JP6201141B2 - Film capacitor - Google Patents

Description

  The present invention relates to a film capacitor that is used in various electronic devices, electric devices, industrial devices, automobiles, and the like, and particularly suitable for smoothing, filtering, and snubber of a motor drive inverter circuit of a hybrid vehicle.

  In recent years, from the viewpoint of environmental protection, all electric devices are controlled by inverter circuits, and energy saving and high efficiency are being promoted. In particular, in the automobile industry, hybrid vehicles (hereinafter referred to as HEVs) that run on electric motors and engines have been introduced into the market, and the development of technologies relating to energy saving and high efficiency has been activated, which is friendly to the global environment.

  Since such an electric motor for HEV has a high operating voltage range of several hundred volts, a film capacitor having high withstand voltage and low loss electric characteristics has attracted attention as a capacitor used in connection with this electric motor. Yes.

  FIG. 8 shows a cross-sectional view of a conventional film capacitor 101. The film capacitor 101 includes capacitor elements 102 and 103, a resin case 104 that accommodates the capacitor elements 102 and 103, and a filled resin 105 that is filled in the resin case 104 so as to cover the capacitor elements 102 and 103. Yes.

  Capacitor elements 102 and 103 are formed by integrally winding a positive and negative electrode layer and a dielectric film in a flat shape. On both end faces of the capacitor element 102, lead electrodes 106 are formed to draw out the positive and negative electrode layers, respectively. In addition, lead electrodes 107 are formed on both end faces of the capacitor element 103.

  The side surfaces of the flat capacitor elements 102 and 103 are constituted by flat flat surfaces 102A and 103A and curved curved surfaces 102B and 103B.

  As a document disclosing an example that approximates the above-described conventional technique, there is, for example, Patent Document 1.

JP 2007-281333 A

  In the conventional film capacitor 101, the capacitance may be reduced.

  The reason is that moisture outside the film capacitor 101 permeates the resin case 104 and enters the filled resin 105. That is, when the moisture that has entered the filling resin 105 reaches the capacitor elements 102 and 103 and is absorbed, for example, in a moisture resistance test, the aluminum constituting the electrode layer on the positive electrode (anode) side and the water in the moisture In some cases, an oxide ion causes an electrochemical reaction to form a film of aluminum hydroxide or aluminum oxide, which is an insulator, and the electrode layer is insulated. This is generally called an anodic oxidation phenomenon. As a result of this anodic oxidation phenomenon, the capacitance of the film capacitor 101 has decreased.

  Therefore, an object of the present invention is to improve the moisture resistance of a film capacitor and suppress a decrease in capacitance.

  In order to achieve this object, in the film capacitor according to claim 1 of the present invention, the capacitor element having a flat shape is arranged inside the resin outer package so that one flat surface of the pair of flat surfaces faces the bottom of the resin outer package. And a metal layer is provided on at least one of the bottom outer surface and the top outer surface of the resin sheathing body.

  In the film capacitor according to claim 2 of the present invention, the flat capacitor element is arranged inside the resin sheathing body so that one flat surface of the pair of flat surfaces faces the side portion of the resin sheathing body. The metal outer layer was provided with a metal layer on the outer side surface.

  Thereby, the film capacitor of this invention can improve moisture resistance.

  The reason is that the penetration of moisture into the film capacitor can be suppressed by the metal layer provided on the surface of the exterior body.

  In a flat capacitor element, the curved portion generally has a small area facing the outside of the resin sheathing body, but the flat surface portion is a flat plate shape close to a flat surface, so the area facing the outside of the resin sheathing body Therefore, the moisture that has entered the inside of the resin sheathing body is easily absorbed.

  Therefore, the present invention suppresses the intrusion of moisture from the outside of the resin sheathing body into the film capacitor by the above configuration. As a result, a decrease in the capacitance of the film capacitor can be suppressed.

The perspective view of the capacitor | condenser element in this invention The figure explaining the manufacturing process of the capacitor element in this invention Sectional drawing of the film capacitor in Example 1 The perspective view of the capacitor | condenser element in Example 1 Sectional drawing of the film capacitor in Example 2 Sectional drawing of the film capacitor in Example 3 Sectional drawing of the film capacitor in Example 4 Cross section of conventional film capacitor

  FIG. 1 is a perspective view of a capacitor element 2 used for a film capacitor 1 in an embodiment of the present invention.

  In the capacitor element 2, a pair of positive and negative electrode layers 3 and 4 and dielectric films 5 and 6 are integrally wound in a flat shape.

