CN216957759U

CN216957759U - Film capacitor and outer case for film capacitor

Info

Publication number: CN216957759U
Application number: CN201990001326.2U
Authority: CN
Inventors: 阪本拓也; 市川智道
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2019-02-13
Filing date: 2019-11-27
Publication date: 2022-07-12
Anticipated expiration: 2029-11-27
Also published as: WO2020166170A1; JP2022053558A

Abstract

The present invention relates to a film capacitor and an exterior case for a film capacitor. The film capacitor of the present invention comprises: a capacitor element including a metallized film in which a metal layer is provided on a surface of a resin film; a resin outer case in which the capacitor element is housed; and a filling resin filled between the capacitor element and the outer case, wherein the outer case has an outer surface convex portion and an outer surface concave portion which positions the outer surface convex portion on an inner side of an outer surface of the outer case, and an inner surface convex portion which protrudes from an inner surface facing the outer surface concave portion.

Description

Film capacitor and outer case for film capacitor

Technical Field

The present invention relates to a film capacitor and an exterior case for a film capacitor.

Background

A film capacitor is manufactured, for example, by housing a capacitor element in which a metallized film having a metal deposition film provided on a surface of a resin film is wound or laminated in an outer case, and then filling the case with a resin and curing the resin.

When such a thin film capacitor is used in a high-temperature and high-humidity environment, if moisture enters the capacitor element, the conductivity of the metal deposited film is lost, and the electrostatic capacitance is lowered. Therefore, the thin film capacitor is required to have improved moisture resistance.

Patent document 1 discloses the following capacitor: a capacitor element formed by winding or laminating metallized films or a combination of a metallized film and an unmetallized film is housed in a capacitor case having an opening, a gap between the capacitor element and the capacitor case and a space on the opening side of the capacitor element are filled with a resin, and the periphery of the capacitor element is filled with a resin. In one embodiment, a pair of metallized polypropylene films are wound around a capacitor element, and a metal sprayed material is formed on both ends in the film width direction, and lead terminals made of copper for external connection are connected to each other and housed in a capacitor case made of polybutylene terephthalate, and thermosetting synthetic resin as epoxy resin is further filled to block the capacitor element from the outside air.

In the above embodiment, it is described that the thickness of the synthetic resin around the capacitor element is secured by providing the rib at the bottom of the capacitor case facing the opening. According to patent document 1, by securing the thickness of the synthetic resin around the capacitor element, it is possible to suppress the penetration of moisture into the capacitor element from the outside.

Patent document 2 discloses that a resin outer case is integrally formed by injection molding of a synthetic resin, and the synthetic resin is polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, or the like.

Patent document 1: japanese patent No. 4356302

Patent document 2: japanese patent laid-open publication No. 2018-026425

In the capacitor described in patent document 1, in order to suppress the intrusion of moisture from the outside, a structure is adopted in which the thickness of the synthetic resin around the capacitor element is secured substantially uniformly.

However, the relationship between the moisture resistance of the film capacitor and the resin outer case manufactured by injection molding as described in patent document 2 has not been studied.

In the case of manufacturing a resin outer case by injection molding, a molten resin injected from a nozzle of an injection molding machine is filled into a cavity in a mold from a roll through a runner and a gate. Generally, a plurality of cavities are connected by runners, and a plurality of cavities can be molded simultaneously. After the resin is solidified by cooling, the mold is opened. The mandrel, the gate, and the resin solidified at the gate are also referred to as a mandrel, a runner, and a gate, respectively.

Fig. 1 is a perspective view schematically showing an example of a molded article obtained by opening a mold after injection molding.

The molded article 100 shown in fig. 1 includes a roll 110, a runner 120, and a gate 130 in addition to an outer case 200. Since the mandrel 110, the runner 120, and the gate 130 are not required, the runner 120 is cut near the gate 130, thereby completing the outer case 200.

In the case where the resin outer case is manufactured by injection molding as described above, a convex portion protruding from the other portion is formed on the outer surface of the outer case which is a cut surface of the resin as a trace of a gate which is an inlet of the resin. Therefore, a recessed portion is formed around the convex portion on the outer surface of the outer case so that the cut surface of the resin does not protrude to the outside.

However, it has been found that a film capacitor in which a capacitor element is housed in an outer case having a convex portion and a concave portion on an outer surface has a problem of insufficient moisture resistance.

SUMMERY OF THE UTILITY MODEL

The present invention has been made to solve the above-described problems, and an object thereof is to provide a film capacitor including an outer case made of resin, which can suppress a decrease in moisture resistance. The present invention also provides an exterior case for a film capacitor.

The present inventors have found that, when a concave portion is formed around a convex portion on the outer surface of an exterior case, the thickness of the exterior case is thinner than other portions by an amount corresponding to the formation of the concave portion, and therefore, moisture is likely to enter from the portion, and the moisture resistance of the film capacitor is lowered, and have completed the present invention.

The film capacitor of the present invention comprises: a capacitor element including a metallized film having a metal layer provided on a surface of a resin film; a resin outer case in which the capacitor element is housed; and a filling resin filled between the capacitor element and the outer case, wherein the outer case has an outer surface convex portion and an outer surface concave portion which positions the outer surface convex portion on an inner side of an outer surface of the outer case, and an inner surface convex portion which protrudes from an inner surface facing the outer surface concave portion.

An exterior case for a film capacitor according to the present invention is an exterior case for a film capacitor for housing a capacitor element therein, the capacitor element including a metallized film having a metal layer provided on a surface of a resin film, the exterior case being made of a resin, the exterior case including an outer surface convex portion on an outer surface thereof and an outer surface concave portion on an inner side of the outer surface of the exterior case, and an inner surface convex portion protruding from an inner surface of the exterior case facing the outer surface concave portion.

