JP6284036B2 - Electrolytic capacitor - Google Patents

Description

  The present invention relates to an electrolytic capacitor having an improved internal structure of a capacitor element.

  In a conventional electrolytic capacitor, an anode foil and a cathode foil are wound through a separator to form a capacitor element, and this capacitor element is impregnated with a driving electrolyte solution and stored in an outer case such as aluminum. The open end of the case is sealed with a sealing member to form an electrolytic capacitor.

  In this type of electrolytic capacitor, a leakage current is generated inside the capacitor element during use, and gas accompanying hydrogen may be generated due to electrolysis of the electrolytic solution component. Since the electrolytic capacitor has a hermetically sealed structure, if gas is generated inside, the internal pressure may increase, and the sealing member and the outer case may be deformed and finally ruptured. Therefore, in an electrolytic capacitor, several grooves are provided on the bottom surface of the outer case to form a mechanical weakened part, and when the internal pressure rises, stress is concentrated on the mechanical weakened part, and the outer case is broken along the groove. A pressure valve that releases an increase in internal pressure is employed (see, for example, Patent Document 1).

  There is also a pressure valve in which a through-hole is provided in the sealing member and the through-hole is closed with an elastic member such as rubber, and when the internal pressure of the electrolytic capacitor rises, the elastic member breaks to release the increase in internal pressure. It has been adopted.

JP 2001-244154 A

  By the way, in emerging countries, it is required that electronic components continue to drive even when the voltage changes because the voltage is not stable, and this voltage is unstable, especially over the rated voltage of the electrolytic capacitor. May be applied, and the application of such an overvoltage may cause a short circuit inside the capacitor element. When a short circuit occurs in this way, there is an influence on the operation of the pressure valve, that is, the operation voltage of the pressure valve varies depending on whether or not the operation of the pressure valve occurs.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly reliable electrolytic capacitor by preventing a short circuit inside a capacitor element and operating a pressure valve reliably in a desired voltage region.

In order to achieve the above object, the electrolytic capacitor of the present invention comprises:
In an electrolytic capacitor in which a capacitor element in which an anode foil and a cathode foil to which a lead terminal is connected is wound through a separator is housed in an outer case,
A gas discharge path for discharging gas generated from the inside of the element is formed at least on the inner peripheral surface of the separator adjacent to the outer peripheral surface of the anode foil.

  The anode foil has a withstand voltage of 250V or more.

  The anode foil is characterized in that it has a thickness that is four times or more the thickness of the cathode foil.

  Further, the anode foil is characterized in that a lead terminal is connected to the outer peripheral side thereof.

  Further, a paper having a gas discharge path is disposed between the separator facing the lead terminal connected to the anode foil.

  Further, a lead terminal is connected to the inner peripheral side of the cathode foil, and the address paper is arranged between the lead terminal and the lead terminal connected to the outer peripheral side of the anode foil.

  According to the electrolytic capacitor of the present invention, any of the following effects can be obtained.

(1) The gas generated inside the capacitor element can be released from the end face of the capacitor element, and short-circuiting due to contact between the anode foil, cathode foil or their lead terminals inside the capacitor element or due to a decrease in insulation of the separator Can be suppressed.

(2) By preventing deformation of the capacitor element, such as the capacitor element expanding in a barrel shape, it is possible to suppress short-circuits due to contact between the anode foil, the cathode foil, or their lead terminals inside the capacitor element, or a decrease in insulation of the separator. .

(3) By providing the gas discharge path at least on the outer peripheral side of the anode foil, the gas generated inside the capacitor element is difficult to stay inside the capacitor element, and is discharged from the end face of the capacitor element to the outside. In particular, the anode foil is harder than the cathode foil, and even when wound, it is easy to act on the outer peripheral side of the capacitor element due to its restoring force. Therefore, the configuration of the present application is preferably applied to the anode side.

