Method for fixing a film to a capacitor element in an electrolytic capacitor

Abstract

To provide a method for fixing a film to a capacitor element and an electrolytic capacitor in which stability of an operation is improved.SOLUTION: A method for fixing a film 12 to a capacitor element 3 includes the steps of: providing an electrolytic capacitor 1 including a case 2 which has a bottom surface 5 and a side surface 6 and has a recess 14 for the film 12 provided on the bottom surface 5, and a capacitor element 3 which is attached to the case 2; embedding the film 12 into the recess 14; embedding an attachment ring 13 made of metal onto the film 12; bringing the film 12 into contact with the attachment ring 13 to deform and fasten them; and fixing the attachment ring 13 with laser welding or riveting. Since riveting can be completed in the whole of the attachment ring 13 or in a part in the attachment ring 13, the film 12 can be fixed by fixing the attachment ring 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor including a case and a capacitor element attached to the case. The capacitor element includes an electrolyte. [Background technology]

[0002] US Pat. No. 3,463,969 discloses an electrolytic capacitor having a molded cover member and a vent inside the cover member.

[0003] U.S. Patent Nos. 2,766,408 and 3,669,302 disclose vent plugs for electrolytic capacitors, which are positioned on an injection molded cover member.

[0004] DE 10 2015 119 844 A1 discloses an electrolytic capacitor with a safety vent inside the case. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 3,463,969 [Patent Document 2] U.S. Patent No. 2,766,408 [Patent Document 3] U.S. Patent No. 3,669,302 [Patent Document 4] German Patent Publication No. 102015119844 Summary of the Invention [Problem to be solved by the invention]

[0006] During long-term operation of an electrolytic capacitor, chemical decomposition caused by basic electrochemical reactions and aging occurs. Both events result in the generation of gases inside the capacitor. This gas generation gradually increases the internal pressure of the capacitor, creating mechanical stresses on the capacitor's case and cover. The internal pressure can cause deformation, such as stretching or swelling, and ultimately can lead to the case exploding, ending the capacitor's lifespan.

[0007] It is an object of the present invention to provide an electrolytic capacitor with improved operational stability. [Means for solving the problem]

[0008] This issue is Below This is solved by the disclosed invention.

[0009] In one embodiment, the present invention relates to an electrolytic capacitor that includes a case, a capacitor element mounted within the case, and an element that controls gas diffusion between the interior and exterior of the case, wherein the control element is embedded in the case.

[0010] The generation of gas increases the internal pressure of the capacitor, causing mechanical stress on the case, so an element that controls the gas exchange between the inside and outside of the capacitor is essential.

[0011] The control element provides a passageway for the gas from the interior to the exterior of the case, and is further configured to control and diffuse the movement of the gas.

[0012] The case may be can-shaped. The capacitor element may be a circular element, particularly a cylindrical element. The capacitor element may comprise a foil, particularly an aluminum foil. The capacitor element may be impregnated with an electrolyte, particularly a liquid electrolyte.

[0013] In one embodiment, the capacitor includes a cavity, and the control element is positioned such that gas from the cavity can flow directly to the control element. The cavity is the largest hollow space within the capacitor. Thus, most of the gas present within the capacitor is stored in the cavity. The cavity may extend along a central axis of the capacitor element. The cavity may be created by winding the foil of the capacitor element around the central axis. The cavity is the largest hollow space within the capacitor. Thus, most of the gas present within the capacitor is stored in the cavity.

[0014] The control element may be located immediately adjacent to the cavity. If the cavity is an axially central cavity of the wound element, the control element may be located at the axial center. Positioning the control element immediately adjacent to the cavity has the advantage that the outer surface of the capacitor element, particularly the wound element, does not obstruct the diffusion path due to the winding.

[0015] In one embodiment, the case of the electrolytic capacitor includes a can and a cover member that seals the can, and the control element is disposed within the can. Preferably, the control element is integrated into the bottom surface of the case. The bottom surface is one side of the case facing the cover member. The cover member may include an elastic material, particularly a rubber material. The cover member may be an element inserted into the can. Terminals for electrical interconnection may pass through the cover member. The cover member does not include the control element. In one embodiment, the electrolytic capacitor includes two or more vertically stacked cover members that seal the can.

