Electrolytic capacitor

The present invention relates to an electrolytic capacitor containing a conductive polymer in an electrolyte.

A conventional electrolytic capacitor is disclosed in Patent Document 1. This electrolytic capacitor includes a main body case, a capacitor element, and a sealing body. The main body case is made of metal to form a bottomed cylinder, and one end of the cylindrical peripheral wall is closed by an end wall to open an opening at the other end.

In the capacitor element, the anode foil on which the dielectric film is formed and the facing cathode foil are wound around the separator and housed in the main body case. A conductive polymer is arranged as an electrolyte between the dielectric film and the facing cathode foil, and the electrolytic solution is impregnated. Further, lead terminals are connected to the anode foil and the facing cathode foil, respectively.

The opening of the main body case containing the capacitor element is sealed with a sealing body such as rubber. At this time, the lead terminal penetrates the sealing body and is pulled out of the main body case.

According to the electrolytic capacitor having the above configuration, since the capacitor element contains a conductive polymer in the electrolyte, the ESR of the electrolytic capacitor can be lowered. In addition, the electrolytic solution repairs defects in the dielectric film, and the withstand voltage of the electrolytic capacitor can be increased.

<p><patcit num="1"><text>Japanese Patent Application Laid-Open No. 2008-10657 (Pages 4-Page 13, Fig. 2)</text></patcit></p>

<p> However, according to the conventional electrolytic capacitor, air is trapped in the main body case at the time of sealing. Further, an oxidizing substance such as air invades the main body case over time from between the main body case and the sealing body or between the lead terminal and the sealing body. Therefore, when the electrolytic capacitor is used for a long period of time, there is a problem that the conductive polymer is oxidized and the ESR of the electrolytic capacitor becomes high.</p><p> An object of the present invention is to provide an electrolytic capacitor capable of suppressing an increase in ESR over time.</p>

<p> In order to achieve the above object, the present invention separates a bottomed tubular main body case having one end of the peripheral wall closed by an end wall and an opening at the other end, and a first electrode body and a second electrode body. A capacitor element that is wound and housed in the main body case and a sealing body that seals the opening are provided, and a conductive polymer is provided between the first electrode body and the second electrode body. In an electrolytic capacitor in which a predetermined liquid agent is arranged, an insulating sheet holding an oxidation inhibitor is provided between the end wall and the capacitor element.</p><p> Further, the present invention is characterized in that, in the electrolytic capacitor having the above structure, the liquid agent contains an electrolytic solution in which an electrolyte of any of an amine salt of an organic acid or an inorganic acid and an amidine salt of an organic acid or an inorganic acid is dissolved.</p><p> Further, the present invention is characterized in that, in the electrolytic capacitor having the above structure, the liquid agent contains a low conductive liquid having no supporting electrolyte.</p><p> Further, in the electrolytic capacitor having the above configuration, the liquid agent is impregnated in the capacitor element, and the insulating sheet is arranged on the end wall and the bottom surface portion is bent from the bottom surface portion and placed on the peripheral wall. It is characterized by having a side surface portion to be arranged.</p><p> Further, in the electrolytic capacitor having the above configuration, the liquid agent is impregnated in the capacitor element, and the insulating sheet is arranged on the end wall and the bottom surface portion is bent from the bottom surface portion to be formed on the peripheral wall. It has a side surface portion to be arranged, and the holding amount of the oxidation inhibitor per unit area of the side surface portion is larger than the holding amount of the oxidation inhibitor per unit area of the bottom surface portion. ..</p><p> Further, the present invention is characterized in that, in the electrolytic capacitor having the above configuration, the insulating sheet is formed in a rectangular shape or a parallelogram, and at least one diagonal line of the insulating sheet is larger than the inner diameter of the main body case.</p><p> Further, in the present invention, in the electrolytic capacitor having the above configuration, the antioxidant may be any of vitamins, amines, phenolic antioxidants, phosphorus-based antioxidants, and saccharide antioxidants. It is characterized by including.</p>