(4) An anode foil for medium- and high-pressure applications in which tunnel-like etching pits are formed by AC etching has high hardness, and the above-described anode foil has a strong winding restoring force. In particular, in the anode foil having a withstand voltage of 250 V or more, the thickness of the oxide film layer formed on the surface of the metal foil is also 0.3 μm or more, the hardness of the anode foil is high, and the outside of the anode foil due to the winding restoring force is increased. The action becomes remarkable, and it is preferable to use it for such an anode foil having a withstand voltage of 250 V or more.

(5) By suppressing a short circuit inside the capacitor element, the pressure valve can be reliably operated in a predetermined voltage region, and a highly reliable electrolytic capacitor can be provided.

(6) Since the lead terminal is connected to the outer peripheral side of the anode foil, a gap can be secured between the anode foil and the separator, and the gas generated inside the capacitor element is efficiently released from the end face of the capacitor element. The Further, even if the anode foil is pressed to the outer peripheral side by the gas generated inside the capacitor element, the extraction terminal is arranged on the inner peripheral side of the anode foil because the extraction terminal is connected to the outer peripheral side of the anode foil. Compared with the case where the anode foil is provided, the anode foil is less likely to be damaged by the lead terminal, and a highly reliable electrolytic capacitor can be obtained.

(7) You may arrange the address paper which formed the gas discharge path in the extraction terminal connected to anode foil.

(8) A lead terminal is connected to the inner peripheral side of the cathode foil, and the addressing paper is placed between the anode foil and the cathode foil so as to face the lead terminal and the lead terminal connected to the outer peripheral side of the anode foil. By arranging, both the lead terminals can be covered with one sheet of paper.

It is a figure which shows an example of the capacitor | condenser element before the case accommodation of an Example. (A) of Modification 1 is a top view of the capacitor element, and (b) is a development view in which the capacitor element is developed. (A) of Modification 2 is a top view of the capacitor element, and (b) is a developed view of the capacitor element.

  EMBODIMENT OF THE INVENTION The form for implementing the electrolytic capacitor which concerns on this invention is demonstrated below based on an Example.

  The electrolytic capacitor according to the embodiment will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the anode foil 2 is made of a valve metal such as aluminum, the surface is roughened by an etching process, and an oxide film layer is formed on the surface. The cathode foil 3 is made of a valve action metal such as aluminum like the anode foil 2, and the surface thereof is roughened by an etching process. The anode-side lead terminal 4 made of aluminum or the like and the cathode-side lead terminal 5 made of aluminum or the like are electrically connected to these bipolar electrodes, respectively, by a connection method such as stitching, cold weld, or ultrasonic welding. . The lead terminals 4 and 5 have a flat part connected to the electrode foil and a lead part for external connection (CP wire), or are composed of a strip-like body, one of which is connected to the electrode foil and the other for external lead-out. There are those that are connected to external terminals provided on the separate sealing member.

The separator 6 interposed between the anode foil 2 and the cathode foil 3 is electrically insulative, and is made of Manila hemp paper, kraft paper, esparto paper, sisal hemp paper, hemp paper, cupra, rayon, cotton or a mixed paper of these, synthetic It consists of fibers, nonwoven fabrics, or mixed papers of these, and includes a single layer or a double structure in which a high density material (high density paper) 9 and a low density material (low density paper) 10 are overlapped. . As the high-density paper 9, kraft paper is mainly used, and as the low-density paper 10, Manila hemp paper and esparto paper are preferably used. The density of the low density paper 10 is preferably 0.3 to 0.5 g / cm ³ , and the density of the high density paper 9 is preferably 0.7 to 0.9 g / cm ³ . In particular, when the low density paper 10 is used as a discharge path of gas generated inside the capacitor element 1 to be described later, the density of the low density paper 10 may be in the range of 0.3 to 0.5 g / cm ^3. preferable.