  Further, the outer periphery of the capacitor element 2 has a pair of end surfaces 9 and 10 on which the extraction electrodes 7 and 8 are respectively formed, and side surfaces between the end surfaces 9 and 10 (first, second, third, and fourth described later). Side surfaces 11, 12, 13, 14).

  The electrode layer 3 is connected to one extraction electrode 8, and the electrode layer 4 is connected to the other extraction electrode 7. Each of the extraction electrodes 8 and 7 is connected to an external extraction terminal (a bus bar 18 in FIG. 3) described later, and is extracted to the outside.

  The side surface of the capacitor element 2 is a flat surface that connects the first side surface 11 and the second side surface 12, which are curved surfaces facing each other, and the first side surface 11 and the second side surface 12 to face each other. A third side surface 13 and a fourth side surface 14. As shown in FIG. 2, the flat capacitor element 2 is generally formed by winding dielectric films 5 and 6 and positive and negative electrode layers 3 and 4 together and then pressing them from above and below into a flat shape. Therefore, the third side surface 13 and the fourth side surface 14 are usually flat surfaces. The third side surface 13 and the fourth side surface 14 are not limited to flat surfaces and may be gently curved surfaces.

  The positive and negative electrode layers 3 and 4 were formed on one surface of the dielectric films 5 and 6 by vapor deposition, respectively. In addition to the configuration in which the electrode layers 3 and 4 are deposited on each side of the dielectric films 5 and 6, the electrode layer 3 is formed on one surface of the dielectric film and the electrode layer 4 is formed on the other surface. May be. In addition to forming the electrode layers 3 and 4 by vapor deposition, a metal foil may be used as the electrode layer. In either case, the positive and negative electrode layers are arranged to face each other with the dielectric film interposed therebetween.

  When the positive and negative electrode layers 3 and 4 are formed by vapor deposition as in the present embodiment, when an excessive current is applied to the capacitor element 2, the electrode layers 3 and 4 are scattered and the insulation is easily recovered. That is, the electrode layers 3 and 4 formed by vapor deposition have a high self-healing property.

  The electrode layers 3 and 4 may be divided into small small electrode portions 15. The small electrode portions 15 are separated by an insulation margin and are connected by a fuse. When an excessive current is applied, the fuse evaporates and blows, so that a short circuit of the capacitor element 2 can be suppressed.

  The small electrode portion 15 may be formed on the entire electrode layers 3 and 4, or may be formed only in a region having a predetermined width with respect to the width direction W connecting the both end surfaces 9 and 10. Good. When forming partially, it is preferable to form in the edge part side on the opposite side to the extraction electrode 8 and the extraction electrode 7 to which the electrode layers 3 and 4 are connected, respectively. Since a large current flows in a region close to the extraction electrode 8 and the extraction electrode 7 to be connected, heat generation becomes smaller when the small electrode portion 15 is provided at a location where the current density is small.

  Moreover, you may form the thick low resistance part 16 in the edge part of the side connected with the extraction electrodes 8 and 7 of the electrode layers 3 and 4. FIG. By increasing the thickness, the adhesion to the extraction electrodes 8 and 7 is increased, and the tan δ of the film capacitor can be lowered.

  Examples of the material for the dielectric films 5 and 6 include polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyphenyl sulfide, and polystyrene.

  Examples of the material of the electrode layers 3 and 4 include aluminum, an alloy made of aluminum and magnesium, silicon, and zinc, and zinc. The low resistance portion 16 can be formed of the same material as that of zinc, aluminum, other electrode layers 3 and 4, or the extraction electrodes 7 and 8.

  Examples of the material for the extraction electrodes 7 and 8 include aluminum, an alloy composed of aluminum and zinc or silicon, and zinc. The extraction electrodes 7 and 8 can be formed, for example, by spraying metal on both end faces 9 and 10 of the capacitor element 2.

Example 1
FIG. 3 shows a cross-sectional view of the film capacitor 1 of the first embodiment. The film capacitor 1 according to the first embodiment includes two capacitor elements 2L and 2R, a resin case 17 that is a resin outer housing that accommodates these capacitor elements 2L and 2R, and an external device that pulls out the electrodes of the capacitor elements 2L and 2R to the outside. A bus bar 18 serving as a lead terminal and a metal layer 19 are provided. In the present specification, the “bottom part” and the “side part” of the resin case 17 refer to a surface located on the lower side and a surface located on the side in FIG. That is, the bottom is a surface in the opposite direction to the opening of the resin case 17, and the side is a surface surrounding the surface in the opposite direction to the opening of the resin case 17.

