JP3439238B2 - Electrolytic capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor, and more particularly to a highly safe electrolytic capacitor. [0002] As a measure against the safety of a conventional electrolytic capacitor, the risk of explosion has been prevented by attaching a safety valve. However, in an electronic device using an electrolytic capacitor, it is often impossible to immediately turn off the power supply of the electronic device even if the electrolytic capacitor operates. Therefore, a secondary phenomenon such as a short circuit may occur after the operation of the valve of the electrolytic capacitor, and the electronic device may be damaged. In addition, the dielectric of the electrolytic capacitor may cause dielectric breakdown due to application of an overvoltage on the circuit to be used, which may cause a short circuit. [0003] Electrolytic capacitors use a metal oxide film as a dielectric, but the dielectric breakdown of the oxide film causes a short circuit phenomenon. Generally, an electrolytic capacitor is manufactured by cutting a metal foil on which an oxide film is formed into a specified size. Therefore, since the cut surface is an extremely thin film of an oxide film that has been oxidized in the air, it does not have the dielectric strength to be used.Therefore, the cut foil is formed in liquid to form an oxide film on the cut surface. Alternatively, it has been commercialized by forming (aging) an oxide film with an electrolytic solution (paste). Although these methods can sufficiently withstand normal use, dielectric breakdown of the dielectric may occur when overvoltage or an unacceptable AC component is superimposed. If the dielectric film is all uniform, the current density will be constant even if an overvoltage is applied.However, if there is a slight defect in the dielectric, the current density in that part will increase and the electron avalanche will occur. This results in electrical breakdown. Normally, when the electrolytic solution is present on the surface of the dielectric film, the defective portion is repaired by supplying the oxide ions. However, when the current density in the defective portion is increased, heat generation due to the resistance of the electrolyte and collision of ions cause dielectric breakdown. [0004] The problem to be solved by the present invention is to suppress the above-mentioned dielectric breakdown of the dielectric oxide film and to prevent a short circuit of the electrolytic capacitor. The present inventor has conducted various studies to solve the above-mentioned problems, and as a result, has found a means for solving the above-mentioned problems. The basic idea of the present invention is to prevent the dielectric breakdown by using the heat generated by the heat of fusion of the thermoplastic resin before the dielectric breakdown of the dielectric oxide film. Regarding the structure of the thermoplastic resin inside the capacitor, it is best that the thermoplastic resin is wound on top of ordinary separator paper. Further, since the resistance of the separator becomes lower as the permeability of the electrolyte solution of the thermoplastic resin becomes better, it is necessary to form each of the fibrous material and the porous material into a sheet. That is, a capacitor element in which an anode foil and a cathode foil are wound through a plurality of separators is formed, and the element is impregnated with an electrolytic solution. An electrolytic capacitor characterized in that at least one of a sheet and a porous thermoplastic resin sheet is overlapped with a separator paper to form a separator, and the thermoplastic resin sheet is wound in contact with an anode foil. It is well known that in the case of a thermoplastic film in a metallized plastic film capacitor, the carbonization phenomenon at the moment of instantaneous destruction is not observed and the film melts and the destruction disappears. Focusing on this, the present invention is applied to an electrolytic capacitor. The electrolytic capacitor causes the pressure inside the capacitor to rise due to the heat generated by the application of the AC component, and causes the valve to operate, the valve to operate due to the rise in internal pressure due to a sudden increase in current due to the application of overvoltage, or a short circuit due to insulation breakdown. Immediately before the valve operation or short-circuit, the heat generated by the increase in current may cause gasification of the electrolyte, so that the surface of the dielectric aluminum oxide film on the electrode surface no longer has the ability to oxidize aluminum, The dielectric breakdown occurs, and the separator is carbonized, leading to conduction. According to the present invention, by arranging an electrolytic capacitor paper or a thermoplastic resin layer mixed with a thermoplastic resin at a place in contact with an aluminum oxide film serving as a dielectric, a heat generation energy is used as a heat of fusion to simulate a gap between electrodes. It can be insulated to prevent instantaneous short circuit after valve operation, and to safely operate the protection circuit of the equipment. Hereinafter, specific embodiments of the present invention will be described. The test was performed using a CE69 type aluminum electrolytic capacitor rated at 400 V and 100 μF. The separator portion of the product is a fibrous thermoplastic resin sheet having a thickness of 40 μm disposed on the anode side, and is wound around electrolytic paper having a thickness of 30 μm with manila paper (Example 1), and a porous thermoplastic resin sheet of 40 μm Thickness was placed on the anode side, and a roll of electrolytic paper with a thickness of 30 μm of manila paper (Example 2) was 10 pieces each.
0 pieces each, impregnated with electrolyte, and rated 400V
A 100 μF aluminum electrolytic capacitor was used. Further, for comparison, 100 separators in which only electrolytic paper was wound as separators were prepared, and a capacitor of 400 V and 100 μF was obtained. (Conventional example) A current of 8 A was applied to each capacitor at room temperature to induce a valve operation, the breakdown voltage of each capacitor was measured, and the short circuit condition was also investigated. The results are shown in Table 1. [Table 1] According to the present invention, as shown in Table 1,
Not only is the withstand voltage increased as compared with the conventional product, but also the short circuit phenomenon after the valve is operated can be eliminated, and its practical value is great.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/02 301 H01G 9/12 H01G 9/048 H01G 9/055

Claims (1)

(57) [Claims 1] A capacitor element in which an anode foil and a cathode foil are wound through a plurality of separators is formed, and the element is impregnated with an electrolytic solution and stored in a case. In an electrolytic capacitor, at least one of a fibrous thermoplastic resin sheet and a porous thermoplastic resin sheet and a separator paper are overlapped to form a separator, and the thermoplastic resin sheet is wound in contact with an anode foil. An electrolytic capacitor characterized by the following: