the two core members 130 and 140 are combined with their mating surfaces (3 locations) in close contact without any gaps, with their respective middle legs 130a and 140a inserted into the through hole 122a and their respective pair of outer legs 130b and 140b positioned within the left and right notches 122b. Furthermore, in this combined state, the two core members 130 and 140 are positioned to some extent in the front-to-back, left-to-right, and up-to-down directions relative to the circuit board 122 (they do not shift significantly to the outside, such as to the through-hole 122a).

[0043] [Core cover] The core cover 150 has a gate-like (or bridge-like, downward-facing U-shaped) form that follows the outer circumferential surfaces of the two core members 130 and 140. The core cover 150 is formed, for example, by press-forming a thin copper plate (for example, about 0.15 mm thick), and has a connecting portion 150a in the center in the left-right direction, as well as a pair of abutment plates 150b on both the left and right sides. The connecting portion 150a extends in a flat plate shape in the left-right direction (X-axis direction) along the mounting surface of the circuit board 122, and the pair of abutment plates 150b are formed by bending downward from both ends in the left and right direction. The width of the pair of abutment plates 150b in the front-rear direction is slightly wider than that of the connecting portion 150a, so that it is positioned to some extent in the front-rear direction within the notch 122b of the circuit board 122 together with the two core members 130 and 140 (it does not shift position significantly). The core cover 150 may be made of a material other than copper (for example, an aluminum plate, a resin plate, etc.), and its plate thickness may differ from that of the example.

[0044] [Core Clip] The core clip 160 has a gate-like shape that surrounds the outer circumferential surfaces of the two core members 130 and 140 from the outside of the core cover 150. The core clip 160 is formed by press-forming a metal plate (stainless steel plate, spring steel plate, etc.), and has a pressing plate portion 160a at the center in the left-right direction, and a pair of shoulder portions 160d are formed adjacent to the left and right sides of this pressing plate portion 160a. At both ends of the core clip 160 in the left-right direction, a pair of gate legs 160b are formed, and at the lower end of the pair of gate legs 160b, a pair of pressing claw portions 160c are formed.

[0045] The pressing plate portion 160a described above is formed, for example, in the shape of a rectangular flat plate, and a pair of shoulder portions 160d extend from both the left and right ends of the pressing plate portion 160a so as to be inclined diagonally upward in the left and right directions. A pair of gate legs 160b extend from both the left and right ends of the pair of shoulder portions 160d so as to be bent downward, and a pair of pressing claw portions 160c protrude from the lower ends of each so as to be bent inward on the left and right sides.

[0046] Furthermore, the core clip 160 has a pair of slits 160e formed on it, extending from the pair of shoulder portions 160d to the gate leg portion 160b. The pair of slits 160e are formed as cuts that penetrate the plate material of the core clip 160 in the thickness direction, and the ends of the groove-like cuts are formed in a circular shape.

[0047] [Example of assembly configuration] Figure 3 shows an example of the assembly configuration of a core device according to one embodiment. Figure 3(A) is a perspective view, Figure 3(B) is a longitudinal cross-sectional view in the left-right direction (cross-sectional view BB of (A)), and Figure 3(C) is a longitudinal cross-sectional view in the front-back direction (cross-sectional view CC of (A)).

[0048] In Figure 3(A): In the assembly configuration of the core device in this example, the two core members 130 and 140 are assembled vertically with a circuit board 122 in between. At this time, the two core members 130 and 140 are formed as a type of core (so-called no-gap core) that does not have a gap between their mating surfaces, and constitute cores corresponding to primary and secondary coils (not shown) formed on the circuit board 122. The axes (coil centers) of the primary and secondary coils are located in the center of the through hole 122a, and the middle leg portions 130a and 140a of the two core members 130 and 140 are assembled along the axis of the coils. The pair of outer leg portions 130b and 140b are each located apart in the left-right direction with a coil formation area (not shown) in between the middle leg portions 130a and 140a, and are each assembled vertically within the notch 122b.