  The inside of the resin case 17 of Example 1 is filled with a filling resin 20. Note that any of the capacitor elements 2L and 2R shown in FIG. 3 uses the capacitor element 2 shown in FIG. 1, and the same reference numerals are given to configurations common to the capacitor element 2 of FIG.

  As shown in FIG. 3, the resin case 17 is a box shape having an upper surface opened in a rectangular shape, and includes a flat bottom portion 21 and flat side walls 22 and 23. The material of the resin case 17 is made of polyphenylene sulfide, polybutylene terephthalate, or the like. The filling resin 20 is made of an epoxy resin or a urethane resin.

  The two capacitor elements 2L, 2R have a horizontal cross section that passes through the major axis (axis P in FIG. 1) of both end faces 9, 10 and is parallel to the direction connecting the both end faces 9, 10 (width direction W). The case 17 is disposed in parallel to the bottom 21. That is, the capacitor elements 2 </ b> L and 2 </ b> R are accommodated in the resin case 17 so that the third side surface 13 that is a flat surface faces the bottom portion 21 of the resin case 17.

  Here, in the flat capacitor elements 2L and 2R, the first side surface that is the curved surface portion and the second side surfaces 11 and 12 have a small area facing the outside, but the third and fourth surface portions that are flat surface portions. Since the side surfaces 13 and 14 have a flat plate shape close to a plane, the area facing the outside is large, and the moisture that has entered the film capacitor 1 is easily absorbed.

  In particular, since the upper portion of the fourth side surface 14 is filled with the filling resin 20 relatively thickly, the third side surface 13 and the outside of the film capacitor 1 are compared with the linear distance between the fourth side surface 14 and the outside of the film capacitor 1. The third side surface 13 is closest to the outer surface of the film capacitor 1, that is, the water intrusion path to the third side surface 13 is shorter than that of the fourth side surface 14.

  Therefore, in the present embodiment, the metal layer 19 is provided on the outer surface 21S of the bottom portion 21 in order to protect the third side surface 13 that is particularly likely to absorb moisture from the outside.

  Thus, by selectively disposing the metal layer 19, the film capacitor 1 of the present embodiment has a configuration in which the capacitor elements 2 </ b> L and 2 </ b> R are protected from moisture that has entered from the outside of the film capacitor 1, and the moisture resistance is improved. It has become.

  In the first embodiment, the metal layer 19 is provided on the outer surface 21 </ b> S of the bottom portion 21. In Example 1, a rectangular aluminum foil is used as the metal layer 19, and both surfaces of the metal layer 19 are covered with a polypropylene layer and a nylon layer, respectively. Here, in this specification, for the purpose, a layer covering the surface on the bottom 21 side of the metal layer 19 is referred to as an “adhesive layer (not shown)”, and a layer covering the surface opposite to the bottom 21 side is referred to. It is defined as “protective layer (not shown)”. That is, in this embodiment, the adhesive layer is made of polypropylene and the protective layer is made of nylon.

  The protective layer made of nylon prevents unintentional conduction between external devices around the film capacitor 1 and the metal layer 19 at the nylon portion when the film capacitor 1 is mounted. Yes. In order to prevent conduction with an external device, any material having insulating properties other than nylon can be used as a protective layer as appropriate. Further, by covering the metal layer 19 with nylon or the like in this way, it is possible to prevent the metal layer 19 from rusting with time. In addition, as this metal layer 19, foils, such as copper other than aluminum foil, may be used, or the metal plate formed with metals, such as aluminum and copper, may be used.

  The aluminum foil used as the metal layer 19 is provided by sticking to the outer surface 21S of the bottom 21 of the resin case 17. Specifically, the polypropylene layer covering the metal layer 19 is melted and thermally fused to the outer surface 21S of the bottom portion 21. As described above, in Example 1, polypropylene was used as an adhesive layer for adhering the metal layer 19 to the outer surface 21S of the bottom portion 21. However, any material having adhesiveness other than polypropylene can be used as the adhesive layer. it can. However, when the film capacitor 1 is mounted on a vehicle or the like, the film capacitor 1 may be exposed to a harsh environment. For example, the heat generated by the surrounding vehicle-mounted equipment may propagate to the film capacitor 1 depending on the installation location. If the adhesive layer is melted by these heats, the metal layer 19 may be peeled off from the bottom 21. Therefore, it is preferable that at least the material used as the adhesive layer has a melting point of 80 ° C. or higher. Note that when the adhesive layer covering the metal layer 19 is heat-sealed to the outer surface 21S of the bottom portion 21, if the melting point of the protective layer is lower than the melting point of the adhesive layer, the protective layer is melted first, and the heat fusion is performed. It is essential that the material used for the protective layer has a higher melting point than the material used for the adhesive layer, because this will hinder the wearing operation. As in Example 1, there is no problem if polypropylene is used as the adhesive layer and nylon is used as the protective layer.

