JPH08153654A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE: To provide an electrolytic capacitor possessed of a sealing body which is capable of preventing driving electrolytic liquid from penetrating through it and high enough in strength. CONSTITUTION: A capacitor element 6 is enveloped in an aluminum case 8, and the opening of the case 8 is hermetically sealed up with a sealer 7. An anode leading terminal 4 and a cathode leading terminal 5 both led out from the capacitor element 6 are led outside of a capacitor through the through-holes 7c and 7d of the sealer 7 and connected to outer electrodes. The sealer 7 is of double-layered structure composed of a lower layer of rubber plug 7a and an upper layer of resin plate 7b pasted onto the surface of the lower layer. The resin plate 7b is impregnated with thermosetting resin and heated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor having an improved sealing structure and improved reliability.

[0002]

2. Description of the Related Art Generally, in a dry foil type electrolytic capacitor, a pair of lead terminals also made of aluminum are connected to a pair of anode / cathode foils made of high-purity aluminum foil, and the pair of anode / cathode foils are connected to each other. A capacitor element formed by winding a spacer paper is used. Further, this capacitor element has its surface roughened by etching in order to increase the surface area of the aluminum anode foil / cathode foil. Further, a dielectric oxide film is formed on the anode foil.

As an electrolytic capacitor using such a capacitor element, for example, the capacitor element is impregnated with a driving electrolytic solution and housed in an aluminum case, and the case opening is provided with an outer casing. Things are used. As a means for sealing and sealing the opening, a sealing body made of elastic rubber, in which through holes of the lead terminals are formed at regular intervals, has been used conventionally.

However, since an organic solvent such as ethylene glycol is used as the driving electrolytic solution with which the capacitor element is impregnated, the sealing member made of rubber is reliable when used at high temperature for a long time. In the sex test, the driving electrolytic solution penetrated through the sealing body, and as a result, there was a problem that the electrostatic capacity decreased and the loss increased.

Further, in recent years, in order to miniaturize the electrolytic capacitor, various measures have been taken, such as making the surfaces of the anode / cathode foil rougher and making the spacer paper thinner.
Further, by further reducing the thickness of the rubber plug that constitutes the sealing body, the space for accommodating the capacitor element in the aluminum case is expanded, and by enlarging the capacitor element, the characteristics of the electrolytic capacitor are improved. .

However, when the rubber plug is thinned as described above, there has been a problem that the above-mentioned permeation of the driving electrolytic solution is further increased. Therefore, conventionally, a technique such as changing the material of the rubber plug constituting the sealing body is applied to suppress the permeation of the driving electrolytic solution from the sealing body to stabilize the performance of the electrolytic capacitor.

However, when a thin rubber plug is used as a sealing body, especially when used for a long time at high temperature,
There has been a problem that the driving electrolytic solution is vaporized from the surface of the capacitor element to be gasified, and the gas causes the rubber plug to be deformed.

For this reason, in recent years, the electrolytic capacitor has been used for accommodating the capacitor element so that the electrolytic capacitor will not be dangerously destroyed even when an abnormal voltage is applied to the electrolytic capacitor or in an atmosphere exceeding the guaranteed temperature. A safety device having a cutout groove is provided on the bottom surface of the aluminum case. However, since such a safety device generally operates by the internal pressure, the rubber plug constituting the sealing body also needs to have sufficient strength to withstand the internal pressure.
For this reason, conventionally, various measures have been taken to improve the strength, such as attaching a resin plate to a rubber plug.

[0009]

However, the conventional electrolytic capacitor in which the strength is enhanced by attaching the resin plate to the thin rubber plug as described above has the following problems. That is, when the rubber plugs to which the resin plates are attached are vertically displaced and stored,
When the case was crimped and fixed, there were cases where it was incomplete to maintain the airtightness. Further, when a resin plate is attached to the rubber plug, a slight gap is unavoidable around the through hole for pulling out the lead terminal and the outer peripheral portion in contact with the aluminum case.

For these reasons, the aluminum case cannot be completely sealed only by attaching the resin plate to the rubber stopper, and it is impossible to prevent a large amount of the driving electrolytic solution from permeating through the sealing body. This is difficult and has been a problem in maintaining the reliability of the electrolytic capacitor.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to prevent permeation of the driving electrolytic solution from the sealing body and to have a sufficient strength. It is to provide an electrolytic capacitor having.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 has a spacer interposed between an anode foil and a cathode foil made of a metal having a valve action and each electrode foil. Each of them is attached with a lead terminal and wound to form a capacitor element. The capacitor element is impregnated with a driving electrolytic solution, the capacitor element is housed in a case, and the opening of this case is sealed with a sealing body. In the electrolytic capacitor, the sealing body has a two-layer structure including a rubber plug arranged on the capacitor element side and a resin plate attached to an upper surface of the rubber plug, and the resin plate is impregnated with a liquid resin. It is characterized by being

According to a second aspect of the present invention, in the electrolytic capacitor according to the first aspect, the liquid resin is a thermosetting resin, and the resin plate is impregnated and then cured. Is.