[0049] As shown in Figure 3(B): the vertical section in the left-right direction, the core formed by the two core members 130 and 140 forms a magnetic path for the magnetic field (magnetic flux) generated by a coil (not shown). The outer surface of the core along this magnetic path is formed as a continuous series of outer surfaces of the two core members 130 and 140. Therefore, the outer surface of the core includes two points where the mating surfaces of the two core members 130 and 140 intersect, particularly the mating surfaces of the pair of outer legs 130b and 140b (in this case, on the left and right end faces).

[0050] The core cover 150, when the two core members 130 and 140 are combined, covers the entire outer surface (in this case, the upper half) of one core member 130 (in this case, the upper) along the magnetic path of the core, and covers at least the area (in this case, a part of the lower half) of the other core member 140 where the mating surfaces of the pair of outer legs 130b and 140b intersect on the outer surface of the core.

[0051] Looking at the core cover 150, the connecting portion 150a and the pair of abutment plates 150b connected thereto cover the entire area where one core member 130 forms the outer circumferential surface of the core. In other words, the entire upper half of the outer circumferential surface of the core as a whole is covered. As for the lower half, a portion of the area where the other core member 140 forms the outer circumferential surface of the core is covered by the pair of abutment plates 150b. However, this portion is not the area located below the core (bottom surface), but rather a part of both the left and right end surfaces, and is the area where the mating surfaces of the pair of outer legs 130b and 140b intersect on the outer circumferential surface as described above.

[0052] In its installed state, the core clip 160 has its lower surface contacting the pressing plate portion 160a, applying a downward force (downward arrow P in the figure) to one of the core members 130 from the outside of the core cover 150. The pair of pressing claw portions 160c also contact the outer surface (lower surface) near the lower corner of the other core member 140 in the installed state, applying an upward force (upward arrow P in the figure) to the other core member 140. As a result, the core clip 160 can hold the two core members 130 and 140 pressed against each other in its installed state.

[0053] In its free state, the pair of shoulder portions 160d of the core clip 160 extend horizontally from the pressing plate portion 160a, each inclined diagonally upward. However, when the core clip 160 is installed, it elastically deforms downward from both sides of the pressing plate portion 160a, reducing the angle of inclination compared to its free state. This is because the core clip 160 is installed by hooking the pair of pressing claw portions 160c onto the underside of the lower core member 140. The restoring force at this time allows the core clip 160 to exert a force (arrow P in the figure) that presses the two core members 130 and 140 against each other, as described above.

[0054] Furthermore, the extent to which the core clip 160 surrounds the two core members 130 and 140 from the outside of the core cover 150 is as follows: With the two core members 130 and 140 pressed together, the core clip 160 surrounds the entire outer surface of one core member (in this case, the upper one) 130 along the magnetic path formed by the core, and surrounds the entire area of ​​the outer surface where the mating surfaces of the pair of outer legs 130b and 140b intersect (in this case, the entire area of ​​both end faces), and a portion of the area where the mating surfaces do not intersect (in this case, a portion of the bottom surface), for the other core member 140.

[0055] Looking at the core clip 160, the pressing plate portion 160a, the pair of shoulder portions 160d connected thereto, and the pair of gate leg portions 160b cover the entire area in which one core member 130 forms the outer circumferential surface of the core from the outside of the core cover 150. In other words, the entire upper half of the outer circumferential surface of the core is covered from the outside of the core cover 150. As for the lower half, a portion of the area in which the other core member 140 forms the outer circumferential surface of the core is covered by the pair of gate leg portions 160b and the pressing claw portion 160c. This area includes the entire area of ​​both the left and right end faces of the core, that is, the entire area where the mating surfaces of the pair of outer leg portions 130b and 140b intersect on the outer circumferential surface, and a portion of the lower surface of the core, that is, a portion of the area where the aforementioned mating surfaces do not intersect on the outer circumferential surface.

[0056] As shown in Figure 3(C): the longitudinal section in the front-rear direction, along the axis of the coil, the middle legs 130a and 140a of the two core members 130 and 140 are in close contact with each other without any gaps and are held together by the core clip 160. As described above, on the upper side, the pressing plate portion 160a of the core clip 160 presses downward against the upper core member 130 from the outside of the core cover 150, and on the lower side, the pressing claw portion 160c presses upward against the lower core member 140 (arrows are not shown).