[0016] The control element may be embedded in a portion of the case opposite the location of the electrical terminals. In one embodiment, the terminals pass through a cover member on the top of the case, while the control element is located on the bottom surface of the case. This allows for a wide range of variation in the location and lateral dimensions of the control element without compromising the location of the terminals or the mechanical stability of the cover member. The can is preferably made of aluminum, so that the mechanical stability of the can is greater than that of the cover member. The terminals for electrically interconnecting the capacitors may be configured in a snap-in manner.

[0017] In one embodiment, the control element is completely embedded in the case. The control element is embedded in the case and does not protrude into or out of the case. Because the control element requires little vertical space, no protrusions are created inside the case. This allows for more space to be reserved for the capacitor element, e.g., the winding element.

[0018] In one embodiment, the bottom surface may be flat from the outside. In another embodiment, the bottom surface may include a protrusion that fits over the control element. In either case, the control element is fully integrated into the case; it does not protrude from the case.

[0019] A distance may be maintained between the control element and the capacitor element. The means for maintaining the distance may be embodied, for example, in the form of a rib. The rib installed inside the case maintains a certain distance between the capacitor element and the control element. The rib forms a hollow space to promote free gas flow from the inside of the capacitor to the control element.

[0020] The control element may comprise a membrane. The dimensions, thickness and exact material composition of the membrane may affect the permeability of the membrane and the rate of gas diffusion through the membrane. These parameters may be adapted to the actual technical requirements.

[0021] In particular, the membrane should be gradually permeable to gases. As the pressure inside the capacitor increases, the gas diffusion also increases. On the other hand, the membrane should preferably be impermeable to liquids, which would risk the loss of liquid electrolyte.

[0022] The membrane may be constructed of a material that is either silicone, ethylene propylene diene monomer rubber (EPDM) or other elastomeric polymers with comparable properties.

[0023] The membrane material can be selected depending on the properties required of the membrane. The required permeability of the membrane must be selected according to several criteria. On the one hand, the membrane must be sufficiently permeable to the gases intended to pass through it. In particular, the membrane should be permeable to hydrogen. On the other hand, the permeability must be sufficiently low to gases and vapors not intended to pass through the membrane. In particular, the membrane may not be permeable to the vapor of the electrolyte solvent or to liquids in general.

[0024] The use of a membrane as a control element has several advantages: the membrane requires little vertical space and volume, therefore less internal volume of the capacitor is consumed by the control element and more internal volume is available for the capacitor element.

[0025] Additionally, the use of a membrane avoids unnecessary dead space.

[0026] Furthermore, membranes made of the above materials have a small thickness. Therefore, the membrane control element is thinner than the wall of the case, which is usually made of alumina. This allows the membrane to be easily incorporated into the case. The membrane control element does not protrude from the case. The internal volume is not wasted by the control element. More of the internal volume can be used for the capacitor element.

[0027] Furthermore, membranes made of elastic materials such as those mentioned above can be tightly clamped, thereby improving the seal.

[0028] The capacitor element can be impregnated with an electrolyte, particularly a liquid electrolyte. The liquid electrolyte, or other liquid inside the capacitor, can flow into the membrane. When the liquid flows into the pores of the membrane, the pores become blocked, reducing the permeability of the membrane.

[0029] In one embodiment, the capacitor is mounted so that the side of the case containing the membrane does not face downward. For example, the side containing the membrane is oriented upward or horizontally. In this case, the liquid electrolyte can be effectively prevented from flowing onto the membrane. Furthermore, contamination of the membrane by the liquid electrolyte can be prevented. This ensures that gas diffusion is maintained.

[0030] In one embodiment, the capacitor is mounted with one side having the control element facing downwards, so that the bottom of the can faces upwards. The terminals may be positioned on the opposite side, so that the terminals face downwards. In a further embodiment, the capacitor is fitted with a membrane vent, and the terminals are located on the horizontal side.

[0031] In one embodiment, if the maximum allowable pressure within the capacitor is exceeded, the membrane acts as an irreversible safety vent.

