Electrolytic capacitor

Abstract

The present disclosure provides an electrolytic capacitor that can reduce swelling of a case. An electrolytic capacitor 1 includes a capacitor element 10 and a case 20 for accommodating the capacitor element 10. The case 20 has a housing 21 having an opening 211 and a sealing body 22 for closing the opening 211 of the housing 21. The housing 21 has a top surface part 212 located on the opposite side of the opening 211 and a side surface part 213 extending from an outer periphery of the top surface part 212 toward the opening 211. The top surface part 212 comprises a plate-like member. An outer surface S11 of the top surface part 212 has a first region A1 recessed toward the opening 211. A first region A1 includes a flat surface part 2121 including a center C of the top surface part 212.

Description

electrolytic capacitor

[0001] The present disclosure relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor including a capacitor element.

[0002] Patent Document 1 discloses an electronic component including an element formed by overlapping and winding an anode foil and a cathode foil with a separator interposed therebetween, a bottomed cylindrical outer case for accommodating the element, and a sealing body for sealing an opening of the outer case. In this electronic component, a plurality of tapered first recesses are formed on the outer peripheral surface of the outer case, the radial depth of which decreases from the bottom surface of the bottomed cylindrical bottom toward the opening, and tapered first protrusions are formed on the inner peripheral surface of the case located behind the first recesses and protruding toward the radial center, and the element is abutted and supported by the first protrusions.

[0003] Reducing the height of electrolytic capacitors is an important issue in order to place them in ever-smaller spaces. Furthermore, when electrolytic capacitors are used in the reflow process or in high-temperature environments, the electrolyte inside them evaporates, causing an increase in internal pressure. This causes the shape of the electrolytic capacitor to change and become swollen. Therefore, to prevent this swelling from interfering with other devices or boards, it is necessary to suppress the swelling of electrolytic capacitors.

[0004] International Publication No. 2017 / 183521

[0005] The present disclosure provides an electrolytic capacitor that can reduce case swelling.

[0006] An electrolytic capacitor according to one aspect of the present disclosure comprises a capacitor element and a case that houses the capacitor element, the case having a housing with an opening and a sealing body that closes the opening of the housing, the housing having a top surface portion located on the opposite side of the opening and a side surface portion extending from the outer periphery of the top surface portion toward the opening, the top surface portion being made of a plate-like member, the outer surface of the top surface portion having a first region that is recessed toward the opening, and the first region including a flat portion that includes the center of the top surface portion.

[0007] FIG. 1 is a schematic perspective view of an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure, taken along line X-X in FIG. 1 . FIG. 3 is a schematic exploded view of an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view showing the periphery of a corner of a housing in an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 5 is a graph showing the relationship between the plate thickness and the maximum displacement of the top surface in an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 6 is a graph showing the relationship between the radius of curvature of the inner surface of a corner in an electrolytic capacitor according to an embodiment of the present disclosure and the maximum displacement of the top surface. FIG. 7 is a schematic perspective view of a housing in an electrolytic capacitor according to a modified embodiment of the present disclosure. FIG. 8 is a schematic perspective view of a housing in an electrolytic capacitor according to another modified embodiment of the present disclosure.

[0008] (Embodiments) (1) Overview Below, electrolytic capacitors according to embodiments will be described with reference to the drawings. However, the following embodiment is merely one of various embodiments of the present disclosure. The following embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, each figure described in the following embodiments is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the figures do not necessarily reflect the actual dimensional ratios.

[0009] 1 to 3, electrolytic capacitor 1 of this embodiment includes capacitor element 10 and case 20. Case 20 includes housing 21 having opening 211 and sealing body 22 that closes opening 211 of housing 21. Housing 21 includes top surface 212 located on the opposite side of opening 211, and side surface 213 that extends from the outer periphery of top surface 212 toward opening 211.

[0010] The top surface 212 is made of a plate-like member. An outer surface S11 of the top surface 212 has a first area A1 that is recessed toward the opening 211. The first area A1 includes a flat surface 2121 that includes the center C of the top surface 212.

