JP7292003B2 - Electrolytic capacitor and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolytic capacitor in which an anode foil and a cathode foil are wound with a separator interposed therebetween and impregnated with an electrolytic solution , and a manufacturing method thereof .

Electrolytic capacitors consist of non-solid electrolytic capacitors in which the electrolyte is a liquid, hybrid electrolytic capacitors with liquid and solid electrolytes, and both electrodes. includes bipolar electrolytic capacitors with dielectric films. In this capacitor element, an anode foil formed by forming a dielectric film on a valve metal foil such as aluminum is opposed to a cathode foil made of the same or other metal, and a separator is interposed between the anode foil and the cathode foil. Let it be composed. The capacitor element is impregnated with an electrolytic solution.

The electrolytic solution uses ethylene glycol or γ-butyrolactone as a solvent and contains carboxylic acids such as 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid and azelaic acid or salts thereof as solutes. This electrolytic solution comes into direct contact with the dielectric film and acts as a true cathode, and also has the effect of repairing the dielectric film. However, the electrolytic solution and the hydrogen gas generated during repairing escape from the electrolytic capacitor over time, causing vaporization and evaporation. As a result, the capacitance of the electrolytic capacitor decreases over time toward dry-up, and the tangent (tan δ) of the loss angle increases over time, finally reaching the end of its life.

Therefore, the capacitor element is housed in an exterior case with a bottom, and the opening of the exterior case is sealed with a sealant to seal the electrolytic solution impregnated in the capacitor element, suppress evaporation and evaporation of the electrolytic solution, and extend the life of the capacitor. We are trying to However, the hydrogen gas generated by repairing the dielectric oxide film is also confined within the exterior case.

JP-A-08-250381

Elastomers such as butyl rubber and ethylene propylene diene rubber (EPDM) are used for the sealing member. The gas permeability of the sealing body varies depending on the type of elastomer. If butyl rubber or the like having a low gas permeability is used, the electrolytic solution vaporized due to the heat generation of the electrolytic capacitor or the like and gas such as hydrogen gas generated by repairing the capacitor will increase the internal pressure of the exterior case. Electrolytic capacitors are equipped with pressure valves that open when the internal pressure reaches a specified level. Scatter it all over.

On the other hand, if ethylene propylene diene rubber or the like, which has a higher gas permeability than butyl rubber, is used as the elastomer, the pressure valve will be difficult to open, but the electrolytic solution will gradually evaporate outside the electrolytic capacitor, and the gas permeability will increase. Compared with the case of using a low elastomer, the decrease in capacitance over time and the increase in tan δ over time become more pronounced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrolytic capacitor having a longer life while suppressing performance deterioration and a method for manufacturing the same, in order to solve the above-described problems of the prior art.

To achieve the above object, the present invention provides an electrolytic capacitor comprising: a capacitor element formed by winding strip-shaped anode foil and cathode foil with a separator interposed therebetween and impregnated with an electrolytic solution; and an exterior housing the capacitor element. A case and a sealing member that seals an opening of the exterior case that accommodates the capacitor element, and the anode foil includes a widened surface portion formed on the surface of the anode foil and a remainder excluding the widened surface portion. and a plurality of dividing portions that divide the enlarged surface portion, and the sealing member includes butyl rubber.

The breaks may extend completely or partially across the foil.

The dividing portions may be provided at intervals having an average pitch of 2.1 mm or less.

The dividing portions may be provided at intervals having an average pitch of 1.0 mm or less.

The dividing portion may have a groove width of 50 μm or less including 0 when the foil is flattened.

The dividing portion may be formed by cracking the enlarged surface portion, and the groove width may be substantially zero when the anode foil is flattened.

A dielectric film may be provided on the surface of the enlarged surface portion and the dividing portion. In order to achieve the above object, the method for manufacturing an electrolytic capacitor of the present invention includes a foil forming step of forming a strip-shaped anode foil, and a winding step of winding the anode foil and the strip-shaped cathode foil with a separator interposed therebetween. an impregnation step of impregnating the capacitor element obtained by the winding step with an electrolytic solution; and a sealing step of sealing the capacitor element, wherein the foil forming step includes a core portion of the anode foil. A first step of forming an enlarged surface portion on the surface excluding the above, and after the first step and before the winding step, the enlarged surface portion is divided and the average pitch is 2.1 mm or less. a second step of providing a plurality of dividing portions; a third step of forming a dielectric film on the inner surfaces of the enlarged surface portions and the dividing portions after the second step and before the winding step; In the winding step, the separated portion formed in the foil forming step is opened and wound, and in the sealing step, the capacitor element is accommodated in an outer case, and the outer case is The opening of is sealed with a sealing body containing butyl rubber.

According to the present invention, hydrogen gas generated during restoration of the dielectric film is reduced due to the presence of the dividing portion. Therefore, even if butyl rubber, which has low gas permeability, is used as the elastomer for the sealing member, the internal pressure does not rise enough to open the valve. Butyl rubber, which is less likely to occur and has low gas permeability, suppresses vaporization and evaporation of the electrolytic solution to the outside, thereby achieving both suppression of performance deterioration and extension of service life.

