JP2864476B2 - Electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor provided with a safety device against a sudden temperature rise and a short circuit accident.

[Prior art]

Electrolytic capacitors called dry electrolytic capacitors have an insulating oxide film formed on the surface of aluminum, etc.
Using a so-called valve metal for the anode, the insulating oxide film is formed by an operation such as anodizing treatment, and this film is used as a dielectric, and a counter electrode is arranged via a liquid electrolyte to form a capacitor. I have. FIG. 2 shows the structure of a general electrolytic capacitor, in which the surface is enlarged by etching, and an insulating oxide film serving as a dielectric layer is formed on the surface by a process such as anodic oxidation. An anode foil 2 obtained by cutting an aluminum foil into a strip, a cathode foil 3 similarly cut into a strip, and a width slightly larger than the two electrode foils 2 and 3 so that the two electrode foils 2 and 3 are separated from each other. The placed separator 4 is overlapped and wound from one end to form a cylindrical capacitor element 1. The capacitor element 1 is impregnated with a liquid electrolyte, that is, an electrolytic solution, in which various inorganic acids, organic acids or salts thereof are dissolved in various solvents such as ethylene glycol and γ-butyrolactone. A strip-shaped anode lead 5 and a cathode lead 6 electrically connected to the anode foil 2 and the cathode foil 3, respectively, are drawn out from the wound end face of the upper part of the capacitor element 1. The capacitor element 1 is housed in a metal outer case 7 formed by pressing a bottomed cylindrical aluminum or the like, and an opening of the outer case 7 has a sealing plate 8 punched into a size substantially equal to the inner diameter of the outer case 7. Is closed by
The sealing plate 8 has a two-layer structure, and is formed by bonding an elastic member 9 such as a synthetic rubber sheet to the surface of a hard insulating plate 10 such as a phenol resin laminate. The sealing plate 8 is locked by a projection on the inner surface of a groove 11 provided around the opening of the outer case 7 and the opening end of the outer case 7 is tightly wound inward to seal the capacitor element 1. I have. External terminals 12 for obtaining an electrical connection with the outside are attached to the outer surface of the sealing plate 8. A rivet 13 that penetrates the sealing plate 8 from the outer end and projects inside is provided with an anode lead 5 and a cathode. The leads 6 are connected to each other by means such as welding. An electrolytic capacitor is characterized in that a small and large-capacity product can be obtained because an extremely thin insulating oxide film is used as a dielectric layer. However, the oxide film may be damaged by a mechanical impact at the time of manufacture, or may be deteriorated due to long-term use or presence of moisture. The electrolytic solution has a function as a true cathode by directly contacting the oxide film and a function of repairing the oxide film that has been deteriorated or damaged by the anodic oxidation reaction. However, an electrolytic capacitor has polarity, and when a reverse voltage is applied, an oxide film is broken and a large amount of current flows between the electrodes. Even if the polarity is normal, if a voltage exceeding the withstand voltage of the oxide film is applied, a short circuit occurs and a current suddenly flows. In such a case, the capacitor element generates heat rapidly due to the large current, and the impregnated electrolyte boils and evaporates, so that the internal pressure rises rapidly. Since the electrolytic capacitor is highly sealed in order to prevent evaporation of the electrolytic solution and intrusion of moisture or impurities from the outside, a sudden increase in the internal pressure leads to explosion and destruction of the electrolytic capacitor. For this reason, in the electrolytic capacitor, as shown in FIG. 2, an explosion-proof groove 13 is formed on the bottom surface of the outer case 7, or a part of the hard insulating plate 10 of the sealing plate 8 is cut off to provide an explosion-proof valve 14. When the internal pressure rises, the thin portion breaks and opens so that the internal high-pressure gas is radiated to the outside to maintain safety. However, although this structure can prevent the explosion, the internal high-pressure gas and the electrolyte, and a part of the capacitor element constituent members may be scattered to the outside. Obstacles such as smoke, explosion, and ignition are inevitable. Sometimes, the scattered electrolyte adheres to other parts, causing secondary accidents.