  In the capacitor element 1, the anode foil 2 and the cathode foil 3, each having one or more lead terminals 4 and 5 connected thereto, are formed from a strip having a predetermined length, and a separator 6 is interposed between the anode foil 2 and the cathode foil 3. It is constructed by interposing and winding. The capacitor element 1 is impregnated with a driving electrolyte and housed in a bottomed cylindrical outer case 8 made of aluminum or the like, and the opening is a sealing member made of an elastic body or a composite member of an elastic body and a hard body. The member 11 is caulked and sealed.

  Here, in an electrolytic capacitor using such a wound capacitor element 1, gas is generated inside the capacitor element 1 when an overvoltage is applied exceeding the rated voltage. Although the capacitor element 1 is wound and held with a constant leveling force by the winding-stopping tape, an action of swelling to the outer peripheral side by the internal gas occurs. This is caused by pressing the anode foil 2 and the cathode foil 3 toward the outer peripheral side because the generated gas is unlikely to be released from the end face of the capacitor element 1 in the vicinity of the center of the capacitor element 1. That is, the capacitor element 1 is deformed into a barrel shape. In this way, the vicinity of the center of the capacitor element 1 swells so that the anode foil 2 and the cathode foil 3 constituting the capacitor element 1 act on the outer peripheral side, and the lead terminals 4 and 5 having particularly hard anode foil 2 and corner portions are provided. It is considered that the opposing separator 6 is pressed to break through the separator 6 and come into contact with the other opposing electrode or the like, or the insulation of the separator 6 is lowered, resulting in a short circuit.

Usually, the separator 6 facing the outer peripheral side of the anode foil 2 or the cathode foil 3 is separated from the pressure of the separator 6 due to the outward swell of the anode foil 2 or the cathode foil 3 when the internal gas is generated. The high density side surface of 6 is opposed to the outer peripheral side of the anode foil 2 and the cathode foil 3, thereby increasing the strength and insulation of the separator 6 and suppressing short circuit. However, when a voltage exceeding the rated voltage is applied, the generated internal gas is brought into close contact with the surface on the high density side of the separator 6 due to the swelling of the anode foil 2 and the cathode foil 3 to the outer peripheral side. It was found that it stayed inside the capacitor element 1 and was not easily released from the end face of the capacitor element 1.
In particular, since the anode foil 2 is likely to act on the outer peripheral side of the capacitor element 1 due to its restoring force after winding, the above phenomenon is likely to occur. In addition, the restoring force of the anode foil 2 varies depending on its hardness, and it is difficult to release the internal gas from the capacitor element 1 particularly in the anode foil 2 for medium to high pressure applications in which tunnel-like etching pits are formed by AC etching. . This depends on the state of the etching pit by the etching technique and the state of the oxide film formed by the chemical conversion treatment. In particular, in the anode foil 2 having a withstand voltage of 250 V or more, the thickness of the oxide film layer formed on the surface of the metal foil is also 0.3 μm or more, the anode foil 2 has high hardness, and the outside of the anode foil 2 due to the restoring force. The effect of is remarkable.
Further, depending on the thickness of the anode foil 2 and the cathode foil 3, the gas may not be easily released. In particular, when the thickness of the anode foil 2 is 4 times or more than the thickness of the cathode foil 3, it is considered that the winding restoring force of the anode foil is extremely high with respect to the cathode foil and the degree of adhesion between the anode foil 2 and the separator is increased. . The thickness of the anode foil 2 is 90 to 120 μm, and the thickness of the cathode foil 3 is 15 to 30 μm.

