Capacitor and method for producing same

Abstract

An open end of a body case 1 is bent inward to form a folded part 9 that faces a surface of a sealing body 4 which is on the outer side of the body case 1, with a prescribed space therebetween. A resin pocket part 10 that is formed between the folded part 9 and the outer peripheral part of the sealing body 4 is formed on the inner surface side of this folded part 9 and on the outer peripheral part side of the body case 1. A coating layer 11 made of a resin is provided to the surface of the sealing body 4 which is on the outer side of the body case 1. This coating layer 11 has a circular shape in plan view, has a smaller thickness at the central part thereof, and has a larger thickness at the outer peripheral part thereof. As illustrated in fig. 1, a portion of the coating layer 11, which has the above shape, has flowed into the resin pocket part 10 of the folded part 9 such that the coating layer 11 forms a support column part 12 between the inner surface of this folded part 9 and the surface of the sealing body 4 which is on the outer surface side of the body case 1.

Description

Capacitor and Method for Manufacturing the Same

[0001] The present invention relates to a capacitor and a method for manufacturing the same.

[0002] The capacitor includes a bottomed cylindrical main body case provided with an opening at one end side, a capacitor element housed in the main body case, and a sealing body provided at the opening of the main body case.

[0003] The capacitor element has a lead terminal drawn out of the main body case through the sealing body. In the main body case, at a portion corresponding to the outer peripheral portion of the sealing body, a constriction portion for pushing the outer peripheral portion of the sealing body inward in the inner circumferential direction is provided, and the open end of the main body case is configured to have a folded-back portion folded inward.

[0004] The sealing body is for sealing the main body case and protecting the capacitor element from the external environment, but deterioration due to oxidation is a problem.

[0005] That is, since the sealing body needs elasticity to adhere to the main body case and the lead terminal for sealing, it is formed of a rubber material. However, the problem is that the rubber material gradually deteriorates due to oxidation.

[0006] Therefore, it has been proposed to cover the surface of the sealing body outside the main body case with a coating layer (as a prior art document similar to this, Patent Document 1 below).

[0007] International Publication No. 2023 / 163134

[0008] In the above prior art document, since the surface of the sealing body outside the main body case is covered with a coating layer, oxidation deterioration of the sealing body can be suppressed.

[0009] However, in the above prior art document, the tip of the folded-back portion of the main body case is configured to abut on the coating layer.

[0010] Due to temperature changes in the use environment, the inside of the main body case expands and contracts. When expanding, the sealing body is pushed to the outside of the main body case, and at this time, the coating layer is strongly pressed against the tip of the folded-back portion.

[0011] When such expansion and contraction are repeated, the coating layer will eventually be damaged by the strong contact of the folded-over tip, resulting in a decrease in the coating layer's effect of suppressing oxidative degradation of the sealing body, and consequently, a decrease in the capacitor's performance.

[0012] Therefore, the present invention aims to suppress the degradation of capacitor performance by preventing damage to the coating layer.

[0013] To achieve this objective, the capacitor of the present invention comprises a bottomed cylindrical main case with an opening at one end, a capacitor element housed within the main case, and a sealing body fitted into the opening of the main case. The capacitor element has lead terminals that penetrate the sealing body and are drawn out of the main case. The main case is provided with a constricting portion in the portion corresponding to the outer periphery of the sealing body, which pushes the outer periphery of the sealing body inward. The end of the opening of the main case is bent inward, forming a folded portion that faces the outer surface of the main case of the sealing body at a predetermined distance. On the inner side of this folded portion, a resin pocket portion is formed between the outer periphery of the sealing body and the outer surface of the sealing body. The outer surface of the main case of the sealing body is provided with a resin coating layer. This coating layer is thin in the center and thicker on the outer periphery. A portion of the coating layer flows into the resin pocket portion. A support column is formed by the covering layer between the inner surface of the folded portion and the outer surface of the sealing body. The tip of the folded portion and the covering layer are in a non-contact state.

[0014] In the capacitor with the above configuration, it is preferable that the sealing body is impregnated with a sealing body degradation inhibitor.

[0015] The capacitor in the above configuration is preferably configured such that a portion of the capacitor element impregnated with the sealing body degradation inhibitor comes into contact with the sealing body.

[0016] Furthermore, the present invention relates to a method for manufacturing a capacitor, which is a method for manufacturing any one of the above-described components, wherein the capacitor element and the sealing body are attached to the main body case, and the constricted portion and the folded portion are formed thereon, the opening is positioned upward, and a fluid resin is supplied from this opening to the outer surface of the sealing body on the main body case, and then the main body case is rotated to generate centrifugal force, and a portion of the resin is moved in the direction of the outer circumference of the main body case by the centrifugal force.

