JP7451382B2 - Electrolytic capacitor - Google Patents

Description

The present invention relates to an electrolytic capacitor, and more particularly, to an electrolytic capacitor in which an anode foil and a cathode foil are overlapped via a separator, a wound capacitor element is impregnated with an electrolytic solution, and the capacitor element is inserted into an exterior case and sealed with a sealing body.

Conventionally, electrolytic capacitors include a capacitor element in which an anode foil and a cathode foil are wound with a separator in between, a capacitor case with a cylindrical bottom that stores the capacitor element together with an electrolyte, and an open end side of the capacitor case. Some are known that have a sealing body for closing. An anode terminal and a cathode terminal are drawn out from the outer end surface of the sealing body, and an anode lead tab and a cathode lead tab are connected to the anode foil and the cathode foil, respectively, at the base end of these terminals as an anode internal terminal and a cathode internal terminal. (See Patent Document 1).

In addition, as a conventional electrolytic capacitor, a liquid reservoir is formed on the inner surface of the sealing body by a continuous groove or the like between two through holes for inserting the anode terminal and the cathode terminal, and the liquid reservoir is used for electrolysis. An electrolytic capacitor configured to increase the amount of electrolytic solution sealed by storing a liquid has been proposed (see Patent Document 2).

Japanese Patent Application Publication No. 04-352313 Japanese Patent Application Publication No. 2005-209902

However, in conventional electrolytic capacitors, when a voltage is continuously applied for a long time at high temperatures, the anode lead tab and the cathode lead tab become electrically damaged due to the presence of condensate that is generated on the inner surface of the sealing body due to evaporation of the electrolyte. There was a problem that leakage current occurred due to conduction between the electrodes and the lead tab on the anode side corroded.

An object of the present invention is to provide an electrolytic capacitor that can suppress corrosion of lead tabs.

The electrolytic capacitor of the present invention includes a capacitor element formed by overlapping and winding a valve metal anode foil to which a first lead tab is connected and a cathode foil to which a second lead tab is connected, with a separator interposed therebetween; a cylindrical exterior case with a bottom for housing the capacitor element; a first through hole that seals the opening of the exterior case and that the first lead tab is inserted through; and a second through hole that the second lead tab is inserted through. an electrolytic capacitor comprising: a sealing body in which a through hole is formed; an inner surface of the sealing body facing the capacitor element includes a first region in which the first through hole is formed; The second region in which the second through hole is formed is formed at different heights in the thickness direction of the sealing body.

According to this configuration, even if condensate generated by evaporation of the electrolyte adheres to the inner surface of the sealing body, the sealing body is formed at different heights in the thickness direction of the sealing body between the anode side and the cathode side. By doing so, it is possible to suppress electrical conduction between the first and second lead tabs due to the condensed liquid. Thereby, generation of inter-terminal current between the first and second lead tabs can be suppressed, and corrosion can be suppressed.

Further, in the electrolytic capacitor of the present invention, in the above configuration, the inner surface of the sealing body is formed such that the second region is located at a greater distance from the capacitor element than the first region. It is characterized by

According to this configuration, it is possible to suppress the cathode side of the capacitor element, which is susceptible to physical stress, from being pressed by the inner surface of the sealing body.

Further, in the electrolytic capacitor of the present invention, in the above configuration, the difference in height between the first region and the second region in the thickness direction of the sealing body is in the range of 0.45 to 0.55 mm. It is characterized by

According to this configuration, it is possible to simultaneously suppress the occurrence of leakage current due to the condensed liquid due to evaporation of the electrolytic solution and suppress the physical stress applied to the cathode side of the capacitor element.

According to the electrolytic capacitor of the present invention, corrosion of the lead tab can be suppressed.

1 is a cross-sectional view showing the configuration of an electrolytic capacitor according to an embodiment of the present invention. FIG. 1 is a perspective view showing a capacitor element according to an embodiment of the present invention. FIG. 1 is a perspective view showing a sealing body according to an embodiment of the present invention. FIG. 2 is a plan view showing the inner surface of the sealing body according to the embodiment of the present invention. FIG. 5 is a cross-sectional view taken along line AA in FIG. 4 of the sealing body according to the embodiment of the present invention. FIG. 2 is a schematic diagram showing the relationship between a sealing body and a capacitor element according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing the state of adhesion of condensate on the inner surface of the sealing body according to the embodiment of the present invention. FIG. 7 is a perspective view showing a sealing body according to another embodiment. FIG. 7 is a perspective view showing a sealing body according to another embodiment.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.
As shown in FIG. 1, a wound type electrolytic capacitor 1 according to the present embodiment mainly includes a capacitor element 2, an exterior case 12, and a sealing body 20.