  The outer surface 21S of the bottom 21 is roughened in order to improve the adhesion with the adhesive layer provided on the surface of the metal layer 19. By roughening in this way, the melted adhesive layer enters the irregularities of the roughened outer surface 21S, and the anchor surface acts, whereby the outer surface 21S and the metal layer 19 can be firmly bonded. If the surface roughness of the outer surface 21S is Ra ≧ 2 μm, it has been confirmed that sufficient adhesion with the adhesive layer of the metal layer 19 can be secured.

  Further, in addition to sticking the metal layer 19 to the bottom portion 21 by using heat fusion as described above, a metal foil or metal plate that becomes the metal layer 19 may be simply stuck with an adhesive. In this case, the adhesive can be applied to the surface of the metal layer 19 and adhered to the outer surface 21S of the bottom portion 21, whereby the metal layer 19 can be adhered to the bottom portion 21 and the workability is excellent. However, since it is considered that moisture permeates from the side (thickness portion) of the adhesive layer after solidification and permeates into the resin case 17, it is preferable to make the thickness of the adhesive layer as thin as possible. As a specific thickness, if the adhesive layer is 1 mm or less, the moisture resistance of the film capacitor 1 is hardly affected. Note that an epoxy resin adhesive or the like can be used as the adhesive.

  Also, when a metal foil such as an aluminum foil is used as the metal layer 19 instead of a metal plate, since the metal foil is generally lighter than the metal plate, the metal layer 19 is made of resin due to vibration received when it is mounted on an automobile. The possibility of peeling from the case 17 can be suppressed. Furthermore, since it is very thin, it does not increase the size of the product. In addition, when using aluminum foil as the metal layer 19, it is preferable to set it as 10 micrometers or more and 100 micrometers or less. If the thickness is too thin, the mechanical strength is weak and the holes are easily opened. As a result, moisture may permeate and moisture resistance may decrease. On the other hand, even if the thickness of the metal layer 19 was made thicker than 100 μm, further improvement in moisture resistance was not seen so much. Therefore, the thickness of the metal layer 19 is preferably 10 μm or more and 100 μm or less.

  Here, as a method other than using a metal plate or a metal foil as the metal layer 19, a method of depositing a metal such as aluminum or copper on the outer surface 21 </ b> S of the bottom portion 21 of the resin case 17 can be cited. Thus, even when the metal layer 19 is formed by vapor deposition, the film capacitor 1 is not increased in weight and size, and is very effective as a method for forming the metal layer 19.

  In Example 1, the outline of the metal layer 19 is larger than the outline of each of the third side surfaces 13, and the projected portion of the third side surface 13 onto the bottom 21 side is all inside the metal layer 19. Layer 19 is provided. Here, in the case of the first embodiment, “the outline of the third side surface 13” refers to an outline obtained by combining the third side surfaces 13 of the two capacitor elements 2 of the capacitor element 2L and the capacitor element 2R. For the purpose of blocking all the linear moisture permeation paths, it is desirable that the outline of the metal layer 19 be larger than the outline of the third side face 13 in this way. Although the metal layer 19 desirably protects a wider area of the bottom portion 21 in this way, at least 80% or more of the area of the third side surface 13 of each capacitor element 2L, 2R facing the bottom portion 21 side is protected. If so, stable moisture resistance can be secured.

  In Example 1, as shown in FIG. 4, the bus bar 18 is connected to the capacitor elements 2L and 2R at the connection portion 24 provided on the extraction electrode 7 (8), and is routed to the third side surface 13 side. Instead, an external connection portion 18A is provided on the fourth side face 14 side, and this external connection portion 18A is exposed from the filling resin, thereby enabling electrical connection with the outside of the film capacitor 1.

