Electrolytic Capacitor With Controlling Element For Gas Diffusion

Abstract

An electrolytic capacitor comprises a case (2), a capacitor element (3) mounted in the case and an element for controlling (11) gas diffusion between inside and outside the case. The controlling element (11) is embedded in the case (2).

Claims

1-18. (canceled)

19. An electrolytic capacitor, comprising a case, a capacitor element mounted in the case, and an element for controlling gas diffusion between inside and outside the case, wherein the controlling element is embedded in the case.

20. The electrolytic capacitor of claim 19, wherein the controlling element provides a passageway for gas from the inside to the outside of the case, and is further configured to control movement of gas to provide diffusion.

21. The electrolytic capacitor of claim 19, wherein the capacitor element comprises a cavity, wherein the controlling element is arranged such that gas from the cavity can flow directly to the controlling element.

22. The electrolytic capacitor of claim 21, wherein the controlling element is arranged directly adjacent to the cavity.

23. The electrolytic capacitor of claim 19, wherein the case comprises a can and a cover member for sealing the can, wherein the controlling element is arranged in the can.

24. The electrolytic capacitor of claim 19, wherein the case includes electrical terminals, the controlling element is embedded in a part of the case opposite to the location of the electrical terminals.

25. The electrolytic capacitor of claim 19, wherein the controlling element is fully integrated in the case.

26. The electrolytic capacitor of claim 19, wherein the controlling element and the capacitor element are separated by a distance to provide a space to permit gas flow.

27. The electrolytic capacitor of claim 19, wherein the controlling element comprises a membrane.

28. The electrolytic capacitor of claim 27, wherein the membrane acts as an irreversible safety vent in the event of exceeding a maximum permissible pressure within the capacitor.

29. The electrolytic capacitor of claim 28, wherein the maximum permissible pressure is determined by the tightness of the membrane.

30. The electrolytic capacitor of claim 27, wherein the membrane consists of a material which is one of silicon, EPDM, or another elastic polymer.

31. The electrolytic capacitor of claim 27, wherein the membrane has a disk shape.

32. The electrolytic capacitor of claim 27, further comprising a mounting ring for fixing the membrane, the mounting ring having an appropriate shape for accommodating the membrane.

33. The electrolytic capacitor of claim 32, wherein a surface of the mounting ring comprises a sealing gate for increasing the tightness of the membrane.

34. The electrolytic capacitor of claim 32, wherein the case comprises a recess to accommodate the membrane and the mounting ring, wherein the recess is arranged either on the inside of the case or on the outside of the case.

35. The electrolytic capacitor of claim 34, wherein an inner surface of the recess comprises a sealing gate for increasing the tightness of the membrane.

36. A method of fixing a membrane on a capacitor element, comprising: providing an electrolytic capacitor comprising a case having a recess for receiving the membrane, the capacitor element being mounted in the case; embedding a membrane in the recess; embedding a mounting ring consisting of metal onto the membrane; deforming and tightening the membrane by contact with the mounting ring; and fixing the mounting ring.

37. An electrolytic capacitor, comprising: a case having a recess; a capacitor element mounted in the case; a membrane for controlling gas diffusion between inside and outside the case, the membrane having a tightness that determines a maximum gas pressure within the case; and a mounting ring for holding the membrane in the recess; and sealing gates located on at least a surface of the recess or on a surface of the mounting ring for controlling the tightness of the membrane.

38. The electrolytic capacitor of claim 37, wherein the sealing gates include structural bumps on the surface of the recess or the mounting ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present disclosure comprises several embodiments and aspects of the invention. Every feature described with respect to one of the embodiments or the method is also disclosed herein with respect to the respective other embodiments and aspects, even if the respective feature is not explicitly mentioned in the context of the specific embodiment or aspect.

[0052] Further features, refinements and expediencies become apparent from the following description of the exemplary embodiments in connection with the figure.

