Film capacitor

Abstract

This film capacitor 1 comprises: a capacitor element 10 that includes an element body 11 and an external electrode 12 provided to an end surface of the element body 11; and an exterior member 20 that accommodates the capacitor element 10 in the interior thereof. The element body 11 includes: a laminate 30 wound in a state in which a dielectric film 31 and an internal electrode layer 32 are laminated; and a protective film 40 covering the outer peripheral surface of the laminate 30 in the lamination direction of the laminate 30. The overall thickness t0 of the protective film 40 in the lamination direction is 0.2-1.0 mm, inclusive.

Description

Film capacitors

[0001] The present invention relates to a film capacitor.

[0002] One type of capacitor is a film capacitor, which is made by winding a dielectric film on the surface of which an internal electrode layer made of a metal vapor deposition film is provided.

[0003] Patent Document 1 discloses a capacitor in which a capacitor base or the capacitor element itself is wrapped in a laminate material made by laminating resin and metal materials, and sealed with the capacitor terminals exposed to the outside. Patent Document 1 also describes that the capacitor element is a film capacitor made by winding two polypropylene films on which aluminum metal is vapor-deposited, with a margin that is an unvapor-deposited area.

[0004] Patent No. 4294446

[0005] In film capacitors that require high reliability, such as those used in automobiles, voltage resistance is generally ensured by hermetically sealing a capacitor element wrapped in a metallized film with an insulator such as resin. Film capacitors with metallized film have a self-healing function that restores insulation by scattering the metal vapor deposition film (internal electrode layer) in the event of localized dielectric breakdown. However, if the discharge energy during self-healing is large, film capacitors that are not sealed with an insulator such as resin may emit sparks or high-temperature gases outside the capacitor element.

[0006] For example, in the film capacitor described in Patent Document 1, a laminate material is used as an exterior member, and the internal capacitor element is not sealed with an insulating material such as resin. Therefore, if sparks or high-temperature gas are released to the outside of the capacitor element, the laminate material will be damaged by the heat, resulting in a loss of sealing ability.

[0007] Furthermore, even in the case of a film capacitor in which the capacitor element is sealed with an insulating material such as resin, if the heat resistance or thickness of the sealing material is insufficient, the same problem as described above will occur, namely, the sealing material will be damaged by sparks or the release of high-temperature gas.

[0008] The present invention has been made to solve the above problems, and aims to provide a film capacitor that has high voltage resistance and is less likely to release sparks or high-temperature gases to the outside of the capacitor element even when a high voltage is applied.

[0009] The film capacitor of the present invention includes a capacitor element including an element body and external electrodes provided on end faces of the element body, and an exterior member housing the capacitor element. The element body includes a laminate formed by winding a dielectric film and an internal electrode layer in a stacked state, and a protective film covering the outer surface of the laminate in the stacking direction. The total thickness of the protective film in the stacking direction is 0.2 mm or more and 1.0 mm or less.

[0010] According to the present invention, it is possible to provide a film capacitor that is unlikely to emit sparks or high-temperature gases to the outside of the capacitor element even when a high voltage is applied, and that has high voltage resistance.

[0011] FIG. 1 is a perspective view schematically illustrating an example of a film capacitor of the present invention. FIG. 2 is a perspective view schematically illustrating an example of a capacitor element constituting the film capacitor shown in FIG. 1. FIG. 3 is a perspective view schematically illustrating an example of an element body constituting the capacitor element shown in FIG. 2. FIG. 4 is a perspective view schematically illustrating an example of a laminate constituting the element body shown in FIG. 3. FIG. 5 is a perspective view schematically illustrating another example of a laminate constituting the element body shown in FIG. 3. FIG. 6 is a cross-sectional view taken along line VI-VI of the capacitor element shown in FIG. 2. FIGS. 7A, 7B, and 7C are schematic views illustrating problems with capacitor elements constituting a film capacitor according to a comparative example outside the scope of the present invention.

[0012] The film capacitor of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. A combination of two or more of the individual preferred configurations of the present invention described below also constitutes the present invention.