[0057] [Manufacturing method] Next, the manufacturing method (assembly process) of the core device of this embodiment will be described. Figures 4 and 5 are sequential diagrams showing the manufacturing method of the core device in order of steps. The following will be explained according to an example procedure.

[0058] [Preparation Steps] Figure 4 (A): The preparation process is carried out. In this process, the circuit board 122 described above is prepared. Note that the circuit board 122 prepared here may or may not have wiring patterns, connection terminal units 124, 126, and other circuit components 128 (see Figure 2) already mounted on it.

[0059] [Assembly process] In Figure 4 (A): In the next assembly step, two separately prepared core members 130 and 140 are assembled to the circuit board 122. Here, as a preferred example, the circuit board 122 is assembled relative to one core member 140 positioned below it, so that the middle leg portion 140a of the core member 140 is inserted through the through hole 122a and the pair of outer leg portions 140b are positioned within the notches 122b. Then, the other core member 130 is assembled from above, so that the middle leg portion 130a is inserted through the through hole 122a and the pair of outer leg portions 130b are positioned within the notches 122b. In this way, the two core members 130 and 140 are assembled without any gap being formed between their mating surfaces. Note that, here, the core members 130 and 140 may also be assembled from above and below the circuit board 122, respectively.

[0060] [Placement process] In Figure 4(B): In the next placement step, the core cover 150 is placed over the two core members 130 and 140 assembled on the circuit board 122, for example, from the upper position indicated by the dashed line. With this placement, the core cover 150 is in the positional relationship with respect to the two core members 130 and 140 as shown in the cross-sectional view in Figure 3(B). Alternatively, the two core members 130 and 140 may be brought closer together with the circuit board 122 to the core cover 150 which has been stopped at the upper position.

[0061] [Installation process] Figure 5 is a sequence of diagrams showing in more detail an example of the installation process following the placement process described above. In this installation process, the core clips 160 are attached to the two core members 130 and 140 from the outside of the core cover 150. As a preferred example, the procedure shown here involves pressing a portion of the core clip 160 against the core members 130 and 140 from the outside of the core cover 150, causing elastic deformation, and then sliding the pressed portion along the outer surface of the core cover 150 to assemble it.

[0062] In Figure 5 (A): First, the entire core clip 160 is brought close to the two core members 130 and 140 to which the core cover 150 is attached, in an inclined position relative to the mounting surface (coil surface) of the circuit board 122. At this time, the inner surface of one of the pair of gate legs 160b is positioned relative to the two core members 130 and 140, while the other gate leg 160b is positioned above the upper core member 130. Also, one of the pressing claws 160c positioned laterally is positioned below the lower core member 140. As a result, the entire core clip 160 is inclined relative to the mounting surface of the circuit board 122 as described above. Then, the core clip 160 is displaced (rotated) in the direction indicated by the arrow in the figure.

[0063] Figure 5 (B): Next, one of the pressing claws 160c (the one hidden by the core member 140 in the figure) is hooked onto the lower surface of the lower core member 140, while the other pressing claw 160c (the one shown in the figure) is pressed against the core member 130 from the outside of the core cover 150, thereby further displacing the entire core clip 160 in the direction indicated by the arrow in the figure. Such displacement can be achieved, for example, by applying a downward force from above to press down on the entire core clip 160, or by applying a left-right force from one side (upper right in the figure) to press the entire core clip 160.

[0064] In Figure 5 (C): As the entire core clip 160 is further displaced, the other pressing claw portion 160c is pressed against the core member 130 via the core cover 150, causing the core clip 160 to elastically deform as a whole, with the pressing claw portion 160c sliding along the outer surface of the core cover 150. At this time, one of the pressing claw portions 160c, which is hooked onto the lower surface of the core member 140, acts as a fulcrum during elastic deformation. Note that, for illustrative purposes, the actual deformation state is not shown in Figure 5, but due to the elastic deformation of the core clip 160 at this time, for example, the distance between the pair of gate legs 160b and pressing claw portions 160c widens compared to the free state, and the inclination angle of the pair of shoulder portions 160d increases compared to the free state.

[0065] In Figure 5 (D): The entire core clip 160 is then finally displaced to its mounting position. As a result, one of the pressing claws 160c, which has slid along the outer surface, rotates under the lower core member 140 due to the restoring force of the core clip 160 itself, assembling the two core members 130 and 140 to be held in a state where they are pressed against each other.

