capacitor

Abstract

This capacitor 1 comprises a capacitor element 3 that holds a prescribed solution between an anode foil 5 and a cathode foil 7 wound with a separator 6 interposed therebetween, a body case 2 that accommodates the capacitor element 3, and a sealed body 4 that seals the body case 2. In this capacitor 1, a portion of the separator 6 makes contact at a plurality of points or surfaces in a state of having conformed to the surface of the sealed body 4 near the capacitor element 3, and a sealed body anti-degradant in which the solution solidifies by oxidation is dissolved in a lipophilic solvent. The solution supplied to the sealed body 4 via the separator 6 penetrates inside the sealed body 4, the outer surface of the sealed body 4 is covered by a cover part 17 in which the sealed body anti-degradant has solidified, and the solution is present inside the sealed body 4 further to the capacitor element 3 side than the cover part 17.

Description

[Technical Field]

[0001] The present invention relates to a capacitor sealed with a sealing body. [Background technology]

[0002] A conventional capacitor is disclosed in Patent Document 1. This capacitor includes a main case, a capacitor element, and a sealing body. The main case is made of metal and has a cylindrical shape with a closed bottom, one end of the cylindrical peripheral wall is closed, and the other end has an opening.

[0003] The capacitor element is made by winding an anode foil and a cathode foil, each with an oxide film formed thereon, with a separator interposed between them, and then encased in a main case. An electrolyte is held between the anode and cathode foils. Lead terminals are connected to the anode and cathode foils, respectively. The opening of the main case encasing the capacitor element is sealed with a seal made of rubber or the like, and the lead terminals penetrate the seal and extend to the outside of the main case.

[0004] When polymers such as rubber are exposed to heat or light energy in the presence of oxygen, such as in the air, radicals are generated, which trigger a chain reaction of oxidation, resulting in a deterioration of physical properties. For this reason, it is said that antioxidants are mixed into the sealing body to suppress oxidation reactions.

[0005] Patent Documents 2 and 3 disclose capacitors that use a solid electrolyte instead of a liquid electrolyte. These capacitors have the same main body case, capacitor element, and sealing body as those in Patent Document 1. A conductive polymer, which serves as a solid electrolyte, is held between the anode foil and cathode foil of the capacitor element. With a capacitor configured as described above, the conductive polymer can reduce the ESR.

[0006] Furthermore, the capacitor of Patent Document 3 holds a functional liquid (for example, water) between the anode foil and the cathode foil. The functional liquid can repair defects in the oxide films formed on the anode foil and the cathode foil. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2000-100670 A (pages 2-4, Figure 1) [Patent Document 2] JP 2016-76562 A (pages 7-16, Figure 2) [Patent Document 3] International Publication No. 2014 / 050913 (pages 9-23, Figure 2) Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, as devices incorporating capacitors have become smaller and more powerful, capacitors are increasingly being placed near motors, engines, high-speed processing semiconductor devices, and other devices that generate a lot of heat. As a result, capacitors are increasingly being used in high-temperature environments.

[0009] In the capacitor disclosed in Patent Document 1, the antioxidant mixed into the sealing body is consumed and gradually lost as it performs its antioxidant function. When the capacitor is used in a high-temperature environment, the sealing body rapidly deteriorates as the antioxidant disappears. This often causes the electrolyte to evaporate outside the main case, ultimately resulting in a state known as "dry-up." This poses a problem in that the capacitor's characteristics cannot be stably maintained over the long term.

[0010] Similarly, the capacitor disclosed in Patent Document 3 also suffers from deterioration of the sealing member when used in a high-temperature environment. As a result, the functional liquid held between the anode foil and the cathode foil leaks out of the main case, making it impossible to repair the oxide film. This poses a problem in that the capacitor's characteristics cannot be stably maintained over the long term.

[0011] Furthermore, if the functional liquid not only repairs the oxide film but also has the function of improving the characteristics of the capacitor, the leakage of the functional liquid makes it impossible to stably maintain the characteristics of the capacitor for a long period of time.

[0012] An object of the present invention is to provide a capacitor that can maintain stable characteristics over a long period of time. [Means for solving the problem]

[0013] In order to achieve the above object, the present invention provides a capacitor comprising a capacitor element in which a predetermined solution is held between an anode foil and a cathode foil wound with a separator interposed therebetween, a main case that houses the capacitor element, and a sealing body that seals the main case, wherein a portion of the separator is aligned along the surface of the sealing body facing the capacitor element and makes contact at multiple points or on the surface, and a sealing body deterioration inhibitor that solidifies upon oxidation is dissolved in a lipophilic solvent, the solution supplied to the sealing body via the separator permeates into the sealing body, and the outer surface of the sealing body is covered by a coating portion in which the sealing body deterioration inhibitor has solidified, and the solution is present inside the sealing body on the capacitor element side of the coating portion.