[0017] As described above, the capacitor of the present invention has a resin coating layer on the outer surface of the main case of the sealing body, which suppresses oxidation and deterioration of the sealing body when it comes into contact with oxygen.

[0018] Furthermore, by making the center of the coating layer thinner and ensuring non-contact with the tip of the folded portion, even if the inside of the main case expands and contracts due to temperature changes in the operating environment, the coating portion will not be strongly pressed against the tip of the folded portion. As a result, the coating layer will not be damaged at the tip of the folded portion, and the oxidative degradation suppression effect of the coating layer on the sealing body will not decrease, thus suppressing a decrease in the performance of the capacitor.

[0019] Furthermore, a portion of the coating layer flows into the resin pocket portion of the folded-over section, and a support column is formed by the coating layer between the inner surface of this folded-over section and the outer surface of the main case of the sealing body. As a result, even if the tip of the folded-over section is not in contact with the sealing body, it is possible to prevent the sealing body from slipping out to the opening side of the main case.

[0020] Figure 1 is a cross-sectional view of a capacitor according to one embodiment of the present invention.

[0021] Embodiments of the present invention will be described below with reference to the drawings.

[0022] (Embodiment 1) In Figure 1, reference numeral 1 denotes a bottomed cylindrical main body case made of aluminum, with an opening 2 provided at one end.

[0023] The main case 1 houses the capacitor element 3.

[0024] The capacitor element 3, as in the prior art described above, is wound with an anode foil (not shown) and a cathode foil (not shown) facing each other via a separator (not shown), and is impregnated with an electrolyte (not shown).

[0025] In the diagram, reference numeral 4 denotes a disc-shaped sealing body attached to the opening 2 of the main case 1, and as an example, one made of rubber is used.

[0026] The capacitor element 3 has lead terminals 5 that penetrate the sealing body 4 and are drawn out to the outside of the main case 1.

[0027] A base plate 6 is provided on the outside of the main case 1, and the lead terminal 5 penetrates this base plate 6, is bent to the left and right, and forms connection electrodes 7 to the circuit board.

[0028] In the main body case 1, a constricting portion 8 is provided in the portion corresponding to the outer circumferential portion of the sealing body 4, which pushes the outer circumferential portion of the sealing body 4 in the inward direction.

[0029] The end of the opening 2 of the main body case 1 (the tip 13, which will be described later) is bent inward toward the sealing body 4, forming a folded portion 9 that faces the outer surface of the main body case 1 of the sealing body 4 at a predetermined distance.

[0030] On the inner surface of this folded portion 9, a resin pocket portion 10 is formed between the outer periphery of the main case 1 and the outer periphery of the sealing body 4.

[0031] This resin pocket portion 10 is donut-shaped (ring-shaped).

[0032] A resin coating layer 11 is provided on the outer surface of the main body case 1 of the sealing body 4.

[0033] This coating layer 11 is circular in shape when viewed from above, but its thickness is thinner in the center and thicker around the outer edge.

[0034] As shown in Figure 1, a portion of the covering layer 11 with this shape flows into the resin pocket portion 10 of the folded portion 9, and a support portion 12 made of the covering layer 11 is formed between the inner surface of the folded portion 9 and the outer surface of the main body case 1 of the sealing body 4.

[0035] The support column 12 is donut-shaped (ring-shaped), and this portion is the thicker part of the covering layer 11.

[0036] In this state, the tip 13 of the folded portion 9 (the end of the opening 2) and the coating layer 11 are not in contact.

[0037] In this embodiment, the tip 13 of the folded portion 9 is bent more shallowly than in the conventional design, and the thickness of the coating layer 11 facing this tip 13 is reduced, so that the tip 13 of the folded portion 9 and the coating layer 11 facing this tip 13 are in a non-contact state.

[0038] The electrolyte impregnated into the capacitor element 3 consists of a solution in which an electrolyte is dissolved in a lipophilic solvent. Alternatively, the capacitor element 3 may hold a solid electrolyte (not shown) or a functional liquid without an electrolyte in a lipophilic solvent instead of the electrolyte.

[0039] Gamma-butyrolactone can be used as a lipophilic solvent. Alternatively, a solution containing a nonionic surfactant in addition to sulfolane, ethylene glycol, and diethylene glycol can be used as a lipophilic solvent.

[0040] As nonionic surfactants, polyethylene glycol or polyglycerin to which a lipophilic group is bonded, polyethylene glycol-polypropylene glycol copolymers, and the like can be used.