[0066] Thus, according to the core device and its manufacturing method of this embodiment, even when the core clip 160 is assembled while elastically deforming its pressing claw portion 160c in contact with the object to be assembled (two core members 130 and 140 covered by the core cover 150) and sliding along the outer surface of the object, the two core members 130 and 140 are protected by the core cover 150, thus reliably preventing them from being damaged. Furthermore, since the contact plate portion 150b of the core cover 150 covers a wide area of ​​the outer surface, spanning the position where the mating surfaces of the two core members 130 and 140 intersect, the lateral force applied by the pressing claw portion 160c is not concentrated only on the upper core member 130, but is distributed across both core members 130 and 140. As a result, the two core members 130 and 140 do not shift position along the mating surface. The advantages of this embodiment will be explained below, in comparison with comparative examples.

[0067] [Examples of protection methods using core covers] Figure 6 is a longitudinal cross-sectional view showing an example of protection configuration by the core cover 150 during the manufacturing process. Of these, Figure 6(A) corresponds to the cross-section along the VIA-VIA line in Figure 5(B), Figure 6(B) corresponds to the cross-section along the VIB-VIB line in Figure 5(C), and Figure 6(C) corresponds to the cross-section along the VIC-VIC line in Figure 5(D). However, in Figures 6(A) and (B), the core clip 160 is shown with a greater displacement than in the states shown in Figures 5(B) and (C), respectively.

[0068] [Core clip displacement in progress (1)] Figure 6(A): The core clip 160 is in the process of being displaced as described above. Here, for the sake of drawing convenience, the deformation state of the core clip 160 is not shown, but in reality, the core clip 160 is elastically deformed as one of the pressing claws 160c is pressed against the upper core member 130 over the core cover 150 during the installation process, causing the angle between the gate leg 160b and the shoulder 160d to open wider than when it is in a free state. Note that before the pressing claw 160c is displaced to the position shown in Figure 6(A), the pressing claw 160c slides laterally (to the left in this case) along the upper surface of the upper core member 130 over the core cover 150, and then passes through the curved corner. During this time, one of the pressing claws 160c scratches the outer surface of the core cover 150 due to the restoring force of the core clip 160, but the upper core member 130 is not damaged.

[0069] [Core clip displacement in progress (2)] In Figure 6 (B): The core clip 160 continues to be in the process of displacement. During the displacement process from the above-mentioned displacement in progress (1), one of the pressing claw portions 160c slides down along the side of the upper core member 130 and then along the side of the lower core member 140 over the core cover 150. During this process, the contact portion (tip) of the pressing claw portion 160c passes over the point where the mating surfaces of the two core members 130 and 140 intersect on the outer circumferential surface of the core. During this time, the pressing claw portion 160c is subjected to a lateral force (indicated by arrow F in the figure) by the restoring force of the core clip 160, but since the lateral outer circumferential surface is covered by the core cover 150 (contact plate portion 150b) that straddles the position of the mating surfaces of the two core members 130 and 140, the force applied from the pressing claw portion 160c is distributed to the two core members 130 and 140. Furthermore, the lower core member 140 receives a force (in the opposite direction to arrow F in the figure) when pressing the core clip 160 due to contact with the pressing claw portion 160c and gate leg portion 160b on the opposite side (not shown), but this force is also distributed to the two core members 130 and 140 by the core cover 150. As a result, the two core members 130 and 140 do not shift laterally along the mating surface. Also, similarly, one of the pressing claw portions 160c scratches the outer surface of the core cover 150, but neither of the two core members 130 and 140 suffers any damage.

[0070] [Core clip installed] In Figure 6 (C): The core clip 160 is fully displaced and in the installed state. As described above, even if the entire core clip 160 is elastically deformed during the manufacturing process while the pressing claw portion 160c of the core clip 160 is in contact with the object, the two core members 130 and 140, which are the object, are not damaged, nor do the mating surfaces become misaligned. This reliably prevents deterioration of the characteristics in the finished state and contributes to the manufacturing process.