[Problems to be solved by the invention]

From such a background, recently, when an abnormality has occurred in the capacitor element, a safety device for a so-called open mode electrolytic capacitor that quickly cuts off a part of an electric circuit and cuts off current is required. As an electrolytic capacitor provided with such an open mode safety device, for example, as disclosed in Japanese Utility Model Application Laid-Open No. 54-86646, a connection between an external lead wire and an outer case is joined by a low-temperature melting alloy. As shown in JP-A-56-169539, a thermal fuse is installed inside a sealing plate. Alternatively, as in JP-A-53-163540, a strip conductor is disposed on the outer surface of a sealing plate at an explosion-proof valve section, and the explosion-proof valve cuts the strip conductor by operation or deformation.
As disclosed in Japanese Unexamined Patent Publication No. 736, a device in which a thermal fuse is provided inside a capacitor element is known. Conventional open mode safety devices, for example, those with a thermal cut-off element such as a thermal fuse installed inside the capacitor element, respond perfectly to the heat generated by the capacitor element, but in the case of electrolytic capacitors, dissimilar metals and impurities Is a cause of a corrosion accident, so that it is difficult to cover these temperature-sensitive shut-off elements with a corrosion-resistant member to prevent corrosion, and the assembling process becomes complicated, which is not practical. Also, the one with the thermo-sensitive shut-off element attached to the sealing plate does not conduct heat sufficiently from the capacitor element,
There is a drawback that the breaking operation is uncertain. In addition, since the disconnection of the electric circuit by the mechanical operation utilizes the deformation of the exterior material due to an increase in the internal pressure or the like, the response to the capacitor element and the heat generation is still not quick. Further, in the case where the current interrupting function is sealed inside the exterior member of the capacitor, the interrupting operation cannot be visually confirmed, and it is difficult to confirm the abnormality of the electrolytic capacitor and the interrupting operation. The safety device for an electrolytic capacitor according to the present invention improves on the above-mentioned disadvantages, and performs a shut-off operation by promptly detecting heat generation of the capacitor element due to an abnormality of the electrolytic capacitor, and makes it easy to confirm the shut-off operation. Further, it is intended to provide a structure free from the possibility of occurrence of corrosion and the like.

[Means for Solving the Problems]

In the electrolytic capacitor of the present invention, the capacitor element is housed inside an outer case having a groove-shaped recess formed in the center of the side surface, and the capacitor element is fixed in the groove-shaped recess, and the opening of the outer case is sealed. To a set of external terminals and relay terminals provided through the front and back of the sealing member to be connected, while connecting one of a set of electrode leads drawn from the capacitor element to one of the external terminals on the inner surface side of the sealing plate,
Connect the other electrode lead to the relay terminal on the inner side of the sealing plate,
In addition, the other external terminal and the relay terminal portion are electrically connected via a temperature-sensitive shut-off element provided in the groove-shaped concave portion of the outer case. That is, in the electrolytic capacitor of the present invention, the electrode lead electrically connected to the anode or the cathode of the capacitor element is not directly connected to the external terminal provided on the sealing plate, and at least one electrode lead is provided on the sealing plate. Further, the relay terminal is connected to the relay terminal, and the relay terminal and the external terminal are electrically connected to each other via a temperature-sensitive shut-off element. The temperature-sensitive shut-off element is disposed in a groove-shaped recess provided in the center of the side surface of the outer case, and the groove-shaped recess fixes the capacitor element on the inner surface of the outer case. Therefore, the temperature-sensitive shut-off element is arranged at the position closest to the capacitor element on the outer surface of the outer case. Further, a temperature fuse, a low-temperature molten alloy, or the like can be used as the temperature-sensitive shut-off element. The setting of the melting temperature of the thermal fuse or the melting temperature of the molten alloy can be appropriately selected depending on various electrolytic capacitors and their intended use. Generally, the maximum operating temperature of electrolytic capacitors is 85 ° C to 130 ° C.
° C, which is due to the increase in current
Since the temperature is 150 ° C. or higher, the above temperature may be set to about 150 ° C. to 170 ° C. from a region exceeding the maximum operating temperature.

[Action]

In the electrolytic capacitor of the present invention, when the current increases due to abnormalities such as short-circuiting of the capacitor element, application of a voltage exceeding the rating, application of a reverse voltage, etc., and the capacitor element generates heat, the heat is provided at the center of the side surface of the outer case. The temperature-sensitive shut-off element disposed in the groove-shaped concave portion is quickly melted by conduction to the groove-shaped concave portion, and a circuit including an electrolytic capacitor can be cut off.