[0014] Furthermore, the present invention is characterized in that in the capacitor having the above configuration, the sealant deterioration inhibitor is a terpenoid, an unsaturated fatty acid, a saturated fatty acid, or a derivative thereof.

[0015] Furthermore, the present invention is characterized in that in the capacitor having the above-mentioned configuration, the sealant deterioration inhibitor is a fat-soluble vitamin.

[0016] Furthermore, the present invention is characterized in that in the capacitor having the above-mentioned structure, the solution comprises an electrolytic solution in which the sealing body deterioration inhibitor and an electrolyte are dissolved in the lipophilic solvent.

[0017] Furthermore, in the capacitor of the present invention having the above configuration, the concentration of the sealing body deterioration inhibitor in the electrolyte is 1% by weight to 90% by weight.

[0018] Furthermore, in the capacitor of the present invention having the above configuration, the concentration of the sealing body deterioration inhibitor in the electrolyte is 3% by weight to 80% by weight.

[0019] Furthermore, the present invention is characterized in that in the capacitor having the above configuration, the lipophilic solvent is gamma-butyrolactone.

[0020] Furthermore, the present invention is characterized in that in the capacitor having the above configuration, the lipophilic solvent contains at least one of sulfolane, ethylene glycol, and diethylene glycol, and a nonionic surfactant.

[0021] Furthermore, the present invention is characterized in that in the capacitor having the above configuration, the lipophilic solvent is polyethylene glycol to which a lipophilic group is bonded, or a polyethylene glycol-polypropylene glycol copolymer.

[0022] Furthermore, in the capacitor having the above configuration, the present invention is characterized in that the width of the separator in the short side direction is larger than the widths of the anode foil and the cathode foil in the short side direction, and the separator protrudes toward the sealing body further than the anode foil and the cathode foil.

[0023] In the capacitor of the present invention having the above configuration, the central portion of the surface of the sealing body facing the capacitor element protrudes more than the outer periphery.

[0024] The present invention is also characterized in that, in the capacitor having the above configuration, the main body case has a protruding portion that protrudes from the inner surface and presses against the outer peripheral surface of the sealing body, and the apex of the protruding portion is positioned further from the capacitor element than the center of the thickness direction of the sealing body. [Effects of the Invention]

[0025] According to the present invention, the capacitor element holds a solution of a sealant degradation inhibitor dissolved in a lipophilic solvent, and the separator is placed along the surface of the sealant facing the capacitor element, contacting it at multiple points or across the surface. The solution supplied through the separator penetrates the sealant, and the sealant degradation inhibitor solidifies as it oxidizes, covering the outer surface of the sealant. This makes it possible to prevent degradation of the sealant due to oxidation over the long term. This prevents the solution held in the capacitor element from leaking out, allowing the capacitor's characteristics to be maintained stably over the long term. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a perspective view of a capacitor according to a first embodiment of the present invention, seen from above; [Figure 2] 1 is a perspective view of a capacitor according to a first embodiment of the present invention, viewed from below; [Figure 3] FIG. 1 is a front cross-sectional view showing a capacitor according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a perspective view showing a capacitor element of a capacitor according to a first embodiment of the present invention; [Figure 5] Detailed view of part H in Figure 3 [Figure 6] FIG. 10 is a diagram showing the results of a durability test on the capacitor according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] First Embodiment Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 and Fig. 2 show perspective views of a capacitor 1 according to a first embodiment, viewed from above and below. Capacitor 1 is an electrolytic capacitor and is mounted on a seat plate 15. Seat plate 15 is made of synthetic resin and holds capacitor 1. Seat plate 15 has a pair of through holes 16 formed therein.

[0028] Capacitor 1 has lead terminals 8 and 9, which are inserted into through holes 16 in base plate 15 and bent outward. As a result, capacitor 1 is placed on a circuit board while the top surface of main body casing 2 is held by an automated machine, and the lead terminals 8 and 9 are soldered to lands on the circuit board for mounting.

[0029] 3 shows a front cross-sectional view of capacitor 1. Capacitor 1 comprises a main case 2, a capacitor element 3, and a sealing member 4. Main case 2 is made of a metal such as aluminum and is formed into a cylindrical shape with a circular cross section and a bottom, with one end closed by a top wall 2a and the other end having an opening 2b. Capacitor element 3 is housed inside main case 2, and opening 2b is sealed by sealing member 4.

[0030] 4 shows a perspective view of capacitor element 3. Capacitor element 3 has anode foil 5, cathode foil 7, and separator 6. Anode foil 5 and cathode foil 7 are each formed into a long strip of metal foil. Separator 6 is also formed into a long strip of nonwoven fabric or the like.

[0031] The capacitor element 3 is formed by winding an anode foil 5 and a cathode foil 7 with a separator 6 interposed therebetween into a cylindrical shape. The strip-shaped anode foil 5, cathode foil 7, and separator 6 are elongated in the winding direction (longitudinal direction), and the width in the direction perpendicular to the winding direction (transverse direction) is shorter than the length in the winding direction. The ends of the anode foil 5 or cathode foil 7 are fixed with tape 12. A lead terminal 8 is connected to the anode foil 5, and a lead terminal 9 is connected to the cathode foil 7.