1 is a schematic diagram of an electrolytic capacitor; FIG. The structure of the anode foil is shown, (a) is a cut view along the longitudinal direction, and (b) is a top view. FIG. 2 is a schematic diagram showing the state of wound anode foils, where (a) shows an anode foil having a split portion, and (b) shows an anode foil without a split portion. (a) shows the dielectric film formed on the inner surface of the split portion, and (b) shows the dielectric film formed on the surface of cracks generated by winding. 4 is a photograph of a cross-section along the longitudinal direction of the anode foil provided with the dividing portion of the present embodiment, according to Example 1. FIG. 4 is a photograph showing the surface of the anode foil having the dividing portion of the present embodiment according to Example 1, wherein the long side direction of the photograph is the width direction of the anode foil, and the short side direction of the photograph is the longitudinal direction of the anode foil. . 4 is a cross-sectional photograph along the longitudinal direction of the anode foil according to Comparative Example 1. FIG. 4 is a graph showing the results of Erichsen tests of Examples 1 to 5 and Comparative Example 1. FIG. 1 is a photograph of a capacitor element in which Example 1 and Comparative Example 1 are wound. 10 is a graph showing the current flowed for each elapsed time during the aging treatment of the electrolytic capacitors of Example 6 and Comparative Example 2. FIG. 10 is a graph showing the tan δ of the electrolytic capacitors of Example 7 and Comparative Examples 3 and 4 over time. 10 is a graph showing changes in weight over time of electrolytic capacitors of Example 7 and Comparative Examples 3 and 4. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an electrolytic capacitor according to the present invention will be described in detail below. In addition, this invention is not limited to embodiment described below.

(Electrolytic capacitor)
The electrolytic capacitor shown in FIG. 1 is a passive element that stores and discharges electric charge by means of electrostatic capacitance. This electrolytic capacitor is constructed by accommodating a cylindrical capacitor element 10 in a bottomed cylindrical exterior case 20 with its axis aligned, and then sealing the opening of the exterior case 20 with a sealing member 30 .

A capacitor element 10 is formed by winding an anode foil 1 and a cathode foil 11 facing each other with a separator 12 interposed therebetween and impregnating them with an electrolytic solution. The separator 12 is superimposed so that one end of the separator 12 protrudes from one end of the anode foil 1 and the cathode foil 11 . Then, the protruded separator 12 is first wound to form a winding core, and then the anode foil 1, the cathode foil 11, and the separator 12 are wound using the winding core as a winding shaft. A lead-out terminal 13 is connected to the anode foil 1 and the cathode foil 11 by stitching, cold welding, ultrasonic welding, laser welding, or the like, and the lead-out terminal 13 penetrates the sealing member 30 and is drawn out of the exterior case 20 .

A gap between exterior case 20 and capacitor element 10 may be filled with insulating resin, and capacitor element 10 may be fixed to exterior case 20 . In addition, the waist opening side of the exterior case 20 is narrowed by caulking, and bites into the side surface of the sealing body 30 or protrudes to the periphery of the upper surface of the sealing body 30, and the adhesion between the sealing body 30 and the exterior case 20 is enhanced. ing. This sealing member 30 suppresses the evaporative evaporation of the electrolytic solution.

After the capacitor element 10 is housed in the outer case 20 and the opening is closed with the sealing member 30, the electrolytic capacitor is energized to perform aging treatment, and defects in the dielectric film 5 generated during the manufacturing process such as winding are removed. Repair by electrolyte.

(electrode foil)
The anode foil 1 and the cathode foil 11 are strip-shaped thin foils made of valve metals such as aluminum, tantalum, titanium, niobium and niobium oxide. The base metal of the valve metal is stretched, or the powder is sintered on both surfaces of the thin plate, and the anode foil 1 and the cathode foil 11 are formed into a foil shape. As shown in FIG. 2, the anode foil 1 is formed with enlarged surface portions 3 on both sides, leaving a core portion 2 at the center in the thickness direction, and a plurality of dividing portions 4 are formed on one or both of the enlarged surface portions 3 . Dielectric film 5 is formed on the surfaces of enlarged surface portion 3 and dividing portion 4 .

Incidentally, the cathode foil 11 may also be formed with the enlarged surface portion 3, formed with the dielectric film 5, and further formed with the dividing portion 4. Alternatively, it is preferable to leave the plane as it is without widening the surface.

The enlarged surface portion 3 has a porous structure. It consists of aligned tunnel-like pits, spongy pits, or gaps between dense particles that are dug down from the surface of the electrode foil toward the center of its thickness. At the center of the thickness of the electrode foil, there remains a core portion 2 which is the base metal of the valve metal and which is rich in flexibility and stretchability. The expanded surface portion 3 is formed by direct current etching or alternating current etching, or by depositing or sintering metal particles or the like on the core portion 2 . The thicknesses of the enlarged surface portion 3 and the core portion 2 are not particularly limited, but the thickness of the enlarged surface portion 3 on both sides of the anode foil 1 is preferably in the range of 40 to 200 μm, and the thickness of the core portion 2 is preferably in the range of 8 to 60 μm.

The dividing portion 4 is a groove having a depth from the surface of the anode foil 1 toward the core portion 2 . The dividing portion 4 should not reach the point where the core portion 2 is completely divided. It can be any depth that penetrates into. In addition, it is not necessary that the depths of all the dividing portions 4 are uniform.

