Electrolytic capacitor

Abstract

Disclosed is an electrolytic capacitor that includes: a wound capacitor element which is formed by winding a laminate; a liquid component with which the capacitor element is impregnated; and a bottomed cylindrical case which houses the capacitor element and the liquid component. The laminate has: an anode foil which has a dielectric layer on the surface thereof; a cathode foil which faces the dielectric layer of the anode foil; a separator which is interposed between the anode foil and the cathode foil; and a conductive polymer which is held by the separator. In a cross-section that is perpendicular to the winding axis of the capacitor element, the ratio of the total cross-sectional area of the anode foil and the cathode foil to the cross-sectional area of the capacitor element is 55% or more.

Description

electrolytic capacitor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2023-202785, filed on November 30, 2023, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to electrolytic capacitors.

[0003] Conventionally, a wound electrolytic capacitor has been known that includes a capacitor element formed by winding an anode foil and a cathode foil with a separator interposed therebetween (for example, Patent Document 1). The electrolytic capacitor of Patent Document 1 includes such a capacitor element and a cylindrical case with a bottom that contains the capacitor element and a liquid component.

[0004] International Publication No. 2018 / 181088

[0005] When a ripple current (AC charge / discharge current) flows through an electrolytic capacitor, the capacitor element, which has an internal resistance (equivalent series resistance: ESR), generates heat. This heat causes evaporation of liquid components and an increase in ESR, shortening the life of the electrolytic capacitor. This phenomenon becomes more pronounced as the ripple current increases. In this situation, the present disclosure provides an electrolytic capacitor with improved heat dissipation.

[0006] One aspect of the present disclosure relates to an electrolytic capacitor including a wound capacitor element formed by winding a laminate, a liquid component impregnated in the capacitor element, and a bottomed cylindrical case that accommodates the capacitor element and the liquid component, wherein the laminate includes an anode foil having a dielectric layer on a surface thereof, a cathode foil facing the dielectric layer of the anode foil, a separator interposed between the anode foil and the cathode foil, and a conductive polymer held by the separator, and in a cross section perpendicular to a winding axis of the capacitor element, a ratio of a total cross-sectional area of ​​the anode foil and the cathode foil to a cross-sectional area of ​​the capacitor element is 55% or more.

[0007] According to the present disclosure, it is possible to improve the heat dissipation of an electrolytic capacitor. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0008] 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor according to the present disclosure; 2 is an exploded perspective view schematically illustrating a capacitor element; 3 is a graph showing the heat dissipation properties of electrolytic capacitors of Examples and Comparative Examples;

[0009] The following describes an example of an embodiment of an electrolytic capacitor according to the present disclosure. However, the present disclosure is not limited to the example described below. While the following description may use specific numerical values ​​and materials, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0010] The electrolytic capacitor according to the present disclosure includes a capacitor element, a liquid component, and a bottomed cylindrical case. As described below, the capacitor element includes a conductive polymer held in a separator. That is, the electrolytic capacitor according to the present disclosure is a so-called solid-liquid hybrid electrolytic capacitor.

[0011] The capacitor element is a wound type capacitor element formed by winding a laminate. The laminate includes an anode foil, a cathode foil, a separator, and a conductive polymer. The anode foil has a dielectric layer on its surface. The cathode foil faces the dielectric layer of the anode foil. The separator is interposed between the anode foil and the cathode foil. The conductive polymer is held by the separator.

[0012] Each of the anode foil and the cathode foil is formed in a strip shape (or a long sheet shape). Each of the anode foil and the cathode foil has a core portion and a porous portion made of a valve metal or an alloy or compound containing a valve metal. Examples of valve metals include aluminum, tantalum, and niobium. The porous portion has a lower density than the core portion and is formed, for example, by etching the surface of the anode foil and the cathode foil. At least a portion of the porous portion of the anode foil is covered with the dielectric layer (for example, an oxide of the valve metal).

