JPH11274013A - Sealing structure for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing structure for an electrolytic capacitor, which while maintaining airtightness, contributes to longer life of the capacitor, improved mechanical strength, and advantages in manufacturing process. SOLUTION: A sealing plate 1 made of fluororesin is provided with a lead hole, with a round rod part 4 of a lead wire 3 inserted in the lead hole. In any of the modes shown in figures (A)-(D), the lead hole is provided with a minimum diameter part 5, whose diameter is smaller than that of the round rod part 4 and a taper part 6 which extends from the round rod part 4 of the minimum diameter part 5 toward the insert opening side, with the diameter of the maximum diameter part of the taper part 6 larger than that of the round rod part 4. For the sealing plate 1 in each mode, the relationship between the diameter of the minimum diameter part 5 of the lead hole and that of the round rod part as represented in the expression is set so that 5%<=(ϕd-ϕc)/ϕd<=50% (the diameter of the minimum diameter part 5 is ϕD and the diameter of round rod part 4 is ϕd) is established.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor, and more particularly to an improvement in a sealing structure for sealing an opening of an outer case.

[0002]

2. Description of the Related Art An electrolytic capacitor has a structure in which a capacitor element is housed in a bottomed cylindrical outer case made of aluminum, hard resin or the like, and the opening of the outer case is sealed with a sealing plate. In such an electrolytic capacitor, the lead wire drawn from the capacitor element has a round bar portion for penetrating the sealing plate, whereas the sealing plate has a lead hole, and the sealing plate has a lead hole. From the viewpoint of maintaining airtightness with the round bar part of the lead wire,
Rubber is used.

In such a sealing structure using a rubber sealing plate, a round rod portion of a lead wire is inserted into a lead hole of a rubber sealing plate, and a caulking lateral groove of an outer case is formed in the sealing plate. By pushing the rubber into the outer periphery, the rubber is deformed in the vertical direction to generate a stress that reduces the size of the lead hole, thereby maintaining the airtightness between the sealing plate and the round bar portion.
However, since rubber has a high gas permeability, when a rubber sealing plate is used, the phenomenon that moisture in the external air invades the outer case, and conversely, the internal electrolytic solution evaporates to the outside And it is difficult to maintain the life reliability of the capacitor. Further, rubber has a problem that the mechanical strength is reduced due to a low elastic modulus.

It is also conceivable to use fluororubber, which is a rubber having excellent airtightness and heat resistance, as a sealing plate. However, since fluororubber has a side chain of a methyl fluoride group as shown below, it is easily attacked by esters, amines, low molecular weight ketones, alkalis, etc.
Also, it is not suitable for electrolytic capacitors because it is easily affected by high-pressure steam.

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On the other hand, there is a sealing plate using a combination of a fluororesin and rubber. However, in a sealing structure using such a sealing plate, a stress in a penetrating direction is applied to an insertion portion of a round bar portion of a lead terminal. By generating, the airtightness between the round bar portion and the sealing plate is maintained. Therefore, high accuracy is required in each manufacturing process such as welding of a lead wire and a round bar portion, element manufacturing, and caulking.

[0006]

As described above, in the sealing structure using the conventional rubber sealing plate, it is difficult to maintain the life reliability of the capacitor while maintaining the airtightness. , Low mechanical strength. Further, in a sealing structure using a sealing plate in which a fluorine resin and rubber are combined, high precision is required in each manufacturing process.

On the other hand, it is conceivable to use a fluororesin as the sealing plate. However, since the fluororesin has a higher elastic modulus than rubber, the above-mentioned rubber is used for the sealing plate made of fluororesin. Even if the crimped lateral groove of the outer case is pushed into the outer periphery as described above, the deformation is small, and it is difficult to maintain sufficient airtightness due to generation of stress.

The present invention has been proposed to solve the above-mentioned problems of the prior art.
An object of the present invention is to provide an electrolytic capacitor sealing structure that can maintain airtightness, contribute to extending the life of the capacitor and improve mechanical strength, and is advantageous in terms of manufacturing.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a fluororesin which was conventionally considered to be difficult to apply to a sealing plate alone from the viewpoint of maintaining airtightness. By focusing on the shape of the through hole of the sealing plate, the fluororesin alone can be applied to the sealing plate.