The dividing portion 4 is formed in the width direction orthogonal to the strip longitudinal direction of the anode foil 1 . The dividing portion 4 extends across the anode foil 1 completely or partially. That is, a part 4 extends from one long side of anode foil 1 to reach the other long side. Moreover, a parting portion 4 extends from one long side of the anode foil 1 to less than or beyond the foil center line and does not reach the other long side. Moreover, a parting portion 4 extends from the other long side of the anode foil 1 to less than or beyond the foil center line and does not reach one long side. The dividing portions 4 formed along the width direction may be connected to each other. It is not necessary that all of the dividing portions 4 extend in the same direction and have the same length.

The groove width of the dividing portion 4 is 50 μm or less, including 0, when the anode foil 1 is flattened without being curved. The groove width of the dividing portion 4 is the length along the longitudinal direction of the anode foil 1 and is measured near the surface layer of the anode foil 1 . If the groove width of the dividing portion 4 is 50 μm or less, a large decrease in the capacitance of the electrolytic capacitor due to a decrease in the surface area of the dielectric film 5 can be suppressed without impairing the flexibility and stretchability of the anode foil 1 .

In addition, the dividing portion 4 is opened at the time of winding to disperse the bending stress, suppress the generation of fine cracks, and prevent the generation of cracks that destroy the core portion 2 as well. However, if the number of the divided portions 4 is small, fine cracks are generated due to the tensile stress due to bending, and cracks that destroy the core portion 2 are also likely to occur from the divided portions 4 . Therefore, the dividing portions 4 are provided at four or more points per range of 10 mm in the strip longitudinal direction of the anode foil 1 . The interval between the adjacent dividing portions 4 should have an average pitch of 2.1 mm or less, and more preferably an average pitch of 1.0 mm or less. When the average pitch is 2.1 mm or less, the Erichsen value becomes larger than that of the anode foil 1 in which the divided portions 4 are not formed.

The average pitch is obtained by arbitrarily selecting several cross sections along the longitudinal direction of the anode foil 1, and calculating the average value of the intervals between four continuous divided portions 4 arbitrarily selected from each cross section photograph, Furthermore, it was calculated by taking the average value of each average value. The interval between the divided portions 4 was obtained by measuring the vicinity of the surface of the anode foil 1 .

The dividing portions 4 may be formed with a uniform average pitch or a number within a unit range along the longitudinal direction of the anode foil 1 . Also, the average pitch and the number within the unit range can be changed in consideration of the curvature at the portion where the divided portion 4 is formed when the anode foil 1 is wound. This is because the smaller the curvature, that is, the closer the coil is to the outer peripheral side when wound, the smaller the bending stress and the less likely cracks will occur.

The dividing portion 4 cracks the enlarged surface portion 3, splits the enlarged surface portion 3, cuts the enlarged surface portion 3 along the thickness direction of the anode foil 1, notches the enlarged surface portion 3, or cuts the enlarged surface portion 3 in the thickness direction of the anode foil 1. It is formed by digging the enlarged surface portion 3 along the . Accordingly, examples of the substance of the dividing portion 4 are cracks, fissures, cuts, cutouts or indentations. However, the mode of the dividing portion 4 is not particularly limited as long as the enlarged surface portion 3 is divided. When the split portion 4 is formed by cracking, tearing, or cutting, the groove width of the split portion 4 is substantially zero. The term "substantially 0" refers to a state in which the interfaces of the divided portions 4 are at least partially in contact with each other when the anode foil 1 is flattened without being curved.

Such a dividing portion 4 is formed by cracking, for example, by pressing electrode foil against a round bar. In the forming method using a round bar, the core portion 2 of the anode foil 1 extends in the longitudinal direction, and as a result, the thickness of the core portion 2 becomes thin. However, by setting the groove width of the dividing portion 4 to 50 μm or less, the thickness of the core portion 2 is less likely to be reduced, and the flexibility and stretchability of the anode foil 1 are improved. Also in this point, it is preferable to set the groove width of the dividing portion 4 to 50 μm or less.

The parting portion 4 may be formed only at the beginning of the winding of the anode foil 1 around the winding shaft. The winding start portion of the anode foil 1 has a large curvature and cracks are likely to occur. Also, the average pitch may be increased in proportion to the winding radius at the location where the dividing portion 4 is located, or the number within the unit range may be reduced in inverse proportion to the radius. As the number of dividing portions 4 is reduced, the influence on capacitance is reduced.

It is desirable that the split portions 4 are formed on the enlarged surface portions 3 on both sides, but from the viewpoint of the elongation of the anode foil 1 during winding, at least the split portions 4 should be formed on the outer side of the foil when the anode foil 1 is wound. is preferably formed on the enlarged surface portion 3 that receives the

Dielectric film 5 is a layer that serves as a dielectric of an electrolytic capacitor, and if anode foil 1 is made of aluminum, it is an aluminum oxide layer obtained by oxidizing enlarged surface portion 3 and dividing portion 4 . This dielectric film 5 is formed on the surface of the enlarged surface portion 3 and the inner surface of the dividing portion 4 . The inner surface of the dividing portion 4 is all or part of the inner wall of the groove and the bottom surface of the groove.