According to the present invention, it is possible to provide a film capacitor including an outer case made of resin, which can suppress a decrease in moisture resistance.

Drawings

Fig. 2 is a perspective view schematically showing a film capacitor according to an embodiment of the present invention.

Fig. 3 is an exploded perspective view of the film capacitor shown in fig. 2.

Fig. 4 (a) and 4 (b) are perspective views schematically showing an example of the outer case constituting the film capacitor shown in fig. 2.

Fig. 5 is an enlarged cross-sectional view schematically showing an example of the outer surface convex portion, the outer surface concave portion, and the inner surface convex portion of the outer case.

Fig. 6 is an enlarged cross-sectional view schematically showing another example of the outer surface convex portion, the outer surface concave portion, and the inner surface convex portion of the outer case.

Fig. 7 (a) and 7 (b) are cross-sectional views schematically showing another example of the film capacitor of the present invention.

Fig. 8 (a) is a perspective view schematically showing an example of a capacitor element constituting the film capacitor of the present invention, and fig. 8 (b) is a cross-sectional view taken along line b-b of the capacitor element shown in fig. 8 (a).

Fig. 9 is a perspective view schematically showing an example of a roll of a metallized film constituting the capacitor element shown in fig. 8 (a) and 8 (b).

Fig. 10 is a perspective view schematically showing another example of a roll of a metallized film constituting the capacitor element shown in fig. 8 (a) and 8 (b).

Fig. 11 is an enlarged sectional view of the outer case used in examples 1 to 4.

Fig. 12 is an enlarged cross-sectional view of an outer case used in comparative example 1.

Detailed Description

Hereinafter, the film capacitor of the present invention will be described.

However, the present invention is not limited to the following configuration, and can be applied with appropriate modifications within a scope not changing the gist of the present invention.

The present invention also includes a structure obtained by combining two or more of the preferred structures of the present invention described below.

The outer case for a film capacitor described below is also one aspect of the present invention.

The film capacitor of the present invention comprises: a capacitor element having a metallized film; a resin outer case in which the capacitor element is housed; and a filling resin filled between the capacitor element and the outer case.

In the film capacitor of the present invention, the outer case has an outer surface convex portion on an outer surface thereof and an outer surface concave portion in which the outer surface convex portion is positioned inward of the outer surface of the outer case, and the outer case has an inner surface convex portion protruding from an inner surface thereof on an inner surface facing the outer surface concave portion.

The outer surface convex portion provided on the outer surface of the resin outer case is a trace of a gate for injecting resin when the outer case is manufactured by injection molding. As described above, by providing the outer surface concave portion around the outer surface convex portion, it is possible to suppress the undesired protrusion of the outer surface convex portion. Further, the thickness of the outer case can be ensured by providing the inner surface convex portion on the inner surface of the outer case, which is opposed to the outer surface concave portion. Therefore, the penetration of moisture into the capacitor element from the outside can be prevented, and the moisture resistance of the film capacitor can be improved.

As described later, the inner surface convex portion of the outer case can be used for positioning the capacitor element disposed inside the outer case.

Fig. 2 is a perspective view schematically showing a film capacitor according to an embodiment of the present invention. Fig. 3 is an exploded perspective view of the film capacitor shown in fig. 2. Fig. 3 shows a state before the capacitor element is housed in the outer case.

The film capacitor 1 shown in fig. 2 includes: a capacitor element 10 (see fig. 3); a resin outer case 20 in which the capacitor element 10 is housed; and a filling resin 30 filled between capacitor element 10 and outer case 20.

As shown in fig. 3, a rectangular parallelepiped space is formed inside the outer case 20. Preferably, capacitor element 10 is disposed at the center of the inside of outer case 20, apart from the inner surface of outer case 20. In order to hold capacitor element 10, filling resin 30 (see fig. 2) such as epoxy resin is filled between the outer surface of capacitor element 10 and the inner surface of outer case 20. Outer case 20 has a bottomed cylindrical shape having an opening at one end, and filled resin 30 is filled into outer case 20 and also into capacitor element 10 from the opening of outer case 20. The epoxy resin is cured by heating, and can bond and fix outer case 20 and capacitor element 10 integrally.

In fig. 3, the capacitor element 10 includes a roll 40 of a metallized film, and a first external electrode 41 and a second external electrode 42 formed on both sides of the roll 40. The first lead terminal 51 is electrically connected to the first external electrode 41, and the second lead terminal 52 is electrically connected to the second external electrode 42. As shown in fig. 2, the first lead terminal 51 and the second lead terminal 52 protrude from the inside of the external case 20 to the outside.

(outer case)

The outer case constituting the film capacitor of the present invention is a resin case manufactured by injection molding. The shape of the outer case is, for example, a bottomed cylinder having an opening at one end.

The outer case 20 shown in fig. 4 (a) and 4 (b) has a substantially rectangular opening 21 at one end, and has a bottom portion 22 and a rectangular-cylindrical side wall portion having four

side walls

23, 24, 25, and 26 protruding from the bottom portion 22 toward the opening 21, the bottom portion 22 facing the opening 21 and the other end sealed. The outer case 20 may have a cylindrical shape such as a bottomed cylindrical shape having a cylindrical side wall portion instead of a quadrangular cylindrical side wall portion.

In fig. 4 (a) and 4 (b), the side wall portion of the outer case 20 includes: a first side wall 23; a second side wall 24 having substantially the same area as the first side wall 23 and disposed apart from the inner surface of the first side wall 23 so as to face the same; a third side wall 25 connecting one side edge of the first side wall 23 and one side edge of the second side wall 24 and having an area smaller than that of the first side wall 23; and a fourth side wall 26 connecting the other side edge of the first side wall 23 and the other side edge of the second side wall 24, having substantially the same area as the third side wall 25, and disposed apart from and facing the inner surface of the third side wall 25.

