JP2945742B2 - Aluminum electrolytic capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum electrolytic capacitor having improved safety, and more particularly to an aluminum electrolytic capacitor used for smoothing an input circuit in a switching power supply or the like.

Conventional technology Conventional aluminum electrolytic capacitors are formed by forming a dielectric oxide film on the surface of an anode foil made of roughened aluminum foil and winding this anode foil and cathode foil made of aluminum foil together with a separator. The capacitor winding element is formed, the capacitor winding element is impregnated with a driving electrolyte, and the capacitor winding element is sealed in a metal case made of aluminum.

The capacitor winding element is wound so that a space is formed at the center, and the diameter of the space at the center is conventionally 3 mm to 6 mm. This is less than 3mm
This is because the core rod cannot be pulled out properly after the winding is completed.

Problems to be Solved by the Invention When abnormal stress such as overvoltage is applied to the aluminum electrolytic capacitor having the above-described structure, a leakage current increases, and a reaction gas with a driving electrolyte solution by electrolytic decomposition causes a capacitor winding element. Generated from the inside of the
A force acts to deform the capacitor winding element inside and outside. In this case, since the outside of the capacitor winding element is stopped by the winding tape, deformation to the outside can be prevented.

However, since a space is formed in the center of the core near the core, when gas is generated from the capacitor winding element and the internal pressure increases, the core core cannot withstand the pressure. Buckles towards the center.

Also, since there is a cutting burr when the electrode foil is cut at the edge of the winding start portion of the electrode foil in the core portion of the capacitor winding element, the force for buckling in the direction of the center as described above is not applied. When working on the capacitor winding element, the cutting burr easily breaks through the separator and short-circuits the electrode foil consisting of the anode foil and the cathode foil.
When this short circuit occurs, there is a problem that the spark at that time ignites the driving electrolyte and the capacitor is ignited.

The present invention solves such a problem, and even when an abnormal stress due to overvoltage application is applied, an aluminum foil in which the electrode foil of the core portion of the capacitor winding element does not buckle in the center direction and short-circuit does not occur. An object of the present invention is to provide an electrolytic capacitor.

Means for Solving the Problems In order to solve the above problems, the present invention provides a capacitor winding element in which an anode foil and a cathode foil are wound together with a separator, and the electrolyte is infiltrated, and the capacitor winding element is housed. A metal case having a bottomed cylindrical shape, a sealing member for sealing an opening of the metal case, and an anode lead terminal and a cathode lead terminal derived from the capacitor winding element. The space is wound so that a space is formed at the center, and the diameter of the space at the center is at least 8 mm to 12 mm.

Operation According to the above configuration, even when the vicinity of the center of the capacitor winding element attempts to buckle to the center due to the gas pressure generated by the application of the overvoltage, the diameter of the space at the center is smaller than the conventional product. Since it is about 2 to 4 times larger, the buckling stress per unit area received by the central portion is reduced by that much, thereby suppressing the anode foil and the cathode foil from buckling toward the central portion. Therefore, it is possible to prevent a short circuit between the electrode foils, which occurs when the cutting burrs of the electrode foil break through the separator.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a capacitor winding element. The capacitor winding element 1 is formed by winding an anode foil and a cathode foil described later together with a separator. The capacitor winding element 1 is impregnated with a driving electrolyte, and the capacitor winding element 1 is provided in a bottomed cylindrical metal case 2 made of aluminum. A pair of anode lead terminals and cathode lead terminals 3a and 3b are led out from the capacitor winding element 1,
And a pair of the anode lead terminal and the cathode lead terminal 3
A pair of external connection terminals 4a and 4b are connected to a and 3b by caulking at a portion of a sealing member 5 formed of a terminal plate. The sealing member 5 made of the terminal plate is disposed in the opening of the metal case 2 and seals the opening of the metal case 2 by curling the open end of the metal case 2. At the bottom of the metal case 2, an explosion-proof valve 6 composed of a thin weak point is formed.

FIG. 2 shows details of the above-described capacitor winding element 1. The capacitor winding element 1 has a dielectric oxide film formed on the surface of an anode foil 7 made of roughened aluminum foil. It is configured by winding a foil 7 and a cathode foil 8 made of an aluminum foil via a separator 9. An anode lead terminal 3a extends from the anode foil 7, and a cathode lead terminal 3b extends from the cathode foil 8. In addition, the capacitor winding element 1 has a space in the center.
It is wound so that 10 is formed, and this space part
Reference numeral 10 denotes a winding rod (not shown) provided on the winding core, the anode foil 7 and the cathode foil 8 are wound via the separator 9, and after this winding, the winding rod on the winding core is pulled out. It is formed by this. The outside of the capacitor winding element 1 is fixed by a winding tape 11.

3 (a) and 3 (b) are cross-sectional views of a capacitor winding element according to the present invention and a conventional example, and a conventional capacitor winding element 1a shown in FIG. Like the capacitor winding element 1, the anode lead terminal 3a 'and the cathode lead terminal 3b' are led out, and a space 10a is formed in the center corresponding to the core. The diameter φ1 of the conventional space portion 10a is 3 mm to 6 mm. However, in the present invention, the diameter φ2 of the space portion 10 is set to a size of 8 mm to 12 mm. 2-4
About twice as large.