[0011] The electrolytic capacitor 1 of this embodiment has the above-described configuration, which makes it possible to reduce swelling of the case 20 that occurs when the internal pressure increases.

[0012] The electrolytic capacitor 1 is typically mounted with the top surface 212 of the housing 21 facing up. When the internal pressure of the electrolytic capacitor 1 increases, the degree of swelling is greatest at the center C of the top surface 212. As shown in FIG. 1 , the electrolytic capacitor 1 of this embodiment has a first region A1, which is a recess, on the outer surface S11 of the top surface 212 of the housing 21. The first region A1 also has a flat portion 2121 that includes the center C of the top surface 212. With this configuration, even when the top surface 212 deforms and bulges outward due to an increase in the internal pressure of the housing 21, the maximum height of the top surface 212 can be reduced compared to when the first region A1 (recess) is not present. This is thought to be because, before the top surface 212 deforms, the center C of the top surface 212 is lower by the depth of the first region A1 (recess). Therefore, even when the top surface 212 bulges, the height of the center C of the top surface 212 can be reduced. In addition, the first region A1 (recess) has a shape recessed toward the inside of the housing 21, which is thought to be related to the fact that it is difficult to deform in the opposite direction to the recessed direction.

[0013] As described above, according to the present disclosure, swelling of the case of the electrolytic capacitor can be reduced.

[0014] (2) Details <Electrolytic Capacitor> The configuration of the electrolytic capacitor 1 according to this embodiment will be described in more detail below. In this embodiment, as a representative example, the electrolytic capacitor 1 will be described as a hybrid electrolytic capacitor 1 that includes both a solid electrolyte such as a conductive polymer and a liquid component such as an electrolytic solution as the electrolyte.

[0015] 1 to 3 includes a capacitor element 10 and a case 20. Capacitor element 10 is impregnated with a liquid component (not shown). The present disclosure can be applied to cases where the electrolytic capacitor 1 contains a liquid component therein, and the internal pressure increases as the liquid component evaporates, and the adoption of the present disclosure is highly beneficial.

[0016] [Capacitor Element] As shown in FIG. 1 , the capacitor element 10 is housed in a case 20. As shown in FIG. 2 , the capacitor element 10 includes a plurality of anode foils 11A and a plurality of cathode foils 11B. Although not shown in FIG. 2 , the capacitor element 10 is a laminated capacitor element in which a plurality of anode foils 11A and a plurality of cathode foils 11B are alternately stacked. On one side (the left side in FIG. 2 ) of the capacitor element 10, only the plurality of anode foils 11A protrude to form an anode portion, while on the other side (the right side in FIG. 2 ) of the capacitor element 10, only the plurality of cathode foils 11B protrude to form a cathode portion. The anode foil 11A includes a metal foil containing a valve metal such as aluminum, tantalum, or niobium, and a dielectric layer formed on the surface of the metal foil. The cathode foil 11B includes a metal foil containing a valve metal such as aluminum, tantalum, or niobium.

[0017] Furthermore, in the capacitor element 10, a separator (not shown) is typically disposed between the anode foil 11A and the cathode foil 11B, along with a conductive polymer (not shown) serving as a solid electrolyte. Examples of materials that can be used for the separator include cellulose, polyethylene terephthalate (PET), vinylon, and aramid fiber. Examples of conductive polymers that can be used include polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene) (PEDOT), and polyaniline. The capacitor element 10 may be formed by sandwiching and laminating a sheet-like separator between the anode foil 11A and the cathode foil 11B. Alternatively, the capacitor element 10 may be formed by inserting a long sheet-like separator between the anode foil 11A and the cathode foil 11B in a zigzag manner. By impregnating the separator with a liquid component, a conductive polymer, or the like, the separator can retain the liquid component, the conductive polymer, or the like.

[0018] 1 to 3 includes a stacked capacitor element 10 as the capacitor element 10. In the stacked capacitor element 10, for example, an anode foil 11A, a cathode foil 11B, and a separator are stacked in a direction from an opening 211 of a housing 21 toward a top surface 212 within a case 20. The electrolytic capacitor 1 may also include other capacitor elements 10, such as a wound type, as the capacitor element 10. In the wound capacitor element 10, for example, an anode foil 11A, a cathode foil 11B, and a separator are wound in a case 20 with a winding axis that intersects with the direction from an opening 211 of a housing 21 toward a top surface 212.