[0071] [Comparative Example] Next, Figure 7 is a sequence diagram showing the manufacturing process of the comparative example. In the comparative example, two core members 230 and 240 form the core, but it differs in that it does not have a core cover 150 like the core device of this embodiment. Also, the two core members 230 and 240 are the same form as those used in the core device of this embodiment, and each has middle leg portions 230a and 240a and a pair of outer leg portions 230b and 240b. Similarly, the core clip 260 is the same form as those used in the core device of this embodiment, and has a pressing plate portion 260a, a pair of shoulder portions 260d, a pair of gate leg portions 260b and a pressing claw portion 260c. Furthermore, the circuit board 222 is assumed to have coils and electrical circuits (not shown) formed on it, and to have through holes 222a and notches 222b formed on it.

[0072] [Core clip displacement in progress (1)] In Figure 7(A): In the comparative example, the core clip 260 is attached in the same manner as in the manufacturing method of this embodiment, and is in the process of being displaced. Also in the comparative example, one of the pressing claw portions 260c slides along the upper surface of the upper core member 230, passes through the corner, and then slides down to the side. At this time, the pressing claw portion 260c is subjected to a lateral force (indicated by arrow F in the figure) by the restoring force of the core clip 260, and this force acts only on the upper core member 230 first (indicated by arrow S in the figure). The lower core member 240 is subjected to a force in the opposite direction (opposite direction to arrow S in the figure) when pressing the core clip 260 due to contact with the pressing claw portion 260c and the gate leg portion 260b. As a result, in the comparative example, the two core members 230 and 240 are misaligned laterally along the mating surface.

[0073] [Core clip displacement in progress (2)] Figure 7(B): The core clip 260 is still in the process of displacement. During the displacement process described above (1), the two core members 230 and 240 shifted positions, causing a portion of the mating surface of the outer leg portion 240b of the lower core member 240 to be exposed upward on the side, creating a step. Therefore, in the comparative example, as the core clip 260 displaces, the contact portion (tip) of one of the pressing claw portions 260c momentarily catches on the exposed portion of the mating surface (it does not stop at this position). During this time, one of the pressing claw portions 260c is also applying a lateral force due to the restoring force of the core clip 260.

[0074] [Core clip installation status (core component damage occurred)] In Figure 7 (C): The core clip 260 then displaces completely from the intermediate stage of displacement (2) described above to reach the mounting position. However, as one of the pressing claws 260c slides down, the outer leg portion 240b of the lower core member 240, which the pressing claw 260c was hooked onto, is partially shaved off, resulting in a missing portion CK. In addition, the two core members 230 and 240 are misaligned laterally along the mating surface. The occurrence of such a missing portion CK is particularly noticeable when the core members 130 and 140 are molded from ferrite.

[0075] [Advantages of this embodiment] The advantages of this embodiment are clear from the comparison with the comparative examples described above. (1) In the comparative example, the two core members 230 and 240 may become misaligned along their mating surfaces during the manufacturing process, whereas in this embodiment, the core cover 150 covers the outer surfaces of the two core members 130 and 140, preventing them from becoming misaligned and allowing their mating surfaces to be kept in close contact at their correct positions in the assembled state. (2) In the comparative example, a defect CK may occur in the lower core member 240 during the manufacturing process, whereas in this embodiment, since the core cover 150 covers the outer surfaces of the two core members 130 and 140, neither of the core members 130 or 140 is damaged, and a sound condition can be maintained upon completion. (3) In the comparative example, misalignment between the two core members 230 and 240, and the occurrence of a defect CK in one of the core members 240, may impair the integrity of the product and worsen its characteristics (inductance). In contrast, the present embodiment is significantly superior in that it does not produce defects that can be expected in the manufacturing process as in the comparative example, guarantees the integrity of the product, and allows the product to stably and effectively exhibit its original characteristics. (4) In order to prevent damage to the core member 240 in the comparative example, the procedure of elastically deforming the core clip 260 while it is in contact with the core member 230 must be eliminated. In this case, an extremely delicate and complex procedure is required, in which the core clip 260 is held in the air by itself, the held core clip 260 is elastically deformed in the air, and then brought to a position where it surrounds the outside of the core members 230 and 240 while avoiding contact with them, and finally the grip is released and it is attached. In contrast, according to this embodiment, the core clip 160 can be elastically deformed through a series of actions, in which the core clip 160 is brought into contact with the core member 130 from the outside of the core cover 150, and then pressed against the core cover 150, allowing it to be easily attached by sliding it along the outer surface of the core cover 150. Therefore, there is no need to perform an action to grip the core clip 150 individually, or an action to elastically deform it based on such an action, which contributes to the automation of the process by automated machinery, and the work procedure can be further simplified and manufacturing efficiency can be improved. Furthermore, such a manufacturing method can be realized by the structure of the core device of this embodiment.