[0013] The separator is formed in a strip shape (or a long sheet shape). The separator may be wider than the anode foil and the cathode foil. The width direction of the separator is parallel to the winding axis of the capacitor element. The separator is made of, for example, a woven fabric, a nonwoven fabric, or a porous sheet such as a microporous membrane. The separator is impregnated with a liquid component in addition to the conductive polymer.

[0014] Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. These derivatives include polymers with polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as their basic skeletons. For example, polythiophene derivatives include poly(3,4-ethylenedioxythiophene). These conductive polymers may be used alone or in combination. Furthermore, the conductive polymer may be a copolymer of two or more monomers. The weight-average molecular weight of the conductive polymer is not particularly limited and is, for example, in the range of 1,000 to 100,000. One preferred example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0015] The conductive polymer may be doped with a dopant. From the viewpoint of suppressing dedoping from the conductive polymer, it is preferable to use a polymer dopant as the dopant. Examples of polymer dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. These may be used alone or in combination of two or more. At least a portion of these may be added in the form of a salt. A preferred example of the dopant is polystyrene sulfonic acid (PSS). The weight-average molecular weight of the dopant is not particularly limited. From the viewpoint of facilitating the formation of a homogeneous conductive polymer layer, the weight-average molecular weight of the dopant is preferably in the range of 1,000 to 100,000.

[0016] The liquid component is impregnated into the capacitor element. The liquid component may be an electrolyte. Examples of the liquid component include a non-aqueous solvent and an electrolyte. The electrolyte may be a mixture of a non-aqueous solvent and an ionic substance (solute, e.g., an organic salt) dissolved therein. The non-aqueous solvent may be an organic solvent or an ionic liquid. Examples of non-aqueous solvents that can be used include ethylene glycol, propylene glycol, sulfolane, γ-butyrolactone, and N-methylacetamide. Examples of organic salts include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate. In this specification, the liquid component may be a component that is liquid at room temperature (25°C) or at the temperature at which the electrolytic capacitor is used.

[0017] The bottomed cylindrical case accommodates the capacitor element and the liquid component. The case may be made of metal (e.g., aluminum or an aluminum alloy). The case may have an opening, which may be sealed with a sealing member.

[0018] A feature of the electrolytic capacitor according to the present disclosure is that, in a cross section perpendicular to the winding axis of the capacitor element, the ratio of the total cross-sectional area of ​​the anode foil and the cathode foil to the cross-sectional area of ​​the capacitor element is 55% or more. This ratio may be, for example, 55% or more and 85% or less, and is preferably 55% or more and 80% or less. Here, the cross-sectional area of ​​the capacitor element is the area of ​​a cross section perpendicular to the winding axis of the capacitor element at any one point in the central region when the capacitor element is divided into three equal parts along the winding axis direction. The cross-sectional area of ​​the capacitor element is determined by dividing the maximum diameter of the cross section D max The minimum diameter of the cross section is D min As an approximation, π·{(D max +D min ) / 2} 2 / 4 = π · (D max +D min ) 2 / 16. In other words, in this specification, the cross-sectional area of ​​a capacitor element at a given cross section is approximately calculated as the area of ​​a circle whose diameter is the average of the maximum and minimum diameters of the cross section. The cross section includes the spiral-shaped anode foil, cathode foil, and separator. The total cross-sectional area of ​​the anode foil and cathode foil (i.e., the sum of the cross-sectional areas of the anode foil and the cathode foil) accounts for 55% or more of the cross-sectional area of ​​the capacitor element. The cross-sectional area of ​​the anode foil (and cathode foil) is approximately calculated as the product of the thickness and length of the anode foil (and cathode foil) measured at the given cross section after disassembling the capacitor element. The thickness of the anode foil (and cathode foil) is calculated as the average of the thickness measurements at any five points, and the length of the anode foil (and cathode foil) is the maximum length measured along its longitudinal direction.

[0019] Here, the thermal conductivity of the anode foil and the cathode foil is higher than that of the separator. In the capacitor element of the electrolytic capacitor according to the present disclosure, the anode foil and the cathode foil, which have high thermal conductivity, occupy a large volume due to the above-described configuration. Therefore, even if heat is generated inside the capacitor element when a ripple current flows through the electrolytic capacitor, the heat can be efficiently dissipated to the outside of the capacitor element. Furthermore, it has been found that this improvement in heat dissipation is significantly enhanced by setting the ratio to 55% or greater. As will be described in more detail below, setting the ratio to 55% or greater significantly improves the heat dissipation of the electrolytic capacitor.