[0032] During operation, especially in the event of an electrical overload, pressure may build up inside the capacitor. The safety vent may be configured to burst if the pressure approaches a critical value exceeding the maximum allowable pressure, thereby preventing uncontrolled explosion of the capacitor. When the critical pressure is reached, the membrane ruptures, allowing the gas inside the capacitor to escape until the pressure is reduced enough to prevent damage to the housing.

[0033] After the membrane ruptures, the liquid electrolyte may leak from the case, potentially contaminating the terminals and / or other components, such as the printed circuit board or bus bars. Positioning the membrane on one side away from the other side of the terminals reduces the risk of contamination and extends the operational life of the electronic components. Thus, in one embodiment, a control element, which functions as an irreversible safety vent, is positioned on the opposite side of the terminals.

[0034] In one embodiment, the capacitor is mounted so that the side with the irreversible safety vent does not face down; in a preferred embodiment, this side faces up.

[0035] In one embodiment, the maximum allowable pressure is determined by the tightness of the membrane. If this maximum allowable pressure is exceeded, the membrane will burst and act as an irreversible safety vent. If the membrane is tightened more tightly by the attachment element, the membrane will become less permeable. In this case, an equivalently lower pressure will cause the membrane to burst. If the membrane is not tightened too tightly by the attachment element, the membrane will become more permeable. In this case, an equivalently higher pressure will be required to burst the membrane. Therefore, the maximum allowable pressure can be set by tightening the membrane with the attachment element.

[0036] In one embodiment, the membrane is in the shape of a disk, which is a preferred and stable structure for membranes used for gas diffusion.

[0037] In one embodiment, the electrolytic capacitor includes a mounting ring that secures the membrane, the mounting ring having an appropriate shape to accommodate the membrane. The mounting ring and the case may be constructed of aluminum. The aluminum of the mounting ring and the case may be of the same grade. In one embodiment, the mounting ring may include a metal other than aluminum. In particular, the mounting ring may be constructed of a material that does not pose a risk or interfere with the operation of the capacitor. The mounting ring is manufactured by punching or impact extrusion.

[0038] Additionally, the mounting ring may include a sealing door on its surface to enhance the airtightness and sealing of the membrane. In one embodiment, the sealing door may also be on a corresponding surface of the mounting ring. The sealing door may include the same material as the mounting ring. Thus, the sealing door may be made of aluminum or another metal. In one embodiment, the sealing door may include a material different from that of the mounting ring. In particular, the sealing door may be made of a material that does not pose a risk or interfere with the operation of the capacitor.

[0039] The sealing doors may be bumps on the surface of the attachment ring. The sealing doors clamp the membrane by deforming the membrane. In one embodiment, the attachment ring may include multiple sealing doors.

[0040] The deformation as a function of the sealing door is achieved by compressing the membrane along a closed curve. The membrane should be compressed to a degree that provides a mechanical fixation. Furthermore, the membrane should be compressed to a degree that provides gas-tightness against liquids within the range of the capacitor's possible operating pressures. On the other hand, damage to the membrane material must be avoided when compressing the membrane.

[0041] The diameter of the mounting ring may be larger than the diameter of the membrane to clamp the membrane. A large mounting ring with appropriate sealing doors can deform the membrane and clamp it tightly. Therefore, the membrane will burst at a relatively low critical pressure that exceeds the relatively low maximum allowable pressure. A relatively small mounting ring with multiple sealing doors can achieve the same effect. The number of sealing doors may be the same as or greater than the number of sealing doors in a relatively large mounting ring.

[0042] A small mounting ring with fewer sealing doors may cause the membrane to deform and clamp less tightly, causing the membrane to burst at a higher critical pressure that exceeds the higher maximum allowable pressure.

[0043] Furthermore, a larger diameter mounting ring can more easily deform the membrane. Therefore, the following applies: the larger the diameter of the mounting ring, the easier it is for the membrane to deform at a given pressure. In addition to the stronger deformation, the membrane will rupture at a lower pressure. Thus, by changing the diameter of the mounting ring, the maximum allowable pressure can be selected and fine-tuned.

[0044] The case of the electrolytic capacitor may include a recess to accommodate the membrane and mounting ring.