<p> According to the present invention, since the insulating sheet arranged between the end wall of the main body case and the capacitor element holds the oxidation inhibitor, the oxidation of the conductive polymer is suppressed. Therefore, it is possible to suppress an increase in ESR of the electrolytic capacitor over time.</p>

<figref num="1">A perspective view of the electrolytic capacitor according to the embodiment of the present invention as viewed from above.</figref><figref num="2">Perspective view of the electrolytic capacitor according to the embodiment of the present invention as viewed from below.</figref><figref num="3">Front sectional view showing a capacitor body of an electrolytic capacitor according to an embodiment of the present invention.</figref><figref num="4">A perspective view showing a capacitor element of an electrolytic capacitor according to an embodiment of the present invention.</figref><figref num="5">A perspective view showing an installed state of an insulating sheet of an electrolytic capacitor according to an embodiment of the present invention.</figref><figref num="6">A perspective view showing an installed state of an insulating sheet of an electrolytic capacitor according to an embodiment of the present invention.</figref><figref num="7">Top view showing the insulation sheet of the electrolytic capacitor which concerns on embodiment of this invention.</figref><figref num="8">Perspective view illustrating a state at the time of manufacturing the insulation sheet of the electrolytic capacitor which concerns on embodiment of this invention.</figref>

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show a perspective view of the electrolytic capacitor 1 of one embodiment as viewed from above and a perspective view as viewed from below. The electrolytic capacitor 1 includes a capacitor body 2 and a seat plate 6. The seat plate 6 is made of synthetic resin and holds the capacitor body 2. The seat plate 6 is provided with a pair of through holes 6a and through holes 6b. The lead terminals 7 and 8 provided on the capacitor body 2 to be described later are inserted into the through holes 6a and 6b, bent, and soldered to the circuit board.

FIG. 3 shows a front sectional view of the capacitor body 2. The capacitor main body 2 includes a main body case 3, a capacitor element 10, an insulating sheet 4, and a sealing body 5. The main body case 3 is formed of a metal such as aluminum into a bottomed cylindrical shape having a circular cross section, and one end of the cylindrical peripheral wall 3b is closed by the end wall 3a to open an opening 3c at the other end.

The capacitor element 10 is housed in the main body case 3, and lead terminals 7 and 8 connected to the first electrode body 11 and the second electrode body 12 (see FIG. 4), which will be described later, are extended. The insulating sheet 4 is arranged between the end wall 3a of the main body case 3 and the capacitor element 10. The insulating sheet 4 prevents a short circuit between the first electrode body 11 and the second electrode body 12 via the main body case 3.

The sealing body 5 is formed in the shape of a disk having a pair of through holes 5a and 5b by a molded product of an elastic material such as rubber. With the sealing body 5 arranged in the opening 3c of the main body case 3, the peripheral surface of the main body case 3 is drawn to form a recess 3d. As a result, the sealing body 5 is fixed, and the opening 3c of the main body case 3 is sealed by the sealing body 5. At this time, the lead terminals 7 and 8 of the capacitor element 10 housed in the main body case 3 are inserted into the through holes 5a and 5b by press fitting, and the capacitor element 10 is fixed.

FIG. 4 shows a perspective view of the capacitor element 10. The capacitor element 10 is formed by winding a long first electrode body 11 and a long second electrode body 12 via an insulator separator 13. The end of the first electrode body 11 or the second electrode body 12 is fixed by the winding stop tape 14.

The first electrode body 11 is made of a valve acting metal such as aluminum, tantalum, niobium, and titanium. A dielectric film of oxide (not shown) is formed on the surface of the first electrode body 11 by chemical conversion treatment. The second electrode body 12 faces the first electrode body 11 via the separator 13 and is formed of aluminum or the like.

The lead terminal 7 is connected to the first electrode body 11 having a dielectric film, and the lead terminal 8 is connected to the second electrode body 12. A dielectric film may be provided on the first electrode body 11 and the second electrode body 12.