[0032] The width of separator 6 in the short side direction (axial direction) is formed to be larger than the width of anode foil 5 and cathode foil 7 in the short side direction. As a result, separator 6 protrudes upward (toward upper wall 2a) and downward (toward opening 2b) relative to anode foil 5 and cathode foil 7, thereby preventing short-circuiting between anode foil 5 and cathode foil 7.

[0033] The anode foil 5 is made of a valve metal such as aluminum, tantalum, niobium, or titanium. The cathode foil 7 faces the anode foil 5 via the separator 6 and is made of aluminum or the like. An oxide film (not shown) is formed on the surfaces of the anode foil 5 and the cathode foil 7.

[0034] An electrolyte is held between the anode foil 5 and the cathode foil 7 of the capacitor element 3. By immersing the capacitor element 3 in the electrolyte for a predetermined period of time, the electrolyte permeates the separator 6 and is held between the anode foil 5 and the cathode foil 7. The electrolyte essentially functions as a cathode. Furthermore, the electrolyte can repair defects in the oxide films of the anode foil 5 and the cathode foil 7.

[0035] The electrolyte solution is a solution in which an electrolyte and a sealant deterioration inhibitor are dissolved in a lipophilic solvent. In this embodiment, gamma-butyrolactone is used as the lipophilic solvent. A lipophilic solvent containing at least one of sulfolane, ethylene glycol, and diethylene glycol and a nonionic surfactant may also be used. Furthermore, a lipophilic solvent in which a lipophilic group is bonded to polyethylene glycol may also be used, or a polyethylene glycol-polypropylene glycol copolymer may also be used.

[0036] The electrolyte dissociates into ions when dissolved in a solvent and exhibits electrical conductivity, and an organic amine salt of a boric acid compound or a carboxylic acid compound is used.

[0037] The sealant deterioration inhibitor is a compound that can dissolve in a lipophilic solvent and solidifies in the presence of oxygen through a series of oxidation-based reactions. Examples of sealant deterioration inhibitors that can be used include terpenoids such as fat-soluble vitamins that have an isoprene skeleton in their molecule (including cases where the main chain of the isoprene skeleton has a single bond, a double bond, or a cyclic structure), unsaturated fatty acids, polyglycerol esters containing unsaturated fatty acid groups in their molecule, saturated fatty acids, and derivatives thereof. Amphipathic compounds may be added to facilitate the dissolution of these sealant deterioration inhibitors in lipophilic solvents.

[0038] Fat-soluble vitamins that solidify upon oxidation include vitamin A, vitamin D, vitamin E, and vitamin K. Vitamin A is a compound with a carotenoid skeleton, and examples include retinol, β-carotene, α-carotene, β-cryptoxanthin, and astaxanthin. Vitamin D includes vitamin D2 and vitamin D3. Vitamin E includes tocopherols (α-tocopherol, β-tocopherol, γ-tocopherol, and δ-tocopherol) and tocotrienols (α-tocotrienol, β-tocotrienol, γ-tocotrienol, and δ-tocotrienol). Vitamin K includes vitamin K1, vitamin K2, and menaquinone 7. The above fat-soluble vitamins, except for α-tocopherol, have double bonds other than those in the aromatic ring within the molecule, making them susceptible to solidification upon oxidation. Furthermore, α-tocopherol does not have any double bonds other than those in the aromatic ring within the molecule, but it solidifies upon oxidation at high temperatures.

[0039] These fat-soluble vitamins are terpenoids with an isoprene skeleton in their molecules, and have a strong affinity with the rubber seal 4. For this reason, it is preferable to use fat-soluble vitamins as seal deterioration inhibitors, as this improves permeability and retention in the seal 4. The number of isoprene units in fat-soluble vitamins is preferably two or more, and more preferably three or more. Vitamin A and vitamin E are more preferable because of their strong antioxidant effects.

[0040] Compounds such as unsaturated fatty acids contained in drying oils and polyglycerol esters (polyglycerol fatty acid esters) containing unsaturated fatty acid groups in their molecules have multiple double and triple bonds in their molecules. Therefore, when reacted with oxygen in the air, the fatty acid groups bond together, increasing the molecular weight and making them prone to solidification. Examples of such compounds include tetraglycerol triesters (oleic acid tetraglycerol triesters) in which oleic acid is the fatty acid group.

[0041] Saturated fatty acids and derivatives such as ester compounds of saturated fatty acids have the property that the carbonyl groups in the molecules are oxidized and solidified in a high-temperature environment such as 160°C in the presence of oxygen.