[0053] FIG. 1 shows a schematic cross-sectional view of a capacitor according to a first embodiment;

[0054] FIG. 2A shows a bottom view of the capacitor according to the first embodiment;

[0055] FIG. 2B shows a bottom view of the capacitor according to a second embodiment;

[0056] FIG. 3 shows a schematic cross-sectional view of a part of the capacitor according to a third embodiment and a detailed view of its controlling element; and

[0057] FIG. 4 shows a bottom view of the capacitor according to the third embodiment.

[0058] Similar elements, elements of the same kind and identically acting elements may be provided with the same reference numerals in the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 shows an electrolytic capacitor 1. The capacitor comprises a case 2 and a capacitor element 3 mounted in the case 2. The capacitor element 3 comprises a winding element. The capacitor element 3 has a cylindrical shape with an axial-centred cavity 4. The cavity extends along the winding element's central axis. The capacitor element 3 comprises foils, in particular aluminum foils. The capacitor element 3, in particular the aluminum foils, is/are impregnated with an electrolyte. The electrolyte is a liquid electrolyte.

[0060] The case 2 has the shape of a circular cylinder. The case 2 comprises a metal. As an example, the case 2 comprises aluminum. The case 2 has the shape of a can.

[0061] The capacitor 1 comprises a bottom 5, a curved lateral side 6 and an upper side 7. The upper side 7 is opposite the bottom 5. A maximum length of the capacitor 1 from the outer edge of the bottom 5 to the outer edge of the upper side 7 amounts more than 35 mm. The maximum length amounts less than or equal to 120 mm. The diameter of the case 2 is in a range from 22 mm or more to 50 mm or less. The bottom 5 is integrally formed with the lateral side 6. Together they form the can. The can comprises a metal, in particular aluminum.

[0062] At the upper side 7, the capacitor 1 comprises terminals 8 for electrically interconnecting the capacitor. One of the terminals 8 is the positive terminal. The other one of the terminals 8 is the negative terminal. The terminals 8 are configured as snap-in terminals. The terminals 8 are connected with the capacitor element 3 by additional connecting elements. The connecting elements comprise a terminal tab 8A and a terminal rivet 8B. The capacitor 1 is configured to be mounted terminal-down, such that the terminals 8 point towards the earth's center. Alternatively, the capacitor 1 is mounted horizontally, for example, if the terminals 8 point in a horizontal direction.

[0063] The capacitor 1 may be mounted at a mounting member (not shown). The mounting member serves to fix the capacitor 1. Additionally, the mounting member may serve to electrically connect the terminals 8. In this case, the mounting member may comprise a printed circuit board or a bus bar, for example.

[0064] At the upper side 7, the case 2 is sealed by a cover comprising two cover members 9A and 9B. The cover members 9A and 9B have the shape of a disk. The cover member 9A comprises a paper laminate. The cover member 9B comprises an elastomer. In an embodiment, the cover member may comprise a rubber material. The terminals 8 are lead through the cover members 9A and 9B. In another embodiment, the cover may comprise only one cover member.

[0065] On the outside of the case 2 on the lateral side 6 a shrinking sleeve 10 is arranged. The shrinking sleeve additionally protects the case 2. The shrinking sleeve comprises a heat-shrinkable polymer. Heat-shrinkable means that the polymer shrinks in length, if heated up.

[0066] The capacitor 1 comprises a controlling element 11. The controlling element 11 provides a passageway for gas connecting the inside and the outside of the case 2. The passageway comprises a hole 15 between the inside and the outside of the case 2. The controlling element 11 further comprises a recess 14 narrowing to the hole 15.

[0067] In the recess 14 a membrane 12 and a mounting ring 13 are arranged. The membrane 12 and the mounting ring 13 are fully integrated in the case 2. They do not protrude beyond the surface of the case 2. The whole controlling element 11 is arranged such that gas from the axial-centred cavity 4 in the capacitor element 3 can flow directly to the controlling element 11.

[0068] The controlling element 11 enables controlled pressure relief. During operation of the capacitor 1, gas generation and pressurization inside the capacitor 1 may occur. These effects are caused by electrochemical reactions. The membrane 12 as a part of the controlling element 11 enables diffusion of the gas to the ambient during the operation of the electrolytic capacitor 1. Thereby the inner pressure is reduced. Thus, the inner pressure can be adapted to ambient pressure.