[0019] As shown in FIG. 2 , the anode foil 11A (anode portion) of the capacitor element 10 is joined to an anode lead portion 221A of a lead portion 221 (described later). The cathode foil 11B (cathode portion) of the capacitor element 10 is joined to a cathode lead portion 221B. "Joining" means joining two members together. Examples of joining methods that can be used include laser welding, ultrasonic welding, and resistance welding. These joining methods electrically and mechanically connect the anode lead portion 221A and the anode foil 11A (anode portion), and electrically and mechanically connect the cathode lead portion 221B and the cathode foil 11B (cathode portion).

[0020] [Case] ​​The case 20 accommodates the capacitor element 10 and the liquid component impregnated in the capacitor element 10. The case 20 has a housing 21 and a sealing body 22, as shown in FIGS.

[0021] [Housing] The housing 21 is a member having an opening 211, and the shape of the housing 21 is, for example, a hollow cube or rectangular parallelepiped with a bottomed square cylinder having an opening on one face.

[0022] The housing 21 can be made of a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy thereof, or a resin such as polyphenylene sulfide (PPS). The housing 21 is preferably made of a metal, and more preferably made of aluminum.

[0023] The housing 21 has a top surface 212 and a side surface 213 .

[0024] (Top Surface) As shown in FIG. 3 , the top surface 212 is a portion of the housing 21 that is located on the opposite side of the opening 211 .

[0025] As shown in FIG. 1, the top surface 212 is generally quadrangular, such as a square or a rectangle, when viewed from a direction perpendicular to the outer surface S11 of the top surface 212.

[0026] The outer surface S11 of the top surface portion 212 has a first region A1 that is recessed toward the opening 211. The first region A1 also includes a flat surface portion 2121 that includes the center C of the top surface portion 212. In other words, the first region A1 is a recessed portion of the top surface portion 212, and the flat surface portion 2121 exists within this first region A1.

[0027] The top surface 212 is made of a plate-like member. That is, the top surface 212 can be obtained by recessing a portion of the plate-like member to form the first region A1. Examples of methods for recessing the plate-like member to form the first region A1 include press working and cutting work.

[0028] 1, the first region A1 has a square shape when viewed from a direction perpendicular to the outer surface S11 of the top surface 212. As shown in Fig. 2, in a cross section perpendicular to the outer surface S11 of the top surface 212, the first region A1 has a tapered shape (approximately an inverted trapezoid) in which the distance between both ends of the region continuously decreases toward the opening 211.

[0029] 1, the flat surface portion 2121 has a square shape when viewed from a direction perpendicular to the outer surface S11 of the top surface portion 212. Furthermore, as shown in FIG. 2, the flat surface portion 2121 has a flat shape in a cross section perpendicular to the outer surface S11 of the top surface portion 212.

[0030] The first region A1 may have a rectangular or circular shape when viewed from a direction perpendicular to the outer surface S11 of the top surface 212. In this case, it is possible to further reduce bulging of the case 20. Furthermore, the flat surface portion 2121 may have a rectangular or circular shape when viewed from a direction perpendicular to the outer surface S11 of the top surface 212.

[0031] When viewed in a direction perpendicular to the outer surface S11 of the top surface portion 212, the ratio of the area of ​​the flat surface portion 2121 to the area of ​​the outer surface S11 of the top surface portion 212 is preferably 5% to 65%, more preferably 10% to 50%, and even more preferably 15% to 35%. Furthermore, when viewed in a direction perpendicular to the outer surface S11 of the top surface portion 212, if the top surface portion 212 and the flat surface portion 2121 are both rectangular, the ratio of the length of a side of the flat surface portion 2121 extending in the same direction to the length of a side of the top surface portion 212 is preferably 20% to 80%, more preferably 30% to 70%, and even more preferably 40% to 60%.

[0032] 2, first region A1 preferably protrudes toward opening 211 on inner surface S12 of top surface portion 212. Such a protruding portion enables top surface portion 212 to press capacitor element 10 held within housing 21, more firmly fixing capacitor element 10 and reducing the inter-electrode distance. In addition, such a shape of top surface portion 212 has the advantage of being easily formed by press-processing a plate-shaped member.

[0033] The degree of recession in the first region A1, i.e., the distance D (see FIG. 2 ) between the outer surface S11 of the top surface 212 and the outer surface S21 of the flat portion 2121 in a direction perpendicular to the outer surface S11 of the top surface 212, is preferably 0.25 mm or more and 5.0 mm or less. In this case, bulging of the case 20 can be further reduced. If the distance D is less than 0.25 mm, it is difficult to achieve the effect of suppressing the height of the center C of the top surface 212 when the top surface 212 bulges. If the distance D exceeds 5.0 mm, the space inside the housing 21 that can accommodate the capacitor element 10 becomes smaller, resulting in a decrease in the capacitance of the electrolytic capacitor 1 or an increase in the size of the electrolytic capacitor 1 to achieve the same capacitance. Furthermore, if the distance D exceeds 5.0 mm, when the housing 21 is formed by press processing, cracks or breakage may occur in the housing 21 during press processing.

[0034] The distance D is more preferably 0.5 mm or more, even more preferably 0.8 mm or more, and particularly preferably 1.5 mm or more. The distance D is more preferably 4.0 mm or less, even more preferably 3.0 mm or less, and particularly preferably 2.5 mm or less. In these cases, the swelling of the case 20 can be further reduced while suppressing a decrease in the capacitance of the electrolytic capacitor 1.

[0035] (Side Surface Portion) As shown in FIG. 3 , the side surface portion 213 is a portion of the housing 21 that extends from the outer periphery of the top surface portion 212 toward the opening 211 .

[0036] The side surface portion 213 is made up of a plurality of (for example, four) portions, and each portion is typically rectangular or square in shape when viewed from the front.

[0037] 4, the housing 21 typically has corners E at the boundaries between the top surface 212 and the side surface 213. The housing 21 typically has a plurality of corners E (for example, four).

[0038] As shown in FIG. 4 , the radius of curvature of the inner surface S32 of the corner E is R1, and the radius of curvature of the outer surface S31 of the corner E is R2. The "radius of curvature" can be calculated as the radius of a circle obtained by approximating a portion of the curve representing the inner surface S32 or the outer surface S31 of the corner E in the cross section shown in FIG. 4 to an arc. The radii of curvature R1 and R2 represent the arithmetic mean values ​​measured at multiple locations (e.g., 10 arbitrary points). When the inner surface S32 or the outer surface S31 of the corner E in the cross section shown in FIG. 4 does not have a curve (when a line parallel to the top surface 212 and a line parallel to the side surface 213 intersect at the corner E and there is no curve), the radius of curvature is 0 (mm).

[0039] The radius of curvature R1 of the inner surface S32 is, for example, 0 mm or more and 10 mm or less, and preferably 0.5 mm or more and 5 mm or less. The radius of curvature R2 of the outer surface S31 is, for example, 0 mm or more and 5 mm or less, and preferably 0.5 mm or more and 2 mm or less. From the viewpoint of reducing bulging of the case 20, it is preferable that the radius of curvature R1 of the inner surface S32 be larger than the radius of curvature R2 of the outer surface S31.

[0040] 1 to 3, the sealing body 22 is a member that closes the opening 211 of the housing 21. The sealing body 22 includes, for example, a lead portion 221 and a sealing portion 222.

[0041] (Lead Portion) The lead portion 221 is composed of an anode lead portion 221A and a cathode lead portion 221B, and is a member that functions as a current collector and an external connection terminal because a portion of its surface is exposed to the outside of the case 20. The lead portion 221 is joined to a substrate on which the electrolytic capacitor 1 is mounted, using solder or the like. The material of the lead portion 221 is usually a metal, and examples of materials that can be used include aluminum, stainless steel, copper, iron, brass, and alloys thereof.

[0042] The lead portions 221A and 221B preferably have a shape that includes a flat surface for connection with the mounting board, such as a simple flat plate shape or an L-shaped plate shape.

[0043] 2, lead portions 221A, 221B typically protrude from sealing body 22 toward the inside of casing 21. Anode lead portion 221A is joined to anode foil 11A (anode portion) of capacitor element 10 and is electrically connected to anode foil 11A. Cathode lead portion 221B is joined to cathode foil 11B (cathode portion) of capacitor element 10 and is electrically connected to cathode foil 11B.

[0044] (Sealing Portion) The sealing portion 222 is formed of a resin such as polybutylene terephthalate (PBT) or polyphenylene sulfide (PPS), and may have a metal frame that surrounds this resin.

[0045] [Liquid Component] The liquid component is impregnated into capacitor element 10. As a result, the liquid component is contained within case 20. More specifically, the liquid component is impregnated into the separator of capacitor element 10, etc.

[0046] The liquid component may be, for example, an electrolyte solution.

[0047] The electrolytic solution may be an organic solvent, for example. Examples of the organic solvent include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, and propylene glycol; sulfone compounds such as sulfolane, dimethyl sulfoxide, and diethyl sulfoxide; lactone compounds such as γ-butyrolactone and γ-valerolactone; carbonate compounds such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; diether compounds of polyhydric alcohols such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; and monohydric alcohols such as methanol, ethanol, and propanol.

[0048] The electrolytic solution may contain a solute, such as an acid component such as an organic acid, an inorganic acid, or a complex acid compound of an organic acid and an inorganic acid; a base component such as an amine or a quaternary ammonium salt; a salt of an acid and a base; a nitro compound; or a phenol compound.

[0049] <Stress Analysis Results> The electrolytic capacitor 1 of this embodiment was evaluated by stress analysis to determine the degree of swelling that occurs when the pressure inside the case 20 increases.

[0050] The stress analysis was performed using "Solidworks 2023" as the modeling software and "Simulation Xpress Analysis Wizard" as the analysis software. The degree of expansion of the case 20 was measured when the internal pressure was 5000 kN / m. ２ The evaluation was carried out by determining the maximum displacement (mm) at the center C of the top surface portion 212 in this case.

[0051] 5 shows the results of the maximum displacement amount at the center C of the top surface 212 when the plate thickness d of the plate-like member constituting the top surface 212 is variously changed. Also, FIG. 6 shows the results of the maximum displacement amount at the center C of the top surface 212 when the radius of curvature R1 of the inner surface S32 of the corner E is variously changed.

[0052] 5 is a graph showing the relationship between the thickness d (mm) of the plate-like member constituting the top surface portion 212 and the maximum displacement (mm) of the top surface portion 212. The size of the top surface portion 212 was 18 mm x 18 mm, the radius of curvature R1 of the inner surface S32 of the corner E was 1 mm, and the radius of curvature R2 of the outer surface S31 was 1 mm. As shown in FIG. 5, it was found that the greater the thickness d, the smaller the maximum displacement. Thus, by increasing the thickness d of the top surface portion 212, deformation of the top surface portion 212 due to internal pressure can be suppressed.

[0053] 5, the thickness d of the top surface 212 is preferably 0.5 mm or more, more preferably 0.7 mm or more, and even more preferably 0.9 mm or more. In this case, the swelling of the case 20 can be further reduced.

[0054] The plate thickness d is, for example, 5.0 mm or less, and preferably 4.0 mm or less, which makes it easier to manufacture the housing 21.

[0055] 6 is a graph showing the relationship between the radius of curvature R1 (mm) of the inner surface S32 of the corner E and the maximum displacement (mm) of the top surface 212. The radius of curvature R2 of the outer surface S31 of the corner E was set to 1.0 mm. The size of the top surface 212 was 18 mm × 18 mm, and the thickness d of the plate-like member constituting the top surface 212 was set to 0.5 mm. As shown in FIG. 6 , it was found that the larger the radius of curvature R1, the smaller the maximum displacement. It was also found that it is preferable to make the radius of curvature R1 of the inner surface S32 of the corner E larger than the radius of curvature R2 of the outer surface S31 of the corner E, which can further reduce bulging of the case 20.

[0056] The reason for this is thought to be that, for example, stress concentration due to an increase in internal pressure of electrolytic capacitor 1 occurs at corner E located at the boundary between top surface portion 212 and side surface portion 213, causing a bulge in top surface portion 212 starting from corner E; by making radius of curvature R1 larger than radius of curvature R2, the plate thickness near corner E increases partially, causing the starting position of the bulge to slide from corner E toward the center, thereby reducing the area of ​​top surface portion 212 that is deformed by the bulge.

[0057] Furthermore, it is preferable that the ratio (R1 / R2) of the radius of curvature R1 to the radius of curvature R2 satisfies the following formula. In this case, the swelling of case 20 can be further reduced: 0<R1 / R2≦5 If the ratio (R1 / R2) of the radius of curvature R1 to the radius of curvature R2 exceeds 5, inner surface S32 of corner E will interfere with capacitor element 10 inside case 20, reducing the space inside housing 21 that can accommodate capacitor element 10. This will result in a decrease in the capacitance of electrolytic capacitor 1 or an increase in the size of electrolytic capacitor 1 to achieve the same capacitance.

[0058] R1 / R2 is more preferably 0.5 or more, even more preferably 0.8 or more, and particularly preferably 1.0 or more. R1 / R2 is more preferably 4.5 or less, even more preferably 4.0 or less, and particularly preferably 3.0 or less.

[0059] The housing 21 having the corners E with the above-described radii of curvature R1 and R2 can be formed by cutting, bending, or the like.

[0060] The maximum displacement of the center C of the top surface portion 212 is, for example, 4 mm or less, preferably 1.0 mm or less, more preferably 0.8 mm or less, even more preferably 0.6 mm or less, and particularly preferably 0.3 mm or less. The lower limit of the maximum displacement is, for example, 0 mm or more, preferably 0.1 mm or more.

[0061] (Modifications) The above embodiment is merely one of various embodiments of the present disclosure, and various modifications can be made to the above embodiment depending on the design and the like as long as the object of the present disclosure can be achieved.

[0062] In the above embodiment, the planar portion 2121 in the first region A1 of the top surface 212 of the electrolytic capacitor 1 has a flat shape, but this is not limited to this, and the planar portion 2121 can have various shapes as long as it includes the center C of the top surface 212, for example, it can have a shape having a recess and / or a protrusion.

[0063] The housing 21 of the electrolytic capacitor 1 according to the modified example of the present disclosure is shown in Figures 7 and 8. Furthermore, these modified examples can also be combined.

[0064] 7, the flat surface portion 2121 of the first area A1 has a linear recess B1 passing through the center C of the top surface portion 212. By having the linear recess B1 on the flat surface portion 2121, it is possible to further reduce the swelling of the case 20.

[0065] In the housing 21 of Figure 7, the linear recess B1 is cross-shaped when viewed from a direction perpendicular to the outer surface S11 of the top surface portion 212, but the linear recess B1 may be any shape as long as it passes through the center C of the top surface portion 212, and may be, for example, a straight line shape, a Y shape, etc.

[0066] 8, the flat surface portion 2121 of the first area A1 has a linear protrusion B2 that passes through the center C of the top surface portion 212. By having the linear protrusion B2 on the flat surface portion 2121, swelling of the case 20 can be further reduced.

[0067] In the housing 21 of Figure 8, the linear protrusion B2 is cross-shaped when viewed from a direction perpendicular to the outer surface S11 of the top surface 212, but the linear protrusion B2 may be any shape as long as it passes through the center C of the top surface 212, and may be, for example, a straight line shape, a Y shape, etc.

[0068] 8, the height of the linear protrusion B2 formed on the flat surface 2121 is lower than the height of the top surface 212. In this way, in the direction perpendicular to the outer surface S11 of the top surface 212, it is preferable that the distance between the outer surface S11 of the top surface 212 and the outer surface of the linear protrusion is smaller than the distance between the outer surface S11 of the top surface 212 and the outer surface of the flat surface 2121. In this case, by lowering the height of the center C of the top surface 212, it is possible to further reduce the bulging of the case 20.

[0069] (Summary) As is clear from the above-described embodiment and modifications, the present disclosure includes the following aspects. In the following, reference numerals are given in parentheses only to clarify the correspondence with the embodiment.

[0070] The electrolytic capacitor (1) of the first aspect includes a capacitor element (10) and a case (20) that houses the capacitor element (10). The case (20) includes a housing (21) having an opening (211) and a sealing body (22) that closes the opening (211) of the housing (21). The housing (21) has a top surface (212) located on the opposite side of the opening (211) and a side surface (213) extending from the outer periphery of the top surface (212) toward the opening (211). The top surface (212) is made of a plate-like member. The outer surface (S11) of the top surface (212) has a first region (A1) that is recessed toward the opening (211). The first region (A1) includes a flat surface (2121) that includes the center (C) of the top surface (212).

[0071] According to the first aspect, the electrolytic capacitor (1) can reduce swelling of the case (20).

[0072] In the electrolytic capacitor (1) of the second aspect, the first region (A1) has a rectangular or circular shape when viewed from a direction perpendicular to the outer surface (S11) of the top surface portion (212) in the first aspect.

[0073] According to the second aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0074] In the electrolytic capacitor (1) of the third aspect, in the first or second aspect, the distance (D) between the outer surface (S11) of the top surface (212) and the outer surface (S21) of the flat portion (2121) in a direction perpendicular to the outer surface (S11) of the top surface (212) is 0.25 mm or more and 5.0 mm or less.

[0075] According to the third aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0076] In the electrolytic capacitor (1) of the fourth aspect, in any one of the first to third aspects, the first region (A1) on the inner surface (S12) of the top surface portion (212) protrudes toward the opening (211).

[0077] According to the fourth aspect, the electrolytic capacitor (1) has a top surface (212) that can press the capacitor element (10) held in the housing (21), thereby more firmly fixing the capacitor element (10). This also reduces the distance between the electrodes. Additionally, the shape of the top surface (212) has the advantage of being easily formed by pressing a plate-shaped member.

[0078] In the electrolytic capacitor (1) of a fifth aspect, in any one of the first to fourth aspects, the plate thickness (d) of the top surface portion (212) is 0.5 mm or more.

[0079] According to the fifth aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0080] In the electrolytic capacitor (1) of the sixth aspect, in the fifth aspect, the thickness (d) of the top surface portion (212) is 5 mm or less.

[0081] According to the sixth aspect, the housing (21) of the electrolytic capacitor (1) can be more easily manufactured.

[0082] In the electrolytic capacitor (1) of a seventh aspect, in any one of the first to sixth aspects, the housing (21) has a corner (E) at the boundary between the top surface (212) and the side surface (213). The radius of curvature (R1) of the inner surface (S32) of the corner (E) is larger than the radius of curvature (R2) of the outer surface (S31) of the corner (E).

[0083] According to the seventh aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0084] In the electrolytic capacitor (1) of the eighth aspect, in the seventh aspect, the ratio R1 / R2 of the radius of curvature R1 to the radius of curvature R2 satisfies 0<R1 / R2≦5.

[0085] According to the eighth aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0086] In the ninth aspect of the electrolytic capacitor (1), in any one of the first to eighth aspects, the planar portion (2121) of the first region (A1) has a linear recess (B1) passing through the center (C) of the top surface portion (212).

[0087] According to the ninth aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0088] In the electrolytic capacitor (1) of the tenth aspect, in any one of the first to eighth aspects, the planar portion (2121) of the first region (A1) has a linear convex portion (B2) passing through the center (C) of the top surface portion (212).

[0089] According to the tenth aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0090] In the electrolytic capacitor (1) of the eleventh aspect, in the tenth aspect, in a direction perpendicular to the outer surface (S11) of the top surface portion (212), the distance between the outer surface (S11) of the top surface portion (212) and the outer surface of the linear convex portion (B2) is smaller than the distance between the outer surface (S11) of the top surface portion (212) and the outer surface (S21) of the flat portion (2121).

