JPH04329621A - Aluminum electrolytic capacitor - Google Patents

Abstract

PURPOSE:To ensure safety by actuating an explosionproof valve surely without breakdown of a molded terminal board even with a sudden rise in inner pressure due to circuit abnormality and the like during operation. CONSTITUTION:A molded terminal board 3 which seals the opening of a metal case 11 containing a capacitor element 1 is constituted of a resin molding mixed with aramide fibers. This constitution reinforces the mechanical strength of the molded terminal board 3 and prevents its breakdown, thereby ensuring explosionproof action.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum electrolytic capacitor with improved safety by improving the structure of a molded terminal plate.

0002

[Prior Art] Generally, aluminum electrolytic capacitors have a capacitor element impregnated with a driving electrolyte that has film repair properties.
The principle is that a small amount of gas is generated because a leakage current flows to repair the film when voltage is applied.

However, during long-term use, the amount of this gas increases, resulting in an increase in internal pressure and the risk of explosion. Therefore, aluminum electrolytic capacitors are equipped with explosion-proof metal cases or terminal plates. Various mechanisms are provided to serve as valves.

These explosion-proof valves are designed to open when the internal pressure gradually increases over a long period of time, so there is no risk of overvoltage, reverse voltage, or overcurrent being applied due to a circuit abnormality during use. If the internal pressure rises instantaneously due to dielectric breakdown, etc., the terminal board may break and explode before the explosion-proof valve operates, and surrounding electronic components may also be destroyed, or a short circuit may occur inside the capacitor. This had the extremely fatal problem of causing a fire.

[0005] Such problems tend to become more pronounced as the capacitor becomes larger.

In order to increase the strength of the terminal board, attempts have been made to increase the thickness of the terminal board itself or to provide reinforcing ribs, but at present no sufficient effect can be expected.

That is, although it is possible to improve the strength to some extent by increasing the thickness of the terminal board itself or by reinforcing ribs, this cannot necessarily be said to be an effective countermeasure given the trend towards miniaturization of electronic components. Although resin is used as the material for these terminal boards, the impact force of the resin itself is limited, and it has not been possible to completely prevent destruction under the above-mentioned phenomenon.

[0008]

[Problems to be Solved by the Invention] As described above, an aluminum electrolytic capacitor sealed with a terminal plate made of resin is subject to an instantaneous increase in internal pressure due to the impact force of the resin itself due to the application of overvoltage. Prior to the operation of the explosion-proof valve, there was a problem in which explosions occurred due to terminal board breakage.

The present invention has been made in view of the above points, and is an aluminum explosion-proof valve that ensures reliable operation of the explosion-proof valve without destroying the terminal board even if there is a sudden increase in internal pressure due to an abnormality in the assembled circuit or the like. The purpose is to provide an electrolytic capacitor.

0010

[Means for Solving the Problems] An aluminum electrolytic capacitor according to the present invention houses a capacitor element formed by winding and impregnating a driving electrolyte between an anode foil and a cathode foil with capacitor paper interposed between the anode foil and the cathode foil in a metal case. In the aluminum electrolytic capacitor formed by sealing the opening of the metal case with a molded terminal plate provided with an explosion-proof valve, the molded terminal plate is made of a thermoplastic resin mixed with aramid fibers. It is characterized by:

[0011]

[Function] According to the aluminum electrolytic capacitor configured as described above, the aramid fibers mixed in the molded terminal board have extremely high tensile strength and are resistant to impact forces, so they can be easily damaged due to circuit abnormalities, etc. The aramid fiber absorbs the force applied to the molded terminal plate when internal pressure increases.