[0013] In this specification, terms indicating the relationship between elements (e.g., "perpendicular," "parallel," "orthogonal," etc.) and terms indicating the shape of elements are not expressions that only express a strict meaning, but are expressions that also include a range of substantial equivalence, for example, a difference of about a few percent.

[0014] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, and other scales may differ from those of the actual product. In the drawings, the same or equivalent parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and duplicate explanations will be omitted.

[0015] Fig. 1 is a perspective view schematically showing an example of a film capacitor of the present invention, and Fig. 2 is a perspective view schematically showing an example of a capacitor element constituting the film capacitor shown in Fig. 1.

[0016] The film capacitor 1 shown in FIG. 1 includes a capacitor element 10 and an exterior member 20 .

[0017] 1 and 2, the capacitor element 10 includes an element body 11 and external electrodes 12 provided on end surfaces of the element body 11. In the example shown in Figures 1 and 2, the external electrodes 12 include a first external electrode 12a provided on one end surface of the element body 11 and a second external electrode 12b provided on the other end surface of the element body 11.

[0018] The exterior member 20 accommodates the capacitor element 10 therein. Specifically, the exterior member 20 has an internal space, and the capacitor element 10 is accommodated in the internal space of the exterior member 20.

[0019] The exterior member 20 is, for example, a metal laminate film including a resin layer and a metal layer. However, the exterior member 20 is not limited to a metal laminate film and may be, for example, an exterior resin that covers the capacitor element 10, or a case in which a sealing resin is filled between the capacitor element 10 and the exterior member 20.

[0020] Hereinafter, an example in which the exterior member 20 is a metal laminate film will be described with reference to FIG.

[0021] When the exterior member 20 is a metal laminate film, the exterior member 20 includes, for example, a first film material 21 a that covers a portion of the capacitor element 10 and a second film material 21 b that covers the remaining portion of the capacitor element 10 .

[0022] The outer edge of the exterior member 20 is provided with a flange portion 22 where the outer edge of the first film material 21a and the outer edge of the second film material 21b are joined together.

[0023] In the flange portion 22, for example, the surfaces of the first film material 21a and the second film material 21b are joined together by heat welding or adhesive.

[0024] The exterior member 20 is, for example, a laminate film having a three-layer structure including, in order from the capacitor element 10 side, a first resin layer, a metal layer, and a second resin layer.

[0025] The first resin layer functions as a layer for thermally welding laminate films together, for example, as a layer for thermally welding the flange portion 22 .

[0026] The first resin layer is preferably made of a polyolefin-based thermoplastic resin such as polypropylene (PP) resin.

[0027] The metal layer acts as a layer to improve the barrier properties against moisture.

[0028] The metal layer is preferably composed of aluminum.

[0029] The second resin layer functions as a layer for protecting the metal layer and further improving the barrier properties against moisture.

[0030] The second resin layer is preferably made of a thermoplastic resin such as polyethylene terephthalate (PET) resin or nylon resin.

[0031] The first resin layer and the metal layer may be bonded with an adhesive or may be bonded by thermocompression.

[0032] The second resin layer and the metal layer may be bonded with an adhesive or may be bonded by thermocompression.

[0033] When exterior member 20 is a metal laminate film, the number of layers of the metal laminate film is not particularly limited as long as it has a thermoplastic resin layer on the surface on the capacitor element 10 side.

[0034] As shown in Fig. 1, the film capacitor 1 preferably further includes lead terminals 25. The lead terminals 25 are electrically connected to the external electrodes 12 and extend to the outside of the exterior member 20. In the example shown in Fig. 1, the lead terminals 25 include a first lead terminal 25a electrically connected to the first external electrode 12a and a second lead terminal 25b electrically connected to the second external electrode 12b.

[0035] When the exterior member 20 is a metal laminate film, the lead-out terminal 25 is led out from between the flange portions 22 to the outside of the exterior member 20 .

[0036] The lead terminal 25 is, for example, a copper plate having a predetermined shape.