[0020] The outermost periphery of the capacitor element may be made of a cathode foil, in which case heat generated inside the capacitor element can be dissipated to the outside of the capacitor element more efficiently than when the outermost periphery of the capacitor element is made of a separator.

[0021] At least a portion of the separator may be in contact with the inner bottom surface of the case, in which case heat generated inside the capacitor element can be efficiently transferred to the case via the contact portion, thereby further improving the heat dissipation of the electrolytic capacitor.

[0022] The ratio of the diameter (maximum diameter) of the capacitor element to the inner diameter of the case may be 85% or more and less than 100%. When this ratio is 85% or more, the distance between the outer peripheral surface of the capacitor element and the inner peripheral surface of the case is sufficiently small, allowing efficient heat transfer between the two. This further improves the heat dissipation of the electrolytic capacitor.

[0023] The anode foil and the cathode foil may be made of a material containing aluminum, which allows for efficient heat dissipation.

[0024] The liquid component may contain a polyol. In this case, deterioration of the conductive polymer due to heat generation can be suppressed. Polyol refers to an organic compound containing two or more hydroxyl groups. Examples of polyols include glycols, glycerins, and sugar alcohols. The polyol may be a hydrocarbon compound substituted with two or more hydroxyl groups. The polyol is preferably soluble in water. The molecular weight of the polyol may be, for example, 500 or less. Examples of glycols include alkylene glycols (ethylene glycol, propylene glycol, etc.), diethylene glycol, triethylene glycol, polyalkylene glycols (e.g., polyethylene glycol), polyoxyethylene polyoxypropylene glycol (ethylene oxide-propylene oxide copolymer), etc. Examples of glycerins include glycerin and polyglycerin. Examples of sugar alcohols include mannitol, xylitol, sorbitol, erythritol, and pentaerythritol. A preferred example of a polyol is ethylene glycol.

[0025] As described above, according to the present disclosure, by increasing the ratio of the total cross-sectional area of ​​the anode foil and cathode foil to the total cross-sectional area of ​​the capacitor element at a given cross section, the heat dissipation of the electrolytic capacitor can be improved. Furthermore, according to the present disclosure, deterioration of the capacitor element can be suppressed, and the life of the electrolytic capacitor can be extended.

[0026] An example of an electrolytic capacitor according to the present disclosure will be described in detail below with reference to the drawings. The components described above can be applied to the components of the example electrolytic capacitor described below. The components of the example electrolytic capacitor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Of the components of the example electrolytic capacitor described below, components that are not essential to the electrolytic capacitor according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0027] 1 and 2 , the electrolytic capacitor 10 of this embodiment includes a wound capacitor element 20 formed by winding a laminate, a liquid component (not shown) impregnated in the capacitor element 20, a bottomed, cylindrical case 30 that accommodates the capacitor element 20 and the liquid component, a sealing member 40 that closes the opening of the case 30, a seat plate 50 that covers the sealing member 40, lead wires 61 and 71 that extend through the seat plate 50, and lead tabs 62 and 72 that connect the lead wires 61 and 71 to electrodes of the capacitor element 20. The vicinity of the open end of the case 30 is drawn inward, and the open end is curled to crimp the sealing member 40. One of the lead wires 61 and the lead tab 62 constitutes an anode lead 60, and the other of the lead wires 71 and the lead tab 72 constitutes a cathode lead 70.