【Example】

Hereinafter, the electrolytic capacitor of the present invention will be described based on examples. FIG. 1 is a perspective view showing an electrolytic capacitor of the present invention. In the figure, a cylindrical capacitor element impregnated with an electrolyte is formed by winding an anode electrode foil and a cathode electrode foil via a separator inside a bottomed cylindrical outer case 32 made of a metal material such as aluminum. It is stored. At the center of the side surface of the outer case 32, a wide groove-shaped outer peripheral recess 33 is formed over the entire circumference. The inner diameter of the outer peripheral recess 33 is set to be substantially the same as or slightly larger than the outer diameter of the internal capacitor element, so that the capacitor element is held and fixed by the outer peripheral recess 33. The upper opening surface of the outer case 32 is closed by a disc-shaped sealing plate 22. On the upper surface of the sealing plate 22, a pair of plate-like external terminals 23 and 24 are fixed at their bases to the sealing plate 22 by rivets 25, and the rivets 25 penetrate the sealing plate 22 and protrude inside. ing. The sealing plate 22 is provided with a relay terminal 26, which also penetrates the sealing plate 22 and protrudes inside. One set of electrode leads drawn from the capacitor element is electrically connected to the rivet 25 of the external terminal 24 on one side. The other electrical lead is electrically connected to the relay terminal 26. A conductive band 27 made of a thin metal plate or the like is connected to the outside of the relay terminal 26. The conductive band 27 is a sealing plate.
It is installed so as to reach the groove-shaped outer peripheral concave portion 33 provided on the side surface of the outer case 32 from the surface of the outer case 22 through the outer peripheral value of the outer case 32. Similarly, the base of the external terminal 23 has a conductive band.
28 is installed from the surface of the sealing plate 22 to the groove-shaped outer peripheral recess 33 provided on the side surface of the outer case 32, and the temperature-sensitive shut-off element 30 is
The groove-shaped outer peripheral recess 33 is provided on the surface. The insulating layer 31 is provided to insulate the conductive bands 27 and 28 or the temperature-sensitive shut-off element 30 from the outer case 32 made of metal such as aluminum. The insulating layer 31 may be provided by means of applying an insulating material to the surface of the outer case 32, or attaching a sheet-like insulating film using an adhesive. Conductive belt 27,2
The insulating layer 31 is not always necessary if an insulated wire is used for 8 and the temperature-sensitive shut-off element 30 has a surface insulated in advance. According to this embodiment, the temperature-sensitive shut-off element 30 is
Since it is arranged in the groove-shaped outer peripheral recess 33 provided on the side surface of 32,
The outer diameter of the electrolytic capacitor does not increase. Further, since the temperature-sensitive shut-off element 30 is exposed to the outside, the operating condition can be easily determined visually. Also, a groove-shaped outer peripheral recess 33 provided on the side surface of the outer case 32 is provided.
However, since it is installed so as to sandwich the internal capacitor element, the external case of heat due to heat generation of the capacitor element
The conductivity of 32 is improved, and the response of the breaking operation is improved. In the embodiment, the outer case 32 is not provided with an insulating outer case. However, a heat-shrinkable vinyl chloride tube or the like may be coated by a known method. In this case, a temperature-sensitive shut-off element
In order to confirm the operation of 30, if it is a transparent exterior coating,
Although the operation can be confirmed even if the surface of the temperature-sensitive shut-off element 30 is directly covered, if it is opaque, it is necessary to provide a window at the portion of the temperature-sensitive shut-off element 30 to check the operation.

【The invention's effect】

As described above, the electrolytic capacitor of the present invention has a groove-shaped recess provided at the center of the side surface of an outer case made of aluminum or the like having good thermal conductivity when an abnormality occurs in the electrolytic capacitor and the capacitor element generates heat. Since the temperature-sensitive shut-off element is disposed in the circumstance, the shut-off operation can be performed very responsively, and an accident can be prevented. Further, since the temperature-sensitive shut-off element is provided outside, the shut-off state can be easily determined. In addition, since no shut-off element is installed inside, it is easy to assemble and it is possible to prevent the occurrence of corrosion.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the electrolytic capacitor of the present invention, and FIG. 2 is a sectional view for explaining a conventional electrolytic capacitor. 23, 24 ... external terminal, 25 ... rivet, 26 ... relay terminal, 27, 28 ... conductive band, 29 ... groove, 30 ... thermosensitive shut-off element, 31 ... insulating layer, 32 ... exterior Case, 33 ... outer peripheral recess

Claims (3)

(57) [Claims] 1. A capacitor element is housed in an outer case made of aluminum or the like having a groove-shaped recess formed in the center of a side surface, and the capacitor element is fixed in the groove-shaped recess. One of a pair of electrode leads drawn from the capacitor element is connected to one of the external terminals on the inner surface side of the sealing plate, to a pair of external terminals and a relay terminal provided through the front and back of the sealing member to be sealed. At the same time, the other electrode lead is connected to a relay terminal on the inner surface side of the sealing plate, and the other external terminal and the relay terminal portion are electrically connected via a temperature-sensitive shut-off element installed in the groove-shaped recess of the outer case. An electrolytic capacitor characterized by being connected to a capacitor. 2. The electrolytic capacitor according to claim 1, wherein the thermal cutoff element is a thermal fuse. 3. The electrolytic capacitor according to claim 1, wherein the temperature-sensitive shut-off element is a low-temperature molten alloy.