[0045] In one embodiment, the recess that accommodates the membrane is located inside the case, so the membrane and attachment ring must be deployed from the inside. In another embodiment, the recess that accommodates the membrane is located outside the case, so the membrane and attachment ring must be deployed from the outside.

[0046] The membrane and mounting ring, recessed in the recess, do not protrude from either the interior or exterior of the case. Because the membrane and mounting ring are flat, the recess requires little volume and low vertical space. Therefore, the case does not consume extra volume inside the capacitor compared to a capacitor without a control element. The internal volume is available for a capacitor element, such as a wound element. In one embodiment, the bottom surface of the case may be flat. In another embodiment, the bottom surface includes a protrusion that fits into the recess in which the membrane and mounting ring are placed.

[0047] Furthermore, the recess that accommodates the membrane may include a sealing door on its inner surface to enhance the airtightness and sealing of the membrane. In such a case, the mounting ring may not have a sealing door.

[0048] In one embodiment, both the inner surface of the recess and the attachment ring may include sealing doors. The inner surface of the recess may be a corresponding surface of the attachment ring. The sealing doors may be fabricated as bumps. Larger or more sealing doors may result in greater deformation, which may increase the membrane's airtightness and sealing ability. A more airtight membrane reduces the maximum allowable pressure.

[0049] The present invention further includes a method for fixing a membrane onto a capacitor element. The method includes several steps. An electrolytic capacitor is provided, including a case with a recess for the membrane and a capacitor element attached to the case. The membrane is embedded in the recess. In one method, the membrane may be embedded externally if the recess is external to the case. In another method, the membrane may be embedded internally to the capacitor if the recess is internal to the case.

[0050] When the membrane is placed in the recess, a metal mounting ring is recessed into the membrane recess. The mounting ring is appropriately shaped to accommodate the membrane. During the assembly process, pressure is applied to the mounting ring and onto the membrane, which may deform the membrane to tighten the system. To achieve a tight seal, the membrane is preferably made of a resilient material such as rubber or other elastomer.

[0051] A sealing door on the inner surface of the recess or on the surface of the mounting ring supports the deformation and sealing process. After the membrane and mounting ring are placed in the recess, the mounting ring is secured by an external process such as cutting, forging, or any type of welding. In one method, the welding method may be laser welding. In another method, the mounting ring is secured by riveting. The riveting can be completed on the entire ring or on a portion of the ring. By securing the mounting ring, the membrane is also secured.

[0052] The present disclosure includes several embodiments and aspects of the invention, and all features described with respect to one of the embodiments or methods are also disclosed herein with respect to each other embodiment and aspect, even if the respective feature is not explicitly mentioned in the context of a particular embodiment or aspect.

[0053] Further features, improvements and advantages will become apparent from the following description of exemplary embodiments taken in conjunction with the drawings. [Brief explanation of the drawings]

[0054] [Figure 1] FIG. 1 is a schematic cross-sectional view of a capacitor according to a first embodiment. [Figure 2A] FIG. 2A shows a bottom view of the capacitor according to the first embodiment. [Figure 2B] FIG. 2B shows a bottom view of the capacitor according to the second embodiment. [Figure 3] FIG. 3 shows a schematic cross-sectional view of a part of a capacitor according to a third embodiment and a detailed view of the control element of this capacitor. [Figure 4]FIG. 4 shows a bottom view of the capacitor according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0055] Similar elements, elements of the same type and elements that function identically are designated by the same reference numerals in the figures.

[0056] FIG. 1 shows an electrolytic capacitor 1. The capacitor includes a case 2 and a capacitor element 3 attached to the case 2. The capacitor element 3 includes a wound element. The capacitor element 3 has a cylindrical shape with an axially central cavity 4. The cavity extends along the central axis of the wound element. The capacitor element 3 includes a foil, particularly an aluminum foil. The capacitor element 3, particularly the aluminum foil, is impregnated with an electrolyte. The electrolyte is a liquid electrolyte.

[0057] The case 2 has a cylindrical shape. The case 2 includes a metal. For example, the case 2 includes aluminum. The case 2 is can-shaped.