[0037] Fig. 3 is a perspective view schematically showing an example of an element body constituting the capacitor element shown in Fig. 2. Fig. 4 is a perspective view schematically showing an example of a laminate constituting the element body shown in Fig. 3.

[0038] As shown in FIG. 3 , the element body 11 constituting the capacitor element 10 (see FIG. 2 ) includes a laminate 30 and a protective film 40 .

[0039] As shown in FIG. 4, the laminate 30 is a wound body in which a dielectric film 31 and an internal electrode layer 32 are wound in a laminated state.

[0040] 4 , the dielectric film 31 includes a first dielectric film 31a and a second dielectric film 31b. The internal electrode layer 32 includes a first internal electrode layer 32a and a second internal electrode layer 32b. Therefore, in the laminate 30, the first internal electrode layer 32a, the first dielectric film 31a, the second internal electrode layer 32b, and the second dielectric film 31b are wound in a stacked state. Specifically, in the laminate 30, the first metallized film 33a, which has the first internal electrode layer 32a provided on one surface of the first dielectric film 31a, and the second metallized film 33b, which has the second internal electrode layer 32b provided on one surface of the second dielectric film 31b, are wound in a stacked state. In addition, in the laminate 30, a first dielectric film 31a having a first internal electrode layer 32a on one side and a second internal electrode layer 32b on the other side, and a second dielectric film 31b having neither the first internal electrode layer 32a nor the second internal electrode layer 32b may be wound in a stacked state.

[0041] The first internal electrode layer 32a and the second internal electrode layer 32b face each other with the first dielectric film 31a or the second dielectric film 31b sandwiched therebetween. Although not shown in Fig. 4, the first internal electrode layer 32a is electrically connected to the first external electrode 12a, and the second internal electrode layer 32b is electrically connected to the second external electrode 12b.

[0042] The first dielectric film 31a and the second dielectric film 31b may have different configurations, but preferably have the same configuration.

[0043] The first internal electrode layer 32a is formed on one surface of the first dielectric film 31a so as to reach one side edge but not the other side edge. On the other hand, the second internal electrode layer 32b is formed on one surface of the second dielectric film 31b so as not to reach one side edge but to reach the other side edge. The first internal electrode layer 32a and the second internal electrode layer 32b are made of a metal such as aluminum.

[0044] 4, it is preferable that the first dielectric film 31a and the second dielectric film 31b are laminated with a shift relative to each other in the width direction (the direction indicated by W in FIG. 4) so ​​that the end of the first internal electrode layer 32a that reaches the side edge of the first dielectric film 31a and the end of the second internal electrode layer 32b that reaches the side edge of the second dielectric film 31b are both exposed from the laminated films. In the example shown in FIG. 4, the laminate 30 is formed by winding the dielectric film 31 and the internal electrode layer 32 in a laminated state, thereby becoming a wound body of the metallized film 33, and is in a stacked state with the internal electrode layer 32 maintained in an exposed state at its end.

[0045] In the laminate 30 shown in FIG. 4, the second dielectric film 31b is wound on the outside of the first dielectric film 31a, and the first internal electrode layer 32a and the second internal electrode layer 32b of each of the first dielectric film 31a and the second dielectric film 31b are wound inward.

[0046] FIG. 5 is a perspective view schematically showing another example of the laminate constituting the element body shown in FIG.

[0047] 5, the laminate 30 is preferably pressed into a flattened shape such as an ellipse or an oval in cross section, which is more compact than a perfectly circular cross section, allowing the entire film capacitor to be miniaturized.

[0048] As shown in FIG. 3 , the protective film 40 covers the outer peripheral surface of the laminate 30 in the stacking direction of the laminate 30 .

[0049] Here, the lamination direction of the laminate 30 means the direction in which the internal electrode layers 32 are laminated via the dielectric films 31. Therefore, the lamination direction of the laminate 30 is not limited to the direction indicated by T in FIGS.

[0050] The protective film 40 is, for example, wound around the outer peripheral surface of the laminate 30. The protective film 40 may be wound around the outer peripheral surface of the laminate 30 one turn or multiple turns.

