JP2003022934A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor which can restrain generation of hydrogen gas or the like generated from a cathode inner terminal and a cathode foil thereabout, prevent short circuit due to contact of a broken part of a cathode inner terminal and a cathode foil thereabout with other electrode and improve life characteristics by improving charge/discharge proofness and ripple proofness. SOLUTION: In an electrolytic capacitor having a capacitor element whereon an anode foil whereto an anode inner terminal is connected and a cathode foil whereto a cathode inner terminal is connected are wound, a part facing an anode foil of the cathode inner terminal is covered with a base material of which surface is coated with metal. Thereby, it is possible to reduce the difference of a surface area between a cathode inner terminal and a cathode foil, to prevent ripple current density from rising in a cathode inner terminal and a cathode foil thereabout, to restrain generation of hydrogen gas generated in the cathode inner terminal and a cathode foil thereabout, to reduce the difference of an applied voltage between a cathode inner terminal and a cathode foil and to prevent short circuit due to breakage of a cathode inner terminal and a cathode foil thereabout.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aluminum electrolytic capacitor.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional aluminum electrolytic capacitor includes an anode foil 2 having an oxide film formed on an etching foil made of a valve metal such as aluminum or titanium, and a valve metal such as aluminum or titanium. The capacitor element 1 is formed by winding a cathode foil 3 made of the above-mentioned etching foil and a separator 6 such as insulating paper. The anode foil 2 and the cathode foil 3 are provided with long and thin foil-shaped anode internal terminals 4 and cathode internal terminals 5 connected to the respective electrode foils by a stitch method or a cold weld method. In some cases, the internal terminal is covered with a protective member such as insulating paper or insulating tape in order to prevent a short circuit due to contact with a convex portion (burr or the like) of the internal terminal or another electrode foil of the connecting portion 7. . Then, the capacitor element 1 is impregnated with a driving electrolytic solution and is housed in a bottomed cylindrical outer case. The opening of the outer case is sealed by a sealing body, and a bipolar internal terminal and a bipolar external terminal derived from the capacitor element are connected to each other via rivets arranged in the sealing member to form an electrolytic capacitor. .

[0003]

However, in the conventional capacitor, since the distance between the anode foil 2 and the cathode foil 3 is short, the discharge current generated from the anode foil 2 remains almost unchanged.
And to the portion of the cathode internal terminal 5 facing the anode foil 2, and the cathode internal terminal 5 is not usually etched and its surface area is smaller than that of the cathode foil 3. Therefore, the surface area between the cathode internal terminal and the cathode foil is different, and, for example, the density per unit area of the ripple current flowing in the cathode internal terminal 5 is higher than that of the cathode foil, and especially in the low frequency region, within a short time. When used in a circuit in which a ripple current far exceeding the allowable ripple is periodically superposed, an excessive ripple current is superposed on the cathode internal terminal 5 at the time of discharging, and the cathode internal terminal and the cathode in the vicinity thereof are superposed. A film formation reaction may occur on the foil. Due to such a reaction, products such as hydrogen gas may be generated, and the internal pressure of the condenser may be increased to cause a malfunction such as operation of the explosion-proof valve.

When the capacitor is used in a charging / discharging circuit having a large voltage difference and a long cycle, the internal surface area of the cathode internal terminal 5 is smaller than that of the cathode foil 3, so that it is higher than that of the cathode foil 3. When a voltage is applied, the products such as hydrogen gas are generated in the cathode internal terminal 5 and the cathode foil in the vicinity of the cathode foil during the discharge, and further, the cathode internal terminal 5 and the cathode foil in the vicinity thereof are generated. There is a possibility that the life characteristics of the capacitor may be deteriorated due to breakage, the broken portion breaking through the separator 6 and contacting the anode foil 2 to cause a short circuit.

In order to solve the above-mentioned problems, an invention in which a small piece of roughened aluminum foil is superposed on a cathode internal terminal connected to a cathode foil (Japanese Patent Laid-Open No. 2000-216058).
(See Japanese Patent Laid-Open No. 2000-277384) in which the surface on the anode foil side of the cathode internal terminal connected to the cathode foil is etched.