As shown in fig. 4 (a) and 4 (b), a recess 27 is preferably provided on the side of the outer case 20 on the four sides of the opening 21. The recess 27 extends along the four sides of the opening 21 side from the opening 21 side toward the bottom 22 side. By providing the recess portion on the opening surface of the outer case, it is possible to prevent the internal pressure from rising due to sealing of the film capacitor and the substrate when the film capacitor substrate is mounted. Further, the housing case may not be provided with the recess.

As shown in fig. 4 (a) and 4 (b), the side wall portion of the outer case 20 is preferably provided with a tapered portion 28 extending along a side connecting the side walls. In fig. 4 (a) and 4 (b), a tapered portion 28 is provided at a corner portion on the bottom portion 22 side of the first side wall 23 and the second side wall 24. A tapered portion is also provided on a side connecting the bottom portion 22 side of the third side wall 25 and the bottom portion 22, and a tapered portion is also provided on a side connecting the bottom portion 22 side of the fourth side wall 26 and the bottom portion 22. The side wall portion of the outer case may not be provided with the tapered portion.

The outer case 20 includes an outer surface convex portion 61 and an outer surface concave portion 62 on an outer surface thereof as shown in fig. 4 (a), and an inner surface convex portion 63 protruding from an inner surface facing the outer surface concave portion 62 on an inner surface thereof as shown in fig. 4 (b). In fig. 4 (a) and 4 (b), the outer surface convex portion 61, the outer surface concave portion 62, and the inner surface convex portion 63 are provided at the bottom portion of the outer case 20, but may be provided at the side wall portion of the outer case 20.

An outer surface a of the outer case is provided with an outer surface convex portion 61 and an outer surface concave portion 62 which positions the outer surface convex portion 61 inward (downward in fig. 5) of the outer surface a of the outer case. The outer surface concave portion 62 is provided in a ring shape so as to surround the outer surface convex portion 61 (see fig. 4 (a)). Further, an inner surface convex portion 63 protruding from the inner surface B is provided on the inner surface B of the outer case facing the outer surface concave portion 62. The inner surface convex portion 63 is provided in a ring shape to be larger than the width of the outer surface concave portion 62 (see fig. 4 (b)).

In fig. 6, the outer surface convex portion 61 and the outer surface concave portion 62 are the same as those in fig. 5, but the inner surface convex portion 63a is provided in a columnar shape so as to be larger than the width of the outer surface concave portion 62.

In the film capacitor of the present invention, the inner surface convex portion of the outer case may protrude only around the inner surface facing the outer surface convex portion as shown in fig. 4 (b) and 5, or may protrude around the inner surface facing the outer surface convex portion as shown in fig. 6. The shape of the inner surface convex portion is not particularly limited to the ring shape shown in fig. 4 (b) and 5 and the columnar shape shown in fig. 6, and is not particularly limited as long as the inner surface opposite to the outer surface concave portion protrudes. For example, even when the outer edge of the outer surface convex portion has a circular shape, the outer edge of the inner surface convex portion may have a polygonal shape such as a quadrangle, or an elliptical shape, without being limited to the circular shape.

Further, the inner surface convex portion of the outer case may be provided discontinuously. For example, a slit may be provided in an annular or columnar inner surface convex portion.

In the film capacitor of the present invention, the shapes of the outer surface convex portion and the outer surface concave portion of the outer case are not particularly limited. The positions of the outer surface convex portion, the outer surface concave portion, and the inner surface convex portion of the outer case are also not particularly limited. For example, the outer surface convex portion, the outer surface concave portion, and the inner surface convex portion of the outer case may be provided at a portion other than the bottom portion of the outer case.

The outer case has a thickness (t in fig. 5 and 6) on the side of the inner surface convex portion₁The length shown) is preferably 0.5mm or more and 3mm or less. The thickness t is more lateral than the inner surface convex part₁Corresponding to the thickness of the outer case.

In the outer case, the minimum thickness of the outer surface recess (t in fig. 5 and 6)₂Length shown) is preferably the thickness t on the side of the inner surface convex portion₁Is equal to or is the t₁The above.

In the outer case, the width of the outer surface concave portion (t in fig. 5 and 6)₃The length shown) is not particularly limited as long as it is larger than the width of the outer surface convex portion, but is preferably 1mm or more and 10mm or less, more preferably 4mm or more and 7mm or less.

The width of the inner surface protrusion of the outer case (t in fig. 5 and 6)₄Length shown) is preferably equal to the width t of the outer surface recess₃Is equal to or is the t₃The above.

In the outer case, the inner surface facing the outer surface concave portion is preferably located on the capacitor element side with respect to the inner surface located on the side of the inner surface convex portion.

In the outer case, the outer surface of the outer surface convex portion is preferably located inward of the outer surface of the outer case rather than the outer surface located laterally of the inner surface convex portion.

In the film capacitor of the present invention, the inner surface convex portion may be in contact with the outer surface of the capacitor element.

In this case, the inner surface convex portion can be used for positioning the capacitor element disposed inside the outer case.

When the inner surface convex portion is in contact with the outer surface of the capacitor element, the inner surface convex portion is preferably formed in a flat shape along the outer surface of the capacitor element.

In order to stably position the capacitor element inside the outer case, line contact or surface contact is preferable to point contact. In addition, the outer surface shape of the capacitor element subjected to the press working is not a stable shape. In order to contact the inner surface convex portion inside the outer case even when the capacitor element has various shapes, the end of the inner surface convex portion is preferably flatter than a point. When the inner surface convex portion is flat, the capacitor element can be appropriately positioned.

When the outer case includes an opening, a bottom portion facing the opening and abutting against the capacitor element, and a side wall portion protruding from the bottom portion toward the opening, it is preferable that a first positioning protrusion protruding toward the capacitor element be provided on the bottom portion, and the inner surface protrusion be the first positioning protrusion.

In the manufacture of a film capacitor, a capacitor element is inserted into an outer case and then molded with a filling resin. In this case, if the inner surface convex portion is provided on the bottom portion of the outer case, the inner surface convex portion can be used as a placement portion for the capacitor element.

Preferably, the inner surface convex portion is a part of the bottom portion, and is provided at a central position of the bottom portion.

If the inner surface convex portion is provided on the most part of the bottom portion of the outer case, the amount of the filling resin entering between the bottom portion of the outer case and the capacitor element becomes small. Therefore, by providing the inner surface convex portion in a part of the bottom portion of the outer case, a space into which the filling resin can enter can be formed. Further, by providing the inner surface convex portion at the center position of the bottom portion, the capacitor element can be stably placed on the bottom portion.

When the first positioning projection is provided on the bottom portion of the outer case and the inner surface projection is the first positioning projection, the side wall portion is preferably provided with a second positioning projection and a third positioning projection which project toward the capacitor element and face each other with the capacitor element interposed therebetween.

In this case, by holding the capacitor element at 3 points, the capacitor element can be stably positioned inside the outer case.

In the case where the exterior case includes an opening, a bottom portion facing the opening and abutting against the capacitor element, and a side wall portion protruding from the bottom portion toward the opening, a first positioning projection protruding toward the capacitor element is provided on the bottom portion, a second positioning projection and a third positioning projection protruding toward the capacitor element and facing each other with the capacitor element interposed therebetween are provided on the side wall portion, and the inner surface projection may be any one of the second positioning projection and the third positioning projection.

In this way, the inner surface convex portion can be used for positioning at the side wall portion. In this case, by holding the capacitor element at 3 points, the capacitor element can be stably positioned in the outer case.

In fig. 7 (a), a first positioning projection 71 projecting toward the capacitor element 10 is provided on the bottom of the outer case 20. In fig. 7 (b), second positioning projection 72 and third positioning projection 73 that project toward capacitor element 10 and face each other with capacitor element 10 interposed therebetween are provided on a side wall portion of outer case 20.

As described above, the first positioning projection 71 may be an inner surface projection, and either one of the second positioning projection 72 and the third positioning projection 73 may be an inner surface projection.

In the film capacitor of the present invention, the outer case is made of a resin composition.

The resin composition constituting the outer case may contain a Liquid Crystal Polymer (LCP) or may contain polyphenylene sulfide (PPS). The exterior case is preferably made of a resin composition containing LCP from the viewpoint of improving the moisture resistance of the film capacitor.

As the LCP contained in the resin composition, for example, an LCP having a p-hydroxybenzoic acid group and a 6-hydroxy-2-naphthoic acid group in the skeleton can be used. In addition, in addition to p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, LCP in which a polycondensate is formed by using various components such as phenol, phthalic acid, and ethylene terephthalate can be used.

When LCP is classified, there are also classification methods of type I, type II, and type III, but the material is the same as LCP formed by the above-described constituent elements.

The resin composition preferably contains an inorganic filler material in addition to the LCP or PPS.

The form of the inorganic filler is not particularly limited, and examples thereof include a form having a longitudinal direction such as a fiber form or a plate form. These inorganic fillers may be used in combination of 2 or more. Therefore, the resin composition preferably contains a fibrous inorganic material and/or a plate-like inorganic material as the inorganic filler.

In the present specification, "fibrous" means a state in which the relationship between the length of the filler in the longitudinal direction and the cross-sectional diameter in a cross section perpendicular to the longitudinal direction is length in the longitudinal direction ÷ cross-sectional diameter ≧ 5 (i.e., the aspect ratio is 5: 1 or more). Here, the cross-sectional diameter is the distance between two points that is the longest on the outer periphery of the cross-section. When the cross-sectional diameters are different in the longitudinal direction, the measurement is performed at a portion where the cross-sectional diameter becomes maximum.

The term "plate-like" means that the relationship between the cross-sectional diameter of a surface having the largest projected area and the maximum height in the direction perpendicular to the cross-sectional surface is defined as cross-sectional diameter ÷ height ≧ 3.

The resin composition may contain an inorganic filler that satisfies both the above-described "fibrous" and "plate-like" conditions. In this case, as the inorganic filler, only one kind of inorganic material is contained. However, in this case, the resin composition is also referred to as "the resin composition contains both a fibrous inorganic material and a plate-like inorganic material as the inorganic filler".

Preferably, at least a part of the inorganic filler is dispersed in the outer case by having a portion oriented from the case bottom side toward the opening and a portion oriented toward the adjacent side wall, in each of the side walls of the side portion of the outer case.

The inorganic filler preferably has at least a size of 5 μm or more in diameter and 50 μm or more in length. In particular, it is preferable that the inorganic filler is dispersed throughout the outer case without aggregating.

Specific examples of the inorganic filler include fibrous glass fillers, and plate-like talc, mica, and the like. In particular, the inorganic filler preferably contains a glass filler as a main component.

(filled resin)

In the film capacitor of the present invention, the filling resin is filled between the capacitor element and the outer case.