[0042] 3, sealing body 4 is formed into a disk shape by molding an insulating elastic material and has a pair of through holes 10 and 11. Lead terminals 8 and 9 of capacitor element 3 are inserted into through holes 10 and 11 by press-fitting. Sealing body 4 can be made of butyl rubber, silicone rubber, fluororubber, or the like.

[0043] Butyl rubber is more desirable because it has high environmental resistance, including heat aging resistance, chemical resistance, and weather resistance, high electrical insulation properties, and low gas permeability. Silicone rubber and fluororubber are less airtight than butyl rubber, but the airtightness can be improved by covering the outer surface of sealing body 4 with covering portion 17, which will be described later.

[0044] The sealing body 4 may contain an antioxidant. By including an antioxidant in the sealing body 4, oxidation of the rubber can be suppressed even before the formation of the covering portion 17. Furthermore, after the formation of the covering portion 17, the consumption of the antioxidant can be suppressed by the covering portion 17, so that the oxidation reaction of the sealing body 4 can be suppressed for a long period of time even in a high-temperature environment.

[0045] With sealing body 4 placed in opening 2b of main case 2, main case 2 is subjected to a drawing process that presses the outer peripheral surface. As a result, main case 2 is formed with protrusion 13 that protrudes toward the inner surface. Protrusion 13 compresses the outer peripheral surface of sealing body 4 in the inward direction, bringing it into close contact with the inner peripheral surface of main case 2. Furthermore, compression of sealing body 4 brings the inner surfaces of through holes 10 and 11 into close contact with lead terminals 8 and 9. As a result, opening 2b of main case 2 is sealed by sealing body 4, preventing the electrolyte held in capacitor element 3 from leaking out of main case 2.

[0046] At this time, apex 13a of protrusion 13 is positioned further from capacitor element 3 than center 4a in the thickness direction of sealing body 4 (position t / 2 from the bottom end, where t is the thickness). As a result, the outer peripheral surface of sealing body 4 is pressed from below in the figure, and the top surface (the capacitor element 3 side) of sealing body 4 curves convexly upward, with the central portion protruding toward capacitor element 3 more than the outer peripheral portion.

[0047] Furthermore, the open end of main body case 2 is folded back to form folded portion 14 on the outer surface of sealing body 4 (the surface opposite capacitor element 3). Folded portion 14 and protruding portion 13 prevent sealing body 4 from slipping out of main body case 2.

[0048] Figure 5 shows a detailed view of part H in Figure 3. At least a portion of separator 6 that protrudes downward relative to anode foil 5 and cathode foil 7 contacts the upper surface of sealing body 4 (the surface facing capacitor element 3) at multiple points or on an area while aligned with the upper surface. At this time, the central portion of the upper surface of sealing body 4 curves so as to protrude upward, so separator 6 reliably contacts sealing body 4 at multiple points or on an area while aligned with sealing body 4.

[0049] The width of separator 6 in the short direction is preferably 0.15 mm to 2.0 mm larger than the widths of anode foil 5 and cathode foil 7. By making the width 0.15 mm or more, more preferably 0.2 mm or more, separator 6 can bend, and the bottom end of separator 6 can be reliably brought into contact with the top surface of sealing body 4 without applying stress to anode foil 5 and cathode foil 7.

[0050] The electrolyte is continuously supplied to the sealing body 4 via the separator 6. The electrolyte penetrates into the sealing body 4 through the intermolecular gaps inside the sealing body 4 and reaches the outer surface of the sealing body 4 (the surface opposite the capacitor element 3). The outer surface of the sealing body 4 is then covered with a coating 17 (see FIG. 3 ) formed by the sealing body deterioration inhibitor solidifying through oxidation. At this time, the electrolyte is present inside the sealing body 4 on the capacitor element 3 side of the coating 17.

[0051] The molecular weight of the sealant deterioration inhibitor is preferably 3000 or less for good permeability, and more preferably 2000 or less. The molecular weight of the sealant deterioration inhibitor is preferably 200 or more for good retention of the sealant 4, and more preferably 250 or more, and even more preferably 300 or more. By using a sealant deterioration inhibitor in this molecular weight range, permeability into the sealant 4 is improved, and the sealant deterioration inhibitor effect can be maintained for a long period of time.

[0052] Furthermore, it is also possible to adjust the permeability into the sealing member 4 and the durability thereof by using two or more types of sealing member deterioration inhibitors with different molecular weights.

[0053] Furthermore, in order to properly adjust the balance between the amount of sealing body deterioration inhibitor in the electrolyte and the amount of penetration into the sealing body 4, it is preferable that the solubility parameter (SP value) of the sealing body deterioration inhibitor be between the SP value of the lipophilic solvent and the SP value of the sealing body 4. Furthermore, it is preferable that the boiling point of the sealing body deterioration inhibitor be higher than the boiling point of the lipophilic solvent so that the sealing body deterioration inhibitor is retained in the sealing body 4 for a long period of time.