[0076] [Case component internal filling configuration] Figure 8 is a cross-sectional view showing another example of a DC-DC converter 100 to which the core device of this embodiment is applied. In Figure 8 (A), the vertical cross-section is shown in the front-to-back direction, and in Figure 8 (B), the vertical cross-section is shown in the width direction (cross-section BB of (A)). The front-to-back direction and width direction referred to here correspond to those shown in Figure 1, respectively. Also, for the sake of explanation, the entire DC-DC converter 100 is shown upside down from its mounted state.

[0077] In Figure 8 (A): The DC-DC converter 100 can be configured such that a portion of the core device, circuit board unit 120, and connection terminal units 124 and 126 of this embodiment are housed inside the case member 110, and the inside is sealed with a filler material 180.

[0078] For example, urethane resin can be used for the filler material 180. During filling, the filler material 180 is heated and becomes fluid, flowing inside the case member 110 to fill the area around the core device, circuit board unit 120, and connection terminal units 124 and 126. After filling, the filler material 180 solidifies and seals the inside of the case member 110, protecting the core device, circuit board unit 120, connection terminal units 124 and 126 from the external environment. The filler material 180 may be filled to a level slightly lower than the opening surface of the case member 110 as shown in Figure 8.

[0079] In Figure 8 (B): The filler material 180 is filled so as to completely fill the gaps around the components of the core device. In particular, even in the narrow space surrounded between the core clip 160, the core cover 150, and one of the core members 130, the core clip 160 has a slit 160e formed in it, which increases the fluidity during filling and allows the filler material 180 to be filled without creating air pockets.

[0080] [Usefulness of core clips in filling applications] Figure 9 is a data comparison diagram showing the results of verifying the usefulness of this embodiment by adopting the core clip 160 when the DC-DC converter 100 is in a filled configuration, in comparison with a product that does not employ the core clip. In particular, data comparisons are made with a standard product for a DC-DC converter 100 using the core device of this embodiment in a filled configuration ((1) core clip-adopted filled product) and a product using the same type of filled configuration with a core device in which two core members are fixed together with tape ((2) untreated tape-fixed filled product). In this case, a DC-DC converter 100 product that is not filled with filler material 180 is used as the standard product. For (1) core clip-adopted filled product, the standard product is the core clip-unadopted filled product (which employs core clip fixing and does not use filler material 180), and for (2) untreated tape-fixed filled product, the standard product is the tape-fixed unadopted filled product (which fixes the core members with tape and does not use filler). The data to be compared are curves showing the relationship between ambient temperature and the rate of change in coil inductance for each standard product and each individual product.

[0081] [Data proofreading] The following calibrations (corrections) are performed when comparing data. First, the curve of inductance change rate shown as "Standard Unfilled Product" in the figure is a calibration of the inductance change rate that appears in the core itself due to changes in ambient temperature for each standard product to a constant value (0.0%) in all temperature ranges (e.g., approximately 20°C to 150°C). In other words, for the standard product, the area around the core is not filled with filler material 180, so there is no effect from the thermal deformation of the filler material 180 (for example, the mating surfaces of the core members 130 and 140 widen and a gap is formed). However, since the core itself also has some temperature characteristics, the inductance will actually change with ambient temperature even in the unfilled product, but here we are mainly focusing on the temperature characteristics due to the "presence or absence of filler material," so this data calibration is performed. As a result, in the following data comparisons, the temperature characteristic component of the core itself is removed, and it becomes possible to compare the data of each product (filled product) and each standard product (unfilled product) in (1) and (2).