  For this reason, in the embodiment, the internal gas generated inside the capacitor element 1 is provided with a gas discharge path on the surface of the separator 6 adjacent to the outer peripheral sides of the anode foil 2 and the cathode foil 3. As this gas discharge path, for example, the inner surface of the separator 6 adjacent to the outer surfaces of the anode foil 2 and the cathode foil 3 is subjected to an uneven surface leading to the end surface of the capacitor element 1, embossing and groove processing, The internal gas can be discharged from the end face through the axial direction of the capacitor element 1. In addition to applying such physical processing to the separator, the separator 6 has a low-density and high-density double structure, and the surface on the low-density side faces the outer peripheral side of the anode foil 2 and the cathode foil 3. It can also be arranged. The internal gas is released from the end surface of the capacitor element 1 by the surface of the separator 6 on the low density side. It is particularly preferable that the low density paper fibers are formed so as not to be oriented in the element winding direction. In low density paper, if the fibers are oriented in the element winding direction, it is difficult to release gas. By providing the gas discharge path in this way, it is possible to prevent the capacitor element 1 from bulging into a barrel shape and to prevent the capacitor element 1 from being short-circuited. Therefore, the operation of the pressure valve of the electrolytic capacitor is stable, and a highly reliable electrolytic capacitor can be provided.

  Next, an electrolytic capacitor according to Modification 1 of this embodiment will be described. 2A is a top view of the capacitor element 1, and FIG. 2B is a diagram illustrating a state in which the capacitor element 1 of FIG. 2A is developed. As shown in FIG. 2A, the capacitor element 1 is formed by winding an anode foil 2 and a cathode foil 3 to which lead terminals 4 and 5 are connected, respectively, via a separator 6. FIG. 2B is an expanded view of a portion where the anode-side extraction terminal 4 and the cathode-side extraction terminal 5 are connected. 2B, the lower side of the drawing shows the inner peripheral side (center side) X of the capacitor element 1, and the upper side of the drawing shows the outer peripheral side Y of the capacitor element 1. The anode foil 2 has an anode-side lead terminal 4 connected to the outer peripheral side Y surface of the capacitor element 1, and the cathode foil 3 has a cathode-side lead terminal 5 on the inner peripheral side X surface of the capacitor element 1. It is connected. Further, from the inner peripheral side X of the capacitor element 1, the anode foil 2 (AC etching: formation voltage 250 V), the double-structure separator 6, the cathode foil 3, and the double-structure separator 6 are arranged in this order. Here, the separator 6 has a double structure of high density (high density paper 9) and low density (low density paper 10: a form in which fibers are not oriented in the element winding direction). The low density paper 10 of the separator 6 is arranged on the outer peripheral side Y surface of the capacitor element 1.

  Thus, since the low density paper 10 of the separator 6 is arranged on the surface of the outer peripheral side Y of the capacitor element 1 of the anode foil 2, even when the anode foil 2 having high hardness is used, the capacitor element 1 The gas generated inside is efficiently discharged from the end face of the capacitor element through the low density paper 10. Further, the anode-side lead terminal 4 is connected to the outer peripheral side Y surface of the capacitor element 1 of the anode foil 2, and since there is a thickness of the lead terminal 4, a gap is secured between the anode foil 2 and the separator 6. The gas generated inside the capacitor element 1 is released from the end face of the capacitor element 1 more efficiently. When the anode-side lead terminal 4 is arranged on the inner peripheral side X of the anode foil 2, the anode foil 2 is pressed against the outer peripheral side Y by the gas generated inside the capacitor element 1. In this case, since the lead terminal 4 is installed on the inner peripheral side X of the anode foil, the corner portion of the lead terminal 4 presses the anode foil 2. However, although the surface of the hard and fragile anode foil may be scratched, in the first modification, the lead-out terminal 4 on the anode side is disposed on the outer peripheral side Y of the anode foil 2, so that it is as described above. There is no damage to the anode foil 2 and a highly reliable electrolytic capacitor can be obtained. In Modification 1, the cathode-side lead terminal 5 is formed on the inner peripheral side X of the cathode foil 3, but the cathode foil 3 itself is thinner and more elastic than the anode foil 2, Even if the gas generated inside the capacitor element 1 is pressed by the lead-out terminal 5 on the cathode side, its influence is low.