[0054] Furthermore, the sealant deterioration inhibitor is preferably a compound that is more easily oxidized than the components of the sealant 4 in the temperature range of 150°C or less. Compounds other than those generally called antioxidants can also be used as sealant deterioration inhibitors as long as they are more easily oxidized than the components of the sealant 4. Compounds that have an antioxidant effect or compounds that contain a double bond in the molecule are preferably selected as such compounds. Furthermore, it is more preferable for the sealant deterioration inhibitor to have the effect of stabilizing or eliminating generated radicals, as this will enhance the sealant deterioration inhibitory effect.

[0055] As a result, even if oxygen penetrates into the interior of the sealing body 4, the sealing body deterioration inhibitor is oxidized before the components of the sealing body 4, thereby providing an antioxidant effect for the sealing body 4. At this time, even if oxidation or thermal decomposition of the sealing body 4 occurs, the sealing body deterioration inhibitor penetrates into the gaps between the molecules of the sealing body 4, making it difficult for the sealing body 4 to shrink. This makes it possible to prevent cracks from occurring in the sealing body 4.

[0056] During the manufacturing process of capacitor 1, the oxide films formed on anode foil 5 and cathode foil 7 are repaired. The repair is performed, for example, by applying a voltage of 35 V between lead terminals 8 and 9 for 30 minutes in a high-temperature environment of 125°C. During the oxide film repair work at high temperatures, the sealant deterioration inhibitor that reaches the outer surface of sealant 4 oxidizes and solidifies, forming coating 17.

[0057] That is, during the oxide film repair work, the outer surface of the sealing body 4 is exposed to a large amount of air outside the main case 2, and is placed in a high-temperature environment. As a result, the outer surface of the sealing body 4 is covered with a coating 17 formed by oxidizing and solidifying the sealing body degradation inhibitor precursor, making the entire sealing body 4 less likely to come into contact with oxygen outside the main case 2. This prevents degradation of the sealing body 4 due to oxidation and prevents the electrolyte from evaporating through cracks in the sealing body 4, etc. Therefore, the characteristics of the capacitor 1 can be stably maintained over the long term, even in high-temperature environments.

[0058] In addition, because the liquid electrolyte has penetrated into sealing body 4 on the capacitor element 3 side of covering portion 17, even if a portion of covering portion 17 deteriorates, the electrolyte is supplied to that portion. This causes the sealing body deterioration inhibitor to solidify, repairing covering portion 17. Therefore, the characteristics of capacitor 1 can be stably maintained for a longer period of time.

[0059] The formation of coating 17 may be performed during the work of repairing the oxide films on anode foil 5 and cathode foil 7, or may be performed in a separate process from the work of repairing the oxide films. In a high-temperature environment, the supply of electrolyte to sealing body 4 is accelerated, and the oxidation reaction of the sealing body deterioration inhibitor is accelerated. For this reason, the temperature during the formation of coating 17 is preferably 105°C or higher, and more preferably 125°C or higher. Note that if the sealing body deterioration inhibitor is a saturated fatty acid or an ester compound of a saturated fatty acid, the solidification reaction takes time, so it is preferable to form coating 17 at 160°C or higher.

[0060] To sufficiently promote the formation of the coating portion 17, the time for leaving it in a high temperature environment is preferably 30 minutes or more, and more preferably 1 hour or more, but if the temperature is 160° C. or higher, it may be shorter.

[0061] The concentration of the sealant deterioration inhibitor in the electrolyte is preferably 1% to 90% by weight. If the content of the sealant deterioration inhibitor in the electrolyte is less than 1% by weight, the oxidation inhibition effect of the sealant 4 cannot be maintained for a long period of time. Furthermore, if the content of the sealant deterioration inhibitor in the electrolyte exceeds 90% by weight, the viscosity of the electrolyte increases. This increases the time required for the electrolyte to be retained in the capacitor element 3 and the time required for the electrolyte to be supplied from the capacitor element 3 to the sealant 4, thereby increasing the number of steps required to manufacture the capacitor 1. It is even more preferable to set the concentration of the sealant deterioration inhibitor in the electrolyte to 3% to 80% by weight, as this provides a stronger oxidation inhibition effect and reduces the number of steps required.

[0062] Next, a durability test was conducted on Capacitor 1 in a high-temperature environment at 150°C, and the defect rate over time was investigated. The results are shown in Table 1 and Figure 6. In Figure 6, the vertical axis represents the defect rate (unit: %), and the horizontal axis represents time (unit: hours).

[0063] [Table 1]

[0064] The electrolyte of the capacitor 1 of this embodiment that underwent the durability test uses gamma-butyrolactone as a lipophilic solvent and α-tocopherol as a sealant deterioration inhibitor. The concentration of the sealant deterioration inhibitor in the electrolyte is 10 wt %. The sealant 4 of the capacitor 1 is made of butyl rubber and contains an antioxidant.