The present invention also aims to improve the above-mentioned problems by suppressing the hydrogen gas and the like generated from the cathode internal terminal and the cathode foil in the vicinity thereof by improving the ripple resistance and charge / discharge resistance. Another object of the present invention is to provide an electrolytic capacitor capable of preventing a short circuit due to contact with the other electrode of the cathode internal terminal and the damaged portion of the cathode foil in the vicinity thereof and improving the life characteristics.

[0007]

In order to solve the above-mentioned problems, an electrolytic capacitor of the present invention comprises a capacitor element formed by winding an anode foil connected to an anode internal terminal and a cathode foil connected to a cathode internal terminal. In the electrolytic capacitor provided, the portion of the cathode internal terminal facing the anode foil is covered with a base material having a surface coated with a metal.

As the base material, paper, non-woven fabric or a mixed paper thereof is used, and a metal is adhered to at least the surface of the base material on the cathode foil side.

A conductive member such as a metal foil is used as the base material, and a metal is deposited on at least the surface of the base material on the anode foil side.

The metal to be deposited is selected from aluminum, tantalum, titanium, niobium, nickel, tin and mixtures thereof, and their nitrides.

That is, by covering the portion of the cathode inner terminal facing the anode foil with the base material having the surface coated with a metal, the cathode inner terminal substantially faces the anode foil is the base material, and the base Since the surface area of the material is expanded by the deposition of the metal, the difference in surface area between the cathode internal terminal and the cathode foil can be reduced. Therefore, the difference in ripple current density per surface area between the cathode internal terminal and the cathode foil is reduced, or the difference is eliminated, and it is possible to prevent the ripple current density from becoming high at a portion of the cathode internal terminal having a small surface area,
It is possible to suppress the generation of hydrogen gas and the like accompanying the film formation reaction that occurs in the cathode internal terminal and the cathode foil in the vicinity thereof. Further, by reducing the difference in the surface area between the cathode internal terminal and the cathode foil, it is possible to reduce the difference in the applied voltage between the cathode internal terminal and the cathode foil, and the cathode internal terminal is more than acceptable. The voltage can be prevented from being applied. Therefore, it is possible to reduce short circuit defects due to damage to the cathode internal terminal and the cathode foil in the vicinity thereof. In the present invention, the metal can be deposited only on the optimum portion of the base material by means such as vapor deposition, spraying, printing, etc., and the manufacturing cost can be reduced and the manufacturing method can be simplified. Further, the metal adhesion layer for increasing the surface area can be formed thin, and the overall thickness is little affected. Furthermore, there are many selected base materials such as paper, non-woven fabric or their mixed materials, metal foils, conductive resin tapes, etc. as the base material to which the metal is attached, and the optimum base material should be selected according to the usage situation. You can

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an electrolytic capacitor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a connection portion of the cathode internal terminal of the electrolytic capacitor in the embodiment of the present invention. FIG. 3 is a cross-sectional view showing a connecting portion of a cathode internal terminal of an electrolytic capacitor according to another embodiment of the present invention.

As shown in FIG. 1, in the electrolytic capacitor of this embodiment, the anode foil 2 is made of a valve-action metal foil such as aluminum or titanium on which an oxide film is formed by etching, and the cathode foil 3 is etched. It consists of a valve metal foil such as aluminum or titanium. On both of these electrode foils, tab terminals in the form of an elongated foil made of aluminum or the like, electrode internal terminals such as a round bar portion, a flat portion and a lead terminal connected to the round bar portion are stitched or cold welded. Connected by law. And the anode foil 2
The capacitor element 1 is formed by winding the cathode foil 3 and the cathode foil 3 with a separator interposed therebetween. The separator 6 is made of an insulating member such as an insulating paper such as a manila paper or a kraft paper, a non-woven fabric or a mixed paper thereof.

Then, as shown in FIG. 2, a portion of the cathode internal terminal 5 connected to the cathode foil 3 facing the anode foil 2 is covered with a base material 8 having a surface coated with a metal.
When the base material 8 covers the portion of the cathode internal terminal 5 facing the anode foil 2, the base material 8 together with the cathode internal terminal 5 is swaged together with the stitches by a stitching needle, or cold. Connect and fix all together by the weld method. The base material 8 is directly fixed to the cathode foil 3 without being fixed to the cathode foil 3 by a stitch method or a cold weld method. Alternatively, the base material 8 is interposed between the cathode foil 3 and the separator 6 by adhering the base material 8 to the cathode foil 3 or the cathode internal terminal 5 with an adhesive. The base material 8 coated with the metal is the same as or wider than the cathode internal terminal 5.