As the filler resin, a resin corresponding to a desired function can be appropriately selected. For example, epoxy resin, silicone resin, urethane resin, or the like can be used. As the curing agent for the epoxy resin, an amine curing agent or an imidazole curing agent can be used. In addition, the filling resin may be only a resin, but a reinforcing agent may be added to improve the strength. The reinforcing agent can be silica, alumina, or the like.

By filling the space between the capacitor element and the outer case with the filling resin, the capacitor element can be blocked from the outside air. Therefore, it is preferable to appropriately select a resin having low moisture permeability and thicken the resin at the opening portion of the outer case.

The thickness of the resin in the opening of the outer case is preferably sufficient within a range in which the volume (body shape) of the entire capacitor is allowed, and specifically, is preferably 2mm or more, and more preferably 4mm or more. In particular, by disposing the capacitor element inside the outer case so as to be located on the bottom surface side of the opening of the outer case, it is more preferable that the thickness of the resin on the opening side of the outer case is made larger than the thickness of the resin on the bottom surface side of the capacitor element.

In the relation between the height of the filling resin and the height of the outer case, the resin in the opening of the outer case may be thickened as much as possible, may reach a position inside the outer case, may be filled completely, or may slightly overflow due to surface tension.

(capacitor element)

In the film capacitor of the present invention, the capacitor element is, for example, a columnar shape having a long circular cross section, and external electrodes formed by, for example, metal plating (thermal spraying) are provided at both ends in the central axis direction thereof.

The capacitor element 10 shown in fig. 8 (a) and 8 (b) includes: a roll of metallized film 40 formed by rolling the first metallized film 11 and the second metallized film 12 in a laminated state; and a first external electrode 41 and a second external electrode 42 connected to both end portions of the roll 40. As shown in fig. 8 b, the first metalized film 11 includes a first resin film 13 and a first metal layer (counter electrode) 15 provided on a surface of the first resin film 13, and the second metalized film 12 includes a second resin film 14 and a second metal layer (counter electrode) 16 provided on a surface of the second resin film 14.

As shown in fig. 8 (b), the first metal layer 15 and the second metal layer 16 face each other with the first resin film 13 or the second resin film 14 interposed therebetween. The first metal layer 15 is electrically connected to the first external electrode 41, and the second metal layer 16 is electrically connected to the second external electrode 42.

The first resin film 13 and the second resin film 14 may have different structures, but preferably have the same structure.

The first metal layer 15 is formed to reach one side edge of one surface of the first resin film 13, but not reach the other side edge. On the other hand, the second metal layer 16 is formed so as not to reach one side edge but to reach the other side edge of the one surface of the second resin film 14. The first metal layer 15 and the second metal layer 16 are made of, for example, aluminum layers.

As shown in fig. 8 (b) and 9, the first resin film 13 and the second resin film 14 are stacked with a gap in the width direction (in the left-right direction in fig. 8 (b)), so that the end portion of the first metal layer 15 on the side reaching the side edge of the first resin film 13 and the end portion of the second metal layer 16 on the side reaching the side edge of the second resin film 14 are exposed from the stacked films. As shown in fig. 9, the first resin film 13 and the second resin film 14 are wound in a laminated state to form a wound body 40, and the first metal layer 15 and the second metal layer 16 are laminated while being exposed at the end portions.

In fig. 8 (b) and 9, the second resin film 14 is wound so that it is the outer side of the first resin film 13, and the first metal layer 15 and the second metal layer 16 face the inner side of each of the first resin film 13 and the second resin film 14.

The first external electrode 41 and the second external electrode 42 are formed by, for example, spray-plating zinc or the like on the respective end surfaces of the roll 40 of the metallized film obtained as described above. The first external electrode 41 is in contact with the exposed end portion of the first metal layer 15, thereby being electrically connected to the first metal layer 15. On the other hand, the second external electrode 42 is in contact with the exposed end portion of the second metal layer 16, and thereby is electrically connected to the second metal layer 16.

In the film capacitor of the present invention, the resin film constituting the capacitor element may contain a curable resin as a main component, or may contain a thermoplastic resin as a main component. The resin film preferably contains a curable resin as a main component from the viewpoint of improving the moisture resistance of the thin film capacitor.

In the present specification, the term "main component of the resin film" refers to a component having the largest weight percentage, and preferably refers to a component having a weight percentage exceeding 50 weight%. Therefore, the resin thin film may contain, for example, an additive such as a silicone resin and an uncured portion of a starting material such as a first organic material and a second organic material described later as components other than the main component.

The curable resin may be a thermosetting resin or a photocurable resin.

In the present specification, the thermosetting resin refers to a resin that can be cured by heat, and is not limited to a curing method. Therefore, as long as the resin is curable by heat, a resin that is curable by a method other than heat (for example, light, electron beam, or the like) is also included in the thermosetting resin. Further, depending on the material, the reaction may start due to the reactivity of the material itself, and a resin which does not necessarily promote curing by applying heat, light, or the like from the outside is also used as a thermosetting resin. The photocurable resin is also not limited to the curing method.

The curable resin may or may not have at least one of a urethane bond and a urea bond. Examples of such a resin include a urethane resin having a urethane bond and a urea resin having a urea bond. Further, the resin may have both urethane bond and urea bond.

The presence of urethane bonds and/or urea bonds can be confirmed using a fourier transform infrared spectrophotometer (FT-IR).

The curable resin is preferably composed of a cured product of the first organic material and the second organic material. For example, a cured product obtained by reacting a hydroxyl group (OH group) of the first organic material with an isocyanate group (NCO group) of the second organic material is exemplified.

In the case where a cured product is obtained by the above reaction, an uncured portion of the starting material may remain in the film. For example, the resin film may contain at least one of an isocyanate group and a hydroxyl group. In this case, the resin film may contain either one of an isocyanate group and a hydroxyl group, or both of an isocyanate group and a hydroxyl group.