[0051] The protective film 40 is preferably fixed to the dielectric film 31 by thermal welding.

[0052] 3 may include a cylindrical winding shaft. The winding shaft is disposed on the central axis of the wound dielectric film 31 and the internal electrode layer 32, and serves as the winding shaft when winding the dielectric film 31 and the internal electrode layer 32.

[0053] The external electrodes 12 are formed by thermally spraying, for example, zinc on each end face of the element body 11 obtained as described above. For example, the first external electrode 12a is formed so as to contact the exposed end of the first internal electrode layer 32a and thereby be electrically connected to the first internal electrode layer 32a, and the second external electrode 12b is formed so as to contact the exposed end of the second internal electrode layer 32b and thereby be electrically connected to the second internal electrode layer 32b.

[0054] FIG. 6 is a cross-sectional view of the capacitor element shown in FIG. 2 taken along line VI-VI.

[0055] In the capacitor element 10 shown in FIG. 6, the total thickness of the protective film 40 in the stacking direction (the direction indicated by T in the cross-sectional view shown in FIG. 6) is ０ The dimension indicated by is 0.2 mm or more and 1.0 mm or less.

[0056] As shown in FIG. 6, the total thickness t ０ By setting the thickness to 0.2 mm or more and 1.0 mm or less, the withstand voltage of the film capacitor 1 shown in FIG. 1 can be improved.

[0057] 7A, 7B, and 7C are schematic diagrams for explaining problems with capacitor elements constituting a film capacitor according to a comparative example outside the scope of the present invention.

[0058] As shown in Fig. 7A, if the protective film 40 covering the outer peripheral surface of the laminate 30 constituting the element body 11 of the capacitor element 10 is thin, and the discharge energy during self-healing increases due to an increase in the operating voltage or the like, sparks and high-temperature gases are generated, and the internal pressure between the film layers included in the laminate 30 increases. As a result, as shown in Fig. 7B, the film layers are pushed apart, creating a space SP. In this case, as shown in Fig. 7C, there is a risk that sparks and high-temperature gases will be released to the outside of the capacitor element 10 via the space SP between the film layers.

[0059] In contrast, in the film capacitor 1, as shown in FIG. ０ By increasing the thickness of the film, it is possible to suppress the spread between the film layers. Therefore, it becomes difficult for sparks and high-temperature gas to escape to the outside of the capacitor element 10, and as a result, the voltage resistance of the film capacitor 1 can be improved.

[0060] Another method for achieving the same effect as above is to cover the periphery of capacitor element 10 with a heat-shrinkable film. However, this method requires additional steps or equipment in the manufacturing process of the film capacitor, and therefore forming a thick protective film as in the present invention is more efficient in terms of production efficiency.

[0061] In the film capacitor 1, the total thickness t of the protective film 40 in the lamination direction ０ When the thickness is 0.2 mm or more, preferably 0.3 mm or more, the spread between the film layers can be suppressed.

[0062] On the other hand, the total thickness t of the protective film 40 in the stacking direction ０ If the total thickness t of the protective film 40 in the lamination direction is too large, the film capacitor may become too large. In addition, the time required to wind the protective film 40 in the winding step during the production of the film capacitor may become long, which may result in a decrease in productivity. ０ is preferably 1.0 mm or less.

[0063] Total thickness t of the protective film 40 in the stacking direction ０When the values ​​of σ and σ are the same, winding a larger number of films with a smaller thickness per layer will have a greater effect in suppressing the generation of spaces (gaps) between film layers than winding a smaller number of films with a larger thickness per layer. This is because a tightening force is generated in the wound film body according to the number of windings. Therefore, it is preferable that the protective film 40 be wound around the outer peripheral surface of the laminate 30 multiple times. In this case, the protective film 40 may be in the form of a single sheet or may be divided into multiple sheets.

[0064] The thickness of one layer of the protective film 40 is preferably 2 μm or more and 1.0 mm or less, and, taking into consideration the above effects and processing time, it is more preferably 8 μm or more and 30 μm or less.