As shown in FIG. 2, the capacitor element 2 includes an anode foil (anode aluminum foil) 3a that has been subjected to an etching process and a dielectric oxide film forming process, and a cathode foil (cathode aluminum foil) 3b that has been subjected to an etching process. It is wound through a separator 4 and fixed with an element fixing tape 9 (FIG. 1). The capacitor element 2 is impregnated with an electrolyte and housed in a bottomed cylindrical outer case 12 (FIG. 1).

The exterior case 12 is made of aluminum, and has a structure in which a sealing body 20 made of resin, rubber, or the like is attached to an opening thereof, and the opening is sealed by drawing. Specifically, the outer circumferential surface 12a of the outer case 12 is formed with a recess 12b that extends annularly along the circumferential direction thereof. The recess 12b is formed by inserting the sealing body 20 into the outer case 12 and then drawing the outer peripheral surface 12a of the outer case 12. The sealing body 20 is made of, for example, an elastic rubber such as isobutylene-isoprene rubber (IIR) or ethylene propylene terpolymer (EPT).

Lead wires 6 and 16 are welded to the lead tabs 5 and 15 drawn out from the capacitor element 2, and are drawn out to the outside through a sealing body 20. The outer case 12 is covered with a sleeve 13.

The lead tab 5 is an anode-side lead tab connected to the anode foil 3a by crimping or welding, and the lead tab 15 is a cathode-side lead tab connected to the cathode foil 3b by crimping or welding. This is the lead tab on the side.

As shown in FIG. 1, in the sealing body 20, through holes 20c and 20d are formed at a predetermined interval and penetrate from the inner surface 20a facing the capacitor element 2 to the outer surface 20b facing the outside. Lead tabs 5 and 15 are inserted through 20c and 20d.

As shown in FIGS. 1, 3, 4, and 5, the inner surface 20a of the sealing body 20 has a linear step portion that divides the inner surface 20a into two and having different heights on the inner surface in the thickness direction of the sealing body 20. 20e is provided. Specifically, regarding the inner surface 20a of the sealing body 20, a first region AR1 includes a through hole 20c through which the lead tab 5 on the anode side is inserted, and a second region AR1 includes a through hole 20d through which the lead tab 15 on the cathode side is inserted. A step portion 20e is provided so as to divide it into two parts, AR2 and AR2. By providing this stepped portion 20e, a height difference is provided between the first region AR1 and the second region AR2 on the inner surface 20a of the sealing body 20.

That is, by providing this stepped portion 20e, the inner surface 20a in the first region AR1 constitutes an upper step surface 20f on the convex side in which the thickness of the sealing body 20 is thicker than the inner surface 20a in the second region AR2, The inner surface 20a in the second region AR2 constitutes a lower surface 20g in which the sealing body 20 is thinner than the first region AR1.

In this embodiment, the thickness T of the sealing body 20 is 4 to 5 mm, and the height of the stepped portion 20e (difference in height between the first region AR1 and the second region AR2) H (FIG. 5) is It is set to 0.45 to 0.55 mm. By setting such a height, it is possible to reduce the physical stress on the capacitor element 2, and even if the condensate evaporated from the electrolyte with which the capacitor element 2 is impregnated adheres to the inner surface 20a, the anode It is possible to prevent condensed liquid from connecting between the lead tabs on the side and the cathode side.

Specifically, when the outer peripheral surface 12a of the outer case 12 is drawn after the sealing body 20 is inserted into the outer case 12, the inner surface 20a (upper surface 20f) of the sealing body 20 comes into contact with the capacitor element 2. In order to reduce the physical stress caused by the pressing, the height H of the stepped portion 20e is configured to be equal to or less than a predetermined height.