[0082] [(1) Filled products using core clips] The curve of inductance change rate shown in the figure for the "filled product with core clip" is data obtained when comparing it with the rate of change of the reference product, which is set to the calibration value (0.0%), as described above. Therefore, although the actual product (filled product with core clip) also exhibits inductance changes due to the temperature characteristics of the core itself, these can be ignored when comparing it with the reference product. As a result, the curve of inductance change rate shows a slight temperature dependence in the region where the ambient temperature of the product is high (temperature T2 to T8), but the rate of change remains within a generally constant range (approximately 0.1% to -2.5%). This means that even if the filler material 180 surrounding the core undergoes thermal deformation and tries to create a gap between the mating surfaces of the two core members 130 and 140, the gap change is minimized by the retention by the core clip 160.

[0083] [(2) Products with untreated tape-fixed fillings] On the other hand, the inductance change rate curve shown in the figure for "untreated tape-fixed and filled product" exhibits a temperature characteristic that is highly dependent on the ambient temperature of the product. Specifically, the rate of change swings sharply to the negative side (approximately -5.0% to -30.0%) in the region where the ambient temperature is high (temperature T3 to T7), and the temperature characteristic is particularly pronounced in the high-temperature region (temperature T4 and above). Similarly, in the actual product (untreated tape-fixed and filled product), inductance changes due to the temperature characteristics of the core itself also appear, but these can be considered negligible when compared to the standard product.

[0084] [Comparative Verification] From this, the following is clear: (1) When the DC-DC converter 100 is filled using the core device of this embodiment, the rate of change of inductance with respect to ambient temperature shows a certain degree of temperature dependence compared to an unfilled standard product, but the temperature dependence is minor compared to other untreated products. (2) In this embodiment, even when the ambient temperature is in the high temperature range (temperature T4 or higher), it does not exhibit the steep temperature-dependent characteristics seen in the untreated tape-fixed-filled product, and the rate of change of inductance is approximately constant in all high temperature ranges (temperature T2 to T8). (3) In cases where the core device of this embodiment is not used, such as in products with untreated tape-fixed filling, the rate of change in inductance becomes significant depending on the ambient temperature, so the disadvantages (deterioration of characteristics) of filling with the filling material 180 outweigh the advantages (internal protection). (4) In contrast, when the core device of this embodiment is used, the DC-DC converter 100 is packed in place, which prevents deterioration of characteristics during temperature changes and allows the sealing effect of the filler material 180 to be fully realized.

[0085] The core device and its manufacturing method of the present invention can be implemented in various ways without being limited to the embodiment described above, and are not limited in any way by the disclosure of one embodiment.

[0086] In one embodiment, the core device is applied to a DC-DC converter 100, but the present invention may be used for other electronic devices or electronic components.

[0087] The two core members 130 and 140 are not limited to EE-type cores; they may also constitute EI-type or IE-type cores, or other types of cores. Furthermore, the material of the core members 130 and 140 may be something other than ferrite.

[0088] The coils formed by the core members 130 and 140 do not necessarily have to be formed by a wiring pattern; they may be coils wound on a bobbin, or they may be of a type without a core such as a bobbin (air-core coil).

[0089] The direction in which the core clip 160 is attached may be reversed left to right or up to down compared to one embodiment. Also, the detailed shape of the core clip 160 may differ from that of one embodiment. For example, it may be in a form without slits 160e, or it may have two or three slits 160e on each side.

[0090] The core cover 150 may have the smallest shape to cover the outer surface of the core members 130 and 140 in the area that comes into contact with the core clip 160 (pressing claw portion 160c) during the manufacturing process. For example, the pressing plate portion 160a may be formed only on one side that comes into contact with the pressing claw portion 160c during the manufacturing process. Furthermore, the connecting portion 150a and the pressing plate portion 160a of the core cover 150 may be formed solely from rod-shaped members, or they may be formed by combining plate-shaped members and rod-shaped members.

[0091] Furthermore, the circuit board 122 does not need to have a notch 122b, and it does not need to have a shape that allows the mating surfaces of the pair of outer legs 130b and 140b to be in close contact and to which the core clip 160 can be attached.