According to a first aspect of the present invention, there is provided a sealing structure including a sealing means for sealing an opening of a bottomed cylindrical outer case for housing a capacitor element. The round bar is configured to be pulled out through the sealing means. And in such a sealing structure, the sealing means is characterized as follows. That is, the sealing means is a sealing plate made of a fluororesin, and the sealing plate is provided with through holes for passing the round bar portions having different diameters in the penetrating direction. A minimum diameter portion smaller than the diameter of the round bar portion is provided in a part of the through hole in the through direction, and the round bar portion is provided at an opening end of the through hole on the side serving as an insertion port of the electrode lead-out means. An insertion-side large-diameter portion having a diameter or more is provided.

According to this structure, first, the minimum diameter portion of the through hole of the sealing plate is made smaller than the round bar portion. The inner peripheral surface of the small diameter portion is brought into close contact with the outer peripheral surface of the round bar portion to maintain airtightness. In addition, by making the diameter of the opening end of the through-hole on the side of the electrode lead-out means insertion opening larger than the diameter of the round bar, the round bar can be easily inserted into the through-hole. Moreover, since the sealing plate is made of a fluororesin, gas permeability can be reduced and chemical resistance can be improved as compared with a case where the sealing plate is made of rubber. Further, since the fluorine resin has a higher elastic modulus than rubber, the mechanical strength can be improved.

Each of the sealing structures according to the second to fourth aspects specifically limits the size and shape of the through hole of the sealing plate in the sealing structure according to the first aspect. According to a second aspect of the present invention, when the diameter of the minimum diameter portion of the through hole is φD and the diameter of the round bar portion is φd, 5% ≦ (φd−φD) / It is characterized in that the relationship of φd ≦ 50% is satisfied. According to this configuration, the inner peripheral surface of the minimum diameter portion of the through hole and the outer peripheral surface of the round bar portion can be sufficiently brought into close contact. Further, since the round bar portion can be moved with respect to the through hole in such a close contact state, there is no hindrance to the insertion operation of the round bar portion. That is, when the above value (φd−φD) / φd is less than 5%, the airtightness at the minimum diameter portion may be deteriorated. Since there is a possibility that the insertion of the round bar becomes difficult, by setting the range of 5% to 50%, the round bar portion can be easily inserted while maintaining the airtightness.

According to a third aspect of the present invention, there is provided the sealing structure according to the first or second aspect, wherein the through hole is provided with a tapered portion extending from the minimum diameter portion toward the insertion-side large diameter portion. I have. According to this configuration, the round bar portion can be easily inserted into the through hole using the tapered portion. That is, since the contact area between the inner peripheral surface of the through hole and the outer peripheral surface of the round bar portion can be reduced, the force required when the round bar portion is inserted can be reduced, and the taper portion can be reduced. Since it also functions as a part insertion guide, insertion of the round bar part becomes easy. Further, even if the contact area between the through hole and the round bar portion is reduced by providing the tapered portion, sufficient airtightness can be maintained by the minimum diameter portion of the through hole.

According to a fourth aspect of the present invention, there is provided the sealing structure according to the third aspect, wherein the opening end of the through hole opposite to the insertion-side large-diameter portion has a large-diameter portion on the opposite side that is larger than the diameter of the round bar portion. And a tapered portion extending from the minimum diameter portion toward the large diameter portion on the opposite side is provided. According to this configuration, the contact area between the inner peripheral surface of the through hole and the outer peripheral surface of the round bar portion can be minimized within a range in which the airtightness can be sufficiently maintained. Force can be reduced, and the insertion of the round bar portion becomes easier.

Each of the sealing structures according to the fifth to seventh aspects specifically limits the size and shape of the outer peripheral portion of the sealing plate in the sealing structure according to the first to fourth aspects. Claim 5
The sealing structure according to any one of claims 1 to 4, wherein at least a part of the sealing plate in the thickness direction is provided with a maximum outer diameter portion larger than the inner diameter of the opening of the outer case. . According to this configuration, the maximum outer diameter of the sealing plate is made larger than the inner diameter of the opening of the outer case, so that the outer peripheral surface of the maximum outer diameter is brought into close contact with the inner peripheral surface of the opening of the outer case to be airtight. Sex can be maintained.