Further, as shown in FIG. 6, by setting the lower surface 20g on the cathode side, the distance G2 between the lower surface 20g (second region AR2) and the capacitor element 2 on the cathode side is the same as the distance on the anode side ( Since the distance between the capacitor element 2 and the first region AR1 is larger than G1, the inner surface 20a of the sealing body 20 presses against the connection between the cathode foil and the lead, which is softer than the anode foil. Physical stress can be effectively suppressed.

Furthermore, although the condensed liquid evaporated from the electrolyte with which the capacitor element 2 is impregnated adheres to the inner surface 20a of the sealing body 20, the stepped portion 20e is formed between the lead tabs 5 and 15. As shown in FIG. 7, the condensate 110 is separated between the upper surface 20f on the anode side and the lower surface 20g on the cathode side, with the step portion 20e as a boundary. This suppresses the connection between the condensate 110 attached to the upper surface 20f on the anode side and the condensate 110 attached to the lower surface 20g on the cathode side, and prevents the condensate 110 from connecting between the lead tabs 5 and 15. The occurrence of leakage current can be suppressed.

The step portion 20e of the sealing body 20 can be manufactured by placing an elastic material such as rubber forming the sealing body 20 into a mold having a shape corresponding to the step 20e, or by molding the step portion 20e without forming the step portion 20e. There is a method of forming the sealing body and then cutting the inner surface 20a side of the sealing body 20 to form the stepped portion 20e.

Next, the manufacturing process of the electrolytic capacitor 1 will be explained.
Lead tabs 5 and 15 (made of aluminum) for external extraction electrodes are crimped and connected to the anode foil 3a (anode aluminum foil) and cathode foil 3b (cathode aluminum foil) cut to a predetermined width, respectively. As the anode foil 3a, an aluminum foil is used as the valve metal, and a dielectric oxide film is formed by etching and chemical conversion treatment on the surface of the valve metal. Further, the cathode foil 3b is also made of aluminum foil in the same manner as the anode foil 3a, and the surface of the aluminum foil is subjected to an etching treatment and a natural oxide film is formed thereon. Note that a dielectric oxide film may be formed on the cathode foil 3b, or carbon, titanium, titanium nitride, titanium carbide, etc. may be formed on the surface. Anode foil 3a and cathode foil 3b are wound with separator 4 mainly made of cellulose interposed therebetween to produce capacitor element 2.

The electrolyte-impregnated capacitor element 2 was then housed in an aluminum case (exterior case 12), and the opening of the exterior case 12 was sealed by curling. The electrolyte includes an electrolytic solution in which a solute is dissolved in a main solvent such as ethylene glycol or γ-butyrolactone, or both a solid electrolyte and an electrolytic solution whose main component is a conductive polymer such as polyethylenedioxythiophene/polystyrene sulfonic acid. can be used. Thereafter, a rated voltage is applied to the aluminum electrolytic capacitor (electrolytic capacitor 1) containing the capacitor element 2 in the outer case 12 in a constant temperature bath set at a predetermined temperature, and an aging treatment is performed to manufacture the electrolytic capacitor 1. Complete the process.

The present invention will be explained in more detail with reference to Examples below.

The aluminum lead tab is crimped and connected to the anode aluminum foil, and the aluminum lead tab is crimped and connected to the cathode aluminum foil. Then, the anode aluminum foil and the cathode aluminum foil are overlapped with a separator interposed therebetween, and the wound aluminum electrolytic capacitor element is impregnated with an electrolytic solution. Then, after inserting the round rods of the anode side lead tab and the cathode side lead tab pulled out from the aluminum electrolytic capacitor element through the insertion holes of the sealing body, insert the aluminum electrolytic capacitor element together with the sealing body into the exterior case. do. Next, the opening of the outer case is curled and the outer peripheral surface is drawn and sealed. As a result, an aluminum electrolytic capacitor with a rating of 450V/120μF (external dimensions: φ18mm in diameter x 31.5mm in length) was manufactured, and the rated voltage (450V) was produced in an environment of 115°C, which exceeds the upper limit temperature of the category. When the voltage was applied, the leakage current (60 second value) and the time until corrosion occurred near the lead tab on the anode side were measured. The occurrence of corrosion means a state in which corrosion products are attached or aluminum is dissolved. The measurement results are shown in Table 1.

The comparative example shows the results of measuring leakage current and corrosion occurrence time when the inner surface 20a of the sealing body 20 is not provided with the stepped portion 20e. This figure shows the results of measuring leakage current and corrosion occurrence time when a 5 mm step portion 20e is provided.

(Comparative example)
When the step portion 20e was not provided in the sealing body 20, the leakage current was 80 to 100 μA, and corrosion occurred in the lead tab after 2000 to 2500 hours.

(Example)
When the sealing body 20 was provided with a stepped portion 20e having a height of 0.5 mm, the leakage current was 20 to 30 μA, and no corrosion occurred in the lead tab until at least 3500 hours had elapsed.

The following can be understood from the above measurement results.
It has been found that when the stepped portion 20e is provided, the leakage current is significantly suppressed compared to the case where the stepped portion 20e is not provided, and as a result, the corrosion occurrence time is significantly extended.

According to the above configuration, the inner surface 20a of the sealing body 20 is provided with the stepped portion 20e that separates the cathode side and the anode side, and the condensed liquid adhering to the inner surface 20a is separated between the anode and the cathode. It is possible to avoid electrical connection between the two via the condensate, suppress the leakage current, and suppress the occurrence of corrosion of the lead tab due to the leakage current.

In addition, by forming the lower surface 20g on the lower stage side on the cathode side with the stepped portion 20e in between, the physical stress generated when the capacitor element 2 is pressed by the inner surface 20a (lower surface 20g) of the sealing body 20 can be reduced. , can be particularly reduced on the cathode side (the joint portion between the lead tab 15 on the cathode side and the cathode foil). This effectively suppresses the occurrence of tearing or wrinkling of the foil due to physical addition by the inner surface 20a of the sealing body 20 to the lead connection portion on the cathode side, which is softer than the anode side where a thick oxide film is formed. be able to.

In the above-described embodiment, a case has been described in which the inner surface 20a of the sealing body 20 is linearly divided into two by the stepped portion 20e, but the present invention is not limited to this, and for example, as shown in FIG. A circular recessed portion may be formed in the lower surface 20g in the thickness direction including the through hole 20d on the cathode side. Conversely, as shown in FIG. 9, a circular convex portion projecting in the thickness direction may be formed on the upper surface 20f on the anode side including the through hole 20c on the anode side.

In addition, the stepped portion 20e is not limited to being formed in a linear shape (FIG. 3) or circular shape (FIGS. 8 and 9), but is essentially formed so that the heights between the anode side and the cathode side are different. Various shapes can be applied as long as the shape is such that it can be used.

Further, in the above embodiment, a lead-shaped aluminum electrolytic capacitor (outside dimensions: diameter φ18 mm x length 31.5 mm aluminum electrolytic capacitor) with a rating of 450 V/120 μF was described, but the present invention is not limited to this, and the chip It can be widely applied to a variety of aluminum electrolytic capacitors, such as aluminum electrolytic capacitors of type, board-standing type, and screw terminal type, and conductive polymer hybrid aluminum electrolytic capacitors.

1 Electrolytic capacitor 2 Capacitor element 3a Anode foil 3b Cathode foil 4 Separator 5, 15 Lead tab 12 Exterior case 13 Sleeve 20 Sealing body 20a Inner surface 20e Step portion 20f Upper surface 20g Lower surface

Claims (3)

A capacitor element formed by stacking a valve metal anode foil to which a first lead tab is connected and a cathode foil to which a second lead tab is connected via a separator and winding them;
a bottomed cylindrical exterior case that houses the capacitor element;
an electrolyte sealing body that seals an opening of the exterior case and has a first through hole through which the first lead tab is inserted and a second through hole through which the second lead tab is inserted . An electrolytic capacitor containing an electrolyte ,
On the inner surface of the sealing body facing the capacitor element, a first region in which the first through hole is formed and a second region in which the second through hole is formed are formed on the inner surface of the sealing body. An electrolytic capacitor characterized in that the capacitor is formed at different heights in the thickness direction, and a boundary between the first region and the second region reaches a peripheral side of the sealing body . The electrolytic capacitor according to claim 1, wherein the inner surface of the sealing body is formed such that the second region is located at a greater distance from the capacitor element than the first region. . Claim 1 or Claim 2, wherein a height difference between the first region and the second region in the thickness direction of the sealing body is in a range of 0.45 to 0.55 mm. Electrolytic capacitors described in .

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