A conductive polymer is arranged between the first electrode body 11 and the second electrode body 12. By immersing the capacitor element 10 in the dispersion liquid of the conductive polymer for a predetermined time and then drying it, the conductive polymer can be arranged between the first electrode body 11 and the second electrode body 12. The ESR of the electrolytic capacitor 1 can be lowered by the conductive polymer.

As the conductive polymer, polythiophene, polypyrrole, derivatives thereof and the like can be used. Polyethylene dioxythiophene is more desirable due to its high electrical conductivity.

Further, by immersing the capacitor element 10 in a predetermined liquid agent for a predetermined time, the liquid agent is impregnated in the capacitor element 10. As a result, the liquid agent is arranged between the first electrode body 11 and the second electrode body 12.

By impregnating the capacitor element 10 with a predetermined liquid agent, the withstand voltage of the electrolytic capacitor 1 can be increased. As the solution to be impregnated in the capacitor element 10, an electrolytic solution in which an electrolyte is dissolved or a low conductive solution having no supporting electrolyte is used. The liquid agent has a higher boiling point and a lower melting point than the operating temperature range of the electrolytic capacitor 1 (for example, -30 ° C to 150 ° C).

As a low conductive liquid for increasing the withstand voltage of the electrolytic capacitor 1, γ-butyrolactone, sulfolane, ethylene glycol, diethylene glycol, polyalkylene glycol, ethylene glycol alkyl ether, diethylene glycol alkyl ether, fatty acid ester of polyalkylene glycol, polyalkylene glycol alkyl Ether, polyglycerin, polyalkylene glycol adduct of polyglycerin, polyglycerin fatty acid ester, fatty acid ester of polyhydric alcohol (sorbitan, etc.), unsaturated fatty acid and the like can be used.

Further, as the electrolytic solution for increasing the withstand voltage of the electrolytic capacitor 1, an electrolytic solution in which an amine salt of an organic acid or an inorganic acid or an amidine salt of an organic acid or an inorganic acid is dissolved in a highly polar solvent is used. Can be done. The highly polar solvent can be selected from the liquid agents exemplified in the above low conductive liquids.

The ESR of the electrolytic capacitor 1 can be further lowered by arranging the electrolytic solution between the first electrode body 11 and the second electrode body 12. Further, since the defect of the dielectric film of the first electrode body 11 is repaired by the oxidizing action of the electrolytic solution, the withstand voltage of the electrolytic capacitor 1 can be increased and the leakage current can be decreased.

The capacitor element 10 may be impregnated with a plurality of liquid agents. At this time, it is more desirable to impregnate the capacitor element 10 with the electrolytic solution and a liquid agent having a boiling point higher than that of the solvent of the electrolytic solution and incompatible with the solvent. As a result, the evaporation rate of the solvent of the electrolytic solution becomes slow, and the life of the electrolytic capacitor 1 can be extended even in a high temperature environment exceeding 150 ° C.

FIG. 5 shows a plan view of the insulating sheet 4. 6 and 7 show perspective views of the installation state of the insulating sheet 4. FIG. 6 shows a view of the inside of the main body case 3, and FIG. 7 shows the upper part of the capacitor element 10 excluding the main body case 3.

The insulating sheet 4 is formed in a square shape by holding an oxidation inhibitor on a base material on which natural cellulose fibers or synthetic resin fibers are laminated. The diagonal line of the insulating sheet 4 is larger than the inner diameter of the main body case 3. Therefore, the insulating sheet 4 has a bottom surface portion 4a arranged on the end wall 3a (see FIG. 3) of the main body case 3 and a side surface portion 4b bent from the bottom surface portion 4a and arranged on the peripheral wall 3b. ..

As an antioxidant held on the insulating sheet 4, one of vitamins (vitamin C, etc.), amine-based antioxidants, phenol-based antioxidants, phosphorus-based antioxidants, saccharide antioxidants, etc. Multiple types can be used.

