JPH0451044B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in a method for manufacturing an electrolytic capacitor element having a wound structure. [Prior art] Electrolytic capacitors with a wound structure use a band-shaped film-forming metal foil such as aluminum as an electrode, and an oxide film on the surface of which is formed as a dielectric is used as an anode, and a separator paper is interposed. In the same way, a cylindrical capacitor element is produced by winding a strip of cathode foil overlapping the same, impregnating it with an electrolyte, and storing it in an exterior case. Since the capacitance of an electrolytic capacitor is proportional to the surface area of the anode, the surface of the anode is enlarged by etching in order to increase the capacitance per unit volume. In recent years, due to the demand for smaller electrolytic capacitors,
Etching for this purpose of enlarging the surface area has become extremely sophisticated. For this reason, the number of holes in the electrode foil increases due to etching, and as a result, the mechanical strength of the electrode foil with respect to bending, tension, etc. is significantly reduced. Furthermore, by forming a dielectric oxide film layer on the surface of the anode foil, the anode foil has the property of increasing its hardness and becoming brittle. This is particularly noticeable in medium-high voltage electrode foils that use hard aluminum foil as a starting material.For example, electrolytic capacitors used for strobe flash charge storage are a specific example of this. Manufacturing devices has become extremely difficult. FIG. 2 shows a conventional winding method for an electrolytic capacitor element, in which a cathode foil 2 and two separator papers 3 are wrapped around a winding shaft 4 in advance. In between, the winding start end 5 of the anode foil 1 is inserted in the direction of the arrow b in the figure, and is then wound together with the cathode foil 2 and the separator paper 3 in the direction of the arrow a in the figure to form a capacitor element. . At this time, the end 5 of the anode foil 1 is straight, and when this end 5 is sandwiched between two sheets of separator paper 3 and rapidly tightened in a spiral shape,
The brittle anode foil 1 will break near the end 5 at the beginning of winding. As a result, the sharp end of the broken anode foil 1 pierces the separator paper 3, resulting in a short circuit with the cathode foil 2. [Problems to be Solved by the Invention] This invention improves the above-mentioned drawbacks of the conventional technology, and makes it possible to wind an etched anode foil with low mechanical strength to form a capacitor element without inconveniences such as breakage. The purpose is to form a highly reliable electrolytic capacitor. [Means for Solving the Problems] The method of the present invention involves winding a band-shaped film-forming metal foil, which has been subjected to surface enlargement treatment by etching and has a dielectric oxide film layer formed on its surface, as an anode. In the method for manufacturing an electrolytic capacitor element, the winding start end of the anode is annealed in advance to soften it, and then winding is performed. [Function] When the anode foil is etched and a dielectric oxide film is formed, its hardness increases and it becomes extremely brittle.
However, according to the method of the present invention, since the anode foil at the winding start end is annealed, this part is softened, and even if it is inserted into the winding start end with a small curvature, it will not suddenly roll. It is possible to follow the winding, and the electrode foil will not break. [Example] Hereinafter, the present invention will be described in detail based on Examples. FIG. 1 shows an embodiment of this invention.
A cathode foil 2 and two separator papers 3 are stacked on the winding shaft 4 so as to sandwich the cathode therebetween, and are previously wrapped about once or several times. Then, the upper surface of the separator paper 3 is etched, and the end 5 of the anode foil 1 on which the dielectric oxide film layer is formed is inserted in the direction of arrow b in the figure, and the separator paper 3 and the cathode foil 2 and are wound in a multilayered manner in the direction of arrow a in the figure. At this time, a region S that is wound about one or two times from the winding start end 6 of the anode foil 1 is heated by a burner flame before winding, and then annealed by natural cooling. There is. In this manner, the wound capacitor element is impregnated with an electrolytic solution by a known method (not shown), provided with electrode extraction means, and housed in an exterior case and sealed to become an electrolytic capacitor. Note that the annealing of the foil is not limited to heating with the above-mentioned burner, but may also be conducted by applying electricity to the electrode foil, induction heating using electromagnetic waves, or the like. Next, a comparison will be made between a capacitor element formed by the method of the present invention and a conventional capacitor element. The experiment was conducted using a cylindrical strobe flash aluminum electrolytic capacitor with a rated voltage of 330 V, a capacitance of 100 μF, an external diameter of 18 φ, and a length of 30 mm. This figure looks at the incidence of short-circuit accidents caused by breakage of the electrode foil. The anode foil used had a thickness of 100 μm and was subjected to advanced etching treatment and then anodized at a voltage of 35 V to form a dielectric oxide film layer.
It is cut into 20mm strips and rolled. In the case of using the method of the present invention, the tip of the anode foil was heated for 2 seconds with a burner before winding, and then the anode foil was naturally cooled. The table shows this result.Lot A
The electrolytic capacitors E to E were divided into approximately two halves, and the capacitor elements were wound using the conventional method and the method of the present invention, and electrolytic capacitors were assembled, and the occurrence rate of short circuit accidents due to breakage of the electrode foil was compared. .

〔Effect of the invention〕

As described above, according to the present invention, even if the electrode foil is highly etched and has low mechanical strength, it is possible to form a wound element without causing breakage, thereby preventing short circuit accidents. A highly reliable electrolytic capacitor can be obtained. Furthermore, since it is possible to wind electrode foil with a high etching ratio, which was conventionally impossible to wind, the capacitance per unit volume can be increased, contributing to miniaturization of electrolytic capacitors. Furthermore, since the occurrence of short-circuit accidents is reduced, the yield in the manufacturing process is improved, and the method is useful as a manufacturing method for electrolytic capacitor elements.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a method of winding an electrolytic capacitor element according to the present invention, and FIG. 2 is a sectional view showing a conventional method of winding a capacitor element. DESCRIPTION OF SYMBOLS 1... Anode foil, 2... Cathode foil, 3... Separator paper, 4... Winding shaft, 5... End part.

Claims (1)

[Claims] 1. A method for manufacturing an electrolytic capacitor element in which a band-shaped film-forming metal foil, which has been subjected to a surface enlargement treatment by etching and has a dielectric oxide film layer formed on its surface, is wound as an anode. A method for manufacturing an electrolytic capacitor element, characterized in that winding is performed after the starting end is annealed in advance.