The presence of the isocyanate group and/or the hydroxyl group can be confirmed by using a fourier transform infrared spectrophotometer (FT-IR).

The first organic material is preferably a polyol having a plurality of hydroxyl groups in the molecule. Examples of the polyol include polyether polyol, polyester polyol, and polyvinyl acetal. As the first organic material, 2 or more organic materials may be used in combination.

The second organic material is preferably an isocyanate compound having a plurality of functional groups in the molecule, an epoxy resin, or a melamine resin. As the second organic material, 2 or more kinds of organic materials may be used in combination. Among the second organic materials, isocyanate compounds are preferable.

Examples of the isocyanate compound include aromatic polyisocyanates such as diphenylmethane diisocyanate (MDI) and Toluene Diisocyanate (TDI), and aliphatic polyisocyanates such as Hexamethylene Diisocyanate (HDI). The modified product of these polyisocyanates may be, for example, a modified product having carbodiimide, urethane or the like.

The epoxy resin is not particularly limited as long as it is a resin having an epoxy ring, and examples thereof include a bisphenol a type epoxy resin, a biphenyl skeleton epoxy resin, a cyclopentadiene skeleton epoxy resin, and a naphthalene skeleton epoxy resin.

The melamine resin is not particularly limited as long as it is an organic nitrogen compound having a triazine ring at the center of the structure and three amino groups at the periphery thereof, and examples thereof include alkylated melamine resins. Further, the modified melamine may be used.

In the film capacitor of the present invention, the resin film constituting the capacitor element is preferably obtained by molding a resin solution containing the first organic material and the second organic material into a film shape, and then curing the film by heat treatment.

In the film capacitor of the present invention, the resin film constituting the capacitor element may contain a vapor-deposited polymer film as a main component. The vapor deposition polymerization film may or may not have at least one of a urethane bond and a urea bond.

The vapor-deposited polymer film is a film formed by a vapor deposition polymerization method, and is basically contained in a curable resin.

In the film capacitor of the present invention, the resin film constituting the capacitor element may contain a thermoplastic resin as a main component. Examples of the thermoplastic resin include polypropylene, polyether sulfone, polyether imide, and polyarylate.

In the film capacitor of the present invention, the resin film constituting the capacitor element may contain an additive for adding another function. For example, smoothness can be imparted by adding a leveling agent. The additive is more preferably a material having a functional group that reacts with a hydroxyl group and/or an isocyanate group and forming a part of the crosslinked structure of the cured product.

Examples of such a material include a resin having at least one functional group selected from an epoxy group, a silanol group, and a carboxyl group.

In the film capacitor of the present invention, the thickness of the resin film constituting the capacitor element is not particularly limited, but is preferably 5 μm or less, more preferably less than 3.5 μm, and still more preferably 3.4 μm or less. The thickness of the resin film is preferably 0.5 μm or more.

The thickness of the resin thin film can be measured using an optical film thickness meter.

In the film capacitor of the present invention, the kind of metal included in the metal layer constituting the capacitor element is not particularly limited, but the metal layer preferably includes any 1 kind selected from aluminum (Al), titanium (Ti), zinc (Zn), magnesium (Mg), tin (Sn), and nickel (Ni).

In the film capacitor of the present invention, the thickness of the metal layer constituting the capacitor element is not particularly limited, but the thickness of the metal layer is preferably 5nm or more and 40nm or less from the viewpoint of suppressing breakage of the metal layer.

The thickness of the metal layer can be determined by observing a cross section of the metalized film cut in the thickness direction using an electron microscope such as a field emission scanning electron microscope (FE-SEM).

In the film capacitor of the present invention, when the capacitor element is formed of a roll of a metallized film, it is preferable that the capacitor element is punched out into a flat shape having an oval or oblong cross-sectional shape as in a roll of a metallized film 40a shown in fig. 10, and is formed into a more compact shape than when the cross-sectional shape is a perfect circle.

In this case, since the outer case can be made smaller by reducing the dead space inside the outer case, the entire film capacitor can be made smaller.

In the film capacitor of the present invention, when the capacitor element is formed of a roll of a metallized film, the capacitor element may have a cylindrical roll axis. The winding shaft is disposed on the central axis of the metallized film in a wound state, and serves as a winding shaft for winding the metallized film.

In the film capacitor of the present invention, since the size and shape of the capacitor element are determined according to the capacitor capacitance, capacitor elements of various sizes can be used.

For example, if the capacitor capacitance is 1 μ F or more and 150 μ F or less, the size of the capacitor element is preferably in a cross-sectional oblong shape, the length in the oblong direction is 15mm or more and 65mm or less, the length in the short circle direction is 2mm or more and 50mm or less, and the length in the longitudinal direction (the far and near direction of the cross-section and including the external electrode) is 10mm or more and 50mm or less.

In this case, the outer shape of the outer case is preferably such that the long side of the bottom portion is 16mm to 73mm, the short side of the bottom portion is 3mm to 58mm, and the height of the outer case is 10.5mm to 50.5 mm. The thickness of the outer case is preferably 0.5mm to 3 mm.

In the film capacitor of the present invention, the volume of the capacitor element is preferably 30% or more and 85% or less with respect to the internal volume of the outer case. If the volume of the capacitor element exceeds 85% of the internal volume of the outer case, it becomes difficult to fix the outer case and the capacitor element with the filling resin. On the other hand, if the volume of the capacitor element is less than 30% of the internal volume of the outer case, the outer case becomes excessively large with respect to the capacitor element, and the film capacitor becomes large.

In the film capacitor of the present invention, the distance between the inner surface of the outer case and the outer surface of the capacitor element is preferably 1mm or more and 5mm or less, and more preferably 1mm or more and 2mm or less.