[0065] The thickness of the protective film 40 can be measured using an optical film thickness meter. The same applies to the thickness of the dielectric film 31.

[0066] The melting point of the protective film 40 is preferably higher than the melting point of the dielectric film 31. In this case, it is possible to obtain a film capacitor 1 that can withstand the heat resistance temperature of the dielectric film 31 when exposed to high temperatures during the manufacturing of the film capacitor 1, which includes processing steps such as drying treatment of the capacitor element 10, or when the film capacitor 1 is used in a high-temperature environment.

[0067] The thermal shrinkage rate of the protective film 40 in the length direction (the direction indicated by L in the unwound portion in FIG. 3 ) is preferably greater than the thermal shrinkage rate of the protective film 40 in the width direction (the direction indicated by W in FIG. 3 ). In addition, the thermal shrinkage rate of the protective film 40 in the length direction is preferably greater than the thermal shrinkage rate of the metallized film having the internal electrode layer 32 provided on the surface of the dielectric film 31 in the length direction. In these cases, spaces (gaps) that occur between the film layers are likely to be suppressed during the manufacture of the film capacitor 1, which includes processing steps such as drying treatment of the capacitor element 10, or during use of the film capacitor 1 in a high-temperature environment.

[0068] Examples of materials that can be used to form the protective film 40 include thermoplastic resins such as polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), and polyethylene naphthalate (PEN).

[0069] The constituent material of the protective film 40 may be the same as or different from the constituent material of the dielectric film 31 .

[0070] An adhesive layer may be provided on the surface of the protective film 40 .

[0071] The surface of the protective film 40 may be provided with, for example, a conductive layer (for example, a metal layer) that functions as a barrier layer against moisture, but it is preferable that no conductive layer is provided.

[0072] The film capacitor of the present invention is not limited to the above-described embodiment, and various applications and modifications can be made within the scope of the present invention with respect to the configurations of the capacitor element and the exterior member, the manufacturing conditions, and the like.

[0073] The dielectric film constituting the laminate included in the element body of the capacitor element may contain a curable resin as a main component, or may contain a thermoplastic resin as a main component. From the viewpoint of improving the heat resistance of the film capacitor, it is preferable that the dielectric film contains a curable resin as a main component.

[0074] In this specification, the term "major component of the dielectric film" refers to the component with the largest weight percentage, preferably the component with a weight percentage of more than 50 wt %. Therefore, the dielectric film may contain components other than the major component, such as additives such as silicone resin, and uncured portions of starting materials such as the first organic material and second organic material described below.

[0075] The curable resin may be a thermosetting resin or a photocurable resin.

[0076] In this specification, thermosetting resin means a resin that can be cured by heat, and the curing method is not limited. Therefore, as long as it is a resin that can be cured by heat, resins that are cured by methods other than heat (for example, light, electron beam, etc.) are also included in thermosetting resins. Furthermore, depending on the material, a reaction may be initiated due to the reactivity of the material itself, and resins that proceed to cure without necessarily applying heat or light from the outside are also considered thermosetting resins. The same applies to photocurable resins, and the curing method is not limited.

[0077] The curable resin may or may not have at least one of a urethane bond and a urea bond. Examples of such resins include a urethane resin having a urethane bond and a urea resin having a urea bond. Alternatively, the curable resin may be a resin having both a urethane bond and a urea bond.

[0078] The presence of urethane bonds and / or urea bonds can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR).

[0079] The curable resin is preferably a cured product of a first organic material and a second organic material, such as 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.

[0080] When a cured product is obtained by the above reaction, uncured portions of the starting material may remain in the film. For example, the dielectric film may contain at least one of an isocyanate group and a hydroxyl group. In this case, the dielectric film may contain either an isocyanate group or a hydroxyl group, or may contain both an isocyanate group and a hydroxyl group.

[0081] The presence of an isocyanate group and / or a hydroxyl group can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR).