[0065] The capacitor 1 of Comparative Example 1 differs from the present embodiment in that the separator 6 and the sealer 4 are not in contact with each other. The capacitor 1 of Comparative Example 2 differs from the present embodiment in that the sealer deterioration inhibitor for the electrolyte is omitted. The capacitor 1 of Comparative Example 3 differs from the present embodiment in that the sealer deterioration inhibitor for the electrolyte is omitted, and the separator 6 and the sealer 4 are not in contact with each other.

[0066] The durability test was carried out on 100 test pieces for each test. Test pieces whose capacitance was lower than 20% of the initial value and test pieces in which cracks were visible on the outer surface of the sealing body 4 were deemed defective, and the defect rate was calculated.

[0067] As a result of the durability test, since the electrolyte in Comparative Examples 2 and 3 did not contain a sealant deterioration inhibitor, after 3000 hours, cracks in the sealant 4 caused the electrolyte to evaporate, resulting in a rapid decrease in capacitance. After 5000 hours, the failure rate for Comparative Examples 2 and 3 reached 100%.

[0068] In Comparative Example 1, the sealant deterioration inhibitor contained in the electrolyte is supplied to the sealant 4, so good characteristics are maintained for a longer period of time than in Comparative Examples 2 and 3. However, because the separator 6 is separated from the sealant 4, the sealant deterioration inhibitor is not stably supplied to the sealant 4, which can result in insufficient formation of the coating 17 or the need for time-consuming repair of the deteriorated coating 17. As a result, defects occurred at 5,000 hours, and the defect rate reached 80% at 7,000 hours.

[0069] In contrast, in the capacitor 1 of this embodiment, the separator 6 is in contact with the sealing body 4, so the sealing body deterioration inhibitor is constantly replenished in the sealing body 4. This allows the coating portion 17 to be stably formed on the outer surface of the sealing body 4, making it possible to suppress the occurrence of cracks even in high-temperature environments. As a result, no defects occurred even after 8,000 hours had passed, and stable characteristics were demonstrated over the long term.

[0070] That is, the outer surface of the sealer 4 is covered with the coating 17 where the sealer deterioration inhibitor has solidified, and the sealer deterioration inhibitor contained in the electrolyte is supplied to the sealer 4 via the separator 6 that is in contact with the sealer 4. This significantly improves the stability of the capacitor 1.

[0071] Similar test results were obtained in durability tests when the sealant deterioration inhibitor was vitamin D3 and when the sealant deterioration inhibitor was oleic acid tetraglycerin triester.

[0072] In this embodiment, capacitor element 3 holds an electrolyte solution in which a sealant degradation inhibitor is dissolved in a lipophilic solvent, and separator 6 is placed along the surface of sealant 4 facing the capacitor element 3, making contact with it at multiple points or across the surface. The electrolyte solution supplied through separator 6 permeates sealant 4, and the outer surface of sealant 4 is covered with coating 17 that has solidified due to oxidation of the sealant degradation inhibitor. This makes it possible to prevent degradation of sealant 4 due to oxidation over the long term. This prevents the electrolyte held in capacitor element 3 from leaking out, allowing the characteristics of capacitor 1 to be stably maintained over the long term.

[0073] Furthermore, because the electrolyte has penetrated into sealing body 4 on the capacitor element 3 side of covering portion 17, even if a portion of covering portion 17 deteriorates, the electrolyte is supplied to that portion. As a result, the sealing body deterioration inhibitor solidifies, repairing covering portion 17 and allowing the characteristics of capacitor 1 to be stably maintained for a longer period of time.

[0074] Furthermore, if the sealant deterioration inhibitor is a fat-soluble vitamin, it is easy to realize a sealant deterioration inhibitor that solidifies through oxidation to form coating portion 17.

[0075] Furthermore, if the concentration of the sealing body deterioration inhibitor in the electrolyte is 1% by weight to 90% by weight, an increase in the number of steps can be suppressed and deterioration of the sealing body 4 can be suppressed for a long period of time.

[0076] Furthermore, if the concentration of the sealing body deterioration inhibitor in the electrolyte is 3% by weight to 80% by weight, an increase in the number of steps can be further suppressed, and deterioration of the sealing body 4 can be suppressed for a long period of time.

[0077] Furthermore, when the lipophilic solvent of the electrolyte is gamma-butyrolactone, an electrolyte in which the sealing body deterioration inhibitor is dissolved can be easily realized.

[0078] Furthermore, if the lipophilic solvent of the electrolyte contains at least one of sulfolane, ethylene glycol, and diethylene glycol, and a nonionic surfactant, it is possible to easily realize an electrolyte in which the sealing body deterioration inhibitor is dissolved.

[0079] Furthermore, if the lipophilic solvent of the electrolyte is polyethylene glycol with a lipophilic group bonded thereto, or a polyethylene glycol-polypropylene glycol copolymer, it is possible to easily realize an electrolyte in which the sealing body deterioration inhibitor is dissolved.