[0058] Capacitor 1 includes a bottom surface 5, curved side surfaces 6, and a top surface 7. Top surface 7 is opposite bottom surface 5. The maximum length of capacitor 1 from the outer edge of bottom surface 5 to the outer edge of top surface 7 is 35 mm or more and 120 mm or less. Case 2 has a diameter ranging from 22 mm to 50 mm or less. Bottom surface 5 is integrally formed with side surfaces 6, which together form a can. The can comprises a metal, particularly aluminum.

[0059] On the top surface 7, the capacitor 1 includes terminals 8 that electrically interconnect the capacitors. One of the terminals 8 is a positive terminal. The other of the terminals 8 is a negative terminal. The terminals 8 are configured as snap-in terminals and are connected to the capacitor element 3 by additional connection elements. The connection elements include terminal tabs 8A and terminal rivets 8B. The capacitor 1 is configured and mounted terminal-down, with the terminals 8 pointing toward the center of the Earth. Alternatively, for example, if the terminals 8 are oriented horizontally, the capacitor 1 can be mounted horizontally.

[0060] The capacitor 1 may be mounted on a mounting member (not shown). The mounting member serves to fix the capacitor 1. Furthermore, the mounting member may also serve to electrically connect the terminals 8. In this case, the mounting member may include, for example, a printed circuit board or a bus bar.

[0061] At the top surface 7, the case 2 is sealed by a cover including two cover members 9A and 9B. The cover members 9A and 9B are disk-shaped. The cover member 9A includes a paper laminate. The cover member 9B includes an elastomer. In one embodiment, the cover members may include a rubber material. The terminals 8 extend through the cover members 9A and 9B. In another embodiment, the cover may include only one cover member.

[0062] A shrink sleeve 10 is disposed on the exterior side 6 of the case 2. The shrink sleeve provides additional protection to the case 2. The shrink sleeve is constructed of a heat-shrinkable polymer. Heat-shrinkable means that the polymer shrinks in length when heated.

[0063] The capacitor 1 includes a control element 11. The control element 11 provides a gas passage connecting the inside and outside of the case 2. The passage includes a hole 15 between the inside and outside of the case 2. The control element 11 further includes a recess 14 that narrows toward the hole 15.

[0064] The membrane 12 and the mounting ring 13 are disposed in the recess 14. The membrane 12 and the mounting ring 13 are completely integrated into the case 2. The membrane 12 and the mounting ring 13 do not protrude from the surface of the case 2. The entire control element 11 is positioned so that gas from the axially central cavity 4 in the capacitor element 3 can flow directly to the control element 11.

[0065] The control element 11 allows for controlled pressure release. During operation of the capacitor 1, gas generation and pressure buildup can occur inside the capacitor 1. These effects are caused by electrochemical reactions. The membrane 12, as part of the control element 11, allows the gas to diffuse to the surroundings during operation of the electrolytic capacitor 1, thereby reducing the internal pressure. This allows the internal pressure to be adapted to the ambient pressure.

[0066] The membrane 12 includes a silicone material. The membrane 12 may further include EPDM or another elastic plastic material. The membrane 12 may also include a rubber material. In particular, the membrane 12 is a thin silicone membrane. The thickness of the membrane 12 is thin compared to the wall thickness of the case 2. Therefore, the vertical space and volume required by the membrane are smaller than other types of vents. Therefore, more internal volume is available for the capacitor element 3. The membrane 12 may be permeable or semi-permeable to gas. The membrane 12 is circular and has a diameter of approximately 3 mm.

[0067] On the membrane 12, a mounting ring 13 is placed in a recess 14. The recess 14 is located outside the case 2, so that both the membrane 12 and the mounting ring 13 are placed externally.

[0068] The mounting ring 13 comprises a metal. In particular, the mounting ring 13 comprises aluminum. The mounting ring 13 may be a stamped part or an impact extruded part. The mounting ring 13 has a shape suitable for accommodating the membrane 12. The mounting ring 13 may include a sealing door 16 on its surface. The sealing door 16 may be formed as a bump. The sealing door 16 increases the deformation of the membrane 12, thereby improving the airtightness.

[0069] The diameter of the attachment ring 13 is larger than the diameter of the membrane 12. The diameter of the attachment ring 13 is in the range of 3 mm to 6 mm. Preferably, the diameter of the attachment ring 13 is in the range between 3 mm and 4 mm. The larger the diameter of the attachment ring 13, the greater the deformation and airtightness of the membrane 12. The additional sealing door 16 also leads to an increase in the deformation and airtightness of the membrane 12.