This dielectric film 5 is formed by chemical conversion treatment after forming the enlarged surface portion 3 and the dividing portion 4 . In the chemical conversion treatment, after the step of forming a dielectric film, the step of forming a dielectric film is repeated through a so-called depolarization step. In chemical conversion treatment, these series of steps are repeated once or twice or more. The depolarization step includes a heat treatment step, a phosphating step, or both.

First, the dielectric film 5 is formed in the dielectric film forming step. In this dielectric film forming step, a conversion solution having low solubility of valve metals and oxides and low electric resistance is used. A voltage is applied to the electrode foil in this anodizing solution. The conversion solution is an aqueous solution containing phosphoric acid, citric acid, adipic acid, boric acid, or a salt thereof, preferably a halogen ion-free solution. Specific chemical conversion solutions include ammonium dihydrogen phosphate, ammonium citrate, ammonium adipate, ammonium borate, organic acid ammonia, and the like. Preferably, ammonium dihydrogen phosphate is used.

The time for immersing the anode foil 1 in the anodizing solution and applying the voltage is preferably 5 to 120 minutes, and it is sufficient if the withstand voltage of the dielectric film 5 reaches the desired voltage and the current settles to a constant value. In order to reduce the amount of electricity for chemical conversion, the anode foil 1 may be immersed in pure water at a temperature of 80° C. or higher before the step of forming the dielectric film to form a boehmite film in advance.

In this dielectric film forming step, voids may be isolated inside the dielectric film 5 . So, the voids are then exposed by a depolarization process that includes a heat treatment step, a phosphating step, or both.

In the heat treatment step, for example, the substrate is exposed to a temperature environment of 450° C. or higher in the air. In this heat treatment step, due to the difference in coefficient of thermal expansion between the core portion 2 of the anode foil 1 and the dielectric coating 5, the dielectric coating was stretched and cracked from the surface toward the voids, or was enclosed in the voids. The gas expands and voids open. As a result, the voids inside the dielectric film are opened, and the voids inside the dielectric film 5 are exposed to the surface.

The phosphating step enlarges cracks and pores leading to voids. In this phosphating step, the electrode foil is immersed in a phosphoric acid solution or an ammonium dihydrogen phosphate solution. This makes it easier for the anodizing solution to penetrate into the voids in the dielectric film forming step. Therefore, when the dielectric film forming step is repeated again, the anodizing liquid penetrates into the voids, and the voids disappear or the size of the voids and the number of voids are reduced. In addition, the phosphating step can also remove surface hydrated oxides. When the dielectric film 5 is also formed on the inner surface of the dividing portion 4 by this chemical conversion treatment, the stability of the anode foil 1 is increased. Further, if the dielectric film 5 is also formed on the inner surface of the dividing portion 4, the amount of electricity (A·s/F) required for the aging treatment for repairing the dielectric film 5 can be reduced.

(sealing body)
The sealing member 30 is a thick disk that fits into the outer case 20 . The sealing member 30 is formed with through-holes penetrating through both sides at regular intervals across the central axis. A pair of lead-out terminals 13 are led out from these through holes. Further, the sealing member 30 may be formed with a pressure valve that opens when the specified pressure is reached. The pressure valve opens when the internal pressure rises due to gas such as hydrogen gas generated when the dielectric film 5 is repaired and reaches a specified pressure. Incidentally, this pressure valve may be formed in the exterior case 20 .

The sealing member 30 is composed of an elastomer. In addition to the elastomer, the sealing member 30 may contain a hard substrate, a resin layer, or the like. The hard substrate is composed of a hard material such as a metal plate, a synthetic resin plate, or a ceramic plate. The metal plate is made of, for example, aluminum, an aluminum alloy containing aluminum or manganese, or stainless steel, and the synthetic resin plate is made of, for example, phenolic resin. , epoxy resin or polyethylene sulfide resin. Various resins can be used for the resin layer, including epoxy resins, fluorine resins, acrylic resins, polyimide resins, silicon resins, phenol resins, melamine resins, urethane resins, unsaturated polyester resins, and the like.

An elastomer with low gas permeability is used for the sealing member 30, and for example, crosslinked or uncrosslinked butyl rubber is mainly included. Butyl rubber includes chlorinated butyl rubber and brominated butyl rubber. In addition, the elastomer 34 may contain butyl rubber (isobutylene isoprene rubber) as a main material and may contain isoprene rubber, silicone rubber, ethylene propylene diene rubber (EPDM), fluororubber (FKM) or styrene butadiene rubber (SBR). good. Alkylphenol-formaldehyde resins, peroxides, quinoids, sulfur and the like can be used as cross-linking agents. As a filler, mica, talc, calcined clay, hydrated silicon, anhydrous silicon, carbon black and the like can be used.

(Wound state)
FIG. 3(a) is a schematic diagram showing the state of the anode foil 1 wound in an electrolytic capacitor which has been subjected to a chemical conversion treatment for forming the dielectric film 5 after forming the dividing portion 4, and FIG. 4 is a schematic diagram showing the state of the wound anode foil in the electrolytic capacitor in which the portion 4 is not formed; FIG.