  In this way, the bus bar 18 is not routed to the third side surface 13 side, and the bus bar 18 is not disposed on the third side surface 13 side, so that the heat of the bus bar 18 propagates to the metal layer 19. Is suppressed. This is to reduce the possibility that the adhesive layer between the metal layer 19 and the outer surface 21S of the bottom portion 21 is melted by heat from the bus bar 18 and the metal layer 19 is peeled off.

  Further, in the first embodiment, the external connection portion 18A is raised from the resin case 17 in the vertical direction, and is electrically connected to an external device above the resin case 17 in FIG. Generally, the periphery of the external connection portion 18A, which is a connection portion between the bus bar 18 and the external device, inevitably has a high resistance, so that a relatively large amount of heat is generated when the film capacitor 1 is used. The external connection portion 18A, which is a heat source, is disposed above the resin case 17 and is kept away from the metal layer 19 as much as possible, whereby the adhesive layer between the metal layer 19 and the outer surface 21S of the bottom portion 21 is separated from the external connection portion 18A. The possibility that the metal layer 19 is peeled off due to melting by heat is reduced.

  As described above, in the first embodiment, the metal layer 19 is provided on the outer surface 21 </ b> S of the bottom portion 21 of the resin case 17. In the first embodiment, the first side surface 11 of the capacitor element 2 </ b> L is close to the side wall 22 of the resin case 17. Further, the second side surface 12 of the capacitor element 2 </ b> R is close to the side wall 23. However, since the 1st side surface 11 and the 2nd side surface 12 are curving, the opposing area with each side wall 22 and 23 is small. Therefore, the influence of the moisture permeation from the side walls 22 and 23 on the characteristics of the film capacitor 1 is not as great as the influence of the water permeation from the bottom 21 side, and the metal layer 19 is formed on the outer surfaces of the side walls 22 and 23. Not provided. Thus, the metal layer 19 is selectively and partially disposed and protected, thereby contributing to the reduction in size and weight of the entire film capacitor 1.

(Example 2)
FIG. 5 shows a cross-sectional view of the film capacitor 31 of the second embodiment.

  The second embodiment is different from the first embodiment in the thickness of the filling resin 20 provided on the upper portions of the capacitor elements 2L and 2R and the position where the metal layer 19 is provided.

  Generally, a film capacitor is often used for HEV as described above, but it is difficult to secure a space for disposing the film capacitor in the vehicle. It is hoped that. Therefore, as illustrated in FIG. 5, when the resin case 17 is lowered and the amount of the filling resin 20 in the resin case 17 is reduced, the thickness of the filling resin 20 layer provided on the upper portions of the capacitor elements 2 </ b> L and 2 </ b> R is reduced. It will be thinner. As a result, moisture outside the film capacitor 31 permeates the filled resin 20 and easily reaches the capacitor elements 2L and 2R.

  In order to solve such a problem, the film capacitor 31 of the second embodiment has a configuration in which the metal layer 19 is provided above the capacitor elements 2L and 2R. According to the configuration of the second embodiment, even if the thickness of the filling resin 20 provided on the capacitor elements 2L and 2R is reduced, the metal layer 19 can suppress the ingress of moisture from the outside, and the film capacitor It is possible to reduce the height while securing 31 moisture resistance.

  The metal layer 19 used in Example 2 is the same as that in Example 1. That is, an aluminum foil having both surfaces coated with polypropylene as an adhesive layer and nylon as a protective layer is used. The metal layer 19 is attached to the filling resin 20 by filling the resin case 17 with the filling resin 20 and solidifying the filling resin 20 sufficiently, and then thermally bonding a polypropylene layer as an adhesive layer. Yes.

  The bus bar 18 has a configuration in which the external connection portion 18A is drawn above the film capacitor 31, but the metal layer 19 of the present embodiment is provided with a through hole in accordance with the position of the external connection portion 18A. The external connection portion 18A is drawn out through the through hole.

(Example 3)
FIG. 6 shows a cross-sectional view of the film capacitor 41 of the third embodiment.

  In the third embodiment, the two capacitor elements 2L and 2R pass through the major axes (axis P in FIG. 1) of both end faces (reference numerals 9 and 10 in FIG. 1) and connect the end face 9 and the end face 10 (FIG. 1). A horizontal section parallel to the width direction W) of the resin case 17 is arranged perpendicularly to the bottom 21 of the resin case 17. That is, the capacitor elements 2L and 2R are accommodated in the resin case 17 so that the third side surface 13 of the capacitor element 2L and the fourth side surface 14 of the capacitor element 2R are opposed to the side wall 22 and the side wall 23, respectively. Has been.

  In the capacitor element 2 </ b> L arranged on the left side in FIG. 6, the third side surface 13 is close to the side wall 22 of the resin case 17.

  In the other capacitor element 2 </ b> R arranged on the right side shown in FIG. 6, the fourth side surface 14 is close to the side wall 23 of the resin case 17.

  A metal layer 19L and a metal layer 19R are formed on the outer surface 22S of the side wall 22 and the outer surface 23S of the side wall 23, respectively. The metal layer 19L and the metal layer 19R have different signs to distinguish their positions, and the configuration is the same for the metal layer 19L and the metal layer 19R as will be described later.

  The metal layer 19L and the metal layer 19R are made of the same material as that of the metal layer 19 of the first embodiment.

  The outlines of the metal layer 19L and the metal layer 19R are larger than the outlines of the third side surface 13 of the capacitor element 2L facing the side wall 22 and the fourth side surface 14 of the capacitor element 2R facing the side wall 23, respectively. The projected portion on the side wall 22 side of the third side surface 13 and the projected portion on the side wall 23 side of the fourth side surface 14 of the capacitor element 2R are respectively in the metal layer 19L and the metal layer 19L so as to be inside the metal layer 19R, A metal layer 19R is provided. The metal layer 19L and the metal layer 19R are provided so as to protect 80% or more of the area of the third side surface 13 and the fourth side surface 14 of the capacitor elements 2L and 2R for the same reason as in the first embodiment. It is desirable that

  Further, in the third embodiment, as shown in FIG. 6, the bus bar 18 is not routed to the third side face 13 side and the fourth side face 14 side of the capacitor elements 2L, 2R, and the first of the capacitor elements 2L, 2R. Are vertically raised from the side surface 11 toward the opening of the resin case 17. The purpose of this configuration is to suppress the possibility that the heat from the bus bar 18 propagates to the metal layers 19L and 19R and the metal layers 19L and 19R peel from the side walls 22 and 23, respectively, as in the first embodiment. is there.

  Description of other configurations similar to those of the first embodiment is omitted.

  As described above, in Example 3, the metal layer 19 is not provided on the bottom 21 side, and the metal layers 19L and 19R are provided only on the outer surface 22S of the side wall 22 of the resin case 17 and the outer surface 23S of the side wall 23. is there. Thus, by selectively and partially arranging and protecting the metal layers 19L and 19R, the film capacitor 41 as a whole can be reduced in size and weight.

  Here, the moisture resistance of the film capacitor 1 and the film capacitor 41 of Example 1 and Example 3 will be described in comparison with Comparative Example 1 described below. About Example 2, since the thickness of the filling resin 20 differs from the comparative example 1, it is not compared.

(Comparative Example 1)
As Comparative Example 1, a conventional film capacitor 101 shown in FIG. The configuration of the film capacitor 101 of Comparative Example 1 is obtained by removing the metal layer 19 that is the point of the present invention from the configuration of the film capacitor 1 of Example 1. Since other configurations are the same as those of the film capacitor 1 of the first embodiment, the description thereof is omitted.

  Using the film capacitors 1, 41, and 101 of Examples 1 and 3 and Comparative Example 1, a moisture resistance test was performed. In the humidity resistance test, a predetermined voltage is applied under a high temperature and high humidity condition of an environmental temperature of 85 ° C. and a humidity of 85%, and the capacitance is measured at regular intervals.

  As a result of the moisture resistance test, in Comparative Example 1, the time during which the capacitance was reduced by 5% was about 500 hours. On the other hand, in Examples 1 and 3, the time during which the capacitance was reduced by 5% was 1000 hours or more, and in film capacitors 1 and 41, a dramatic improvement in moisture resistance was confirmed.

  Thus, according to the structure of this invention, the moisture resistance of a film capacitor can be improved dramatically and the capacity | capacitance reduction of a film capacitor can be suppressed.

  The reason is that, in the first embodiment, as shown in FIG. 3, the metal layer 19 provided on the outer surface 21 </ b> S of the bottom 21 of the resin case 17 prevents moisture from entering from the outside.

  Moreover, in Example 3, as shown in FIG. 6, the metal layers 19L and 19R provided on the side walls 22 and 23 of the resin case 17 suppress the entry of moisture from the outside.

  That is, when the flat capacitor elements 2L and 2R are used, the third side surface 13 and the fourth side surface 14 which are flat surfaces are substantially flat, so that the area facing the outside of the film capacitors 1 and 41 is the same. The moisture that has permeated through the resin case 17 and the filling resin 20 is easily absorbed from the third side surface 13 and the fourth side surface 14.

  On the other hand, in Examples 1 and 3, since the metal layer 19 is provided, moisture can be prevented from entering the film capacitors 1 and 41, and moisture absorption by the capacitor elements 2L and 2R can be suppressed. As a result, the oxidation of the electrode layers 3 and 4 can be suppressed, and the capacity reduction of the film capacitors 1 and 41 can be suppressed.

  In the case where the metal layer 19 of the film capacitor 1 shown in FIG. 3 has an area of 80% or more of the area of the opposing third side surface 13, until the capacitance is reduced by 5% in the humidity resistance test. The time was 1000 hours or more. Further, when the metal layers 19L and 19R of the film capacitor 41 have an area of 80% or more of the areas of the third side surface 13 and the fourth side surface 14 that face each other, the capacitance decreases by 5% in the moisture resistance test. The time to do was over 1000 hours.

  On the other hand, when the metal layer 19 of the film capacitor 1 has an area of 70% of the area of the third side surface 13 facing each other, the time until the capacitance decreases by 5% in the moisture resistance test. , Sometimes less than 1000 hours. Further, when the metal layers 19L and 19R of the film capacitor 41 have an area of 70% of the area of the third side surface 13 and the fourth side surface 14 facing each other, the capacitance is reduced by 5% in the moisture resistance test. In some cases, the time to do this was less than 1000 hours.

  Therefore, the metal layers 19L and 19R have a surface area of 80% or more of the areas of the third side surface 13 and the fourth side surface 14 that face each other, so that the moisture resistance can be particularly stably improved.

Example 4
FIG. 7 shows a cross-sectional view of the film capacitor 51 of the fourth embodiment.

  In Example 4, the resin case 17 is not used, but the exterior resin 52 itself covered by the capacitor elements 2L and 2R is used as the resin exterior body.

  As shown in FIG. 7, in Example 4, the bus bar 18 except for the capacitor elements 2L and 2R and the external connection portion 18A is covered with an exterior resin 52 formed of an epoxy resin. The capacitor elements 2L and 2R are protected from the external environment. The exterior resin 52 is in a state in which an epoxy resin is solidified, and this film capacitor 51 is formed by placing the capacitor elements 2L, 2R and the bus bar 18 at predetermined positions of the mold and pouring the epoxy resin into a solid state. It is formed by removing it from the mold. The exterior resin 52 is solidified so as to surround the capacitor elements 2L and 2R with a predetermined thickness, and has a shape of a substantially rectangular parallelepiped with four corners chamfered as shown in FIG. Yes.

  As shown in FIG. 7, the bottom 53 of the exterior resin 52 formed in a substantially flat plate shape is parallel to the third side surface 13 of the capacitor elements 2L, 2R in the exterior resin 52, and the capacitor elements 2L, 2R The third side surface 13 and the bottom 53 are opposed to each other. The metal layer 19 is attached to the outer surface 53S of the bottom 53. The metal layer 19 can be a metal foil or a metal plate formed of aluminum or copper as in the first embodiment.

  As a method for attaching the metal layer 19, an adhesive layer provided on the surface of the metal layer 19 may be heat-sealed to the bottom 53 of the exterior resin 52 as in the film capacitor 1 of Example 1, or the metal layer 19. Alternatively, an adhesive may be applied to the base 53 and attached to the bottom 53.

  In particular, when an epoxy resin is used as the exterior resin 52 as in Example 4, the adhesive layer of the metal layer 19 is previously subjected to corona treatment, and innumerable fine irregularities are formed on the adhesive layer, so that heat fusion can be achieved. The metal layer 19 can be easily attached to the bottom 53 of the exterior resin 52 without application of adhesive or adhesive. When this corona treatment is performed and the metal layer 19 is stuck to the bottom 53, it is formed of polypropylene as an adhesive layer for the metal layer 19.

  Also in the film capacitor 51 of the fourth embodiment having the above-described configuration, the metal layer 19 can suppress the intrusion of moisture from the outside into the film capacitor 51 similarly to the film capacitor 1 of the first embodiment. The moisture resistance of is excellent. Moreover, since the film capacitor 51 has a so-called caseless structure that does not use the resin case 17, the film capacitor 51 has a relatively light weight structure.