[0082] The first organic material is preferably a polyol having multiple hydroxyl groups in the molecule. Examples of polyols include polyether polyol, polyester polyol, and polyvinyl acetal. Two or more organic materials may be used in combination as the first organic material.

[0083] The second organic material is preferably an isocyanate compound, an epoxy resin, or a melamine resin having multiple functional groups in the molecule. Two or more organic materials may be used in combination as the second organic material. Among the second organic materials, an isocyanate compound is preferred.

[0084] Examples of the isocyanate compound include aromatic polyisocyanates such as diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI), and aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI). Modified products of these polyisocyanates, such as modified products having carbodiimide or urethane, may also be used.

[0085] The epoxy resin is not particularly limited as long as it is a resin having an epoxy ring, and examples thereof include bisphenol A type epoxy resin, biphenyl skeleton epoxy resin, cyclopentadiene skeleton epoxy resin, and naphthalene skeleton epoxy resin.

[0086] The melamine resin is not particularly limited as long as it is an organic nitrogen compound having a triazine ring at the center of its structure and three amino groups on the periphery thereof, and examples thereof include alkylated melamine resins, etc. Modified melamine resins may also be used.

[0087] The dielectric film constituting the laminate included in the element body of the capacitor element is preferably obtained by forming a resin solution containing the first organic material and the second organic material into a film, and then heat-treating it to harden it.

[0088] The dielectric film constituting the laminate included in the element body of the capacitor element may contain a vapor-deposited polymer film as a main component. The vapor-deposited polymer film may or may not have at least one of a urethane bond and a urea bond.

[0089] The vapor deposition polymerized film refers to a film formed by vapor deposition polymerization, and is basically included in the category of curable resins.

[0090] The dielectric film constituting the laminate included in the element body of the capacitor element may contain a thermoplastic resin as a main component, such as polypropylene, polyethersulfone, polyetherimide, or polyarylate.

[0091] The dielectric film constituting the laminate included in the element body of the capacitor element may also contain additives to impart other functions. For example, adding a leveling agent can impart smoothness. The additive is preferably a material having a functional group reactive with a hydroxyl group and / or an isocyanate group and forming part of the crosslinked structure of the cured product. Examples of such materials include resins having at least one functional group selected from the group consisting of epoxy groups, silanol groups, and carboxyl groups.

[0092] The thickness of the dielectric film constituting the laminate included in the element body of the capacitor element is not particularly limited, but may be set appropriately according to the required capacitance and required element volume of the capacitor to be produced.

[0093] The thickness of the dielectric film can be measured using an optical film thickness meter.

[0094] The type of metal contained in the internal electrode layer constituting the laminate contained in the element body of the capacitor element is not particularly limited, but it is preferable that the metal layer contains any one selected from the group consisting of aluminum (Al), titanium (Ti), zinc (Zn), magnesium (Mg), tin (Sn), and nickel (Ni).

[0095] The thickness of the internal electrode layer constituting the laminate included in the element body of the capacitor element is not particularly limited, but from the viewpoint of suppressing damage to the internal electrode layer, the thickness of the internal electrode layer is preferably 5 nm or more and 40 nm or less.

[0096] The thickness of the internal electrode layer can be determined by observing a cross section of the metallized film cut in the thickness direction using an electron microscope such as a field emission scanning electron microscope (FE-SEM).

[0097] The present specification discloses the following:

[0098] <1> A film capacitor comprising: a capacitor element including an element body and external electrodes provided on end surfaces of the element body; and an exterior member that houses the capacitor element, wherein the element body includes a laminate in which dielectric films and internal electrode layers are stacked and wound, and a protective film that covers an outer peripheral surface of the laminate in a stacking direction of the laminate, and wherein the overall thickness of the protective film in the stacking direction is 0.2 mm or more and 1.0 mm or less.

[0099] <2> The film capacitor according to <1>, wherein the exterior member is a metal laminate film including a resin layer and a metal layer.

[0100] <3> The film capacitor according to <1> or <2>, wherein the protective film has a total thickness in the stacking direction of 0.3 mm or more and 1.0 mm or less.