[0014]

The operation of the present invention having the above construction will be described below.

That is, according to the invention of claim 1,
The sealing body of the electrolytic capacitor has a double structure of a resin plate and a rubber plug, and the aluminum case accommodating the capacitor element is sealed and caulked by the sealing body, and then the resin plate is impregnated with the liquid resin. As a result, it is possible to close a small gap that occurs between the resin plate of the sealing body and the aluminum case, or between the lead-out terminal led out from the capacitor element and the through hole, so that it evaporates from the surface of the capacitor element. It is possible to prevent the driving electrolyte solution from leaking to the outside through the sealing body.

According to the second aspect of the invention, by using a thermosetting resin such as an epoxy resin as the liquid resin, the resin plate is impregnated and then heated, whereby the thermosetting resin is added. Since it can be cured, the strength of the resin plate can be improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electrolytic capacitor according to the present invention will be specifically described below with reference to the drawings.

In the electrolytic capacitor of this embodiment, as shown in FIG. 1, a capacitor element 6 impregnated with a driving electrolytic solution composed of an organic solvent is housed in an aluminum case 8. The opening is sealed by the sealing body 7. Further, the sealing body 7 has a two-layer structure, the lower layer is the rubber stopper 7a, and the upper layer is the rubber stopper 7a.
And a resin plate 7b attached to the surface of the. Further, the sealing body 7 has a pair of through holes 7c and 7c.
d is formed.

The resin plate 7b is made of porous resin such as laminated phenol resin or laminated epoxy resin. The outer diameter of the resin plate 7b is set to be the same as or slightly smaller than the diameter of the rubber plug 7a. Further, the sealing body 7 having the two-layer structure is formed by setting the resin plate in a mold and injecting molten rubber when molding the rubber stopper.

Further, an anode lead terminal 4 and a cathode lead terminal 5 are led out from the capacitor element 6 via internal lead wires 4a and 5b. These lead-out terminals 4 and 5 are drawn out from the through holes 7c and 7d to the outside of the capacitor and are connected to external electrodes (not shown) outside the capacitor.

Next, the structure of the capacitor element 6 is shown in FIG.
It will be described based on. That is, the capacitor element 6
Comprises a pair of anode foil 1 and cathode foil 2 made of high-purity aluminum foil. The anode lead 1 and the cathode foil 2 are provided with the internal lead wires 4a and 5a at arbitrary positions in the width direction. Is attached to. The lead terminals 4 and 5 are led out through the internal lead wires 4a and 5a. Further, a spacer 3 made of kraft paper or manila paper is interposed between the anode foil 1 and the cathode foil 2, and these are wound together to form a capacitor element 6.

Next, the step of sealing the sealing body 7 will be described. That is, after closing the opening of the aluminum case 8 accommodating the capacitor element 6 with the sealing body 7 having the two-layer structure, the prepared epoxy resin is placed on the surface of the resin plate 7b which is the upper layer of the sealing body 7, The pressure is reduced and the resin plate 7b is impregnated. Then, the epoxy resin is heated. Since the epoxy resin is a liquid thermosetting resin, the epoxy resin uniformly penetrates into the gap between the resin plate 7b and the aluminum case 8 and the gap between the resin plate 7b and the lead terminals 4 and 5, and is then cured by heating. To do.

In the electrolytic capacitor of the present embodiment having the above-mentioned structure, since many fine pores and slight gaps in the resin plate 7b are all closed by the epoxy resin, the evaporated driving electrolytic solution Is a rubber stopper 7
Even if the portion b is transmitted, it is not transmitted through the resin plate 7b. In this way, by impregnating the resin plate 7b with the epoxy resin and curing it, it is possible to prevent the driving electrolytic solution from permeating from the sealing body 7. Further, since the epoxy resin is cured by heating, the strength of the resin plate 7b impregnated with the epoxy resin can be improved.

As described above, according to the electrolytic capacitor of this embodiment, it is possible to effectively prevent an increase in loss of the electrolytic capacitor and a decrease in electrostatic capacitance even when used for a long time at high temperature. Therefore, a more reliable electrolytic capacitor can be obtained. Further, since the epoxy resin that has penetrated into the resin plate is cured to increase the strength of the resin plate, sufficient strength can be secured even if the rubber plug of the sealing body is extremely thin. Furthermore, since the rubber plug can be made thin, a space is provided inside the electrolytic capacitor, and a larger capacitor element can be accommodated.

Next, the results of comparing the characteristics of the electrolytic capacitor of this embodiment and the electrolytic capacitor of the prior art will be described.

First, an electrolytic capacitor having the structure of this example (hereinafter referred to as the product A of the present invention) was manufactured with the following specifications. That is, the surface of a high-purity aluminum foil is roughened with an etching solution to increase the surface area, and then an anodic oxide film is formed to obtain anode foil 1. Similarly, the surface of the aluminum foil is roughened with an etching solution to increase the surface area to form the cathode foil 2. The width of the anode foil 1 is 16 mm,
The length was formed to 300 mm.

Next, a spacer 3 made of kraft paper, manila paper, or the like is interposed between the anode foil 1 and the cathode foil 2, and internal lead wires 4a and 5a are provided at arbitrary positions on the anode foil 1 and the cathode foil 2. The anode internal terminal 4 and the cathode internal terminal 5 are attached and wound via the capacitor element 6
To form. Next, this capacitor element 6 was immersed in a driving electrolytic solution and decompressed to complete the impregnation. Then, the internal terminals 4 and 5 led out from the capacitor element 6 were respectively drawn out through the through holes 7c and 7d of the sealing body 7 and connected to external electrodes.

On the other hand, the capacitor element 6 itself was housed in the aluminum case 8, and the opening of the aluminum case 8 was sealed by the sealing body 7. The sealing body 7 has a porous resin plate 7b with a thickness of 1 mm and a thickness of 4 mm.
The rubber plug 7a has a two-layer structure attached to the surface thereof. Further, the prepared epoxy resin was placed on the surface of the porous resin plate 7b, the pressure was reduced to allow the resin to soak into the resin plate 7b, and then the resin was cured by heating.

Next, two types of electrolytic capacitors using conventional techniques were manufactured. That is, first, an electrolytic capacitor having a rubber plug having a thickness of 5 mm as a sealing body (hereinafter, conventional product B)
Was manufactured. Further, as in the case of the product A of the present invention, it has a two-layer structure in which a porous resin plate having a thickness of 1 mm is attached to the surface of a rubber stopper having a thickness of 4 mm, but an epoxy resin is immersed in the porous resin plate. Another electrolytic capacitor (hereinafter referred to as conventional product C) having a sealing body that is not impregnated was manufactured. Except for the specifications regarding the structure of the sealing body, the manufacturing specifications of the conventional product B and the conventional product C were all the same as those of the product A of the present invention. The ratings of the product A of the present invention, the products B and C of the related art were all 10V-3300 μm.

After that, a life test was carried out at 105 ° C. for each of the three electrolytic capacitors of the present invention product A, the conventional product B and the conventional product C, and the change in the electrostatic capacitance of each electrolytic capacitor was investigated. The result is shown in FIG. FIG.
As is clearer, in the long-term use, the product A of the present invention has a markedly smaller decrease in capacitance than the conventional products B and C. As a result, the present invention product A
Was confirmed to be able to maintain its performance at a higher level than conventional products.

The present invention is not limited to this embodiment, but can be applied with various modifications. For example, when the resin plate 7b is impregnated with the epoxy resin, in this embodiment, the epoxy resin is applied on the surface of the resin plate 7b and then the pressure is reduced. At this time, the capacitor itself is put in the prepared epoxy resin. After that, you may reduce the pressure.

[0032]

As described above, according to the present invention, it is possible to suppress the driving electrolytic solution from penetrating the sealing body, so that a highly reliable electrolytic capacitor having a stable function is provided. be able to. Further, since the epoxy resin that has penetrated into the resin plate is cured to increase the strength of the resin plate, sufficient strength can be secured even if the rubber plug of the sealing body is extremely thin. As a result, a larger space can be accommodated in the interior of the electrolytic capacitor, so that a larger capacitor element can be accommodated. Therefore, an aluminum case of the same size can be used to obtain a rating with a larger capacitance.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of an electrolytic capacitor of the present invention.

FIG. 2 is a developed perspective view showing a configuration of a capacitor element according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration of a sealing body according to an embodiment of the present invention.

FIG. 4 shows the number of hours of use of an electrolytic capacitor manufactured according to an embodiment of the present invention (invention product A) and two types of electrolytic capacitors manufactured by conventional techniques (conventional product B and conventional product C). The figure showing the change of the electrostatic capacitance accompanying.

[Explanation of symbols]

 4 ... Anode lead terminal 5 ... Cathode lead terminal 4a, 5a ... Internal lead wire 6 ... Capacitor element 7 ... Sealing body 7a ... Rubber plug 7b ... Resin plate 7c, 7d ... Through hole 8 ... Aluminum case

Claims (2)

[Claims] 1. A capacitor element is formed by interposing a spacer between an anode foil and a cathode foil made of a metal having a valve action, and attaching lead terminals to each electrode foil to form a capacitor element, and driving the capacitor element. While impregnating the electrolytic solution, the capacitor element is housed in a case, in the electrolytic capacitor formed by sealing the opening of the case with a sealing body, the sealing body, a rubber plug disposed on the capacitor element side, An electrolytic capacitor having a two-layer structure consisting of a resin plate attached to the upper surface of this rubber plug, wherein the resin plate is impregnated with a liquid resin. 2. The electrolytic capacitor according to claim 1, wherein the liquid resin is a thermosetting resin, and is cured after impregnating the resin plate.