  The metal layer 19 may be formed by evaporating a metal such as aluminum or copper on the outer surface 53S of the bottom 53 of the exterior resin 52 in addition to using a metal plate or a metal foil. Thus, even when the metal layer 19 is formed by vapor deposition, it is very effective as a method for forming the metal layer 19 without causing an increase in weight and size of the film capacitor 51.

  In the film capacitor 51 of Example 4, the metal layer 19 is disposed on the bottom 53. However, like the film capacitor 41 of Example 3, the third side surface 13 and the fourth side surface 14 of the capacitor elements 2L and 2R are When the capacitor elements 2L and 2R are arranged in the exterior resin 52 so as to face the left and right sides of the exterior resin 52, the metal layer 19 is applied to the outer surfaces of the left and right sides of the exterior resin 52. It may be formed.

  In the above description, in the first to fourth embodiments, the plurality of capacitor elements 2L and 2R are arranged. However, the present invention is not limited to this, and one capacitor element may be accommodated in the resin case 17 or the exterior resin 52.

  3, 5, 6, and 7, the opening of the resin case 17 and the external connection portion 18 </ b> A take-out side of the exterior resin 52 are illustrated upward, but this is for the sake of simple explanation. In actual use, it is not limited to this mode. That is, the top and bottom may be reversed and the opening of the resin case 17 and the external connection portion 18A take-out side of the exterior resin 52 may be in a downward state. Or you may use in the state in which the opening part of the resin case 17 and the external connection part 18A extraction side of the exterior resin 52 face a horizontal direction.

  The film capacitor according to the present invention has excellent moisture resistance and can be suitably used as a capacitor used in various electronic devices, electrical devices, industrial devices, automobiles and the like. It is particularly useful in the automotive field where high moisture resistance is required.

DESCRIPTION OF SYMBOLS 1, 31, 41, 51 Film capacitor 2, 2L, 2R Capacitor element 3, 4 Electrode layer 5, 6 Dielectric film 7, 8 Lead electrode 9, 10 End surface 11 1st side surface 12 2nd side surface 13 3rd Side surface 14 Fourth side surface 15 Small electrode portion 16 Low resistance portion 17 Resin case 18 Bus bar 18A External connection portion 19, 19L, 19R Metal layer 20 Filled resin 21, 53 Bottom portion 21S, 22S, 23S, 53S Outer surface 22, 23 Side wall 24 connection part 52 exterior resin

Claims (7)

A flat capacitor having a pair of extraction electrodes on both end surfaces, a pair of flat surfaces whose side surfaces between the both end surfaces face each other, and a pair of curved curved surfaces connecting the pair of flat surfaces Elements,
A pair of external lead terminals connected to a pair of lead electrodes of the capacitor element;
A resin case containing the capacitor element and a resin case that accommodates at least a part of the external lead terminal therein and a filled resin filled in the resin case ; and
The capacitor element is disposed inside the resin sheathing body such that one flat surface of the pair of flat surfaces faces the bottom of the resin case ,
A metal layer is provided on the outer surface of the bottom of the resin case ,
The thickness of the metal layer is Ri der than 100μm or less 10 [mu] m,
A film capacitor in which the outer surface of the bottom of the resin case has at least part of an uneven portion, and the metal layer is adhered to the uneven portion . A flat capacitor having a pair of extraction electrodes on both end surfaces, a pair of flat surfaces whose side surfaces between the both end surfaces face each other, and a pair of curved curved surfaces connecting the pair of flat surfaces Elements,
A pair of external lead terminals connected to a pair of lead electrodes of the capacitor element;
The capacitor element, and a resin sheathing that accommodates at least a part of the external lead terminal therein,
The capacitor element is disposed inside the resin sheathing body such that one of the pair of flat surfaces faces one side of the resin sheathing body,
Wherein the outer surface of the other side opposed to the outer surface and said one side of said one side of the resin sheathing body has a metal layer is provided,
The film capacitor having a thickness of the metal layer of 10 μm or more and 100 μm or less. The film capacitor according to claim 1, wherein the metal layer is provided in a state of being adhered to an outer surface of the resin sheathing body. The film capacitor according to claim 1, wherein the metal layer is made of a metal foil. The film capacitor according to claim 1, wherein the metal layer is formed by depositing a metal. The film capacitor according to claim 1, wherein the outer surface of the bottom portion of the resin sheathing body is planar. The film capacitor according to claim 2, wherein an outer surface of the side portion of the resin sheathing body is planar.

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