[0069] The membrane 12 comprises a silicon material. The membrane 12 may further comprise EPDM or another elastic plastic material. The membrane 12 may also comprise a rubber material. In particular, the membrane 12 is a thin silicon membrane. The thickness of the membrane 12 is thin compared to the wall thickness of the case 2. Thus, a membrane requires less vertical space and volume than other types of vents. Therefore more inner volume is available for the capacitor element 3. The membrane 12 may be permeable or semi-permeable for gas. The membrane 12 is circular shaped. The diameter of the membrane 12 is around 3 mm.

[0070] Onto the membrane 12 the mounting ring 13 is arranged in the recess 14. Both the membrane 12 and the mounting ring 13 are arranged from the outside, since the recess 14 is positioned at the outside of the case 2.

[0071] The mounting ring 13 comprises a metal. In particular, the mounting ring 13 comprises aluminum. The mounting ring 13 may be a punched part or impact-extruded. The mounting ring 13 has an appropriate shape to accommodate the membrane 12. The mounting ring 13 may comprise sealing gates 16 on its surface. The sealing gates 16 may be created as bumps. The sealing gates 16 increase the deformation, and therefore the tightness, of the membrane 12.

[0072] The diameter of the mounting ring 13 is larger than the diameter of the membrane 12. The diameter of the mounting ring 13 is in a range between 3 mm and 6 mm. Preferably, the diameter of the mounting ring 13 is in a range between 3 mm and 4 mm. A larger diameter of the mounting ring 13 leads to increasing deformation and tightness of the membrane 12. Additional sealing gates 16 also lead to increasing deformation and tightness of the membrane 12.

[0073] The mounting ring 13 is fixed by an external process such as riveting, cutting-in, forging or any kind of welding process. By fixing the mounting ring 13 the membrane 12 is fixed as well. Therefore the mounting ring 13 has two main functions: Tightening of the membrane 12 and fixing of the membrane 12.

[0074] A distance 17 is kept between the bottom of the case 5 comprising the controlling element 11 and the capacitor element 3. The distance is kept by inner ribs ensuring a certain space between the capacitor element 3 and the membrane 12 to get a free gas flow to the membrane 12. The distance 17 amounts about 0.5 mm. In an embodiment, the distance 17 amounts exactly 0.5 mm.

[0075] Furthermore, the inner surface of the recess 14 comprises sealing gates 16 to deform and tighten the membrane 12. The sealing gates 16 are created as bumps. A higher number of sealing gates 16 leads to increasing deformation and tightness of the membrane 12.

[0076] Additionally, the membrane 12 acts as an irreversible safety vent in the event of an impermissible overpressure within the capacitor. If a critical pressure exceeding the maximum permissible pressure is reached, the membrane 12 bursts.

[0077] The maximum permissible pressure is determined by the tightness of the membrane. The tighter the membrane the more the maximum permissible pressure decreases. The looser the membrane, the more the maximum permissible pressure increases.

[0078] A mounting orientation of the capacitor 1 is beneficial where the bottom 5 of the case 2 of the capacitor 1 points upwards. This orientation corresponds to a terminal-down mounting orientation. This construction prevents the membrane 12 from being covered with liquid electrolyte.

[0079] When the membrane 12 is located at a lower side of the capacitor 1, liquid electrolyte may cover the membrane 12 due to gravity and thus block diffusion of the gas. This may result in cumulative pressurization until the membrane 12 bursts. This phenomenon reduces the efficiency of the operation of the membrane 12. When the membrane 12 is positioned at an upper side of the capacitor 1 it is kept from liquid electrolyte such that gradual diffusion is maintained.

[0080] When the membrane 12 bursts a bottom-up orientation helps to avoid liquid electrolyte leakage to the outside of the capacitor 1. This further prevents ambient devices from being contaminated by the liquid electrolyte.