[0041] Electrolytes dissociate into ions upon dissolution in a solvent, exhibiting electrical conductivity. Organic amine salts of boric acid compounds or carboxylic acid compounds are commonly used.

[0042] Furthermore, the electrolyte contains a sealant degradation inhibitor dissolved in a lipophilic solvent.

[0043] The sealing body deterioration inhibitor reacts with oxygen and suppresses the oxidation of the sealing body 4 as will be described in detail later. The sealing body deterioration inhibitor is soluble in a lipophilic solvent and is a compound that solidifies by a series of reactions based on an oxidation reaction in the presence of oxygen. As the sealing body deterioration inhibitor, 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 can be used. In order to facilitate the dissolution of these sealing body deterioration inhibitors in the lipophilic solvent, an amphiphilic compound may be added.

[0044] Examples of the fat-soluble vitamin include vitamin A (retinol, α-carotene, β-carotene, β-cryptoxanthin), vitamin D (vitamin D2, vitamin D3), vitamin E (tocopherol, tocotrienol), vitamin K (vitamin K1, vitamin K2, menaquinone 7), and the like. The above fat-soluble vitamins except α-tocopherol have double bonds other than aromatic rings in the molecule and are likely to solidify by oxidation. Also, α-tocopherol does not have a double bond other than an aromatic ring in the molecule, but solidifies by oxidation at high temperatures.

[0045] When the concentration of the sealing body deterioration inhibitor in the electrolytic solution is less than 1% by weight, the oxidation suppression effect on the sealing body 4 cannot be continuously maintained for a long time.

[0046] Also, when the concentration of the sealing body deterioration inhibitor in the electrolytic solution exceeds 30% by weight, the viscosity of the electrolytic solution becomes high. For this reason, the time for holding the electrolytic solution in the capacitor element 10 becomes long, and the man-hours for manufacturing the capacitor increase. Therefore, it is desirable to set the concentration of the sealing body deterioration inhibitor in the electrolytic solution to 1% to 30% by weight.

[0047] Moreover, when the concentration of the sealing body deterioration inhibitor in the electrolytic solution is set to 3% to 20% by weight, it is more desirable because the oxidation suppression effect can be exhibited and the man-hours can be reduced.

[0048] In the present embodiment, a part of the end portion of the separator constituting the capacitor element 3 on the side of the sealing body 4 touches the sealing body 4, so that the sealing body deterioration inhibitor is supplied to the sealing body 4 to suppress the oxidative deterioration of the sealing body 4.

[0049] While the sealing body 4 may be directly impregnated with a sealing body degradation inhibitor, to ensure long-term oxidative degradation of the sealing body 4, it is preferable to dissolve the sealing body degradation inhibitor in an electrolyte solution and continuously supply it to the sealing body 4, as in this embodiment.

[0050] In this case, the electrolyte is continuously supplied to the sealing body 4 via the separator. The electrolyte penetrates into the interior of the sealing body 4 through the intermolecular gaps inside the sealing body 4 and reaches the outer surface of the sealing body 4 (the side opposite the capacitor element 3). The outer surface of the sealing body 4 is then covered by a coating portion in which the sealing body degradation inhibitor has solidified due to oxidation. At this time, the sealing body degradation inhibitor is present inside the sealing body 4 on the side of the coating portion that is closer to the capacitor element 3.

[0051] In this embodiment, the sealing body deterioration inhibitor impregnated into the capacitor element 3 is supplied to the sealing body 4. Furthermore, as described above, a resin coating layer 11 is provided on the outer surface of the main body case 1 of the sealing body 4.

[0052] The reason for this is that it takes a certain amount of time for the sealing body degradation inhibitor impregnated into the capacitor element 3 to penetrate the entire sealing body 4, and during this time, the coating layer 11 prevents oxygen from coming into contact with the sealing body 4.

[0053] Furthermore, as mentioned above, the thickness of the central part of the coating layer 11 is reduced, so even if cracks appear in this part due to long-term use, the cracked area can be covered with the sealing body deterioration inhibitor to prevent oxygen from coming into contact with the sealing body 4.

[0054] I will now explain why the thickness of the central part of the coating layer 11 is made thinner.

[0055] The capacitor expands and contracts inside the main case 1 due to temperature changes in the operating environment. When it expands, the sealing body 4 deforms so as to be pushed outwards from the main case 1, thereby mitigating the pressure rise inside the main case 1.

[0056] In other words, it is important that the sealing body 4 deforms outward from the main case 1 when the temperature rises, so the thickness of the central part of the coating layer 11 is made thinner so as not to hinder this deformation.

[0057] The coating layer 11 is formed of epoxy resin, and the thin-walled portion can deform outwards from the main case 1 together with the sealing body 4. In other words, it does not hinder the deformation of the sealing body 4 outwards from the main case 1 when the temperature rises.

[0058] Furthermore, in this embodiment, as described above, the tip 13 of the folded portion 9 is bent more shallowly than in the conventional design, and the thickness of the coating layer 11 facing this tip 13 is reduced, so that the tip 13 of the folded portion 9 and the coating layer 11 are in a non-contact state.

[0059] Therefore, even if the thin portion of the coating layer 11 deforms outward from the main case 1 together with the sealing body 4, the tip 13 of the folded portion 9 will not come into contact with the thin portion, and as a result, the thin portion of the coating layer 11 will not be damaged by the tip 13 of the folded portion 9.

[0060] Furthermore, since the thin-walled portion of the coating layer 11 is thin, it is conceivable that cracks may form after multiple subsequent deformations. Therefore, in this embodiment, as described above, the sealing body deterioration inhibitor impregnated into the capacitor element 3 is supplied to the sealing body 4.

[0061] On the other hand, unlike conventional designs, if the tip 13 of the folded portion 9, the covering layer 11, and the sealing body 4 are not in contact, there is a risk that the sealing body 4 may fly out of the main case 1 when the pressure inside the main case 1 increases.

[0062] Therefore, in this embodiment, as described above, a portion of the coating layer 11 is allowed to flow into the resin pocket portion 10 of the folded portion 9, as shown in Figure 1, and a support portion 12 made of the coating layer 11 is formed between the inner surface of the folded portion 9 and the outer surface of the main body case 1 of the sealing body 4.

[0063] Therefore, the outer circumference of the sealing body 4 comes into contact with the inner surface of the folded portion 9 via the support portion 12, and as a result, the sealing body 4 will not fly out of the main case 1 when the pressure inside the main case 1 rises.

[0064] In this embodiment, the method for manufacturing the capacitor involves, with the capacitor element 3 and sealing body 4 mounted on the opening 2 of the main body case 1, which has a constricted portion 8 and a folded portion 9 formed thereon, a fluid resin (with appropriate viscosity) is supplied from this opening 2 to the outer surface of the sealing body 4 on the main body case 1. Next, the main body case 1 is rotated, and a portion of the resin is moved outward by centrifugal force, thereby causing a portion of the coating layer 11 to flow into the resin pocket portion 10 of the folded portion 9, as shown in Figure 1. A support portion 12 made of the coating layer 11 is formed between the inner surface of the folded portion 9 and the outer surface of the sealing body 4 on the main body case 1. At the same time, the central part of the coating layer 11 is made thin.

[0065] This invention can be used in electrolytic capacitors and in automobiles, electronic devices, and the like, where electrolytic capacitors are mounted in control circuits.

[0066] 1. Main case 2. Opening 3. Capacitor element 4. Sealing body 5. Lead terminals 6. Base plate 7. Connecting electrodes 8. Constricted section 9. Folded section 10. Resin pocket section 11. Covering layer 12. Support column section 13. Tip

Claims

1. The device comprises a bottomed cylindrical main case with an opening at one end, a capacitor element housed within the main case, and a sealing body fitted into the opening of the main case, wherein the capacitor element has lead terminals that penetrate the sealing body and are pulled out of the main case, the main case has a constricting portion that pushes the outer periphery of the sealing body inward, the end of the opening of the main case is bent inward, forming a folded portion that faces the outer surface of the main case of the sealing body at a predetermined distance, the inner surface of this folded portion and the outer periphery of the main case, a resin pocket portion formed between the sealing body and the outer periphery, and the outer surface of the main case of the sealing body is provided with a resin coating layer, which is thin in the center and thick at the outer periphery. A portion of the coating layer flows into the resin pocket, and a support column is formed by the coating layer between the inner surface of the folded portion and the outer surface of the main body case of the sealing body, and the tip of the folded portion and the coating layer are in a non-contact state in the capacitor.

2. The capacitor according to claim 1, wherein the sealing body is impregnated with a sealing body deterioration inhibitor.

3. The capacitor according to claim 2, wherein a portion of the capacitor element impregnated with the sealing body deterioration inhibitor is in contact with the sealing body.

4. A method for manufacturing a capacitor according to any one of claims 1 to 3, comprising: supplying a fluid resin from the opening to the outer surface of the sealing body of the main body case with the opening facing upwards, with the capacitor element and the sealing body mounted on the main body case having the constricted portion and the folded portion formed thereon; and then rotating the main body case to generate centrifugal force, thereby moving a portion of the resin in the direction of the outer circumference of the main body case.

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