As shown in FIG. 3(a), in the anode foil 1 in which the divided portions 4 are formed, the divided portions 4 are opened at the time of winding, so that the extension of the dielectric film 5 is relaxed and the tensile stress is reduced. . Therefore, the occurrence of fine cracks 6 in anode foil 1 is suppressed. In addition, the bending stress is shared and received by the plurality of dividing portions 4, and the bending stress is distributed to each dividing portion 4. - 特許庁Therefore, concentration of stress that would lead to breakage of core 2 is suppressed, breakage of core 2 is avoided, and anode foil 1 is smoothly curved and wound without bending.

On the other hand, as shown in FIG. 3B, in the anode foil in which the dividing portion 4 is not formed, the dielectric film 5 with reduced flexibility and stretchability is stretched during winding. A large number of fine cracks 6 due to tensile stress are generated in the dielectric film 5 in which the stress has decreased. Moreover, in the worst case, a crack 6 that destroys the core portion 2 also occurs at a portion of the crack 6 where stress is concentrated.

Moreover, FIG. 4(a) is an enlarged view of the dividing portion 4 in the electrolytic capacitor which was subjected to the chemical conversion treatment after forming the dividing portion 4, and FIG. 4 is an enlarged view of the body membrane 5; FIG.

As shown in FIG. 4( a ), in the anode foil 1 that has been subjected to chemical conversion treatment accompanied by depolarization treatment after the division 4 is formed, the dielectric film 5 is also formed on the inner surface of the division 4 . there is Also, the voids 7 in the dielectric film 5 formed on the inner surface of the dividing portion 4 are eliminated or reduced by the depolarization treatment. On the other hand, as shown in FIG. 4(b), in the anode foil in which the dividing portion 4 is not formed, a dielectric film 5 is formed by aging treatment on the inner surface of the crack 6 generated by winding. However, it is considered that voids 7 remain in the dielectric film 5 formed on the inner surface of the crack 6 because the depolarization treatment cannot be performed by the aging treatment.

Therefore, although it is speculation, if the anode foil is not formed with the dividing portion 4, defects associated with the use of the electrolytic capacitor are more likely to occur. As a result, the anode foil in which the dividing portion 4 is not formed needs to be repaired more by the electrolytic solution, and the amount of hydrogen gas generated increases. On the other hand, fine cracks 6 are less likely to occur in anode foil 1 in which divided portions 4 are formed. A dielectric film 5 is also formed on the inner surface of the dividing portion 4 by chemical conversion treatment accompanied by depolarization treatment. Therefore, the electrolytic capacitor including the anode foil 1 in which the dividing portion 4 is formed is less likely to have defects due to use as compared with the case where the dividing portion 4 is not formed. Therefore, the amount of hydrogen gas generated from the electrolytic capacitor is suppressed.

Then, in this electrolytic capacitor, the amount of hydrogen gas generated is suppressed, and since butyl rubber with low gas permeability is used for the elastomer of the sealing member 30, the pressure valve is difficult to open, and the electrolytic solution evaporates and evaporates. It is difficult to achieve both long life and suppression of performance deterioration over time. Further, in this electrolytic capacitor, cracks 6 are less likely to occur, and smooth curved winding is possible. Therefore, the densely wound capacitor element 10 can be accommodated in the exterior case 20, the capacitance per unit volume can be improved, or a small-sized large-capacity electrolytic capacitor can be realized.

(Example 1)
Anode foil 1 showing this embodiment was produced as follows. First, an aluminum foil having a thickness of 110 μm, a width of 10 mm, a length of 55 mm and a purity of 99.9% by weight or more was used as a base material. Then, enlarged surface portions 3 were formed on both surfaces of this aluminum foil. Specifically, the aluminum foil was immersed in an acidic aqueous solution having a liquid temperature of 25° C. and about 8% by weight of hydrochloric acid as a main electrolyte, and was subjected to an etching treatment. In the etching treatment, a current of 10 Hz alternating current and a current density of 0.14 A/cm ² was applied to the substrate for about 20 minutes to expand both sides of the aluminum foil.

After the etching process, the dividing part 4 was formed in the aluminum foil whose both surfaces were etched. The dividing portion 4 was generated perpendicular to the longitudinal direction of the aluminum foil strip. Specifically, as a physical treatment method, for a round bar of φ0.5 mm, the wrap angle indicating the size of the contact area between the round bar and the aluminum foil is set to 180 degrees, and the aluminum foil is pressed to cut the part. 4 was formed. Further, after forming the dividing portion 4 , chemical conversion treatment was performed to form a dielectric film 5 on the surfaces of the enlarged surface portion 3 and the dividing portion 4 .

As a result, as shown in FIGS. 5 and 6, in the anode foil 1 of Example 1, the expanded surface portions 3 having the dielectric film 5 are present on both sides of the core portion 2 with a thickness of 36 μm, respectively, and the thickness is 38 μm. A core part 2 remained. The groove width of the dividing portion 4 was 10 μm. The divided portions 4 were formed by cracking due to the pressing of the round bar, the average pitch of the divided portions 4 was 70 μm, and the number of divided portions 4 per 10 mm range was 143.

