JPH0216570B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrolytic capacitor, and an object of the present invention is to improve the performance of the capacitor by improving the sealing body. Generally, electrolytic capacitors are made by forming a dielectric film on the surface of a metal foil with valve action such as aluminum or tantalum through anodizing treatment to form an anode body, as shown in Figures 1 and 2. The capacitor element 1 is wound with a separator impregnated with a driving electrolyte (hereinafter referred to as electrolyte) between the cathode foil and the capacitor element 1, and the internal lead 5 is drawn out from the capacitor element 1. 5 is connected to an external lead wire 4, which is housed in a metal case 2. In the case of FIG. 2, the internal lead 5 on the cathode side is connected to the case 2, and the opening of the case 2 is sealed with an elastic sealing member 3. Since such electrolytic capacitors use an electrolytic solution, when the temperature rises, it passes through the elastic sealing member 3 and dissipates to the outside. Therefore, when used in a high-temperature atmosphere for a long period of time, the electrolytic solution evaporates and dries up. However, it has disadvantages such as the capacitor becoming hard and not functioning as a capacitor, and the loss value of the capacitor increasing. For this reason, ethylene propylene rubber is also frequently used as a sealing material with excellent heat resistance, and ethylene propylene rubber can withstand long-term use at high temperatures of around 150°C and exhibits relatively little change in hardness. However, its gas permeability is comparable to that of natural rubber, and it cannot maintain airtightness at high temperatures with respect to electrolytes using organic solvents such as highly volatile dimethylformamide (hereinafter referred to as DMF). In order to eliminate the above-mentioned drawbacks, the present invention uses a two-layer elastic sealing body made of polyester elastomer and ethylene propylene rubber as the rubber material for the sealing body. The present invention will be explained below based on the embodiments shown in FIGS. 3 and 4. Table 1 shows nitrogen gas permeability, Table 2 shows 125
A comparison is shown with the initial value of curing measured after being left at room temperature for 1000 hours at ℃.

【table】

[Table] Table 3 shows the changes in rubber when immersed in DMF at 125°C for 500 hours.

[Table] These test results show that ethylene propylene rubber is excellent against electrolytes using DMF as a solvent, but it has high gas permeability and lacks airtightness as an elastic sealant. Although polyester elastomer has good airtightness, it is not suitable for areas that come into contact with an electrolyte containing DMF as a solvent. Therefore, when using an electrolytic solution containing DMF, ethylene propylene rubber 6b is placed on the side in contact with the electrolytic solution, and in order to maintain airtightness,
By using a two-layer elastic sealing body with a polyester elastomer 6a disposed on the outside thereof, a highly reliable electrolytic capacitor can be obtained. It goes without saying that even in the case of a stable solvent such as ethylene glycol, a more reliable electrolytic capacitor can be obtained by using the two-layer sealing body 6 made of ethylene propylene rubber 6a and polyester elastomer 6b. Next, as an elastic sealing body for an electrolytic capacitor with a rating of 10V, 220μF (10mmφ x 20mmL) and a rating of 50V, 10μF (8mmφ x 16mmL), two layers consisting of conventional ethylene propylene rubber, the polyester elastomer of the present invention, and ethylene propylene rubber were used. 2000 in a 125℃ atmosphere for products using an elastic sealant of
The life test results of applying the rated voltage for hours are shown in Table 3, FIG. 5, and FIG. 6.

[Table] The electrolyte used in this test was a solvent mixed with DMF. Moreover, the measured values show the average value of each 20 samples. As is clear from the test results, the electrolytic capacitor using the two-layer elastic seal of the present invention is a high-performance, long-life, highly reliable capacitor that can guarantee high temperatures. The above-mentioned elastic sealing body is not limited to a two-layer structure, but can also be used as a multi-layer structure by laminating silicone rubber or other materials, or as a rubber material for bonding with a resin base material such as phenol. It will be done. As described above, the present invention greatly contributes to improving the reliability of electrolytic capacitors and has extremely great industrial value.

[Brief explanation of drawings]

1 and 2 are sectional views of a conventional electrolytic capacitor, FIG. 3 is a sectional view of an electrolytic capacitor according to an embodiment of the present invention, and FIG. 4 is a perspective view of an elastic sealing body of a capacitor according to the present invention. , 5 and 6 are characteristic examples of electrolytic capacitors comparing a conventional product and a product of the present invention, in which A is a capacitance change rate-time characteristic diagram and B is a tan δ-time characteristic diagram, respectively. 1: Capacitor element, 2: Case, 4: External lead wire, 5: Internal lead, 6: Elastic sealing body, 6
a: polyester elastomer, 6b: ethylene propylene rubber.

Claims (1)

[Claims] 1. An electrolytic capacitor characterized in that an elastic sealing body made of polyester elastomer with ethylene propylene rubber arranged on the surface facing the capacitor element is sealed to the opening of a case containing a capacitor element.