[0028] The capacitor element 20 is a wound body as shown in FIG. 2 and is formed by winding a laminate as described above. The laminate includes an anode foil 21 connected to the lead tab 62 of the anode lead 60, a cathode foil 22 connected to the lead tab 72 of the cathode lead 70, a separator 23 interposed between the anode foil 21 and the cathode foil 22, and a conductive polymer (not shown) held by the separator 23. The anode foil 21 has a dielectric layer (not shown) on its surface. The cathode foil 22 faces the dielectric layer of the anode foil 21 via the separator 23. The cathode foil 22 has a conductive polymer layer (not shown) made of a conductive polymer formed on the surface of the dielectric layer. The material of the anode foil 21 and the cathode foil 22 preferably contains aluminum. The liquid component preferably contains polyol. The liquid component may be an electrolyte solution.

[0029] Anode foil 21 and cathode foil 22 are wound with separator 23 interposed therebetween. The outermost periphery of capacitor element 20 is made up of cathode foil 22 and is fixed with stop tape 25. Note that FIG. 2 shows a partially unfolded state of capacitor element 20 before the outermost periphery is secured. It is preferable that at least a portion of separator 23 contacts the inner bottom surface of case 30. It is preferable that the ratio of the diameter (maximum diameter) of capacitor element 20 to the inner diameter of case 30 be 85% or more and less than 100%.

[0030] In a cross section (or transverse cross section) perpendicular to the winding axis of the capacitor element 20, the ratio of the total cross-sectional area of ​​the anode foil 21 and the cathode foil 22 to the cross-sectional area of ​​the capacitor element 20 is 55% or more. This significantly improves the heat dissipation of the electrolytic capacitor 10. Note that this ratio may be 55% or more and 85% or less, and is preferably 55% or more and 80% or less. By setting the preferred upper limit of this ratio to 85% or 80%, the separator thickness can be maintained at a certain level, improving the impregnation of the conductive polymer and preventing an increase in the ESR of the electrolytic capacitor 10.

[0031] <<Appendix>> The above embodiments disclose the following technologies. (Technology 1) An electrolytic capacitor comprising: a wound-type capacitor element formed by winding a laminate; a liquid component impregnated in the capacitor element; and a bottomed cylindrical case that accommodates the capacitor element and the liquid component, wherein the laminate comprises: an anode foil having a dielectric layer on its surface; a cathode foil facing the dielectric layer of the anode foil; a separator interposed between the anode foil and the cathode foil; and a conductive polymer held by the separator, wherein, in a cross section perpendicular to the winding axis of the capacitor element, the ratio of the total cross-sectional area of ​​the anode foil and the cathode foil to the cross-sectional area of ​​the capacitor element is 55% or more. (Technology 2) The electrolytic capacitor according to Technology 1, wherein the outermost periphery of the capacitor element is formed by the cathode foil. (Technology 3) The electrolytic capacitor according to Technology 1 or 2, wherein at least a portion of the separator contacts the inner bottom surface of the case. (Technology 4) The electrolytic capacitor according to any one of Technologies 1 to 3, wherein the ratio of the diameter of the capacitor element to the inner diameter of the case is 85% or more and less than 100%. (Technology 5) The electrolytic capacitor according to any one of Technologies 1 to 4, wherein the material of the anode foil and the cathode foil contains aluminum. (Technology 6) The electrolytic capacitor according to any one of Technologies 1 to 5, wherein the liquid component contains polyol.

[0032] The heat dissipation performance of each of the electrolytic capacitors in Examples 1 to 6 and Comparative Examples 1 to 12 shown below was evaluated. The heat dissipation performance was evaluated based on the magnitude of the heat dissipation coefficient β of each electrolytic capacitor, which was obtained according to the following procedures 1 to 4. (Procedure 1) An electrolytic capacitor was fabricated, and the relationship between its ESR and temperature (surface temperature of the case) (i.e., the ESR temperature characteristics) was measured. (Procedure 2) The electrolytic capacitor was mounted on a circuit board. (Procedure 3) A ripple current was applied to the electrolytic capacitor with a thermocouple attached to the surface (specifically, the top surface) of the case. After that, the temperature measured by the thermocouple was allowed to stabilize, and the temperature rise was calculated from the difference between the stabilized temperature and the ambient temperature. This was performed for multiple ripple currents. (Procedure 4) The ESR of the electrolytic capacitor after heat generation, calculated from the ESR temperature characteristics obtained in Procedure 1, was defined as R (unit: Ω), the effective value of the ripple current applied in Procedure 3 was defined as I (unit: A), and the surface area of ​​the electrolytic capacitor's case was defined as S (unit: cm). 2 ) and the temperature range obtained in step 3 is ΔT (unit: °C), S·ΔT corresponds to the horizontal axis (x-axis) and R·I 2 The slope of the vertical axis (y-axis) is the heat dissipation coefficient β (unit: W / (°C cm 2 )) is obtained.