[0092] Furthermore, all the various forms shown in the illustrations are merely examples, and the present invention can be implemented by modifying them as appropriate. [Explanation of Symbols]

[0093] 100 DC-DC converter 110 Case components 122 Circuit board 130,140 Core members 130a,140a Middle leg 130b,140b Outer leg 150 Core Cover 160 Core Clips 180 Filling material

Claims

1. Two core members that form a core corresponding to the coil, assembled in a direction along the axis of the coil without creating a gap between their mating surfaces, A core clip is assembled to surround the outside of the core, including at least two points on the outer surfaces of the two core members where the mating surfaces intersect, and is capable of holding the two core members pressed together in a direction along the axis of the coil. A core cover provided between the core clip and the core, covering the outer surfaces of the two core members, including at least one location where the mating surfaces intersect. A core device equipped with a core.

2. In the core device according to claim 1, The aforementioned core clip is With the two core members pressed together, one core member encloses the entire area of ​​the outer circumferential surface along the magnetic path formed by the core, and the other core member encloses the entire area where the mating surfaces of the outer circumferential surface intersect and a portion of the area where the mating surfaces do not intersect. The aforementioned core cover is In the combined state of the two core members, one core member covers the entire area of ​​the outer circumferential surface, while the other core member covers at least the area where the mating surfaces of the outer circumferential surfaces intersect. A core device characterized by the following features.

3. In the core device according to claim 1 or 2, The two core members are, Each of the two components has a middle leg portion formed along the axis of the coil in a combined state, and a pair of outer leg portions formed parallel to the axis of the coil with the coil sandwiched between them, and the mating surfaces are formed on the end faces of the middle leg portion and the pair of outer leg portions, respectively. The aforementioned core cover is The outer surface of the two core members covers the point where the mating surfaces formed on the pair of outer legs intersect. A core device characterized by the following features.

4. In the core device according to claim 1, A circuit board having the coil and electrical circuit formed using a wiring pattern, and the two core members being mounted in combination through through holes formed at least at the axis of the coil, A case member that houses the two core members, the core clip, and the core cover together with the circuit board, A filler material is filled inside the case member and seals the circuit board, the two core members, the core clip, and the core cover inside the case member. A core device further equipped with [the following].

5. In the core device according to claim 4, The aforementioned core clip is It is composed of a plate-shaped elastic member that surrounds the outside of the core, and a slit is formed in the plate-shaped portion that penetrates in the thickness direction. A core device characterized by the following features.

6. A step of preparing a circuit board having a coil and an electrical circuit formed using a wiring pattern, wherein a through hole is formed at least at the position of the axis of the coil, The process involves assembling two core members, which are assembled to the circuit board through the through-hole in a direction along the axis of the coil to form a core corresponding to the coil, such that no gap is formed between their mating surfaces. The process of placing a core cover over the outer surfaces of the two core members, which are assembled on the circuit board, in a range that includes at least one point where the mating surfaces intersect, The process involves attaching a core clip from the outside of the core cover to the two core members to which the core cover is attached, in such a manner that it surrounds the outside of the core, including at least two points on the outer surface of the two core members where the mating surfaces intersect, thereby pressing the two core members together in a direction along the axis of the coil and exerting a holding force that can maintain the assembled state on the circuit board. A method for manufacturing a core device that performs this task.

7. In the method for manufacturing a core device according to claim 6, In the aforementioned arrangement process, With the two core members assembled, the core cover is placed on the two core members, covering the entire outer surface of one core member along the magnetic path formed by the core, and covering at least the area where the mating surfaces of the outer surfaces of the other core member intersect. In the aforementioned installation process, With the two core members pressed together, the core clip is attached to one core member from the outside of the core cover, with the clip having a shape that surrounds the entire outer surface of the outer surface of one core member from the outside of the core cover, and surrounds the entire area where the mating surfaces of the outer surface of the other core member intersect and a part of the area where the mating surfaces do not intersect, while bringing the core clip close to the two core members from the outside of the core cover and sliding a part of the core clip along the outer surface of the core cover. A method for manufacturing a core device, characterized by the following:

8. In the method for manufacturing a core device according to claim 7, In the aforementioned installation process, In the process of sliding a portion of the core clip along the outer surface of the core cover, the core clip is elastically deformed against the elastic force that contributes to the exertion of the holding force. A method for manufacturing a core device, characterized by the following:

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