(lead terminal)

In the film capacitor of the present invention, the lead terminals protrude to the outside from the filling resin filled in the outer case.

Since the portions of the lead terminals electrically connected to the external electrodes of the capacitor element are provided in a small area of the external electrodes, if a load is applied to the lead terminals, the lead terminals may be separated from the external electrodes. Therefore, the filling resin is positioned outside the external electrode of the capacitor element and the lead terminal in the outer case, and the filling resin is fixed to the external electrode and the lead terminal in close contact with each other. Thus, even if a load is applied to the protruding portions of the lead terminals, the connection between the lead terminals and the external electrodes can be strengthened by the filling resin, and separation between the lead terminals and the external electrodes can be suppressed.

The connection position between the external electrode and the lead terminal may be the central portion of the external electrode, or may be an electrode end portion near the opening as described in fig. 1 of patent No. 4733566.

(other embodiments)

Fig. 2 shows an example in which a single capacitor element is housed in a single outer case, but a plurality of capacitor elements may be housed in a single outer case as described in, for example, japanese patent application laid-open No. 2012-69810.

In addition, although the winding type film capacitor in which the first metalized film and the second metalized film are wound in a laminated state has been described above, a laminated type film capacitor in which the first metalized film and the second metalized film are laminated may be used. The above-described operation and effect of the present invention can be obtained even in a film capacitor such as a laminated film capacitor.

Examples

Hereinafter, embodiments in which the film capacitor of the present invention is more specifically disclosed are shown. The present invention is not limited to these examples.

Fig. 11 is an enlarged sectional view of the outer case used in examples 1 to 4. On the other hand, fig. 12 is an enlarged cross-sectional view of the outer case used in comparative example 1.

(example 1)

A dielectric resin film made of a polypropylene (PP) film as a thermoplastic resin was prepared. Aluminum was deposited on the dielectric resin film, and a metallized film as an electrode was wound, thereby obtaining a capacitor element. Using the obtained capacitor element, a capacitor sample was produced. As the outer case, a PPS case having a shape shown in fig. 11 was used. In FIG. 11, t will be equivalent to the thickness of the case₁Is set to 1mm, and the minimum thickness t of the outer surface concave part is set₂Is set to 1 mm.

Comparative example 1

A dielectric resin film made of a PP film as a thermoplastic resin was prepared. Aluminum was deposited on the dielectric resin film, and a metallized film as an electrode was wound, thereby obtaining a capacitor element. Using the obtained capacitor element, a capacitor sample was produced. As the outer case, a PPS case having a shape shown in fig. 12 was used. In FIG. 12, t will be equivalent to the thickness of the case₁Is set to 1mm, and the minimum thickness t of the outer surface concave part is set₂Is set to 0.5 mm.

The capacitor samples prepared in example 1 and comparative example 1 were measured for the capacitance decrease rate when a moisture-resistant load test was performed under an atmosphere of 85 ℃ and 85% RH under a condition of applying a voltage of 300V.

The time during which the rate of decrease in the electrostatic capacitance was 5% relative to the initial value was measured, and the results for 1500 times or longer were evaluated as "good", and the results for less than 1500 times were evaluated as "poor". The results are shown in Table 1.

[ Table 1]

Resin film

External casing

Inner surface convex part

t₁

t₂

Moisture resistance load test

Example 1

PP

PPS

Is provided with

1mm

1600hr(○)

Comparative example 1

PP

PPS

Is not provided with

1mm

0.5mm

1100hr(×)

As is clear from comparison between example 1 and comparative example 1, in the outer case, the moisture resistance of the film capacitor is improved by providing the inner surface convex portion around the inner surface facing the outer surface convex portion. It is considered that the minimum thickness t of the outer surface concave portion is preferable in the outer case₂The thickness t is set to be more lateral than the inner surface convex part₁Is equal to or is the t₁The above.

(example 2)

A dielectric resin film made of a thermosetting resin obtained by curing a mixture of polyvinyl acetal and a polyisocyanate is prepared. Aluminum was deposited on the dielectric resin film, and a metallized film as an electrode was wound, thereby obtaining a capacitor element. Using the obtained capacitor element, a capacitor sample was produced. As the outer case, a PPS case having a shape shown in fig. 11 was used. In FIG. 11, t will be equivalent to the thickness of the case₁Is set to 1mm, and the minimum thickness t of the outer surface concave part is set₂Is set to 1 mm.

The moisture resistance load test described above was also performed on the capacitor sample produced in example 2. The results are shown in Table 2.

[ Table 2]

Resin film

External casing

Inner surface convex part

t₁

t₂

Moisture load resistance test

Example 2

Thermosetting resin

PPS

Is provided with

1mm

1700hr(○)

Example 1

PP

PPS

Is provided with

1mm

1600hr(○)

Comparative example 1

PP

PPS

Is not provided with

1mm

0.5mm

1100hr(×)

As is clear from a comparison between example 1 and example 2, the moisture resistance of the film capacitor is improved as compared with the thermoplastic resin by using the thermosetting resin as the material of the resin film constituting the capacitor element.

(example 3)

A dielectric resin film made of a thermosetting resin obtained by curing a mixture of polyvinyl acetal and polyisocyanate is prepared. For the dielectric resin filmThe film was aluminum-evaporated and a metallized film as an electrode was wound, thereby obtaining a capacitor element. Using the obtained capacitor element, a capacitor sample was produced. As the outer case, an LCP case having a shape shown in fig. 11 was used. In FIG. 11, t will be equivalent to the thickness of the case₁Is set to 1mm, and the minimum thickness t of the outer surface concave part is set to₂Is set to 1 mm.