(Example 2)
Using the same substrate as in Example 1, the same etching treatment and chemical conversion treatment as in Example 1 were performed. The conditions for forming the dividing portion 4 are the same except that a round bar of φ6 mm is used. The order of the etching treatment, the forming treatment of the dividing portion 4, and the chemical conversion treatment was the same as in Example 1.

As a result, the anode foil 1 of Example 2 had the same thicknesses of the core portion 2, the enlarged surface portion 3, and the dielectric film 5 as those of Example 1. The divided portions 4 were formed by cracking, the average pitch of the divided portions 4 was 220 μm, and the number of divided portions 4 per 10 mm range was 45.

(Example 3)
Using the same base material as in Examples 1 and 2, the same etching treatment and chemical conversion treatment as in Example 1 were performed. The conditions were the same as in Examples 1 and 2, except that a round bar of φ13 mm was used for forming the dividing portion 4 . As a result, the anode foil 1 of Example 3 was formed by cracks at the dividing portions 4, and the average pitch of the dividing portions 4 was 950 μm, and the number of pieces per 10 mm range was 10 pieces.

(Example 4)
Using the same substrate as in Examples 1 to 3, the same etching treatment and chemical conversion treatment as in Examples 1 to 3 were performed. The conditions are the same as in Examples 1 to 3, except that a round bar of φ16 mm was used for forming the dividing portion 4 . As a result, the anode foil 1 of Example 4 was formed by cracks at the dividing portions 4, and the average pitch of the dividing portions 4 was 2100 μm, and the number of pieces per 10 mm range was 4.

(Reference example)
The same etching treatment and chemical conversion treatment as in Examples 1 to 4 were performed. The conditions are the same as in Examples 1 to 4, except that a round bar of φ22 mm was used for forming the dividing portion 4 . As a result, the anode foil 1 of the reference example was formed by cracks at the divided portions 4, and the average pitch of the divided portions 4 was 3100 μm, and the number of pieces per 10 mm range was 3.

(Comparative example 1)
Using the same base material as in Examples 1 to 4 and Reference Example , the same etching treatment and chemical conversion treatment as in Examples 1 to 4 and Reference Example were performed. However, the process of forming the dividing portion 4 is omitted, and the dividing portion 4 is not yet formed. As a result, as shown in FIG. 7, the anode foil of Comparative Example 1 was provided with the enlarged surface portions 3 on both sides of the core portion 2 as in Examples 1 to 4 and the Reference Example. The thickness of the expanded surface portion 3 provided with the film 5 and the dielectric film 5 was 36 μm, respectively, and the thickness of the core portion 2 was 38 μm.

(Erichsen test)
The Erichsen test was performed on the anode foils 1 of Examples 1 to 4 and Reference Example , and the anode foil of Comparative Example 1. In the Erichsen test, the anode foil 1 of Examples 1 to 4 and Reference Example and the anode foil of Comparative Example 1 were sandwiched at 10 kN with a die having an inner diameter of 33 mm and a wrinkle presser, and were pressed with a chisel-shaped punch. The chisel-shaped punch has a width of 30 mm and a tip end of which is spherical with a diameter of 4 mm in cross section. The chisel portion of the punch was pushed in perpendicular to the longitudinal direction of the strip of the anode foil 1 . The pushing speed of the punch was set to 0.5 mm/min.

The results of this Erichsen test are shown in FIG. FIG. 8 is a graph in which the horizontal axis represents the average pitch of the divided portions 4 and the vertical axis represents the Erichsen value. As shown in FIG. 8, the Erichsen value of Comparative Example 1 was 1.4 mm, while the Erichsen value of Reference Example was 1.5 mm. In other words, it can be seen that the bending stress during winding is dispersed by providing the dividing portion 4, and the flexibility and stretchability of the anode foil 1 are improved.

Further, when the average pitch of the dividing portions 4 was set to 2100 μm or less, the Erichsen value was 1.7 mm or more, which was a clear difference compared to the case where the dividing portions 4 were not formed. That is, it can be seen that the bending stress at the time of winding is well dispersed by providing the dividing portions 4 at an average pitch of 2100 μm or less, and good flexibility and stretchability are imparted to the anode foil 1 .

In particular, when the average pitch of the dividing portions 4 was 950 μm or less, the Erichsen value was 2.0 mm or more, which was significantly superior to the case where the dividing portions 4 were not formed. That is, it can be seen that the bending stress at the time of winding is extremely well dispersed and the anode foil 1 is endowed with extremely good flexibility and stretchability by providing the dividing portions 4 at an average pitch of 950 μm or less. Furthermore, when the average pitch of the dividing portions 4 was set to 220 μm or less, the Erichsen value was 2.6 mm or more, which was significantly superior to the case where the dividing portions 4 were not formed.

(Winding test)
Anode foil 1 of Example 1 and anode foil of Comparative Example 1 were actually wound to form capacitor element 10 . The wound anode foil 1 of Example 1 and the anode foil of Comparative Example 1 both had dimensions of 5.6 mm in width and 125 mm in length. The results are shown in FIG. 9 is a photograph of rolled anode foil 1 of Example 1 and anode foil of Comparative Example 1. FIG. As shown in (a) of FIG. 9, when the anode foil of Comparative Example 1 is wound, it can be seen that many folds occur in various places near the winding core. In addition, it can be seen that a large number of bends occur in various places even near the middle layer where the curvature increases away from the core. Furthermore, it can be seen that bending occurs in part in the vicinity of the outer peripheral surface of the capacitor element.