[0012] Therefore, the explosion-proof valve operates reliably without destroying the molded terminal plate, and fatal defects such as explosion, short circuit, and ignition are eliminated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. That is, as shown in FIG. 1, capacitor paper is wound between an anode foil and a cathode foil, and an internal lead-out terminal 2 of a capacitor element 1 impregnated with a driving electrolyte is attached to a rivet portion 4 of a molded terminal plate 3. Connecting. This molded terminal plate 3 is made of polyphenylene sulfide, polypropylene, phenol.
Either aramid fibers are mixed into a thermoplastic resin such as polyphenylene sulfide, polypropylene, phenol, etc., and then the aramid fibers are placed in a molding mold beforehand. is injected into a mold and molded, and screw terminals 5 are insert-molded at appropriate locations, and a rubber packing 7 is inserted into an explosion-proof hole 6 and a metal washer 8 is inserted at an arbitrary location as shown in Figure 2. , and an explosion-proof valve 9 is provided.

In FIG. 1, reference numeral 10 indicates a stepped portion on which a rubber ring is placed.

The capacitor element 1 is housed in a cylindrical metal case 11 with a bottom, the molded terminal plate 3 is placed in the opening of the metal case 11, and then the metal case is closed.
The tip of the opening of the terminal plate 11 is tightened and bitten into a rubber ring 12 disposed on the stepped portion 10 on the outer periphery of the molded terminal plate 3 for sealing.

[0016] According to the aluminum electrolytic capacitor constructed as described above, even if the internal pressure suddenly increases due to abnormality in the circuit during use when the aluminum electrolytic capacitor is assembled into a necessary circuit, the molded terminal plate 3 will not contain aramid fibers mixed therein. It is composed of a molded body of thermoplastic resin and has extremely high strength.
The explosion-proof valve operates reliably without destroying the molded terminal plate 3, and fatal defects such as explosion, short circuit, and ignition can be prevented.

Next, a comparison of characteristics between the present invention and a conventional example will be explained based on experimental results. (Invention A) An electrolytic capacitor with a rating of 400V-33,000 μF and a case size of 76 mm in diameter and 190 mm in length, constructed using a molded terminal plate made of polyphenylene sulfide resin mixed with 40% aramid fiber. (Conventional example B) Rated 400V constructed using a molded terminal plate molded only using polyphenylene sulfide resin
-33000μF, case size diameter 76mm x length 1
90mm electrolytic capacitor.

Using the above-described present invention A and conventional example B as samples, these samples were tested at 65°C using the circuit shown in FIG.
An overvoltage of 0V was applied, and the destruction of each molded terminal plate was investigated, and the results are shown in the table below. The number of samples was 20 for both (A) and (B).

[0019]

【table】

As is clear from the above table, in the conventional example (B), there was no explosion-proof valve operation, all the samples were destroyed in the molded terminal board, and ignition occurred quite frequently, whereas in the present invention (A) The explosion-proof valves in all of them worked, and there was no damage to the resin-molded terminal boards or any fires from the capacitors, demonstrating an extremely high level of safety.

[0020]

[Effects of the Invention] According to the present invention, even if there is a sudden increase in internal pressure due to a circuit abnormality, etc., the explosion-proof valve operates reliably without destroying the molded terminal board, and the explosion-proof valve does not cause a short circuit inside the capacitor and ignition. A highly safe aluminum electrolytic capacitor can be obtained.

[Brief explanation of drawings]

FIG. 1 is a front cross-sectional view showing an aluminum electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an explosion-proof valve provided on the molded terminal plate configuring FIG. 1;

FIG. 3 is a circuit diagram used in an experiment to compare characteristics of the present invention and a conventional example.

[Explanation of symbols]

1 Capacitor element 3 Molded terminal board 9 Explosion-proof valve 11 Metal case

Claims (1)

[Claims] 1. A capacitor element formed by winding a capacitor paper between an anode foil and a cathode foil and impregnating it with a driving electrolyte is housed in a metal case, and the opening of the metal case is closed. An aluminum electrolytic capacitor sealed with a molded terminal plate provided with explosion-proof valves at arbitrary locations, the aluminum electrolytic capacitor characterized in that the molded terminal plate is molded from a thermoplastic resin mixed with aramid fibers.