The atmosphere inside the main body case 3 contains oxidizing substances such as air trapped when the condenser main body 2 is sealed and air that invades due to long-term use. Oxidizing substances in the atmosphere inside the main body case 3 are supplemented by the oxidation inhibitor retained in the insulating sheet 4 or chemically changed into a compound having low oxidation. Thereby, the oxidation of the conductive polymer can be suppressed.

In addition, the liquid agent impregnated in the capacitor element 10 may contain an oxidizing substance. The liquid agent convects on the insulating sheet 4 from the contact region between the bottom surface 4a of the insulating sheet 4 and the axial end surface of the capacitor element 10. Therefore, the oxidizing substance in the liquid agent is supplemented by the oxidation inhibitor or chemically changed to a compound having low oxidation property, and the oxidation of the conductive polymer is suppressed.

The oxidation inhibitor held on the insulating sheet 4 elutes into the liquid agent from the contact region between the bottom surface portion 4a and the axial end surface of the capacitor element 10. Since the side surface portion 4b of the insulating sheet 4 does not come into contact with the axial end surface of the capacitor element 10, the elution of the oxidation inhibitor is small. Therefore, by providing the side surface portion 4b, the oxidation inhibitor is retained on the insulating sheet 4 for a long period of time. As a result, oxidation of the conductive polymer can be suppressed for a long period of time.

An oxidation inhibitor that is insoluble or has low solubility in the liquid agent impregnated in the capacitor element 10 may be used.

Further, when the liquid agent impregnated in the capacitor element 10 contains an electrolytic solution, the first electrode body 11 is oxidized by the electrolytic solution when a defect of the dielectric film occurs, and the dielectric film is repaired. At this time, the oxidation inhibitor held on the insulating sheet 4 reduces the repairing action of the dielectric film by the electrolytic solution.

Therefore, the holding amount of the oxidation inhibitor per unit area of the side surface portion 4b of the insulating sheet 4 is larger than the holding amount of the oxidation inhibitor per unit area of the bottom surface portion 4a. As a result, the amount of elution from the bottom surface portion 4a facing the axial end surface of the capacitor element 10 into the liquid agent is reduced, and the concentration of the oxidation inhibitor in the vicinity of the dielectric film can be reduced. Therefore, the repairing action of the dielectric film by the electrolytic solution can be maintained high.

Further, since the hardening of the bottom surface portion 4a is suppressed by the retention of the oxidation inhibitor, the liquid agent permeates the laminate of the natural cellulose fiber or the synthetic resin fiber, and the softness of the bottom surface portion 4a is maintained. As a result, the bottom surface portion 4a with which the axial end surface of the capacitor element 10 is in contact functions as a cushioning material, and damage to the capacitor element 10 can be prevented.

FIG. 5 described above shows the distribution of the antioxidant on the insulating sheet 4, and in the figure, the density of the antioxidant increases as the density of black increases. As shown in the figure, in the present embodiment, the density of the antioxidant is increased from the central portion in the X direction parallel to one side of the insulating sheet 4 toward the end portion. As a result, the holding amount of the oxidation inhibitor per unit area of the side surface portion 4b can be made larger than the holding amount of the oxidation inhibitor per unit area of the bottom surface portion 4a.

FIG. 8 is a perspective view illustrating a state of the insulating sheet 4 of the present embodiment at the time of manufacture. The base material of the insulating sheet 4 is processed into a long tape-shaped body 4'and wound to form a roll of the tape-shaped body 4'. Next, the roll of the tape-shaped body 4'is immersed in a solution of the antioxidant, impregnated with the solution of the antioxidant, then removed from the solution and dried.

At this time, since the tape-shaped bodies 4'adjacent in the radial direction of the roll are in close contact with each other, the solvent of the solution of the oxidation inhibitor escapes from the axial direction of the roll. Therefore, the oxidation inhibitor dissolved in the solvent moves in the tape-like body 4'in the axial direction of the roll together with the solvent, and the density of the oxidation inhibitor at the end portion is higher than that at the center portion in the axial direction (X direction). .. Then, by cutting the tape-shaped body 4'with a cutting line D perpendicular to the longitudinal direction, a square insulating sheet 4 having the distribution of the oxidation inhibitor shown in FIG. 5 can be obtained.

The insulating sheet 4 may be formed into a rectangle other than a square, or the tape-shaped body 4'may be formed into a parallelogram (including a rhombus) cut by a cutting line D inclined in the longitudinal direction. .. In this case as well, at least one diagonal line of the insulating sheet 4 can be made larger than the inner diameter of the main body case 3 to form the bottom surface portion 4a and the side surface portion 4b.

According to the present embodiment, since the insulating sheet 4 arranged between the end wall 3a of the main body case 3 and the capacitor element 10 holds the oxidation inhibitor, the oxidation of the conductive polymer is suppressed. Therefore, it is possible to suppress an increase in ESR of the electrolytic capacitor 1 over time.

Further, when the liquid agent impregnated in the capacitor element 10 contains an electrolytic solution in which an electrolyte of either an organic acid or an inorganic acid amine salt or an organic acid or an inorganic acid amidin salt is dissolved, the ESR of the electrolytic capacitor 1 is lowered. can do. In addition, defects in the dielectric film can be repaired by the oxidizing action of the electrolytic solution, so that the withstand voltage of the electrolytic capacitor 1 can be reliably increased and the leakage current can be reduced.

Further, when the liquid agent impregnated in the capacitor element 10 contains a low conductive liquid having no supporting electrolyte, the withstand voltage of the electrolytic capacitor 1 can be easily increased.

Further, the insulating sheet 4 has a bottom surface portion 4a arranged on the end wall 3a of the main body case 3, and a side surface portion 4b bent from the bottom surface portion 4a and arranged on the peripheral wall 3b of the main body case 3. As a result, since the amount of the oxidation inhibitor eluted from the side surface portion 4b into the liquid agent is small, the oxidation inhibitor is retained on the insulating sheet 4 for a long period of time, and the oxidation of the conductive polymer can be suppressed for a long period of time.

Further, when the capacitor element 10 is impregnated with a liquid agent containing an electrolytic solution, the holding amount of the oxidation inhibitor per unit area of the side surface portion 4b is larger than the holding amount of the oxidation inhibitor per unit area of the bottom surface portion 4a. It's getting bigger. As a result, since the amount of elution from the bottom surface 4a into the liquid agent is small, the concentration of the oxidation inhibitor in the vicinity of the dielectric film can be reduced, and the repairing action of the dielectric film by the electrolytic solution can be maintained high.

Further, since the insulating sheet 4 is formed in a rectangular or parallelogram shape and at least one diagonal line of the insulating sheet 4 is larger than the inner diameter of the main body case 3, the insulating sheet 4 having the bottom surface portion 4a and the side surface portion 4b can be easily formed. It can be realized.

Further, since the antioxidant retained in the insulating sheet 4 contains any one of a vitamin antioxidant, an amine antioxidant, a phenolic antioxidant, a phosphorus antioxidant, and a saccharide antioxidant, oxidation The insulating sheet 4 that holds the inhibitor can be easily realized.

In the present embodiment, the capacitor element 10 is impregnated with the liquid agent, but the capacitor element 10 may be immersed in the liquid agent filled in the main body case 3.

The present invention can be used in automobiles, electronic devices, etc. in which an electrolytic capacitor and an electrolytic capacitor are mounted in a control circuit.

1 Electrolytic capacitor 2 Capacitor body 3 Body case 3a End wall 3b Peripheral wall 3c Opening 3d Recess 4 Insulation sheet 4a Bottom part 4b Side part 4'Tape-like body 5 Sealing body 6 Seat plate 7, 8 Lead terminal 10 Condenser element 11 1st Electrode body 12 2nd electrode body 13 Separator 14 Winding tape D Cutting wire