[0033] Example 1 The heat dissipation performance of an electrolytic capacitor corresponding to Embodiment 1 was evaluated, in which the ratio of the combined cross-sectional area of ​​the anode foil and cathode foil to the cross-sectional area of ​​the capacitor element in a cross section perpendicular to the winding axis of the capacitor element (hereinafter simply referred to as the area ratio) was 55.2%, the outermost periphery of the capacitor element was formed by cathode foil, at least a portion of the separator was in contact with the inner bottom surface of the case, and the ratio of the diameter of the capacitor element to the inner diameter of the case was 85% or more but less than 100%. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Example 1 was 1.29.

[0034] Example 2 The heat dissipation performance of an electrolytic capacitor corresponding to Embodiment 1 was evaluated, the electrolytic capacitor having an area ratio of 55.6%, the outermost periphery of the capacitor element being made of cathode foil, at least a portion of the separator being in contact with the inner bottom surface of the case, and the ratio of the diameter of the capacitor element to the inner diameter of the case being 85% or more and less than 100%. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Example 2 was 1.33.

[0035] Example 3 The heat dissipation performance of an electrolytic capacitor corresponding to Embodiment 1 was evaluated, the electrolytic capacitor having an area ratio of 55.8%, the outermost periphery of the capacitor element being made of cathode foil, at least a portion of the separator being in contact with the inner bottom surface of the case, and the ratio of the diameter of the capacitor element to the inner diameter of the case being 85% or more and less than 100%. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Example 3 was 1.35.

[0036] Example 4 The heat dissipation performance of an electrolytic capacitor corresponding to Embodiment 1 was evaluated, the electrolytic capacitor having an area ratio of 56.7%, the outermost periphery of the capacitor element being made of cathode foil, at least a portion of the separator being in contact with the inner bottom surface of the case, and the ratio of the diameter of the capacitor element to the inner diameter of the case being 85% or more and less than 100%. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Example 4 was 1.43.

[0037] Example 5: The heat dissipation performance of an electrolytic capacitor corresponding to Embodiment 1 was evaluated, the electrolytic capacitor having an area ratio of 57.1%, the outermost periphery of the capacitor element being made of cathode foil, at least a portion of the separator being in contact with the inner bottom surface of the case, and the ratio of the diameter of the capacitor element to the inner diameter of the case being 85% or more and less than 100%. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Example 5 was 1.49.

[0038] Example 6 The heat dissipation performance of an electrolytic capacitor corresponding to Embodiment 1 was evaluated, the electrolytic capacitor having an area ratio of 57.5%, the outermost periphery of the capacitor element being made of cathode foil, at least a portion of the separator being in contact with the inner bottom surface of the case, and the ratio of the diameter of the capacitor element to the inner diameter of the case being 85% or more and less than 100%. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Example 6 was 1.53.

[0039] Comparative Example 1: The heat dissipation performance of an electrolytic capacitor having an area ratio of 54.7%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 1 was 1.25.

[0040] Comparative Example 2: The heat dissipation performance of an electrolytic capacitor having an area ratio of 54.2%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 2 was 1.19.

[0041] Comparative Example 3: The heat dissipation performance of an electrolytic capacitor having an area ratio of 53.7%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 3 was 1.15.

[0042] Comparative Example 4: The heat dissipation performance of an electrolytic capacitor having an area ratio of 53.6%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 4 was 1.15.

[0043] Comparative Example 5: The heat dissipation performance of an electrolytic capacitor having an area ratio of 53.2%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 5 was 1.13.

