JP3170589B2 - Electrolytic capacitor and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrolytic capacitor having excellent flame retardancy and a method for producing the same.

(Prior Art) In general, in manufacturing an electrolytic capacitor, a separator or a separator and a cathode foil are wound around a winding shaft several times, and then an anode foil is inserted and wound to form a capacitor element. After being impregnated with the electrolytic solution, the capacitor element is sealed in a metal case such as aluminum. An explosion-proof valve is usually formed in the metal case.

When the electrolytic capacitor is in an abnormal use state such as application of an overvoltage, heat generation and generation of hydrogen gas occur inside the capacitor. If the abnormality lasts for a long time, the explosion-proof valve opens to release the gas inside the capacitor to prevent the capacitor from exploding. However, in the case of a sudden abnormality, sparks may be generated due to discharge or short-circuit of the electrode foil, and in some cases, a fire may occur due to application to gas or electrolyte.

When a fire occurs in the electrolytic capacitor, not only the surrounding parts and the like are damaged, but also the fire in which the electrolytic capacitor is incorporated may spread, which is a serious problem.

Therefore, in recent years, there has been an increasing demand for making electrolytic capacitors flame-retardant.

(Problems to be Solved by the Invention) There are several methods for making an electrolytic capacitor flame-retardant. For example, a method of enclosing the electrolytic capacitor itself in a case containing a digestive agent is known. However, there is a problem that the size of the electrolytic capacitor becomes large and it is not adapted to miniaturization, and the cost increases.

There is also known a method in which a large amount of boric acid is added to an electrolytic solution to make the electrolytic solution itself difficult to burn. However, when a large amount of boric acid is added to the electrolytic solution, the characteristics at high temperatures become unstable, which is contrary to the purpose of extending the life at high temperatures.

The present invention has been made in view of the above problems,
It is an object of the present invention to provide an electrolytic capacitor which is inexpensive and excellent in flame retardancy by only slightly changing the structure, and a method of manufacturing the same.

(Means for Solving the Problems) An electrolytic capacitor according to the present invention having the above object is an electrolytic capacitor having a capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween. On the formed core, formed by winding a cathode foil composed of a separator and an aluminum foil, a reinforcing layer having a thickness of 1 mm or more and 2 mm or less without the presence of an anode foil is characterized in that I have.

The present invention also provides a capacitor element formed by winding a separator between an anode foil and a cathode foil, and impregnating an electrolytic solution into a case to produce an electrolytic capacitor. With a cathode foil consisting of 1 mm or more and 2 mm thick without an anode foil
A method for manufacturing an electrolytic capacitor, further comprising forming a cylindrical immersion portion having a reinforcing layer of not more than mm, and then winding the anode foil to form a capacitor element.

(Operation) In order to simulate the operation of the explosion-proof valve, a test was performed in which a DC overvoltage was applied to the electrolytic capacitor. In the case of the conventional structure, the cylindrical core of the capacitor element collapsed, and the separator near the core was broken. And the electrode foil bends toward the core (FIG. 3 (a)). In this portion, the electrode foils are short-circuited to generate a spark. This is considered to be due to the collapse of the cylindrical core by the pressure of the hydrogen gas that is rapidly generated by the application of the overvoltage.

In this regard, in the present invention, the cylindrical core portion is formed by winding a separator and a cathode foil made of aluminum foil in a thickness of 1 m.
A reinforcing layer of not less than m and not more than 2 mm is formed. For this reason, even if gas is generated suddenly, it is possible to suppress deformation of the element such that the core is crushed and the vicinity of the core is bent. For this reason, generation of spark can be prevented, and as a result, ignition of the capacitor can be suppressed and flame retardancy can be improved.

However, if the anode foil is interposed in the reinforcing layer, the anode foil is thick and brittle because the oxide film is formed and the core is not strong, and the core is crushed by gas pressure and the vicinity of the core is deformed. It will be.

On the other hand, a reinforcing layer formed by winding a flexible separator made of kraft paper, Manila hemp, a porous synthetic resin sheet, or the like, and a flexible cathode foil made of aluminum foil into a multilayer having a thickness of 1 mm or more and 2 mm or less. When formed on the core, the core can be formed so as not to be crushed by the pressure of the hydrogen gas generated rapidly by the application of the overvoltage.

(Examples) Hereinafter, the present invention will be described in detail based on examples.

Example 1 Example product A separator and a cathode were wound around the core and the thickness was 2 mm.
After forming a cylindrical core portion on which a reinforcing layer 10 (d = 2 mm in FIG. 2) was formed, an anode foil was wound thereon to produce a capacitor element 12 of φ30 mm × 30 mmL (FIG. 1). After the capacitor element 12 was impregnated with the electrolytic solution, the capacitor element was sealed in an aluminum case to obtain a 250 V 470 μF capacitor. Reference numeral 14 denotes an electrode extraction tab.