[0070] The attachment ring 13 is fixed by an external process such as riveting, notching, forging or any kind of welding process. Fixing the attachment ring 13 also fixes the membrane 12. Therefore, the attachment ring 13 has two main functions: clamping the membrane 12 and fixing the membrane 12.

[0071] A distance 17 is maintained between the bottom of the case 5 containing the control element 11 and the capacitor element 3. This distance is maintained by an internal rib that provides a constant space between the capacitor element 3 and the membrane 12, allowing free gas flow to the membrane 12. Distance 17 is approximately 0.5 mm. In one embodiment, distance 17 is exactly 0.5 mm.

[0072] Furthermore, the inner surface of the recess 14 includes sealing doors 16 for deforming and fastening the membrane 12. The sealing doors 16 are made as bumps. The more sealing doors 16 there are, the greater the deformation of the membrane 12 and the greater the airtightness.

[0073] Furthermore, the membrane 12 functions as an irreversible safety vent in the event of an unacceptable overpressure within the capacitor: if a critical pressure is reached that exceeds the maximum allowable pressure, the membrane 12 will burst.

[0074] The maximum allowable pressure is determined by the tightness of the membrane. The tighter the membrane, the lower the maximum allowable pressure. The looser the membrane, the higher the maximum allowable pressure.

[0075] It is beneficial to mount the capacitor 1 with the bottom surface 5 of the case 2 facing upwards, which corresponds to a mounting orientation with the terminals facing downwards. This structure prevents the membrane 12 from being covered with liquid electrolyte.

[0076] If the membrane 12 is positioned on the underside of the capacitor 1, gravity can cause the liquid electrolyte to cover the membrane 12 and block gas diffusion. This can result in cumulative pressure buildup, potentially leading to the membrane 12 bursting. This phenomenon reduces the operating efficiency of the membrane 12. If the membrane 12 is positioned on the top surface of the capacitor 1, the membrane 12 is spaced apart from the liquid electrolyte to maintain slow diffusion.

[0077] When the membrane 12 ruptures, the bottom side facing up helps to avoid the liquid electrolyte leaking out of the capacitor 1, thereby further preventing the liquid electrolyte from contaminating the surrounding device.

[0078] 2A shows a view of the bottom surface 5 of the capacitor 1 according to FIG. 1. The bottom surface 5 is part of the case 2 of the capacitor 1 and is made of aluminum. At the axial center, a recess 14 is recessed into the exterior of the case 2. A membrane 12 and a mounting ring 13 are arranged inside the recess 14. The membrane 12 covers a hole 15 according to FIG. 1. A shrink sleeve 10 surrounds the capacitor 1 for protection.

[0079] The attachment ring 13 is configured to receive and clamp the membrane 12. Furthermore, the attachment ring 13 secures the membrane 12. The attachment ring 13 may include a sealing door 16. The attachment ring 13 is partially secured by riveting. Therefore, a single rivet 18 is applied.

[0080] In a second embodiment, as shown in Figure 2B, riveting is completed around the entire circumference of the attachment ring 13. Complete riveting provides a stronger fixation between the attachment ring 13 and the membrane 12. Partial riveting saves material and therefore reduces costs.

[0081] In other embodiments, the attachment ring may be secured by another process such as cutting, forging or any type of welding, preferably laser welding.

[0082] 3 shows a partial cross-sectional view of a portion of capacitor 1, including the bottom surface 5 of case 2 and part of its side surface 6. In the third embodiment shown, a recess 14 for embedding membrane 12 and mounting ring 13 is located inside case 2. Recess 14 is axially centrally positioned. Gas from axially central cavity 4 in the center of capacitor element 3 can therefore flow directly to membrane 12. For protection, a shrink sleeve 10 surrounds side surface 6 of capacitor 1.

[0083] The control element 11 is enlarged in the detailed view so that it can be seen better. The control element 11 is arranged in the axial center of the bottom surface 5 of the case 2. A recess 14 is recessed into the inside of the case 2. The recess 14 narrows towards a hole 15 connecting the inside and outside of the case 2. A membrane 12 is arranged in the recess 14.