The moisture resistance load test described above was also performed on the capacitor sample produced in example 3. The results are shown in Table 3.

[ Table 3]

Resin film

External casing

Inner surface convex part

t₁

t₂

Moisture load resistance test

Example 3

Thermosetting resin

LCP

Is provided with

1mm

1800hr(○)

Example 2

Thermosetting resin

PPS

Is provided with

1mm

1700hr(○)

Example 1

PP

PPS

Is provided with

1mm

1600hr(○)

Comparative example 1

PP

PPS

Is not provided with

1mm

0.5mm

1100hr(×)

As is clear from comparison between example 2 and example 3, by using LCP as the material of the outer case, the moisture resistance of the film capacitor is improved as compared with PPS.

(example 4)

A dielectric resin film made of a thermosetting resin obtained by curing a mixture of polyvinyl acetal and polyisocyanate is prepared. Aluminum was deposited on the dielectric resin film, and a metallized film as an electrode was wound, thereby obtaining a capacitor element. Using the obtained capacitor element, a capacitor sample was produced. As the outer case, an LCP case having a shape shown in fig. 11 was used.In FIG. 11, t will be equivalent to the thickness of the case₁Is set to 0.5mm, the minimum thickness t of the outer surface recess is set to₂Is set to 0.5 mm.

The moisture resistance load test described above was also performed on the capacitor sample produced in example 4. The results are shown in Table 4.

[ Table 4]

Resin film

External casing

Inner surface convex part

t₁

t₂

Moisture-proof load test

Example 4

Thermosetting resin

LCP

Is provided with

0.5mm

1500hr(○)

From the results of example 4, it is understood that, in the case where the material of the resin film constituting the capacitor element is a thermosetting resin and the material of the outer case is LCP, the moisture resistance of the film capacitor can be secured even if the thickness of the outer case is 0.5 mm.

Description of the reference numerals

1 … film capacitor; 10 … capacitor elements; 11 … a first metallized film; 12 … a second metallized film; 13 … a first resin film; 14 … a second resin film; 15 … a first metal layer; 16 … second metal layer; 20. 200 … outer casing; 21 … opening part; 22 … bottom; 23 … first side wall; 24 … second side wall; 25 … a third side wall; 26 … fourth side wall; 27 … recess; 28 … taper; 30 … filled resin; 40. 40a … rolls of metallized film; 41 … a first outer electrode; 42 … second external electrode; 51 … first lead terminal; 52 … second lead terminal; 61 … external surface protrusions; 62 … outer surface recesses; 63. 63a … inner surface protrusions; 71 … a first locating tab; 72 … second locating tab; 73 … third locating tab; 100 … molded article; 110 … reels of paper; 120 … flow path; 130 … gate; t is t₁… thickness lateral to the inner surface convex part; t is t₂… minimum thickness of the outer surface recess; t is t₃… width of the outer surface recess; t is t₄… width of the inner surface projection; a … outer surface of the outer case; b … is fitted on the inner surface of the outer case.

Claims

1. A thin film capacitor is provided with: a capacitor element including a metallized film having a metal layer provided on a surface of a resin film; a resin outer case in which the capacitor element is housed; and a filling resin filled between the capacitor element and the outer case, wherein the filling resin is a resin having a specific composition,

the outer case has an outer surface convex portion and an outer surface concave portion which positions the outer surface convex portion on an inner side of an outer surface of the outer case, and an inner surface convex portion which protrudes from an inner surface facing the outer surface concave portion.

2. A film capacitor according to claim 1,

in the outer case, a minimum thickness t of the outer surface concave portion₂The thickness t is more lateral than the inner surface convex part₁Is equal to or is the t₁The above.

3. A film capacitor according to claim 2,

in the outer case, an inner surface facing the outer surface concave portion is positioned closer to the capacitor element than an inner surface on a side of the inner surface convex portion.

4. A film capacitor in accordance with any one of claims 1 to 3,

in the outer case, an outer surface of the outer surface convex portion is located inward of an outer surface of the outer case than an outer surface located laterally of the inner surface convex portion.

5. A film capacitor according to any one of claims 1 to 3,

the inner surface convex portion is in contact with an outer surface of the capacitor element.

6. A film capacitor according to claim 5,

the inner surface convex portion is formed in a flat shape along an outer surface of the capacitor element.

7. A film capacitor according to claim 5,

the outer case includes an opening, a bottom portion facing the opening and abutting the capacitor element, and a side wall portion protruding from the bottom portion toward the opening,

a first positioning projection projecting toward the capacitor element side is provided on the bottom portion,

the inner surface protrusion is the first positioning protrusion.

8. A film capacitor according to claim 7,

the inner surface convex part is a part of the bottom part and is arranged at the central position of the bottom part.

9. A film capacitor according to claim 7 or 8,

the side wall portion is provided with a second positioning projection and a third positioning projection which project toward the capacitor element side and face each other with the capacitor element interposed therebetween.

10. A film capacitor in accordance with claim 5,

the side wall portion is provided with a second positioning convex portion and a third positioning convex portion which protrude toward the capacitor element side and face each other with the capacitor element interposed therebetween,

the inner surface convex portion is one of the second positioning convex portion and the third positioning convex portion.

11. An outer case for a film capacitor for housing a capacitor element in the inside, the capacitor element comprising a metallized film having a metal layer provided on a surface of a resin film,

the outer case is made of resin, and has an outer surface convex portion on an outer surface thereof and an outer surface concave portion in which the outer surface convex portion is positioned inward of the outer surface of the outer case, and has an inner surface convex portion protruding from an inner surface thereof on the inner surface facing the outer surface concave portion.