Comparative Example Product After the separator and the cathode foil were wound empty to form a cylindrical core having a thickness of 0.5 mm, the anode foil was wound and wound to form a capacitor element. Hereinafter, 25 in the same manner as in Example 1.
A capacitor of 0V470μF was produced.

Conventional Example A capacitor element having a cylindrical core portion in which a separator or a separator and a cathode foil were wound about several times was produced, and a 250 V470 μF capacitor was obtained in the same manner as in Example 1.

Reference example product After forming only a separator and forming a cylindrical core having a reinforcing layer 10 having a thickness of 1 mm by winding the separator only, an anode foil and an anode foil are wound thereon to form a capacitor element 12 of φ30 mm × 30 mmL. Formed. Thereafter, a capacitor of 250 V and 470 μF was formed in the same manner as in Example 1.

385vDC was applied to the produced capacitor, and an overvoltage test was conducted to investigate the state of valve operation. The results are shown in Table 1.

As is clear from Table 1, the products of Examples and Reference Examples according to the present invention had no internal spark at all as compared with the conventional products, and could achieve flame retardancy.

After the test, the capacitor was disassembled, the capacitor element was cut into a circle, and the cross section was examined. As shown in FIG. 3, in the conventional product, the cylindrical core was crushed, and the area near the core was bent inward. I was short. On the other hand, in the example product and the reference example product, the cylindrical core portion was not crushed, and no abnormality was observed near the core portion.

Further, in the comparative example product in which the reinforcing layer of the core portion of the capacitor element was less than 1 mm, sparks were generated, and a sufficient effect was not obtained.

Example 2 A separator and a cathode foil were wound around a core portion, or a separator alone was wound around to form a cylindrical core portion in which a reinforcing layer 10 having a thickness shown in Table 2 was formed. φ30mm × 50
An mmL capacitor element 12 was manufactured. After the capacitor element 12 was impregnated with the electrolytic solution, the capacitor element was sealed in an aluminum case to obtain a 250 V820 μF capacitor. This capacitor has a larger capacity, a longer length, and a larger size than the capacitor manufactured in Example 1.

When the thickness of the reinforcing layer was 3 mm, the obtained capacitor element could not be inserted into the aluminum case.

For the manufactured capacitor, a passing voltage test for applying 385 VDC was performed in the same manner as in Example 1. The results are shown in Table 2.

As is clear from Table 2, in the electrolytic capacitor according to the present invention including the cylindrical core having the reinforcing layer having a thickness of 1 mm or more formed by winding the separator and the cathode foil in an empty manner,
Even if the capacity and size of the electrolytic capacitor are larger than those of the electrolytic capacitor, no internal spark is generated.

On the other hand, even if an electrolytic capacitor having a reinforcing layer with a thickness of 1 mm or more formed by winding only a separator, or a reinforcing layer formed by winding a separator and a cathode foil, the thickness is less than 1 mm. In an electrolytic capacitor having a reinforcing layer, an internal spark is generated.

Thus, even if the separator and the cathode foil are wound to form the reinforcing layer on the cylindrical core portion, if the thickness of the reinforcing layer is less than 1 mm, or Even if a reinforcing layer of 1 mm or more is formed on the cylindrical core, the electrolytic capacitor with a large capacity and large size also increases the amount of hydrogen gas generated rapidly due to the application of overvoltage, resulting in an increase in gas pressure. Is increased, and the cylindrical core becomes unable to withstand the gas pressure and collapses.

(Effects) According to the present invention, it is possible to provide an electrolytic capacitor having improved flame retardancy, and it is possible to achieve a manufacturing method by slightly improving the conventional method, thereby being inexpensive.

[Brief description of the drawings]

FIG. 1 is a perspective view of an electrolytic capacitor element according to the present invention, FIG. 2 is a bottom view of the electrolytic capacitor element according to the present invention, and FIG. 3 is a diagram showing a conventional example (a) and an embodiment (b) of the present invention after an overvoltage test. FIG. 10 ... reinforcement layer, 12 ... capacitor element, 14 ... electrode lead-out tab

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Claims (2)

(57) [Claims] An electrolytic capacitor having a capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween, wherein a cathode foil made of a separator and an aluminum foil is provided on a cylindrical core of the capacitor element. An electrolytic capacitor, characterized in that a reinforcing layer having a thickness of 1 mm or more and 2 mm or less without an anode foil, which is formed by winding in a hollow shape, is formed. 2. A capacitor element formed by winding a separator between an anode foil and a cathode foil and impregnating with an electrolytic solution into a case to produce an electrolytic capacitor. After forming a cylindrical core having a reinforcing layer having a thickness of 1 mm or more and a thickness of 2 mm or less in which no anode foil is present, the anode foil is wound and a capacitor element is formed. A method for manufacturing an electrolytic capacitor, comprising: