JP3406247B2 - Aluminum electrolytic capacitor - Google Patents

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 mounted on various electric / electronic devices.

[0002]

2. Description of the Related Art Among various capacitors, an aluminum electrolytic capacitor (hereinafter referred to as an electrolytic capacitor) is
As shown in FIG. 1, a capacitor element 2 in which an anode foil, a cathode foil, and a separator are wound, and a bottomed tubular capacitor case 3 made of aluminum and accommodating the capacitor element 2.
And a synthetic resin sealing body 4 that closes the open end side of the capacitor case 3. An anode terminal 41 and a cathode terminal 42 are formed on the outer end surface of the sealing body 4, and lower end portions of these terminals 41 and 42 are anode tab terminals drawn out from the capacitor element 2 as an anode internal terminal 43 and a cathode internal terminal 44. 21 and the cathode tab terminal 22 are electrically connected. Here, each of the anode tab terminal 21 and the cathode tab terminal 22 is cut out from an aluminum plate of about 200 μm. These tab terminals 21,
Out of 22, the cathode tab terminal 22 used is not anodized and the anode tab terminal 21 used is anodized. However, for both tab terminals 21 and 22, Plane thick aluminum foil that has not been roughened by etching is used.

Further, in both the anode tab terminal 21 and the cathode tab terminal 22, the electric connection with the anode foil or the cathode foil is made by connecting the anode foil 26 and the cathode foil 27 to the surface of the anode foil as shown in FIG. This is done by caulking 5 (or welding) with the tab terminal 21 and the cathode tab terminal 22 overlapped.

The behavior of the electrolytic capacitor 1 when charging / discharging occurs is as follows. In the electrolytic capacitor 1, as the cathode foil 27, an aluminum foil having a thickness of, for example, 20 μm to 50 μm is etched and then subjected to a film formation treatment of about several volts by anodic oxidation, and a case where the etching is forced only by etching. In some cases, a film that does not undergo a film formation process is used, but even when the film formation is not compulsorily performed, the aluminum foil surface reacts with water in the atmosphere or water in the electrolytic solution to reach about 1.0V. A film with pressure resistance is formed. Therefore, the electrostatic capacitance of the electrolytic capacitor is composed of the combined capacitance of the electrostatic capacitance of the anode foil oxide film that holds the breakdown voltage and the electrostatic capacitance of the cathode foil in series. Here, the capacitance per unit area of the anode foil is Ca (μF / cm ² ), and the capacitance per unit volume of the cathode foil is Cc (μF / cm ² ).
And V is the voltage with which the electrolytic capacitor 1 is charged, and Va and Vc are the voltages sharing this voltage V on the anode side and the cathode side.
Then, the voltage Vc ′ applied to the cathode foil 27 during discharge is
Becomes [Equation 1].

[0005]

[Equation 1]

Here, if the voltage applied to the cathode foil 27 during discharge is too high, an unfavorable phenomenon occurs such that a film is formed on the cathode foil 27 and gas is generated in the capacitor. Therefore, if the voltage at which a film is not formed on the cathode foil 27 even if a voltage is applied to the cathode foil 27 during discharge is V ', it is necessary to satisfy [Equation 2] during discharge.

[0007]

[Equation 2]

Here, since Va = V-Vc, [Equation 3] is derived from the above equation.

[0009]

[Equation 3]

If the above [Equation 3] is satisfied, no film is formed on the cathode foil 27 even if a voltage is applied to the cathode foil during discharge.
Therefore, conventionally, as the cathode foil 27, one having a large capacitance or the withstand voltage of the oxide film that would be generated on the cathode foil 27 by the charging / discharging current is previously formed so as to satisfy [Equation 3]. In order to improve the ripple resistance performance and the charge / discharge resistance performance of the electrolytic capacitor 1 such as using a cathode foil 27 or an anode foil 26, an electrolytic solution,
Responses have been made mainly by developing or improving materials such as separators.

[0011]

However, there is a limit to improving the ripple resistance and charge / discharge resistance of the electrolytic capacitor 1 by developing such a basic material. That is, in the experiment repeated by the inventor of the present application, the electrolytic capacitor 1 subjected to the ripple resistance test and the charge / discharge resistance test was investigated and analyzed, and it was found that a ripple current that far exceeded the allowable ripple in a short time was periodic. For the electrolytic capacitor 1 used in the circuit applied to the battery and the charging / discharging circuit having a large voltage difference and a short cycle, no matter how close to the ideal cathode foil 27 is used, the cathode tab terminal 22 and the cathode foil 27 in the vicinity thereof are not affected. Since the film formation reaction occurs in the capacitor, gas is generated in the capacitor, which leads to new findings that malfunctions such as explosion-proof valve operation due to an increase in internal pressure occur.

Therefore, an object of the present invention is to prevent the formation of a film on the cathode side at the time of discharge from the structural aspect of the capacitor element, thereby significantly improving the charge / discharge resistance and the ripple current resistance. An object of the present invention is to provide a method for manufacturing an electrolytic capacitor and a capacitor element used therefor.

[0013]

In order to solve the above-mentioned problems, the inventors of the present application have found from repeated experiments that a ripple current far exceeding the allowable ripple is applied to an electrolytic capacitor in a short time and periodically. The reason why the film formation reaction occurs on the cathode foil around the cathode tab terminal in an electrolytic capacitor used in a charge / discharge circuit with a large voltage difference and a short cycle is that the discharge current is low because the cathode tab terminal has a low capacity per unit area. We have come to the conclusion that a high voltage is applied to the cathode tab terminal and its surroundings when it flows to the cathode tab terminal. Therefore, in the present invention, a small piece of aluminum foil having a capacity per unit area of 0.3 times or more that of the cathode foil is superposed on the surface of the cathode tab terminal while being electrically connected to the cathode tab terminal. Therefore, what actually faces the anode foil at the portion where the cathode tab terminal is located is a small piece of aluminum foil having a capacitance per unit area of 0.3 times or more that of the cathode foil. Since such a small piece has a larger capacitance per unit area than the cathode tab terminal,
Even if a ripple current far exceeding the allowable ripple is periodically applied to the electrolytic capacitor in a short time, a high voltage is not applied to the cathode tab terminal and its surroundings. Therefore, since no film is formed on the cathode tab terminal and its surroundings, gas generation in the capacitor can be prevented.

That is, a capacitor element in which an anode foil to which an aluminum anode tab terminal is electrically connected and a cathode foil to which an aluminum cathode tab terminal is electrically connected are wound or laminated through a separator. An aluminum electrolytic capacitor obtained by impregnating a driving electrolytic solution with a capacitor, wherein a small piece of aluminum foil having a capacity per unit area of 0.3 times or more that of the cathode foil is laminated on the cathode tab terminal. It is a capacitor.

An aluminum electrolytic capacitor is characterized in that a small piece of the aluminum foil is crimped or welded to the cathode foil.

Further, the aluminum electrolytic capacitor is characterized in that the small piece of the aluminum foil is crimped or welded to the cathode foil together with the cathode tab terminal.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the structure of an electrolytic capacitor. 2 and 3 are an explanatory view showing a structure of a capacitor element used in the electrolytic capacitor according to the present embodiment and an explanatory view showing a method for manufacturing the capacitor element, respectively. The electrolytic capacitor of this embodiment also
Since the basic structure is common to conventional electrolytic capacitors,
Corresponding parts are designated by the same reference numerals.

As shown in FIGS. 1 and 2, in the electrolytic capacitor 1, an anode foil 26 obtained by subjecting an etching foil to anodization (chemical conversion treatment), an etching foil having no anodization film or a thin anodization film is used. A cathode element 27 formed of an etching foil and a capacitor element 2 around which a separator 28 is wound, a bottomed cylindrical aluminum-made capacitor case 3 and the open end side of the capacitor case 3. It has a synthetic resin sealing body 4 for closing the capacitor and an element fixing member 30 for fixing the capacitor element 2 to the capacitor case 3. The capacitor element 2 is impregnated with a driving electrolytic solution. An anode terminal 41 and a cathode terminal 42 are formed on the outer end surface of the sealing body 4, and the lower ends of these terminals 41, 42 serve as an anode internal terminal 43 and a cathode internal terminal 44, respectively. The anode tab terminal 21 and the plurality of cathode tab terminals 22 are electrically connected to each other. Here, each of the anode tab terminal 21 and the cathode tab terminal 22 is cut out from a thick aluminum foil having a thickness of about 200 μm. Of these tab terminals 21 and 22,
Although the cathode tab terminal 22 is not anodized and the anode tab terminal 21 is anodized, both tab terminals 21 and 22 are anodized. You may use what gave.

