Film capacitor

Abstract

In a film capacitor with a flattened winding, the occurrence of gaps in the inner circumference is suppressed. [Solution] The film capacitor comprises a winding of a dielectric film on which a metal film is formed. The winding is flattened in shape. The winding comprises a first film portion having an inner end in the winding, and a second film portion continuous with the first film portion and positioned opposite to the first film portion. The first and second film portions have multiple folds spaced apart from each other along the long axis of the flattened shape. In the portion inside the ends along the long axis of the part where the first and second film portions face each other, the number of folds is six or more.

Description

TECHNICAL FIELD

[0001] The present invention relates to a film capacitor provided with a wound dielectric film.

BACKGROUND ART

[0002] Patent Document 1 describes a film capacitor. The film capacitor of Patent Document 1 includes a dielectric film on which an electrode film is formed. The dielectric film is wound to constitute a wound body. The wound body has a flat shape.

[0003] The flat-shaped wound body is configured by crushing a cylindrical wound body with a press.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, in the conventional configuration, when the wound body is pressed into a flat shape, a gap may be formed in the inner peripheral portion.

[0006] Such a gap in the inner peripheral portion causes metallicon to enter in the subsequent step of forming external connection electrodes, which becomes a factor causing characteristic deterioration. In addition, the wound body becomes thick, which may hinder downsizing of the film capacitor.

[0007] Accordingly, an object of the present invention is to suppress the occurrence of a gap in the inner peripheral portion in a film capacitor provided with a flat-shaped wound body.

MEANS FOR SOLVING THE PROBLEMS

[0008] A film capacitor according to one embodiment of the present invention comprises a winding of a dielectric film on which a metal film is formed. The winding is flattened in shape. The winding comprises a first film portion having an inner end in the winding, and a second film portion continuous with the first film portion and positioned opposite to the first film portion. The first film portion and the second film portion each have a plurality of folds that are spaced apart from each other along the long axis of the flattened shape. In the portion inside the ends of the long axis in the part where the first film portion and the second film portion face each other, the number of folds is 6 or more.

[0009] In this configuration, the dielectric film bends at a pair of folds in multiple fold sections, thereby achieving a more stable flattened shape. This suppresses the formation of gaps between the first and second film sections. In this case, by setting the number of folds in the flattened state, i.e., the number of folds before flattening to eight or more (the number of folds that are not actually folded after flattening to six or more), one of the pairs of folds is more likely to become the folds at both ends when the flattened shape is formed. This ensures that the flattened wound body is constructed more reliably. [Effects of the Invention]

[0010] This method can suppress the occurrence of gaps in the inner circumference of a film capacitor that has a flattened winding. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view showing an example of a film capacitor according to an embodiment of the present invention. [Figure 2] Figure 2(A) is a perspective view of a wound body according to an embodiment of the present invention, and Figure 2(B) is a view of the wound body according to an embodiment of the present invention viewed from the end face. [Figure 3] Figure 3 is a view from the end face of the wound body according to the embodiment of the present invention, before it is made into a flattened shape. [Figure 4] Figure 4 is a plan view of the area near the inner end of a wound body according to an embodiment of the present invention, after it has been opened. [Figure 5]Figure 5(A) is a perspective view of the core material's appearance, and Figure 5(B) is a view of the core material from the end face. [Figure 6] Figure 6(A) shows the state in which the dielectric film is wound around the core material to form a wound body before flattening, and Figure 6(B) is a magnified view of a part of the corner of the core material. [Figure 7] Figures 7(A) and 7(B) show an example of the process of crushing a coiled body into a flattened shape. [Modes for carrying out the invention]

[0012] A film capacitor according to an embodiment of the present invention will be described with reference to the figures. Figure 1 is a perspective view showing an example of a film capacitor according to an embodiment of the present invention.

[0013] As shown in Figure 1, the film capacitor 1 comprises a wound body 10, an end electrode 31, and an end electrode 32.

[0014] The wound body 10 is constructed by overlapping a pair of dielectric films, each having a metal vapor-deposited electrode formed on its surface, and winding them together. The wound body 10 has a flattened shape.

[0015] As the dielectric film, for example, a plastic film containing a thermoplastic resin such as polyethylene terephthalate, polypropylene, polyphenylene sulfide, or polyethylene naphthalate can be used, or a plastic film containing a thermosetting resin such as a cured product obtained by the reaction of hydroxyl groups (OH groups) of a first organic material and isocyanate groups (NCO groups) of a second organic material can be used.

[0016] The end electrode 31 is formed on one end face of the wound body 10. The end electrode 31 is connected to a metal vapor-deposited electrode formed on one of the dielectric films in the pair of dielectric films.

[0017] The end face electrode 32 is formed on the other end face of the wound body 10. The end face electrode 32 is connected to a metal deposited electrode formed on the other dielectric film of the pair of dielectric films.

[0018] For the end face electrode 31 and the end face electrode 32, a metal such as aluminum or zinc can be used.

[0019] FIG. 2(A) is a perspective view of the wound body according to the embodiment of the present invention, and FIG. 2(B) is a view of the wound body according to the embodiment of the present invention viewed from the end face. FIG. 3 is a view of the wound body according to the embodiment of the present invention in a state before being formed into a flat shape, viewed from the end face. FIG. 4 is a plan view of the vicinity of the inner end portion of the wound body according to the embodiment of the present invention after the wound body is unrolled. Note that FIG. 2(A), FIG. 2(B), FIG. 3, and FIG. 4 depict the pair of dielectric films as an integrated single dielectric film.

[0020] As shown in FIG. 2(A) and FIG. 2(B), the wound body 10 has a flat shape. In other words, the outer surface of the wound body 10 is constituted by a pair of flat surfaces and a pair of curved surfaces connected to both ends of the pair of flat surfaces.

[0021] The wound body 10 includes an inner end portion E11 and an outer end portion E12 of the wound form of the dielectric film. The wound body 10 includes a first film portion 21 having a substantially flat shape and having the inner end portion E11, and a second film portion 22 continuous with the first film portion 21 and disposed to face the first film portion 21. The wound body 10 is further provided with other film portions in a form wound around the laminate of the first film portion 21 and the second film portion 22.

[0022] The first film portion 21 and the second film portion 22 of the wound body 10 are provided with a plurality of crease portions 101-108. The plurality of crease portions 101-108 are provided at intervals from each other along the major axis direction of the flat shape.

[0023] The wound body 10 has a crease portion 105 at the position where the first film portion 21 and the second film portion 22 connect, that is, at the position where it first bends (curves) extending from the inner end E11 of the dielectric film. The crease portion 105 becomes a fold that forms one end in the longitudinal direction of the flattened shape when the wound body 10 is made flat.

[0024] The wound body 10 has a fold portion 101 at a position where the second film portion 22 is close to the inner end E11, that is, at the position where it bends (curves) for the second time from the inner end E11 in the dielectric film. The fold portion 105 becomes the fold portion that constitutes the other end in the long axis direction of the flattened shape when the wound body 10 is made into a flattened shape.

[0025] The wound body 10 has a plurality of folds 102, 103, and 104 on the surface of the first membrane portion 21 facing the second membrane portion 22. The wound body 10 also has a plurality of folds 106, 107, and 108 on the surface of the second membrane portion 22 facing the first membrane portion 21. Thus, the wound body 10 has six folds in the portion inside the long axis ends (where the folds 101 and 105 were before flattening) in the portion where the first membrane portion 21 and the second membrane portion 22 face each other.

[0026] Multiple folds 102, 103, and 104 correspond to the "multiple first folds" of the present invention, and multiple folds 106, 107, and 108 correspond to the "multiple second folds" of the present invention.

[0027] As shown in Figure 3, the multiple folded portions 101-108 are formed by shaping the wound body 10, before it becomes flattened, into a rectangular tube that is a regular octagon when viewed from the end face. Thus, the wound body 10, before it becomes flattened, has eight corners when viewed from the end face. In other words, by having eight folded portions before it becomes flattened, a pair of folded portions becomes a folded portion, and six folded portions can be formed in the portion inside the ends in the longitudinal direction of the part where the first membrane portion 21 and the second membrane portion 22 face each other.

[0028] By forming eight corners in the dielectric film, linear fold marks are formed at these eight corners, as shown in Figure 4. These fold marks become multiple crease sections 101-108.

[0029] The multiple folds 101-108 are arranged in the following order from the inner end E11 of the dielectric film: fold 102, fold 103, fold 104, fold 105, fold 106, fold 107, fold 108, and fold 101. The spacing of these multiple folds 101-108 along the winding direction of the dielectric film is equal spacing PCH. Note that "equal spacing" here includes manufacturing tolerances.

[0030] As shown in Figure 2(B), when viewed in the winding axis direction of the wound body 10, the folded portion 102 of the first film portion 21 and the folded portion 108 of the second film portion 22 overlap, the folded portion 103 of the first film portion 21 and the folded portion 107 of the second film portion 22 overlap, and the folded portion 104 of the first film portion 21 and the folded portion 106 of the second film portion 22 overlap. Note that "overlapping" here includes the range of manufacturing tolerances.