[0101] <4> The film capacitor according to any one of <1> to <3>, wherein the protective film is wound around the outer peripheral surface of the laminate for a plurality of turns.

[0102] <5> The film capacitor according to <4>, wherein the thickness of one layer of the protective film is 2 μm or more and 1.0 mm or less.

[0103] <6> The film capacitor according to any one of <1> to <5>, wherein the melting point of the protective film is higher than the melting point of the dielectric film.

[0104] <7> The film capacitor according to any one of <1> to <6>, wherein the thermal shrinkage rate of the protective film in the length direction is larger than the thermal shrinkage rate of the protective film in the width direction.

[0105] <8> The film capacitor according to any one of <1> to <7>, wherein the thermal shrinkage rate in the longitudinal direction of the protective film is greater than the thermal shrinkage rate in the longitudinal direction of a metallized film in which the internal electrode layer is provided on the surface of the dielectric film.

[0106] EXAMPLES Hereinafter, examples will be given that more specifically disclose the film capacitor of the present invention, but the present invention is not limited to these examples.

[0107] In the following examples, film capacitors were fabricated with an exterior packaged in an aluminum laminate film. The number of turns of the dielectric film and the protective film were varied during winding of the film capacitor to produce multiple test samples. High-voltage tests were conducted using the resulting film capacitors.

[0108] <Process for Producing Metallized Films> First, a resin solution was prepared by mixing a phenoxy resin, a bisphenol A-type epoxy resin, as the first organic material and diphenylmethane diisocyanate as the second organic material. The resulting resin solution was then molded into a film and cured by heat treatment to produce a first dielectric film and a second dielectric film. The first dielectric film and the second dielectric film had a width of 25 mm and a thickness of 3.6 μm.

[0109] Then, a first metallized film was fabricated by depositing aluminum on the main surface of the first dielectric film to form a first internal electrode layer. At this time, the first internal electrode layer was formed so as to reach one side edge of the first metallized film in the width direction but not the other side edge of the first metallized film. The film resistance of the first internal electrode layer was 8 Ω / sq.

[0110] A second metallized film was fabricated by depositing aluminum on the main surface of the second dielectric film to form a second internal electrode layer. The second internal electrode layer was formed so as to extend beyond one side edge of the second metallized film in the width direction, but to extend to the other side edge of the second metallized film. The film resistance of the second internal electrode layer was 8 Ω / sq.

[0111] <Process for producing element body> First, a first film reel having a first metallized film wound around a first reel shaft and a second film reel having a second metallized film wound around a second reel shaft were prepared. Then, the first metallized film was unwound from the first film reel, and the second metallized film was unwound from the second film reel. At this time, the first metallized film and the second metallized film were unwound so that the main surface of the first dielectric film on the side where the first internal electrode layer was not formed faced the main surface of the second dielectric film on the side where the second internal electrode layer was formed.

[0112] The unwound first and second metallized films were then overlapped with a 1.0 mm shift in the width direction to form a metallized film body, which was then wound around a reel.

[0113] After the first metallized film and the second metallized film were wound a predetermined number of times, a 12 μm thick protective film made of PET film was wound around the outer periphery to a predetermined thickness, and the wound body was then sandwiched in a direction perpendicular to the width direction and pressed into an elliptical cylindrical shape.

[0114] <Step of forming external electrodes> A zinc-aluminum alloy was sprayed onto the end surface of the wound body to form a first external electrode connected to the first metallized film. Similarly, a second external electrode was formed to connect to the second metallized film.

[0115] A flat lead terminal was connected to the external electrode by resistance welding. The flat lead terminal had an insulating film that provided sealing and insulating properties with the aluminum laminate film.

[0116] <Formation of exterior member> Two aluminum laminate films were formed into a cup shape to fit the shape of the element pressed into an elliptical cylindrical shape. The aluminum laminate films were composed of a PET layer, an aluminum layer, and a PP layer from the outside, and had thicknesses of 12 μm, 40 μm, and 80 μm, respectively.