According to a sixth aspect of the present invention, in the sealing structure according to the fifth aspect, the insertion-side small-diameter portion having an inner diameter equal to or smaller than the inner diameter of the opening of the outer case is provided at the insertion-side end of the sealing plate in the thickness direction. And a tapered portion extending from the insertion-side small-diameter portion toward the maximum outer-diameter portion is provided. According to this configuration, the sealing plate can be easily inserted into the outer case opening using the tapered portion. That is, since the contact area between the outer peripheral surface of the sealing plate and the inner peripheral surface of the outer case opening can be reduced, the force required when the sealing plate is inserted can be reduced, and the tapered portion is Since it also functions as an insertion guide, the mounting of the sealing plate becomes easy. Further, even if the contact area between the sealing plate and the outer case opening is reduced, sufficient airtightness can be maintained by the maximum outer diameter portion of the sealing plate.

According to a seventh aspect of the present invention, in the sealing structure according to the sixth aspect, the end opposite to the small-diameter portion on the insertion side in the thickness direction of the sealing plate is also opposed to the inside diameter of the opening of the outer case. A small-diameter portion is provided, and a tapered portion extending from the small-diameter portion on the opposite side toward the maximum outer-diameter portion is provided. According to this configuration, the contact area between the outer peripheral surface of the sealing plate and the inner peripheral surface of the outer case opening can be minimized within a range in which the airtightness can be sufficiently maintained.
The force required when inserting the sealing plate can be made smaller, and the mounting of the sealing plate becomes easier.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of a sealing structure of an electrolytic capacitor according to the present invention.

[1. Lead hole of fluororesin sealing plate] [1-1. Configuration] FIGS. 1A to 1D are cross-sectional views showing a plurality of different forms applied to lead holes (through holes) of a sealing plate in a sealing structure of an electrolytic capacitor according to the present invention. In the plurality of embodiments shown in FIG. 1, a lead hole 2 is provided in a sealing plate 1 made of a fluororesin, and a round bar portion 4 of a lead wire 3 is inserted into the lead hole 2. Has become. Then, FIG.
In any of the embodiments shown in (D), the lead holes 2
It has a minimum diameter portion 5 having a diameter smaller than the diameter of the round bar portion 4, and a tapered portion 6 extending from the minimum diameter portion 5 toward the insertion port side of the round bar portion 4. The diameter of the diameter portion is larger than the diameter of the round bar portion 4.

In the sealing plate 1 of each embodiment shown in FIG. 1, the diameter of the minimum diameter part 5 of the lead hole 2 and the diameter of the round bar part 4 are φD, the diameter of the minimum diameter part 5 and the diameter of the round rod part 4. 5% when φd
≦ φ (d−φD) / φd ≦ 50%. That is, the diameter of the minimum diameter portion 5 is smaller by 5% to 50% than the diameter of the round bar portion 4.

The specific shapes of the lead holes 2 will be described below for each of the sealing plates 1 shown in FIGS. 1A to 1D. First, in the sealing plate 1 shown in FIG. 1A, the lead hole 2 has a linear minimum diameter portion 5 having a diameter smaller than the diameter of the round bar portion 4, and a round rod 5 from the minimum diameter portion 5. It is composed of a tapered portion 6 expanding toward the insertion opening side of the portion 4, and has a maximum diameter portion at the end of the tapered portion 6 (insertion-side large diameter portion).
Is larger than the diameter of the round bar 4.

In the sealing plate 1 shown in FIG. 1B, the lead hole 2 has a tapered portion 6 on the insertion port side of the round bar portion 4.
In addition, a tapered portion 7 having the same size and shape is provided on the opposite side. That is, the linear minimum diameter portion 5 is sandwiched between the pair of tapered portions 6 and 7. The diameter of the largest diameter portion (larger diameter portion on the insertion side) at the end of the tapered portion 6 and the diameter of the largest diameter portion (larger diameter portion on the opposite side) at the end of the tapered portion 7 are:
It is larger than the diameter of the round bar portion 4.

On the other hand, in the sealing plate 1 shown in FIG. 1C, the lead hole 2 has a tapered portion having a minimum diameter portion 5 provided in a spot shape at one end opposite to the insertion opening of the round bar portion 4. 6 only. Also in this lead hole 2, the diameter of the minimum diameter portion 5 is smaller than the diameter of the round bar portion 4,
The diameter of the maximum diameter portion of the tapered portion 6 is larger than the diameter of the round bar portion 4.