[0031] As described above, by having multiple folds 101-108, the wound body 10 bends from its pre-flattened shape (as shown in Figure 3) by being compressed, with the multiple folds acting as the starting points. In this case, the wound body 10 bends with the starting points being pairs of folds located symmetrically with respect to the center of the regular octagon. For example, in the case of Figure 3, the pair of fold 101 and fold 105 in the multiple folds 101-108 act as the starting points for bending.

[0032] In this case, the distance from the inner edge E11 of the dielectric film to the fold portion 105 and the distance from the fold portion 105 to the fold portion 101 are approximately the same.

[0033] Therefore, the wound body 10 takes on a stable, flattened shape with the kinked portion 101 and the kinked portion 105 at both ends. As a result, the flattened shape of the wound body 10 prevents gaps from forming between the innermost first membrane portion 21 and the second membrane portion 22 of the wound body 10.

[0034] As a result, the film capacitor 1 can suppress the metallicon used to form the end electrodes 31 and 32 from entering the center of the winding body 10, thereby suppressing performance degradation. Furthermore, the film capacitor 1 can suppress the thickness of the winding body 10, enabling miniaturization and thinning.

[0035] Furthermore, as described above, by making the number of folds formed on the winding body 10 before it is flattened eight or more, any pair of folds is more likely to become the folds (actual folds) that cause the pair of winding bodies 10 to bend significantly. As a result, the film capacitor 1 can be more reliably constructed with a flattened winding body 10.

[0036] For example, in the above example, the combination of the bent portion 101 and the bent portion 105 forms a bent portion in which the pair of windings 10 bends significantly. However, the combination of the bent portion 102 and the bent portion 106, the combination of the bent portion 103 and the bent portion 107, and the combination of the bent portion 104 and the bent portion 108 can also form a bent portion in which the pair of windings 10 bends significantly. This makes it possible to more reliably form a flattened winding 10 in the film capacitor 1.

[0037] Furthermore, the multiple fold portions 101-108 are preferably arranged at intervals of 1 / 3 or less of the flattening distance in the winding direction of the dielectric film, with the distance between each of the fold portions where the pair of winding bodies 10 bends significantly being the flattening distance, and more preferably at 1 / 5 or less.

[0038] For example, in the example shown in Figure 2(B), the distance between the folded portion 101 and folded portion 105 where the wound body 10 is greatly bent is defined as the flattening distance. In this state, the distance between the inner end E11 and folded portion 102, the distance between folded portion 102 and folded portion 103, the distance between folded portion 103 and folded portion 104, the distance between folded portion 104 and folded portion 105, the distance between folded portion 105 and folded portion 106, the distance between folded portion 106 and folded portion 107, the distance between folded portion 107 and folded portion 108, and the distance between folded portion 108 and folded portion 101 are preferably 1 / 3 or less of the flattening distance, and more preferably 1 / 5 or less.

[0039] As a result, the film capacitor 1 can properly set the spacing between adjacent folds, and can more reliably bend any set of folds in the set of multiple folds symmetrical with respect to the center of the regular octagon described above into a fold.

[0040] The wound body 10 with the above configuration can be manufactured, for example, as follows.

[0041] Figure 5(A) is a perspective view of the core material's appearance, and Figure 5(B) is a view of the core material from the end face. Figure 6(A) shows the state in which the dielectric film is wound around the core material to form a wound body before flattening, and Figure 6(B) is a magnified view of a part of the corner of the core material.

[0042] As shown in Figures 5(A) and 5(B), the core material 80 is a regular octagonal prism when viewed from the end face. The core material 80 has multiple edges RL1-RL8 that form corners when viewed from the end face, and multiple planes P1-P8 that connect adjacent edges.

[0043] The core material 80 is constructed, for example, by forming eight cut surfaces on a cylindrical CY80 as shown by the dotted line in Figure 5(B). These cut surfaces become multiple planes P1-P8, and the remaining uncut portions become multiple edges RL1-RL8.

[0044] As shown in Figure 6(A), the dielectric film is wound along the circumferential surface of a core material 80, which is composed of multiple ridges RL1-RL8 and multiple planes P1-P8. The dielectric film bends along the multiple ridges RL1-RL8. This bending produces a winding body 10 that has the aforementioned multiple folds 101-108 before it becomes flattened.

[0045] After the dielectric film is wound around it, the core material 80 is pulled out from the winding body 10 before it is flattened. At this point, the dielectric film has a predetermined elasticity. Therefore, as shown in Figure 6(B), the winding body 10 made of dielectric film before it is flattened is in contact with multiple ridges RL1-RL8 but not with multiple planes P1-P8, and has a gap GAP.