As the base material 8, a conductive member such as paper, non-woven fabric or a mixed paper thereof, a metal foil or a conductive resin tape is used. And metal is vacuum-deposited on the surface,
An adhesion layer 9 applied by spraying, printing or the like is formed. As the metal, for example, aluminum, tantalum, titanium, tin, nickel, niobium, a mixture thereof, or a nitride thereof may be used. These metals are not corroded by the driving electrolyte impregnated in the capacitor element, and the reliability thereof is improved.

When paper, non-woven fabric or a mixed paper thereof is used as the base material 8, as shown in FIG.
The surface of the base material 8 on the side of the cathode foil is mainly covered with a metal.
Metal is adhered to the portion that comes into contact with. This allows
The portion of the cathode internal terminal 5 facing the anode foil 2 is the base material 8
Since the driving electrolytic solution which is covered with the metal adhesion layer 9 and is impregnated in the capacitor element 1 penetrates into the paper, the non-woven fabric or the mixed paper thereof used as the insulating material, the cathode internal terminal 5 Is substantially opposed to the anode foil 2 by the base material 8, particularly the metal adhesion layer 9, and the adhesion layer 9 of the base material 8 has a larger surface area than the cathode internal terminal 5, The difference in surface area between the internal terminals and the cathode foil is reduced. Therefore, the difference in ripple current density between the cathode internal terminal 5 and the cathode foil 3 is reduced, and generation of hydrogen gas from the cathode internal terminal 5 and the cathode foil in the vicinity thereof can be prevented.
Further, since the difference in surface area between the cathode internal terminal 5 and the cathode foil 3 is reduced, the difference in applied voltage between the cathode internal terminal 5 and the cathode foil 3 can be reduced, and the cathode internal terminal can be reduced. 5
It is possible to prevent a voltage higher than the allowable voltage from being applied. Therefore, it is possible to reduce short-circuit defects due to damage to the cathode internal terminal 5 and the cathode foil in the vicinity thereof. It suffices that the metal adhesion layer 9 is formed on at least the surface of the base material 8 on the side of the cathode foil, and the adhesion to the surface of the base material 8 on the side of the anode foil is optional. The surface of the paper, non-woven fabric or their mixed paper used as the base material 8 has an uneven shape, and the surface area of the adhered layer 9 can be greatly expanded by applying a metal to the shape. Therefore, the difference in ripple current density per unit area between the metal deposition layer 9 and the cathode foil 3 can be significantly reduced. In addition, the metal can be deposited only on the optimum portion of the base material by means of vapor deposition, spraying, printing, etc., which reduces the manufacturing cost and simplifies the manufacturing method. Furthermore, the metal adhesion layer 9 can be formed thin, and the thickness of the capacitor element 1 is not affected.

Further, conventionally, the convex portion of the internal terminal and the connecting portion 7 are
If a protective member made of insulating paper or the like used for protection of is used as a base material and the metal is adhered to the surface thereof, a new base material is not used and the manufacturing method can be simplified. is there. Further, by using the same insulating paper as the separator, the manufacturing cost can be reduced and the manufacturing method can be greatly simplified.

Further, by depositing a metal on the surface and covering the portion of the cathode internal terminal 5 facing the anode foil 2 with an insulating base material made of paper, nonwoven fabric or a mixed paper thereof, the cathode of the cathode internal terminal 5 can be covered. It is possible to prevent the connecting portion 7 and the convex portion to the foil 3 from breaking through the separator 6 and coming into contact with or short-circuiting with the anode foil 2. Further, even if an unacceptable voltage is applied to the cathode internal terminal 5 and the cathode foil in the vicinity thereof. Even if the damage is caused by the above, since the cathode internal terminal 5 is covered with the insulating base material made of the paper, the non-woven fabric or the mixed paper thereof, a short circuit due to the contact of the damaged portion with the anode foil 3 is prevented. can do.