Further, in the sealing plate 1 shown in FIG. 1D, the lead hole 2 has a minimum diameter portion 5 provided in a spot shape at the center in the penetrating direction, and a pair of the same size and shape spread on both sides thereof. It is composed of tapered portions 6 and 7. The diameter of the minimum diameter part 5 is smaller than the diameter of the round bar part 4, and the diameter of the maximum diameter part at the end of the tapered part 6 (the insertion-side large diameter part) and the maximum diameter of the end of the tapered part 7. The diameter of the portion (the large-diameter portion on the opposite side) is larger than the diameter of the round bar portion 4.

[1-2. Action / Effect] According to the sealing plate 1 made of the fluororesin having the above configuration, the minimum diameter 5 of the lead hole 2 of the sealing plate 1 is made smaller than the round bar portion, so that the material of the sealing plate 1 is While employing a fluororesin having a higher elastic modulus than rubber, the inner peripheral surface of the minimum diameter portion 5 can be kept in close contact with the outer peripheral surface of the round bar portion 4 to maintain airtightness. Particularly, since the diameter of the minimum diameter portion 5 of the lead hole 2 is smaller than the diameter of the round bar portion 5 by 5% or more, sufficient airtightness can be maintained.

Further, since the diameter of the opening end of the lead hole 2 on the side of the lead wire insertion opening is equal to or larger than the diameter of the round bar portion 4, the round bar portion 4 can be easily inserted into the lead hole 2. Particularly, since the tapered portion 6 extending from the minimum diameter portion 5 toward the insertion opening side of the round bar portion 4 is provided, the contact area between the inner peripheral surface of the lead hole 2 and the outer peripheral surface of the round bar portion 4 is reduced. Therefore, the force required when inserting the round bar portion 4 can be reduced. In addition, since the tapered portion 6 also functions as an insertion guide for the round bar portion 4, the insertion of the round bar portion 4 becomes easy from this point as well.

Further, in the sealing plate 1 shown in FIGS. 1B to 1D, the tapered portion 7 is provided at the opening end of the lead hole 2 on the side opposite to the insertion opening side of the round bar portion 4. Alternatively, by providing a minimum diameter portion 5 at the opening end side and forming a tapered portion 6 extending toward the insertion port side, the inner peripheral surface of the lead hole 2 and the round bar portion are provided within a range where airtightness can be sufficiently maintained. 4 has a small contact area with the outer peripheral surface. Therefore, the force required when inserting the round bar portion 4 can be further reduced. Especially,
Since the sealing plate 1 shown in FIGS. 1C and 1D has the minimum diameter portion 5 provided in a spot shape, the force required when the round bar portion 4 is inserted can be minimized. .

When the diameter of the minimum diameter portion 5 of the lead hole 2 is extremely small, it may be difficult to insert the round bar portion 4 into the lead hole 2, but each sealing plate shown in FIG. In the first lead hole 2, since the diameter of the minimum diameter portion 5 is made smaller than 50% of the diameter of the round bar portion 4, the round bar portion 4 is easily inserted into the lead hole 2. it can.

Further, in each of the embodiments shown in FIG. 1, since the sealing plate 1 is made of a fluororesin, the gas permeability can be reduced as compared with the conventional case where the sealing plate is made of rubber. And chemical resistance can be improved. Furthermore, since fluororesin has a higher elastic modulus than rubber,
If a single fluorocarbon resin is used for the sealing plate 1, the sealing plate 1 having higher mechanical strength than a conventional rubber sealing plate can be obtained.

[2. Airtight structure of outer peripheral portion of fluororesin sealing plate] [2-1. Types of hermetic structure] (A) to (C) of FIG.
FIG. 4 is a cross-sectional view showing a plurality of different forms applied to the hermetic structure of the outer peripheral portion of the sealing plate in the sealing structure of the electrolytic capacitor according to the present invention.

In the embodiment shown in FIG. 2A, the outer peripheral portion of the sealing plate 1 made of fluororesin is kept airtight by crimping the lateral groove 9 provided in the outer case 8 and the curl 1.
This is performed by sandwiching the sealing plate 1 between the sealing plate 1 and the sealing plate 1. That is, the crimped lateral grooves 9 provided in the outer case 8 are provided.
After the outer peripheral portion of the sealing plate 1 is placed on the upper part, the opening end of the outer case 8 is deformed to form a curl 10, and the curl 10 is crimped on the upper surface of the outer peripheral portion of the sealing plate 1. The airtightness of the outer peripheral portion of the sealing plate 1 is maintained.