[0080] Furthermore, since separator 6 protrudes further toward sealing member 4 than anode foil 5 and cathode foil 7, separator 6 can reliably contact sealing member 4 at multiple points or surfaces while following sealing member 4.

[0081] Furthermore, since the central portion of the surface of sealing member 4 facing capacitor element 3 protrudes more than the outer periphery, separator 6 can be brought into contact with sealing member 4 more reliably.

[0082] Furthermore, apex 13a of protrusion 13 protruding from the inner surface of main body case 2 is located farther from capacitor element 3 than center 4a in the thickness direction of sealing body 4. This makes it easy to form sealing body 4 in which the central portion of the surface facing capacitor element 3 protrudes more than the outer periphery.

[0083] Note that because the upper surface (the surface facing the capacitor element 3) of the sealing body 4 protrudes, the lower surface (the surface opposite the capacitor element 3) is recessed. As a result, the lower surface of the sealing body 4 is recessed relative to the flat surface, increasing the surface area and increasing the contact area between the sealing body 4 and the covering portion 17 that covers the lower surface. As a result, the integration strength between the sealing body 4 and the covering portion 17 can be increased. This reliably prevents the electrolyte held in the capacitor element 3 by the covering portion 17 from leaking out, allowing the characteristics of the capacitor 1 to be maintained stably for a longer period of time.

[0084] The surface area of ​​the underside of sealing body 4 can also be increased by making the center of the underside of sealing body 4 protrude outward. In this case, the contact area between covering portion 17 and sealing body 4 is also increased, and the same effect can be achieved.

[0085] Second Embodiment Next, a second embodiment will be described. In this embodiment, the capacitor element 3 holds a solid electrolyte (not shown) and a predetermined functional liquid instead of an electrolytic solution. The other parts are the same as those in the first embodiment.

[0086] The solid electrolyte is made of a conductive polymer or the like. The conductive polymer can reduce the ESR of the capacitor 1. Examples of conductive polymers that can be used include polythiophene, polypyrrole, and derivatives of these. Polyethylenedioxythiophene is more preferable because of its high electrical conductivity.

[0087] By immersing capacitor element 3 in a dispersion of conductive polymer for a predetermined time and then drying it, a solid electrolyte made of conductive polymer can be held between anode foil 5 and cathode foil 7.

[0088] A functional liquid having the function of increasing the withstand voltage of the capacitor 1 is held between the anode foil 5 and the cathode foil 7. The functional liquid is composed of a solution in which a sealant deterioration inhibitor is dissolved in a lipophilic solvent. Gamma-butyrolactone can be used as the lipophilic solvent. A lipophilic solvent containing at least one of sulfolane, ethylene glycol, and diethylene glycol and a nonionic surfactant can also be used. Furthermore, a lipophilic solvent in which a lipophilic group is bonded to polyethylene glycol or a polyethylene glycol-polypropylene glycol copolymer can also be used. These lipophilic solvents can increase the withstand voltage and dissolve the sealant deterioration inhibitor.

[0089] As described above, the sealant deterioration inhibitor may be a terpenoid such as a fat-soluble vitamin, an unsaturated fatty acid, a polyglycerol ester containing an unsaturated fatty acid group in the molecule, a saturated fatty acid, or a derivative thereof. An amphipathic compound may be added to facilitate dissolution of the sealant deterioration inhibitor in a lipophilic solvent.

[0090] Fat-soluble vitamins include vitamin A (retinol, α-carotene, β-carotene, β-cryptoxanthin, astaxanthin), vitamin D (vitamin D2, vitamin D3), vitamin E (tocopherol, tocotrienol), vitamin K (vitamin K1, vitamin K2, menaquinone 7), etc.

[0091] Furthermore, the solid electrolyte is swollen by the functional liquid, which increases the adhesion of the solid electrolyte to the anode foil 5 and the cathode foil 7 that sandwich the solid electrolyte. This reduces the ESR of the capacitor 1. Therefore, the functional liquid also has the function of reducing the ESR of the capacitor 1.

[0092] As in the first embodiment, the separator 6 of the capacitor element 3 is placed along the top surface of the sealing body 4 (the surface facing the capacitor element 3) and makes contact with it at multiple points or across the surface. The functional liquid is continuously supplied to the sealing body 4 via the separator 6. The functional liquid permeates into the interior of the sealing body 4 through intermolecular gaps inside the sealing body 4 and reaches the outer surface of the sealing body 4 (the surface opposite the capacitor element 3). The outer surface of the sealing body 4 is then covered with a coating 17 (see FIG. 3 ) formed by the sealing body degradation inhibitor solidified by oxidation.

[0093] This prevents the entire sealing body 4 from coming into contact with oxygen outside the main case 2, thereby preventing deterioration of the sealing body 4 due to oxidation. This prevents the functional liquid from evaporating through cracks in the sealing body 4. This allows the characteristics of the capacitor 1 to be stably maintained over the long term, even in high-temperature environments.