On the other hand, as shown in FIG. 9B, when the anode foil 1 of Example 1 is wound, no bending occurs not only in the vicinity of the outer peripheral surface of the capacitor element 10 but also in the vicinity of the winding core. , is smoothly curved and wound. Therefore, as shown in (a) of FIG. 9, the diameter of the capacitor element wound with the anode foil of the same length is expanded to 7.36 mm in Comparative Example 1, whereas (b) of FIG. , the radius of the capacitor element 10 wound with the same length of the anode foil 1 was within 7.10 mm in the first embodiment.

(Example 6)
An electrolytic capacitor of Example 6 was produced by using the same as the anode foil 1 of Example 1 having the divided portion 4 on the surface of which the dielectric film 5 was formed and winding. The anode foil 1 of Example 6 had dimensions of 5.6 mm in width and 125 mm in length. Aluminum foil was used for the cathode foil 11 . The cathode foil 11 was formed with the enlarged surface portion 3 and was not formed with the dielectric film 5 . A cellulose fiber was used for the separator 12 . The electrolytic solution used was a γ-butyrolactone solution of amidinium phthalate. Then, the opening of the exterior case 20 was sealed with a sealing member 30 using butyl rubber, and crimping was performed.

(Comparative example 2)
An electrolytic capacitor of Comparative Example 2 was produced by winding the foil as the anode foil of Comparative Example 1 in which the dividing portion 4 was not formed. An electrolytic capacitor of Comparative Example 2 was produced in the same manner as the electrolytic capacitor of Example 6, except that the divided portion 4 was not formed on the anode foil.

(Aging evaluation)
The produced electrolytic capacitors of Example 6 and Comparative Example 2 were subjected to aging treatment, and the amount of electricity required for the aging treatment was measured. In the aging treatment, the aging treatment was performed by applying a rated voltage under a temperature condition of 100°C. During this aging process, changes in the current flowing between the anode terminal and the cathode terminal were measured. The values of the electric currents applied to the electrolytic capacitors of Example 6 and Comparative Example 2 at the start of the aging process are the same. FIG. 10 is a graph showing the percentage of the current value at each elapsed time with respect to the starting point of the aging process, assuming that the current value at the starting point of the aging process is 100%.

As shown in FIG. 10, in the capacitor of Example 6 using the anode foil 1 of Example 1, the current value began to decrease within 2 minutes, and the current value reached about 30% of the aging start point in about 3 minutes. value decreased. On the other hand, in the electrolytic capacitor of Comparative Example 2 using the anode foil of Comparative Example 1, a decrease in the current value was observed in less than 3 minutes after exceeding 2 minutes, and the current value decreased to about 30% of the time at the start of aging. It took me about 5 minutes. That is, as shown in FIG. 10, in Example 6, the current value began to decrease one minute or more earlier than in Comparative Example 2, and the product of the current value and time from the start of aging until 5 minutes passed was lower than that of the dielectric film 5. It was confirmed that the amount of electricity required for the aging process was reduced when the anode foil 1 was provided with the divided portions 4 formed on the surface thereof, as compared with the case where the divided portions 4 were not formed.

(Example 7)
An electrolytic capacitor of Example 7 was manufactured by using the same as the anode foil 1 of Example 1 having the divided portion 4 on the surface of which the dielectric film 5 was formed and wound. This electrolytic capacitor had a rated voltage of 450 V and a capacitance of 68 μF. Aluminum foil was used for the cathode foil 11 . The cathode foil 11 was formed with the enlarged surface portion 3 and was not formed with the dielectric film 5 . A cellulose fiber was used for the separator 12 . Then, the opening of the exterior case 20 was sealed with a sealing member 30 using butyl rubber, and crimping was performed.

The electrolytic solution contains ethylene glycol, polyalkylene glycol, azelaic acid, 1,7-octanedicarboxylic acid, boric acid, mannite and diethylamine. The electrolyte contains 73 wt% ethylene glycol, 12 wt% polyalkylene glycol, 5 wt% azelaic acid, 3 wt% 1,7-octanedicarboxylic acid, and 1 wt% boric acid with respect to the total amount of the electrolyte. , 2 wt% mannite and 4 wt% diethylamine were added.

(Comparative Example 3)
An electrolytic capacitor of Comparative Example 3 was manufactured by using the anode foil 1 of Example 1 having the dividing portion 4 with the dielectric film 5 formed on the surface and winding it. In this electrolytic capacitor, the opening of the exterior case 20 was sealed with a sealing body 30 using ethylene propylene diene rubber (EPDM), and crimping was performed. The electrolytic capacitor of Comparative Example 3 was manufactured in the same manner as the electrolytic capacitor of Example 7, including the fact that the anode foil 1 was formed with the dividing portion 4, except that the sealant 30 was made of EPDM.

(Comparative Example 4)
An electrolytic capacitor of Comparative Example 4 was produced by winding the foil as the anode foil of Comparative Example 1 in which the dividing portion 4 was not formed. The electrolytic capacitor of Comparative Example 4 was produced in the same manner as the electrolytic capacitor of Example 7, except that the anode foil did not have the dividing portion 4 and that the sealant 30 was made of butyl rubber.