[0046] This reduces the contact area between the pre-flattened winding body 10 and the core material 80. Consequently, the frictional resistance when pulling out the core material 80 from the pre-flattened winding body 10 can be reduced. As a result, the core material 80 can be pulled out without distorting the shape (regular octagonal tube) of the pre-flattened winding body 10. Therefore, the pre-flattened winding body 10 can be manufactured stably.

[0047] Furthermore, grooves parallel to the multiple ridges RL1-RL8 may be provided on multiple planes P1-P8. This further reduces the frictional resistance when pulling the core material 80 out of the winding body 10 before it is flattened. Therefore, the winding body 10 before it is flattened can be manufactured more stably. In addition, the multiple ridges RL1-RL8 may be rounded to the extent that they can form a bend. This reduces damage to the bend portion.

[0048] Figures 7(A) and 7(B) show an example of the process of crushing a coiled body into a flattened shape.

[0049] As shown in Figure 7(A), the wound body 10 is positioned between the press die 91 and die 92. In this case, it is preferable that one of the pair of fold portions be positioned perpendicular to the direction in which the die 91 and die 92 are aligned. For example, in the example in Figure 7(A), the fold portion 101 and the fold portion 105 are positioned perpendicular to the direction in which the die 91 and die 92 are aligned.

[0050] In this state, pressure P is applied to bring mold 91 and mold 92 closer together. As a result, the wound body 10 is crushed from a regular octagonal cylindrical shape to a flattened shape. At this time, a pair of folds (folds 101 and 105 in Figures 7(A) and 7(B)) positioned perpendicular to the direction in which mold 91 and mold 92 are aligned act as the starting points for the wound body 10 to bend and become a stable flattened shape.

[0051] By using this manufacturing method, flattened coiled bodies 10 can be manufactured stably and reliably.

[0052] In the above description, an example was shown with eight folds, but the number of folds can be six or more, and an even number of eight or more is more preferable. However, if the number of folds is too large, the shape will approach a circle, so it is preferable to set an appropriate number. For example, it is even more preferable to have around 10, 12, 14, or 16 folds. In other words, it is even more preferable that the spacing (distance) between adjacent folds is between 1 / 8 and 1 / 5 of the flattening distance.

[0053] However, if the number of creases is less than eight, the winding body 10 must be positioned in the specified orientation with greater precision relative to the molds 91 and 92 when it is crushed before it is flattened. On the other hand, by having eight or more creases, the degree of freedom in positioning the winding body 10 relative to the molds 91 and 92 is improved. Therefore, the flattened winding body 10 can be manufactured more easily.

[0054] Furthermore, in the above configuration, it is preferable that the intervals between the multiple fold portions 101-108 along the winding direction of the dielectric film be equal. However, the above-described flattened shape can be achieved even if the intervals are not equal, as long as there is at least one pair of fold portions located symmetrically with respect to the center of the shape before flattening. [Explanation of Symbols]

[0055] 1: Film capacitor 10: Coiled body 21: First membrane section 22: Second membrane section 31, 32: End electrode 80: Core material 91, 92: Mold 101-108: Folded section CY80: Cylinder E11: Inner end E12: Outer end GAP: Gap P1-P8: Plane RL1-RL8: Ridge

Claims

1. It comprises a winding of a dielectric film on which a metal film is formed, The aforementioned wound body is It has a flattened shape, The first membrane portion having an inner end in the aforementioned wound body, A second membrane portion is continuous with the first membrane portion and is positioned opposite to the first membrane portion, Equipped with, The first film portion and the second film portion are The flattened shape has multiple bent portions spaced apart from each other along its long axis, In the portion of the first and second membrane portions facing each other, the number of the multiple folds is six or more in the portion inside the ends in the longitudinal direction. Film capacitor.

2. The aforementioned multiple folds are, A plurality of first fold portions are provided in the first film portion at a position opposite to the second film portion, It is composed of a plurality of second fold portions provided in the second film portion at a position opposite to the first film portion, The number of the plurality of first fold portions and the number of the plurality of second fold portions are equal. The film capacitor according to claim 1.

3. When viewed in a direction perpendicular to the flat surface due to the flattened shape, the plurality of first fold portions and the plurality of second fold portions overlap. The film capacitor according to claim 2.

4. The aforementioned multiple folds are provided at equal intervals along the winding direction. A film capacitor according to any one of claims 1 to 3.

5. The distance between the folded portions at both ends of the flattened shape is defined as the flattening distance. The plurality of folded portions are arranged at intervals of 1 / 3 or less of the flattening distance in the winding direction of the dielectric film. A film capacitor according to any one of claims 1 to 4.

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