[0044] Comparative Example 6: The heat dissipation performance of an electrolytic capacitor having an area ratio of 52.3%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 6 was 1.08.

[0045] Comparative Example 7: The heat dissipation performance of an electrolytic capacitor having an area ratio of 52.1%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 7 was 1.07.

[0046] Comparative Example 8: The heat dissipation performance of an electrolytic capacitor having an area ratio of 51.6%, a capacitor element having an outermost periphery formed of cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 8 was 1.04.

[0047] Comparative Example 9: The heat dissipation performance of an electrolytic capacitor having an area ratio of 51.1%, a cathode foil forming the outermost periphery of the capacitor element, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was 1.00 (reference value).

[0048] Comparative Example 10: The heat dissipation performance of an electrolytic capacitor having an area ratio of 51.1%, a capacitor element in which the outermost periphery was made of cathode foil, and a separator not in contact with the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 10 was 0.86.

[0049] Comparative Example 11: The heat dissipation performance of an electrolytic capacitor having an area ratio of 51.1%, in which the outermost periphery of the capacitor element was made of a separator, and in which at least a portion of the separator was in contact with the inner bottom surface of the case, was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 11 was 0.95.

[0050] Comparative Example 12: The heat dissipation performance of an electrolytic capacitor having an area ratio of 49.9%, a capacitor element having an outermost periphery formed of a cathode foil, and at least a portion of the separator contacting the inner bottom surface of the case was evaluated. The heat dissipation coefficient β of the electrolytic capacitor of Comparative Example 9 was set to 1.00, and the heat dissipation coefficient of the electrolytic capacitor of Comparative Example 12 was 0.95.

[0051] The above evaluation results are shown in Figure 3 as a graph, with the area ratio on the horizontal axis and the relative value of the heat dissipation coefficient β on the vertical axis. As can be seen from the figure (particularly from the difference in the slope of the two approximation lines corresponding to the multiple white circles in the graph), setting the area ratio to 55% or higher significantly increases the heat dissipation coefficient β, i.e., significantly improves the heat dissipation performance of the electrolytic capacitor. In Figure 3, Comparative Example 9, which serves as the reference value, is represented by a black circle (●), Comparative Example 10, in which the separator and case do not contact, is represented by a white triangle (△), Comparative Example 11, in which the outermost periphery of the capacitor element is made of a separator, is represented by a white square (□), and the other Examples and Comparative Examples are represented by white circles (○).

[0052] The present disclosure can be used for electrolytic capacitors.

[0053] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0054] 10: Electrolytic capacitor 20: Capacitor element 21: Anode foil 22: Cathode foil 23: Separator 25: Winding tape 30: Case 40: Sealing member 50: Seat plate 60: Anode lead 61: Lead wire 62: Lead tab 70: Cathode lead 71: Lead wire 72: Lead tab

Claims

1. An electrolytic capacitor comprising: a wound type capacitor element formed by winding a laminate; a liquid component impregnated in the capacitor element; and a bottomed cylindrical case that accommodates the capacitor element and the liquid component, wherein the laminate comprises: an anode foil having a dielectric layer on a surface thereof; a cathode foil facing the dielectric layer of the anode foil; a separator interposed between the anode foil and the cathode foil; and a conductive polymer held by the separator, wherein in a cross section perpendicular to the winding axis of the capacitor element, a ratio of a total cross-sectional area of ​​the anode foil and the cathode foil to a cross-sectional area of ​​the capacitor element is 55% or more.

2. The electrolytic capacitor according to claim 1, wherein the outermost periphery of the capacitor element is formed by the cathode foil.

3. The electrolytic capacitor according to claim 1 or 2, wherein at least a portion of the separator is in contact with the inner bottom surface of the case.

4. The electrolytic capacitor according to claim 1 or 2, wherein the ratio of the diameter of the capacitor element to the inner diameter of the case is 85% or more and less than 100%.

5. The electrolytic capacitor according to claim 1 or 2, wherein the material of the anode foil and the cathode foil includes aluminum.

6. The electrolytic capacitor according to claim 1 or 2, wherein the liquid component includes a polyol.