[0081] FIG. 2A shows a view on the bottom 5 of the capacitor 1 according to FIG. 1. The bottom 5 is a part of the case 2 of the capacitor 1 and is made from aluminum. In an axial-centred position the recess 14 is recessed at the outside of the case 2. The membrane 12 and a mounting ring 13 are arranged inside the recess 14. The membrane 12 covers the hole 15 according to FIG. 1. A shrinking sleeve 10 surrounds the capacitor 1 for protection.

[0082] The mounting ring 13 is shaped to accommodate and tighten the membrane 12. Furthermore, the mounting ring 13 fixates the membrane 12. The mounting ring 13 may comprise sealing gates 16. The mounting ring 13 is partially fixed by riveting. Therefore single rivets 18 are applied.

[0083] In a second embodiment, riveting is completed on the whole perimeter of the mounting ring 13 as shown in FIG. 2B. Fully riveting allows a stronger fixation of the mounting ring 13 and the membrane 12. Partial riveting saves material, and therefore costs.

[0084] In another embodiment, the mounting ring may be fixed by another process such as cutting-in, forging or any kind of welding, preferably laser welding.

[0085] FIG. 3 shows a partial cross-sectional view of a part of the capacitor 1 comprising the bottom 5 of the case 2 and a part of its lateral side 6. In the shown third embodiment the recess 14 for embedding the membrane 12 and the mounting ring 13 is inside the case 2. The recess 14 is positioned axial-centred. Therefore, the gas from the axial-centred cavity 4 in the centre of the capacitor element 3 can flow directly to the membrane 12. For protection a shrinking sleeve 10 surrounds the capacitor 1 at its lateral side 6.

[0086] The controlling element 11 is enlarged in a detail view for better recognition. The controlling element 11 is arranged axial-centred in the bottom 5 of the case 2. The recess 14 is recessed in the inner side of the case 2. The recess 14 narrows to a hole 15 connecting the inside and the outside of the case 2. In the recess 14 the membrane 12 is arranged.

[0087] When the membrane 12 is arranged in the recess 14, the mounting ring 13 is embedded into the recess 14 onto the membrane 12. The mounting ring 13 is suitably formed to accommodate the membrane 12. During the assembly process, pressure is applied to the mounting ring 13, which is transported to the membrane 12. As a result, the membrane 12 is deformed to make the system tight. By using a larger mounting ring 13 the membrane 12 may be tightened more strongly.

[0088] Sealing gates 16 on the inner surface of the recess 14 support the deforming and sealing process. After the membrane 12 and the mounting ring 13 are arranged in the recess 14, the mounting ring 13 is fixed by an external process like cutting-in, forging or any kind of welding. By fixing the mounting ring the membrane is fixed as well.

[0089] In another embodiment, the surface of the mounting ring 13 comprises sealing gates 16. The sealing gates 16 may be created as bumps.

[0090] FIG. 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 5. The membrane 12 covers the mounting ring 13 and the recess 14 inside the case 2 according to FIG. 3. The hole 15 is axial-centred. For protection a shrinking sleeve 10 surrounds the capacitor 1.

[0091] Possible embodiments of the present invention are not limited to the embodiments shown in the FIGS. 1 to 4. Different types of capacitors comprising different types of capacitor elements can be constructed with the disclosed controlling element and are also disclosed herein. Besides the disclosed terminals configured in a snap-in style for electrically contacting the capacitor, other types of terminals are realized in other embodiments of the present invention. For example, the terminals may be configured as screw-type terminals.

LIST OF REFERENCE SIGNS

[0092] 1 electrolytic capacitor [0093] 2 case [0094] 3 capacitor element [0095] 4 axial-centred cavity in the capacitor element [0096] 5 bottom [0097] 6 lateral side [0098] 7 upper side [0099] 8 terminal [0100] 8A terminal tab [0101] 8B terminal rivet [0102] 9A cover member (paper laminate) [0103] 9B cover member (elastomer) [0104] 10 shrinking sleeve [0105] 11 controlling element [0106] 12 membrane [0107] 13 mounting ring [0108] 14 recess in the case 2 [0109] 15 hole in the case 2 [0110] 16 sealing gate [0111] 17 inner distance between capacitor element 3 and controlling element 11 [0112] 18 rivet