[0094] In this embodiment, capacitor element 3 holds a functional liquid in which a sealant degradation inhibitor is dissolved in a lipophilic solvent, and separator 6 contacts sealant 4. The functional liquid supplied through separator 6 permeates sealant 4, and the outer surface of sealant 4 is covered with coating 17 that solidifies due to oxidation of the sealant degradation inhibitor. This makes it possible to prevent degradation of sealant 4 due to oxidation over the long term. This prevents the functional liquid held in capacitor element 3 from leaking out, and allows the characteristics of capacitor 1 to be stably maintained over the long term.

[0095] Furthermore, since the functional liquid penetrates into sealing body 4 closer to capacitor element 3 than covering portion 17, even if a portion of covering portion 17 deteriorates, the functional liquid is supplied to that portion. As a result, the sealing body deterioration inhibitor solidifies, repairing covering portion 17 and allowing the characteristics of capacitor 1 to be stably maintained for a longer period of time.

[0096] In this embodiment, the functional liquid has the function of increasing the withstand voltage of the capacitor 1, but it may also have the function of improving other characteristics of the capacitor 1.

[0097] Alternatively, instead of the functional liquid, an electrolytic solution similar to that in the first embodiment may be held between the anode foil 5 and the cathode foil 7. Holding a solid electrolyte and an electrolytic solution between the anode foil 5 and the cathode foil 7 enhances the oxide film repair function and further reduces the ESR of the capacitor 1. [Industrial Applicability]

[0098] The present invention can be used in capacitors such as electrolytic capacitors, and in automobiles, electronic devices, and the like in which capacitors are mounted in circuits. [Explanation of symbols]

[0099] 1 capacitor 2 Main unit case 2b opening 3 Capacitor elements 4 Sealing body 5 Anode foil 6 Separator 7 Cathode foil 8, 9 Lead terminal 10, 11 Through holes 12 Tape 13 Protrusion 13a Vertex 14 Folded section 15 Seat board 16 through holes 17 Covering part

Claims

1. a capacitor element in which a predetermined solution is held between an anode foil and a cathode foil wound with a separator interposed therebetween; a main body case that houses the capacitor element; a sealing body that seals the main body case; In a capacitor comprising: the width of the separator in the short side direction is greater than the widths of the anode foil and the cathode foil; a part of the separator is in contact with the surface of the sealing body on the capacitor element side at multiple points or across a surface while being aligned along the surface, The solution contains a sealer deterioration inhibitor that solidifies by oxidation dissolved in a lipophilic solvent, the sealing body is supplied with the solution through the separator, and the solution permeates the sealing body; an outer surface of the sealing body is covered with a coating portion of the solidified sealing body deterioration inhibitor, and the solution is present inside the sealing body on the capacitor element side of the coating portion; the separator protrudes toward the sealing body further than the anode foil and the cathode foil, the main body case has a protrusion that protrudes from the inner surface and presses against the outer circumferential surface of the sealing body, a surface of the sealing body facing the capacitor element is convexly curved, and a distance between the ends of the anode foil and the cathode foil facing the sealing body in the lateral direction and a center of the surface of the sealing body facing the capacitor element is narrower than a width from the ends of the anode foil and the cathode foil facing the sealing body in the lateral direction to the end of the separator facing the sealing body in the lateral direction, A capacitor characterized in that the end of the separator on the sealing body side in the short direction is in contact with at least the central portion of the sealing body's surface on the capacitor element side while bending along the curvature of the sealing body's surface on the capacitor element side.

2. 2. The capacitor according to claim 1, wherein the sealant deterioration inhibitor is a terpenoid, an unsaturated fatty acid, a saturated fatty acid, or a derivative thereof.

3. 2. The capacitor according to claim 1, wherein the sealant deterioration inhibitor is a fat-soluble vitamin.

4. 4. The capacitor according to claim 1, wherein the solution is an electrolytic solution obtained by dissolving the sealing body deterioration inhibitor and an electrolyte in the lipophilic solvent.

5. 5. The capacitor according to claim 4, wherein the concentration of the sealing body deterioration inhibitor in the electrolyte is 1% by weight to 90% by weight.

6. 5. The capacitor according to claim 4, wherein the concentration of the sealing body deterioration inhibitor in the electrolyte is 3% by weight to 80% by weight.

7. 7. The capacitor according to claim 4, wherein the lipophilic solvent is gamma-butyrolactone.

8. 7. The capacitor according to claim 1, wherein the lipophilic solvent contains at least one of sulfolane, ethylene glycol, and diethylene glycol, and a nonionic surfactant.

9. 7. The capacitor according to claim 1, wherein the lipophilic solvent is polyethylene glycol to which a lipophilic group is bonded, or a polyethylene glycol-polypropylene glycol copolymer.

10. A capacitor as described in claim 1, characterized in that the apex of the protrusion is positioned on a side farther from the capacitor element than the center of the thickness direction of the sealing body.

Images