In the embodiment shown in FIG.
The airtightness of the outer peripheral portion of the sealing plate 1 made of fluororesin is
This is performed by pushing a crimped lateral groove 9 provided in the outer case 8 into the outer peripheral surface of the sealing plate 1. That is,
With the sealing plate 1 inserted into the opening of the outer case 8, a caulking lateral groove 9 is formed at the insertion position of the sealing plate 1 in the outer case 8, or formed in advance before the sealing plate 1 is inserted. By pressing the sealing plate 1 into the crimped lateral groove 9, the crimped lateral groove 9 is pushed into the outer peripheral surface of the sealing plate 1, and the sealing plate 1 is fixed at a predetermined position on the opening side of the outer case 8. After fixing the sealing plate 1 in this manner, the opening end of the outer case 8 is deformed to form a curl 10, and the curl 10 is pressed against the upper surface of the outer peripheral portion of the sealing plate 1, whereby the sealing plate is 1 is kept airtight.

Further, in the embodiment shown in FIG. 2C, the outer diameter of the sealing plate 1 made of fluororesin is kept airtight by making the outer diameter of the sealing plate 1 larger than the inner diameter of the opening of the outer case 8. It is done by that. That is, the outer peripheral surface of the sealing plate 1 is brought into close contact with the inner peripheral surface of the outer case opening by utilizing the difference between the outer diameter of the sealing plate 1 and the inner diameter of the outer case opening. Airtightness is maintained.

The configuration shown in FIG.
Since it is not necessary to provide a caulking lateral groove 9 in FIG.
As compared with the configurations (B) and (B), the workability at the time of attaching the sealing plate 1 can be improved.

[2-2. Specific shape of outer periphery of sealing plate]
The configuration shown in FIG. 2A shows a case where the outer diameter of the sealing plate 1 is simply increased to form a linear maximum outer diameter portion 11, as shown in FIG. 3A. However, the specific shapes of the outer peripheral portion of the sealing plate 1 are shown in FIGS.
As shown in FIG.

Of these, the outer peripheral portion of the sealing plate 1 shown in FIG. 3B has a linear maximum outer diameter portion 11 having a diameter larger than the inner diameter of the outer case opening, and insertion into the outer case 8. The diameter of the smallest diameter portion (insertion-side small diameter portion) at the end of the tapered portion 12 is smaller than the inner diameter of the outer case opening.

The outer peripheral portion of the sealing plate 1 shown in FIG. 3C has a tapered portion having a maximum outer diameter portion 11 provided in a spot shape at one end of the sealing plate 1 on the side opposite to the side inserted into the outer case 8. 1
It is composed of only two. Also in this outer peripheral portion, the diameter of the maximum outer diameter portion 11 is larger than the inner diameter of the outer case opening, and the diameter of the minimum diameter portion of the tapered portion 12 is larger than the inner diameter of the outer case opening.

Further, the outer peripheral portion of the sealing plate 1 shown in FIG. 3D has a maximum outer diameter portion 11 provided in the center in the thickness direction in the form of a spot and a pair of tapered portions 12 extending on both sides thereof. , 13. The diameter of the maximum outer diameter portion 11 is larger than the inner diameter of the outer case opening, and the diameter of the minimum diameter portion at the end of the tapered portion 12 (small diameter portion on the insertion side) and the minimum diameter of the end of the tapered portion 13. The diameter of the portion (opposite side small diameter portion) is smaller than the inner diameter of the outer case opening.

According to the sealing plate 1 shown in FIGS. 3 (B) to 3 (D), a minimum diameter portion smaller than the inner diameter of the outer case opening is provided at the outer peripheral portion of the sealing plate 1 on the side of insertion into the outer case 8. Since the tapered portion 12 is provided, the contact area between the outer peripheral surface of the sealing plate 1 and the inner peripheral surface of the outer case opening is reduced as long as airtightness can be sufficiently maintained. Therefore, the force required when inserting the sealing plate 1 can be made smaller than that of the sealing plate 1 shown in FIG. In addition, since the tapered portion 12 also functions as an insertion guide for the sealing plate 1, the insertion of the sealing plate 1 is facilitated from this point as well. Especially,
Since the sealing plate 1 shown in FIGS. 1C and 1D has the maximum outer diameter portion 11 provided in a spot shape, the force required when the sealing plate 1 is inserted can be minimized. .

[3. Other Embodiments] The present invention
It is not limited to the embodiment described above,
Various other embodiments are possible within the scope of the present invention. For example, the specific shapes of the lead holes and the outer peripheral portion of the sealing plate can be freely selected. In addition, each shape of the lead hole and the outer peripheral portion of the sealing plate can be freely selected, and can be freely combined, thereby maintaining the airtightness of each airtight portion,
Both the lead wire mounting work and the sealing plate mounting work are facilitated.

[0041]

As described above, according to the present invention,
In the through hole of the sealing plate made of fluororesin, a minimum diameter portion smaller than the diameter of the round bar portion of the lead wire is provided, and the diameter of the end portion on the side to be the insertion port of the lead wire is equal to or larger than the diameter of the round bar portion. By doing so, it is possible to maintain the airtightness of the lead wire penetrating portion, contribute to prolonging the life of the capacitor and improve the mechanical strength, and to provide an electrolytic capacitor sealing structure that is advantageous in terms of manufacturing.

[Brief description of the drawings]

FIGS. 1A to 1D are cross-sectional views showing a plurality of different forms applied to lead holes (through holes) of a sealing plate in a sealing structure of an electrolytic capacitor according to the present invention.

FIGS. 2A to 2C are cross-sectional views showing a plurality of different forms applied to an airtight structure at an outer peripheral portion of a sealing plate in a sealing structure of an electrolytic capacitor according to the present invention.

3 (A) to 3 (D) are cross-sectional views showing a plurality of forms of the sealing structure of the electrolytic capacitor according to the present invention in which the shape of the outer peripheral portion of the sealing plate is different.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sealing plate 2 ... Lead hole 3 ... Lead wire 4 ... Round bar part 5 ... Minimum diameter part 6, 7, 12, 13 ... Tapered part 8 ... Outer case 9 ... Caulking lateral groove 10 ... Curl 11 ... Maximum outer diameter part

Claims (7)

[Claims] 1. A sealing device for sealing an opening of a cylindrical outer case having a bottom for storing a capacitor element, wherein a round bar portion of an electrode lead-out means drawn out of the capacitor element serves as the sealing means. In the sealing structure of the electrolytic capacitor configured to be pulled out and pulled out, the sealing means is a sealing plate made of a fluororesin, and the sealing plate has a through hole for passing the round bar portion in the penetration direction. , A minimum diameter portion smaller than the diameter of the round bar portion is provided in a part of the through hole in the penetration direction, and an insertion port of the electrode lead means in the through hole. A large-diameter portion on the insertion side having a diameter equal to or greater than the diameter of the round bar portion is provided at an opening end on the side of the sealing member. 2. The diameter of the minimum diameter portion of the through hole is φD,
When the diameter of the round bar is φd, 5% ≦ (φd−φ
2. The sealing structure for an electrolytic capacitor according to claim 1, wherein a relationship of D) / φd ≦ 50% is satisfied. 3. The sealing structure for an electrolytic capacitor according to claim 1, wherein the through hole is provided with a tapered portion extending from the minimum diameter portion toward the insertion-side large diameter portion. 4. A large-diameter portion on the opposite side of the through-hole opposite to the large-diameter portion on the insertion side, which is larger than the diameter of the round bar portion. 4. The sealing structure for an electrolytic capacitor according to claim 3, wherein a tapered portion extending toward the radial portion is provided. 5. The device according to claim 1, wherein at least a part of the sealing plate in the thickness direction is provided with a maximum outer diameter portion larger than the inner diameter of the opening of the outer case. The sealing structure of the electrolytic capacitor described in 1. 6. An insertion-side small-diameter portion having an inner diameter equal to or less than an inner diameter of an opening of the outer case is provided at an insertion-side end of the sealing plate in the thickness direction of the outer case. 6. The sealing structure for an electrolytic capacitor according to claim 5, wherein a tapered portion extending toward the portion is provided. 7. A small-diameter portion on the opposite side to the small-diameter portion on the insertion side in the thickness direction of the sealing plate is provided with a small-diameter portion on the opposite side that is smaller than the inner diameter of the opening of the outer case. 7. The sealing structure for an electrolytic capacitor according to claim 6, wherein a tapered portion expanding toward a maximum outer diameter portion is provided.