[0084] Once the membrane 12 is placed in the recess 14, the attachment ring 13 is recessed into the recess 14 on the membrane 12. The attachment ring 13 is appropriately shaped to accommodate the membrane 12. During the assembly process, pressure is applied to the attachment ring 13 and transferred to the membrane 12, causing the membrane 12 to deform and tighten the system. Using a larger attachment ring 13 allows for a tighter tightening of the membrane 12.

[0085] A sealing door 16 on the inner surface of the recess 14 supports the deformation and sealing process. After the membrane 12 and attachment ring 13 are placed in the recess 14, the attachment ring 13 is secured by an external process such as cutting, forging, or any type of welding. By securing the attachment ring, the membrane is also secured.

[0086] In another embodiment, the surface of the attachment ring 13 includes a sealing door 16. The sealing door 16 may be formed as a bump.

[0087] Figure 4 shows a bottom view of the third embodiment of the capacitor 1. From the outside, only the membrane 12 is visible through the hole 15 in the bottom surface 5. According to Figure 3, the membrane 12 covers the mounting ring 13 and the recess 14 inside the case 2. The hole 15 is axially central. For protection, a shrink sleeve 10 surrounds the capacitor 1.

[0088] Possible embodiments of the present invention are not limited to the embodiments shown in Figures 1-4. Different types of capacitors, including different types of capacitor elements, may be constructed with the disclosed control elements and are also disclosed herein. In addition to the disclosed terminals configured in a snap-in manner for electrical contact to the capacitor, other types of terminals are realized in other embodiments of the present invention. For example, the terminals may be configured as screw terminals. [Explanation of symbols]

[0089] 1 electrolytic capacitor 2 cases 3 Capacitor elements 4. Axial central cavity within the capacitor element 5 Bottom 6 Side 7 Top side 8 terminals 8A terminal tab 8B Terminal Rivet 9A Cover member (paper laminate) 9B Cover material (elastomer) 10 shrink sleeve 11 Control element 12 membrane 13 Mounting ring 14 Recessed portion in case 2 15 Hole in case 2 16 Sealed Door 17 Internal distance between capacitor element 3 and control element 11 18 Rivets

Claims

1. A method for fixing a membrane (12) to a capacitor element (3), comprising the steps of: providing an electrolytic capacitor (1) comprising: a case (2) including a can having a bottom and a side, the bottom of the can having a recess (14) for the membrane (12); and the capacitor element (3) attached to the case (2); embedding said membrane (12) in said recess (14); embedding a metal attachment ring (13) on the membrane; deforming and clamping the membrane (12) by contacting it with the attachment ring (13); and fixing the mounting ring (13) by riveting, The riveting can be completed on the entire attachment ring (13) or on a portion of the attachment ring (13), and by securing the attachment ring (13), the membrane (12) is also secured.

2. 2. The method of claim 1, wherein the attachment ring (13) has a suitable shape to accommodate the membrane (12).

3. 3. The method according to claim 1 or 2, wherein the surface of the attachment ring (13) comprises bumps (16) that deform the membrane (12) to improve the airtightness and sealing of the membrane (12).

4. 3. The method according to claim 1 or 2, wherein the membrane (12) acts as an irreversible safety vent if the maximum allowable pressure in the electrolytic capacitor (1) is exceeded.

5. 5. The method of claim 4, wherein the maximum allowable pressure is determined by the tightness of the membrane (12).

6. 3. The method of claim 1 or 2, wherein the membrane (12) is made of a material that is one of the following: silicone, EPDM (ethylene propylene diene monomer rubber), or another elastic polymer.

7. 3. The method according to claim 1 or 2, wherein the membrane (12) is disc-shaped.

8. 3. The method according to claim 1 or 2, wherein the recess (14) is located either inside the case (2) or outside the case (2).

9. 3. The method according to claim 1 or 2, wherein the inner surface of the recess (14) comprises bumps (16) that deform the membrane (12) to improve its airtightness and sealing.

10. 3. The method of claim 1 or 2, wherein the riveting is completed around the entire circumference of the attachment ring (13).

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