As another embodiment, as shown in FIG. 3, at least when a metal foil or a conductive resin tape is used as the base material 8 covering the portion of the cathode internal terminal 5 facing the anode foil 2, A metal is adhered to the surface of the base material 8 on the anode foil side. As a result, the cathode inner terminal substantially faces the anode foil 2 by the metal deposition layer 9 of the substrate 8, and the deposition layer 9 reduces the difference in surface area between the cathode inner terminal 5 and the cathode foil 3. Therefore, the difference in ripple current density between the cathode internal terminal 5 and the cathode foil 3 is reduced, and the generation of hydrogen gas due to the film formation reaction from the cathode internal terminal 5 and the cathode foil in the vicinity thereof can be prevented. Further, since the difference in surface area between the cathode internal terminal 5 and the cathode foil 3 is reduced, the difference in applied voltage between the cathode internal terminal 5 and the cathode foil 3 can be reduced, and the cathode internal terminal can be reduced. It is possible to prevent a voltage higher than the allowable voltage from being applied to 5. Therefore, it is possible to reduce short-circuit defects due to damage to the cathode internal terminal 5 and the cathode foil in the vicinity thereof. The metal foil is aluminum, tantalum,
It is made of a valve metal such as titanium. The metal adhesion layer 9 may be formed on at least the surface of the base material 8 on the side of the anode foil, and may be adhered to the surface of the base material 8 on the side of the cathode foil.

The above-mentioned capacitor element 1 is impregnated with a driving electrolytic solution, and is housed in a bottomed cylindrical outer case made of aluminum. The opening of the outer case is sealed by a sealing member, and the bipolar internal terminal and the bipolar external terminal led out from the capacitor element are connected to each other via a rivet arranged in the sealing member to form an electrolytic capacitor.

[0021]

As described above, the electrolytic capacitor of the present invention is an electrolytic capacitor having a capacitor element formed by winding an anode foil to which an anode internal terminal is connected and a cathode foil to which a cathode internal terminal is connected. By covering the portion of the cathode internal terminal facing the anode foil with the base material coated with a metal, by reducing the difference in surface area between the cathode internal terminal and the cathode foil, the cathode internal terminal and its vicinity It is possible to prevent the ripple current density from increasing in the cathode foil, and to suppress the generation of hydrogen gas accompanying the film formation reaction that occurs in the cathode internal terminal and the cathode foil in the vicinity thereof, and between the cathode internal terminal and the cathode foil. It is possible to reduce the difference in applied voltage between the two, and it is possible to reduce short circuit defects due to damage to the cathode internal terminal and the cathode foil in the vicinity thereof.

[Brief description of drawings]

FIG. 1 is a perspective view showing an electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a connection portion of the cathode internal terminal of the electrolytic capacitor in the example of the present invention.

FIG. 3 is a sectional view showing a connection portion of a cathode internal terminal of an electrolytic capacitor according to another embodiment of the present invention.

FIG. 4 is a perspective view showing a conventional electrolytic capacitor.

[Explanation of symbols]

1 Capacitor element 2 Anode foil 3 cathode foil 4 Anode internal terminal 5 Cathode internal terminal 6 separator 7 connection 8 base materials 9 Adhering layer

Claims (4)

[Claims] 1. An electrolytic capacitor having a capacitor element formed by winding an anode foil connected to an anode internal terminal and a cathode foil connected to a cathode internal terminal, wherein the cathode internal terminal is formed by a base material having a metal coated on the surface thereof. Electrolytic capacitor that covers the part facing the anode foil of. 2. The electrolytic capacitor according to claim 1, wherein a paper, a non-woven fabric, or a mixed paper thereof is used as the base material, and a metal is deposited on at least the surface of the base material on the cathode foil side. 3. The electrolytic capacitor according to claim 1, wherein a conductive member such as a metal foil is used as the base material, and a metal is deposited on at least the surface of the base material on the anode foil side. 4. The deposited metal is selected from aluminum, tantalum, titanium, niobium, nickel, tin and mixtures thereof, and their nitrides.
4. The electrolytic capacitor according to any one of 3 to 3.