In the present embodiment, the electrical connection between the anode tab terminal 21 and the anode foil 26 is performed by crimping 5 (or welding) with the anode tab terminal 21 overlaid on the surface of the anode foil 26, as in the conventional case. Is done by doing. However, in this embodiment, on the surface of the cathode tab terminal 22, a small piece 6 of aluminum foil having a capacity per unit area of 0.3 times that of the cathode foil or more is electrically connected to the cathode tab terminal 22. It is piled up in the state. That is, the small piece 6 of aluminum foil is stacked on the cathode tab terminal 22 so as to cover the cathode tab terminal 22, and in this state, the small piece 6 of aluminum foil is put together with the cathode tab terminal 22 on the cathode foil 27. Are crimped 6 (or welded) and electrically connected. In this embodiment, as such a small piece 6, an aluminum foil used as the cathode foil 27 is cut out to have a width wider than that of the cathode tab terminal 22 and a width dimension substantially the same as that of the cathode foil 27. Further, as the cathode foil 27 and the small pieces 6, either an etching foil having no anodized film formed thereon, an etching foil having a thin anodized film formed thereon, or a foil obtained by subjecting the etching foil surface to vapor deposition or the like may be used.

[0020]

EXAMPLES The results of the evaluation test relating to the present invention will be described below. φ63 × 60mm, rated 400V 1500
A μF electrolytic capacitor was manufactured and a voltage difference of 150 V, 0.
A 25 sec charge / discharge test was performed and the results shown in Table 1 were obtained. (10 samples for each condition)

[0021]

[Table 1]

Although Examples 1 to 4 according to the present invention did not cause valve actuation, the conventional example and the comparative example caused valve actuation. It can be seen that when the capacity of a small piece of aluminum foil stacked on the cathode tab terminal is less than 0.3 times the capacity of the cathode foil, a film is formed on the cathode foil and the valve operates. Therefore, the capacity of a small piece of aluminum foil needs to be 0.3 times or more the capacity per unit area of the cathode foil.

In the electrolytic capacitor 1 of the present embodiment thus constructed, the capacitance per unit area is 0.
The small piece 6 of aluminum foil having a capacity of three times or more is opposed to the anode foil 26 so as to cover the cathode tab terminal 22, and the cathode tab terminal 22 is not directly opposed.
Unlike the cathode tab terminal 22, the small piece 6 is roughened by a method such as etching in a hydrochloric acid bath, and therefore has a smaller capacitance per unit area than the cathode tab terminal 22. Pretty big. Therefore, even at the portion where the cathode tab terminal 22 is located, the value derived by the equation on the right side of the above [Equation 3] is small, so that the ripple current far exceeding the allowable ripple in a short time is periodic. Applied to the cathode tab terminal 22 and its surroundings, no high voltage is applied to the cathode tab terminal 22 and its surroundings. Therefore, even if a harsh ripple application test or a charge / discharge test is performed, a film is not formed on the cathode tab terminal 22 and its surroundings, so that gas generation in the electrolytic capacitor 1 can be prevented.

When the capacitor element 2 used for such an electrolytic capacitor 1 is manufactured, the cathode tab terminal 22 is electrically connected to the cathode foil 27 in the winding process of the capacitor element 2, as schematically shown in FIG. In connection with each other, in the cathode tab terminal mounting area 80 of the element winding machine 8, the cathode tab terminal 22 supplied from the tab supply section (not shown) and the small piece supply section (not shown). After the supplied aluminum foil pieces 6 are stacked on the surface of the cathode foil 27 in this order, the cathode foil 27, the cathode tab terminals 22 and the pieces 6 are collectively caulked (or welded) by a caulking device 82. The anode foil 26 electrically connected to the anode tab terminal (see FIG. 2) and the cathode foil electrically connected to the aluminum cathode tab terminal 22 are wound via a separator 28. To form a capacitor element 2.

In the above embodiment, the capacitor element 2 in which the anode foil 26 and the cathode foil 27 are wound with the separator 28 in between has been described as an example, but the anode foil 26 and the cathode foil 2 are described.
The present invention may be applied to the electrolytic capacitor 1 using the capacitor element 2 in which 7 is laminated via the separator 28.

(Other Embodiments) In the above embodiment, the cathode tab terminal 22 and the small piece 6 are attached to the cathode foil 27.
The structure is such that the cathode tab terminal 22
And the small piece 6 overlap with each other, and the cathode tab terminal 22 and the small piece 6 are electrically connected to the cathode foil 27 separately by a method such as caulking or welding (FIG. 5).
Can also be applied to. Further, in the above embodiment, the synthetic resin mold plate having the terminals embedded therein is used as the sealing body 4, but the present invention can also be applied to an electrolytic capacitor having a configuration in which a rubber-bonded laminated plate is used as the sealing body 4.

[0027]

As described above, the aluminum electrolytic capacitor according to the present invention is a small piece of aluminum foil having a capacitance per unit area of 0.3 times or more that of the cathode foil on the surface of the cathode tab terminal. Since they are superposed in a state of being electrically connected to the cathode tab terminal, the fact that the capacity per unit area is 0.3 times or more that of the cathode foil is that the cathode tab terminal actually faces the anode foil. It is a small piece of aluminum foil with a capacity. Since such a small piece has a larger capacitance per unit area than the cathode tab terminal, even if a ripple current far exceeding the allowable ripple is periodically applied within a short time, the voltage difference is large. Even when used in a charge / discharge circuit having a short cycle, a high voltage is not applied to the cathode tab terminal and its surroundings. Therefore, since no film is formed on the cathode tab terminal and its surroundings, gas generation in the capacitor can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the structure of an electrolytic capacitor.

FIG. 2 is an explanatory diagram showing a structure of a capacitor element used in an electrolytic capacitor to which the present invention is applied.

FIG. 3 is an explanatory diagram showing a method of manufacturing the capacitor element shown in FIG.

FIG. 4 is an explanatory diagram showing a structure of a capacitor element used in a conventional electrolytic capacitor.

FIG. 5 is an explanatory diagram showing a structure of a capacitor element used in an electrolytic capacitor according to another embodiment of the present invention.

[Explanation of symbols]

1 Electrolytic capacitor 2 Capacitor element 3 capacitor case 4 Sealing body 5, 7 Caulking (or welding) 6 Small pieces of aluminum foil 8-element winder 21 Anode tab terminal 22 Cathode tab terminal 26 Anode foil 27 cathode foil 28 Separator 30 element fixing material 41 Anode terminal 42 Cathode terminal 43 Anode internal terminal 44 Cathode internal terminal 81 Cathode tab terminal mounting area 82 Crimping device

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01G 9/008 H01G 9/04 340

Claims (3)

(57) [Claims] 1. A capacitor element in which an anode foil to which an aluminum anode tab terminal is electrically connected and a cathode foil to which an aluminum cathode tab terminal is electrically connected are wound or laminated through a separator. An aluminum electrolytic capacitor having a driving electrolyte impregnated therein, characterized in that a small piece of aluminum foil having a capacity per unit area of 0.3 times or more that of the cathode foil is laminated on the cathode tab terminal. Electrolytic capacitor. 2. The aluminum electrolytic capacitor according to claim 1, wherein the small piece of aluminum foil is caulked or welded to the cathode foil. 3. The aluminum electrolytic capacitor according to claim 1, wherein the small piece of aluminum foil is caulked or welded to the cathode foil together with the cathode tab terminal.