  Next, an electrolytic capacitor according to Modification 2 of this embodiment will be described. 3A is a top view of the capacitor element 1, and FIG. 3B is a diagram illustrating a state in which the capacitor element 1 of FIG. 3A is developed. In the second modification, the lead terminal 4 connected to the outer peripheral side Y surface of the capacitor element 1 of the anode foil 2 of the capacitor element 1 and the lead terminal connected to the inner peripheral side X surface of the capacitor element 1 of the cathode foil 3. 5 is the same as that of the first modification except that the address paper 7 is disposed together with the separator 6.

  The addressing paper 7 may be inserted between the anode-side extraction terminal 4 and the separator 6 or between the cathode-side extraction terminal 5 and the separator 6. Moreover, the address paper 7 may be arrange | positioned at the separator 6 through the adhesive material. In the second modification, the address paper 7 is arranged on the surface of the separator 6 on the anode foil side through an adhesive material. Examples of the adhesive material to which the addressing paper 7 is attached include phenol-based, epoxy-based, cyanoacrylate-based, polyimide-based, acrylic-based, silicone-based, rubber-based, and hot-melt-based materials. Of these, polypropylene and polyvinyl alcohol are preferably used. Further, the address paper 7 is the same as the material of the separator described above, and a single one or a double structure in which a low-density material and a high-density material are overlapped is used. A gas discharge path for discharging the gas generated inside the capacitor element 1 may be formed on the address sheet 7 as well. As described above, the gas discharge path can be processed with unevenness, embossing and grooving, and the paper 7 has a low density and high density dual structure, and the low density side is arranged on the outer peripheral surface of the anode foil. (See FIG. 3B).

  In the modified example 2, as shown in FIG. 3B, the paper 7 is attached to the separator 6 via an adhesive material. In particular, the anode-side extraction terminal 4 and the cathode-side extraction terminal 5 are connected to the opposing surfaces of the anode foil 2 and the cathode foil 3 (the outer peripheral side Y surface of the anode foil and the inner peripheral side X surface of the cathode foil), respectively. A continuous strip-shaped paper 7 is disposed on the separator 6 so as to face the two lead-out terminals 4, 5, that is, to overlap the two-pole lead terminals 4, 5. In addition to the action of the first modification, in the second modification, the paper 7 protects against the pressure applied to the separator 6 by the lead terminals 4 and 5 of both poles due to the expansion of the capacitor element 1 to the outer peripheral side Y by the internal gas. The occurrence of short circuit can be suppressed. Further, by arranging the address paper 7 so as to face the lead terminals 4 and 5 of both poles, the address paper itself can be made into one sheet without arranging the address paper individually for each of the output terminals. Can be simplified.

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode foil 3 Cathode foil 4 Anode-side lead-out terminal 5 Cathode-side lead-out terminal 6 Separator 7 Addressing paper 8 Outer case 9 High-density paper 10 Low-density paper 11 Sealing member

Claims (6)

In an electrolytic capacitor in which a capacitor element in which an anode foil and a cathode foil to which a lead terminal is connected is wound through a separator is housed in an outer case,
An electrolytic capacitor in which a gas discharge path for discharging a gas generated from the inside of an element is formed on at least an inner peripheral surface of a separator adjacent to an outer peripheral surface of an anode foil. The electrolytic capacitor according to claim 1, wherein the anode foil has a withstand voltage of 250 V or more.   The electrolytic capacitor according to claim 1, wherein the anode foil has a thickness that is four times or more the thickness of the cathode foil.   The electrolytic capacitor according to claim 1, wherein a lead terminal is connected to the anode foil on an outer peripheral side thereof. 5. The electrolytic capacitor according to claim 4, wherein a paper having a gas discharge path is disposed between a separator facing the lead terminal connected to the anode foil.   The lead-out terminal is further connected to the inner peripheral side of the cathode foil, and the addressing paper is arranged between the lead-out terminal and the lead-out terminal connected to the outer peripheral side of the anode foil. Electrolytic capacitor.

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