FIG. 4 is a schematic diagram showing how a force is applied to the capacitor winding element 1 when an abnormal stress such as an overvoltage is applied to the aluminum electrolytic capacitor.

When an abnormal stress such as an overvoltage is applied to the aluminum electrolytic capacitor, a leakage current increases, and a reaction gas with a driving electrolyte solution generated from the electrolysis is generated from the inside of the capacitor winding element 1 to increase the internal pressure. Thus, a force acts to deform the capacitor winding element 1 inward and outward. In this case, since the outside of the capacitor winding element 1 is stopped by the winding tape 11, deformation to the outside can be prevented.

However, since the space 10 is formed in the center of the winding core near the core, when gas is generated from the capacitor winding element 1 and the internal pressure increases, the vicinity of the core can withstand the pressure. Instead of buckling towards the center.

In this case, the pressure f per unit area received by the electrode foil composed of the anode foil and the cathode foil inside the capacitor winding element 1 is:
f = F / S, where F is the total pressure received by the entire inner peripheral portion of the capacitor winding element 1, and this total pressure F
Is constant if the total area of the electrode foil is constant. Also,
S is the area of the inner peripheral portion of the capacitor winding element 1. Therefore, the larger the diameter of the central portion 10 which is the core, the larger the value of S.
When the diameter φ2 of 10 is increased from 8 mm to 12 mm as compared with the conventional product, S becomes large, so that the pressure f per unit area received by the electrode foil composed of the anode foil and the cathode foil becomes small. Since the buckling that occurs toward the electrode foil does not occur, a short circuit between the electrode foil including the anode foil and the cathode foil hardly occurs.

FIG. 5 is a graph of the above description. 4 is a graph in which the horizontal axis represents the diameter φ of the space at the center of the capacitor winding element, and the vertical axis represents the buckling pressure for buckling the capacitor winding element. As described above, the buckling pressure f decreases as the diameter φ of the space increases. When φ is in the range of 3 mm to 6 mm, which is the range of the conventional example, the buckling pressure f is larger than the buckling resistance limit force f1, so buckling occurs and a short circuit occurs. However, when φ is in the range of 8 mm to 12 mm, which is the range of the present invention, the buckling pressure f is smaller than the buckling resistance limit force f1, and buckling in the center direction does not occur. The lower limit φ = 8 mm of the range of the present invention is a value experimentally determined as a point where the buckling pressure and the buckling resistance limit force coincide at this time. That is, buckling does not occur above this value. The upper limit φ = 12 mm of the present invention was determined for the following reason. That is, as the diameter of the space portion increases, the capacitor winding element becomes soft and easily collapsed. If the diameter of the center space is 12 mm or more,
This is because, during the production process, even if a small force is applied, the capacitor winding element is easily crushed, which makes production of the electrolytic capacitor difficult.

As is clear from the description of the above embodiments, the aluminum electrolytic capacitor of the present invention has a diameter of a space formed in the center portion when winding the capacitor winding element having a size of 8 mm to 12 mm. Therefore, even when an abnormal stress such as overvoltage is applied to the aluminum electrolytic capacitor, it is possible to suppress buckling of the electrode foil composed of the anode foil and the cathode foil toward the center, thereby reducing the cutting burrs of the electrode foil. It is possible to prevent a short circuit between the electrode foils generated by breaking through the separator.

[Brief description of the drawings]

FIG. 1 is a sectional view of an aluminum electrolytic capacitor showing one embodiment of the present invention, FIG. 2 is a perspective view showing a winding state of a capacitor winding element in the capacitor, and FIGS. 3 (a) and 3 (b).
FIG. 4 is a cross-sectional view of a capacitor winding element according to the present invention and a conventional example, FIG. 4 is a schematic view showing how a force is applied to the capacitor winding element when an overvoltage is applied to the capacitor, and FIG. 4 is a graph showing the relationship between the diameter of the central space of the element and the buckling stress applied to the inside. 1 ... Capacitor winding element, 2 ... Metal case, 3a ...
Anode lead terminal, 3b Cathode lead terminal, 5 Sealing member, 7 Anode foil, 8 Cathode foil, 9 Separator, 10 Space part.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Toru Yamaguchi 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (72) Inventor Toshinori Watanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshichika Fujiwara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72 ) Inventor Hiroshi Uchida 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-3-241726 (JP, A) Fully open 1979-157846 (JP, U) Fully open 1955-145039 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01G 9/048

Claims (1)

(57) [Claims] 1. A capacitor winding element formed by winding an anode foil and a cathode foil together with a separator and infiltrating an electrolytic solution, a bottomed cylindrical metal case for accommodating the capacitor winding element, and the metal case A sealing member for closing the opening of the capacitor, and an anode lead terminal and a cathode lead terminal derived from the capacitor winding element. The capacitor winding element is wound such that a space is formed at the center. Turn, and make the diameter of this central space at least 8 mm
Aluminum electrolytic capacitor with a size of ~ 12mm.