[0117] The capacitor element was dried at 125°C for 2 hours and then placed in a cup-shaped aluminum laminate film. The four edges of the laminate film were then heat-sealed to seal the capacitor. To expel the air and moisture inside, the sealing process was preferably carried out under reduced pressure, at -95 kPa.

[0118] In this way, a film capacitor was produced.

[0119] <Evaluation of Film Capacitors> A high-voltage test was conducted at 125°C using the film capacitors prepared by the above method. A voltage was applied between the terminal electrodes drawn from both ends of the capacitor. The voltage was increased in 50 V increments from 750 V, and the holding time at each voltage was one hour. An evaluation was conducted to determine whether the aluminum laminate film, which is the exterior member, was damaged by sparks or the release of high-temperature gas before the voltage reached 1600 V. Table 1 shows the damage failure rate of the exterior member when 10 capacitors were evaluated for each condition of the number of turns of the dielectric film and the total thickness of the protective film.

[0120]

[0121] The results in Table 1 show that the breakage failure rate of the exterior member decreases as the total thickness of the protective film increases. Specifically, when the total thickness of the protective film is 0.2 mm or more, the breakage failure rate of the exterior member can be reduced to 10% or less. In particular, when the total thickness of the protective film is 0.3 mm or more, the breakage failure rate of the exterior member can be reduced to 0%, regardless of the number of turns of the dielectric film. This is thought to be because, by forming the protective film thick, no space (gap) is generated between the film layers even when the internal pressure increases during self-healing, preventing sparks and the release of high-temperature gas to the outside.

[0122] On the other hand, if the total thickness of the protective film exceeds 1.0 mm, the overall size of the capacitor increases, and the winding of the protective film in the winding step takes a long time, resulting in reduced productivity.

[0123] From the above, it is considered that the appropriate total thickness of the protective film in the lamination direction in a film capacitor is 0.2 mm or more and 1.0 mm or less, and that 0.3 mm or more and 1.0 mm or less is preferable.

[0124] REFERENCE SIGNS LIST 1 film capacitor 10 capacitor element 11 element body 12 external electrode 12a first external electrode 12b second external electrode 20 exterior member 21a first film material 21b second film material 22 flange portion 25 lead terminal 25a first lead terminal 25b second lead terminal 30 laminate 31 dielectric film 31a first dielectric film 31b second dielectric film 32 internal electrode layer 32a first internal electrode layer 32b second internal electrode layer 33 metallized film 33a first metallized film 33b second metallized film 40 protective film t ０ Total thickness of protective film SP Space between film layers

Claims

1. A film capacitor comprising: a capacitor element including an element body and external electrodes provided on end faces of the element body; and an exterior member that houses the capacitor element, wherein the element body includes a laminate in which dielectric films and internal electrode layers are wound in a stacked state, and a protective film that covers the outer surface of the laminate in the stacking direction of the laminate, and the overall thickness of the protective film in the stacking direction is 0.2 mm or more and 1.0 mm or less.

2. The film capacitor according to claim 1, wherein the exterior member is a metal laminate film including a resin layer and a metal layer.

3. The film capacitor according to claim 1 or 2, wherein the total thickness of the protective film in the stacking direction is 0.3 mm or more and 1.0 mm or less.

4. A film capacitor according to any one of claims 1 to 3, wherein the protective film is wound around the outer circumferential surface of the laminate multiple times.

5. The film capacitor according to claim 4, wherein the thickness of one layer of the protective film is 2 μm or more and 1.0 mm or less.

6. A film capacitor according to any one of claims 1 to 5, wherein the melting point of the protective film is higher than the melting point of the dielectric film.

7. A film capacitor according to any one of claims 1 to 6, wherein the thermal shrinkage rate of the protective film in the length direction is greater than the thermal shrinkage rate of the protective film in the width direction.

8. A film capacitor according to any one of claims 1 to 7, wherein the thermal shrinkage rate in the longitudinal direction of the protective film is greater than the thermal shrinkage rate in the longitudinal direction of a metallized film having the internal electrode layer provided on the surface of the dielectric film.

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