[0091] According to the eleventh aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20).

[0092] In a twelfth aspect of the electrolytic capacitor (1), in any one of the first to eleventh aspects, the capacitor element (10) includes an anode foil (11A), a cathode foil (11B), and a separator and a conductive polymer disposed between the anode foil (11A) and the cathode foil (11B). In the case (20), the anode foil (11A), the cathode foil (11B), and the separator are stacked in a direction from an opening (211) of the housing (21) toward a top surface (212).

[0093] According to the twelfth aspect, the electrolytic capacitor (1) can further reduce swelling of the case (20) even when the capacitor element (10) is a laminated type.

[0094] In the electrolytic capacitor (1) of the thirteenth aspect, in any one of the first to twelfth aspects, the capacitor element (10) is impregnated with a liquid component.

[0095] According to the thirteenth aspect, the electrolytic capacitor (1) contains a liquid component inside, which makes it possible to apply the present invention when there is an increase in internal pressure, and there are great benefits to adopting the present disclosure.

[0096] REFERENCE SIGNS LIST 1 electrolytic capacitor 10 capacitor element 20 case 211 opening 212 top surface portion 213 side surface portion A1 first region 2121 flat surface portion C center of top surface portion

Claims

1. An electrolytic capacitor comprising: a capacitor element; and a case that houses the capacitor element, wherein the case has a housing with an opening and a sealing body that closes the opening of the housing, wherein the housing has a top surface located on the opposite side of the opening and a side surface extending from the outer periphery of the top surface toward the opening, wherein the top surface is made of a plate-like member, and wherein the outer surface of the top surface has a first region that is recessed toward the opening, and wherein the first region includes a flat portion that includes the center of the top surface.

2. The electrolytic capacitor according to claim 1, wherein the first region has a rectangular or circular shape when viewed in a direction perpendicular to the outer surface of the top surface portion.

3. The electrolytic capacitor according to claim 1 or 2, wherein the distance between the outer surface of the top surface portion and the outer surface of the flat portion in a direction perpendicular to the outer surface of the top surface portion is 0.25 mm or more and 5.0 mm or less.

4. The electrolytic capacitor according to claim 1 or 2, wherein the first region on the inner surface of the top surface portion protrudes toward the opening.

5. The electrolytic capacitor according to claim 1 or 2, wherein the thickness of the top surface is 0.5 mm or more.

6. The electrolytic capacitor according to claim 5, wherein the thickness of the top surface is 5 mm or less.

7. The electrolytic capacitor according to claim 1 or 2, wherein the housing has a corner at the boundary between the top surface and the side surface, and the radius of curvature R1 of the inner surface of the corner is greater than the radius of curvature R2 of the outer surface of the corner.

8. The electrolytic capacitor according to claim 7, wherein a ratio R1 / R2 of the radius of curvature R1 to the radius of curvature R2 satisfies 0<R1 / R2≦5.

9. The electrolytic capacitor according to claim 1 or 2, wherein the flat portion of the first region has a linear recess passing through the center of the top surface portion.

10. The electrolytic capacitor according to claim 1 or 2, wherein the flat portion of the first region has a linear convex portion passing through the center of the top surface portion.

11. The electrolytic capacitor according to claim 10, wherein, in a direction perpendicular to the outer surface of the top surface portion, the distance between the outer surface of the top surface portion and the outer surface of the linear convex portion is smaller than the distance between the outer surface of the top surface portion and the outer surface of the flat portion.

12. The electrolytic capacitor according to claim 1 or 2, wherein the capacitor element includes an anode foil, a cathode foil, and a separator and conductive polymer disposed between the anode foil and the cathode foil, and the anode foil, the cathode foil, and the separator are stacked within the case in a direction from the opening of the housing toward the top surface.

13. The electrolytic capacitor according to claim 1 or 2, wherein the capacitor element is impregnated with a liquid component.

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