(Evaluation of electrolyte volatilization)
Changes in tan δ, weight changes, and valve opening times of the electrolytic capacitors of Example 7 and Comparative Examples 3 and 4 were measured. A rated voltage was continuously applied to each electrolytic capacitor for a maximum of 6000 hours under a temperature environment of 125°C. The results are shown in Table 1 below, FIGS. 11 and 12. Table 1 shows the initial tan δ, the tan δ after 5000 hours, and the valve opening time according to the type of sealing rubber and the presence or absence of the dividing portion 4 . FIG. 11 shows the relationship between tan δ and elapsed time. FIG. 12 shows the relationship between weight change and elapsed time of the electrolytic capacitor.

As shown in Table 1, the electrolytic capacitors of Example 7 and Comparative Example 3 using the anode foil 1 in which the dividing portion 4 was formed did not open even after 5000 hours. The electrolytic capacitor of has opened after 5000 hours. That is, when the dividing portion 4 is formed in the anode foil 1, even if butyl rubber with low gas permeability is used for the sealing member 30, the pressure valve is equivalent to using EPDM with high gas permeability for the sealing member 30. 32 did not open, and extended service life was achieved. In addition, tan δ at 6000 hours could not be measured for the electrolytic capacitor of Comparative Example 4. This is considered to be because the valve opened at 5000 hours, the electrolyte vaporized, and the capacitor did not function as an electrolytic capacitor.

Further, as shown in Table 1, FIG. 11 and FIG. 12, the electrolytic capacitor of Example 7 using the anode foil 1 in which the dividing portion 4 was formed and using butyl rubber for the sealing member 30 did not have the dividing portion 4. Compared to the electrolytic capacitor of Comparative Example 3 in which EPDM was used as the sealing member 30, the tan δ was less likely to increase and remained within a favorable range even after 5000 hours.

Summarizing the above, since the amount of gas generated is suppressed by the anode foil 1 in which the dividing portion 4 is formed, it becomes possible to use butyl rubber with low gas permeability as the sealing member 30. It has been confirmed that when it can be used as the evaporator, evaporation and volatilization of the electrolytic solution is suppressed, thereby achieving both suppression of performance deterioration and extension of the life of the electrolytic capacitor.

1 Anode foil 2 Core 3 Enlarged surface 4 Separation 5 Dielectric film 6 Crack 7 Void 10 Capacitor element 11 Cathode foil 12 Separator 13 Lead terminal 20 Exterior case 30 Sealing body

Claims (8)

a capacitor element comprising strip-shaped anode foil and cathode foil wound with a separator interposed therebetween and impregnated with an electrolytic solution;
an exterior case in which the capacitor element is housed;
a sealing body that seals the opening of the exterior case that accommodates the capacitor element;
with
The anode foil is
an enlarged surface portion formed on the surface of the anode foil;
a core portion which is the remaining portion excluding the enlarged surface portion;
a plurality of dividing portions that divide the enlarged surface portion and are provided at intervals with an average pitch of 2.1 mm or less;
a dielectric film formed on the inner surface of the dividing portion before the winding;
has
The capacitor element is formed by winding the anode foil having the divided portion that opens at the time of winding,
wherein the sealing body contains butyl rubber;
An electrolytic capacitor characterized by: The dividing part is
extending completely or partially across the anode foil;
The electrolytic capacitor according to claim 1, characterized by: The dividing part is
provided with an average pitch of 220 μm or less,
3. The electrolytic capacitor according to claim 1 or 2, characterized by: The dividing part is
Provided with an average pitch of 1.0 mm or less,
3. The electrolytic capacitor according to claim 1 or 2, characterized by: The dividing portion has a groove width of 50 μm or less, including 0, when the anode foil is flattened;
5. The electrolytic capacitor according to any one of claims 1 to 4, characterized by: the dividing portion is formed by cracking the enlarged surface portion, and the groove width is substantially zero when the anode foil is flattened;
5. The electrolytic capacitor according to any one of claims 1 to 4, characterized by: Having a dielectric film on the surface of the enlarged surface portion and the dividing portion;
7. The electrolytic capacitor according to any one of claims 1 to 6, characterized by: a foil forming step of forming a strip-shaped anode foil;
A winding step of winding the anode foil and strip-shaped cathode foil with a separator interposed therebetween;
an impregnation step of impregnating the capacitor element obtained by the winding step with an electrolytic solution;
a sealing step of sealing the capacitor element;
including
The foil forming step includes
a first step of forming an enlarged surface portion on the surface of the anode foil excluding the core portion;
After the first step and before the winding step, a second step of dividing the enlarged surface portion and providing a plurality of divided portions at intervals of an average pitch of 2.1 mm or less;
a third step of forming a dielectric film on the inner surfaces of the enlarged surface portion and the dividing portion after the second step and before the winding step;
has
In the winding step, winding while taking the initiative to open the divided portion formed in the foil forming step,
In the sealing step, the capacitor element is housed in an exterior case, and the opening of the exterior case is sealed with a sealing body containing butyl rubber;
A method for manufacturing an electrolytic capacitor characterized by.

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