Can for Electrolytic Capacitor

Abstract

A can for an electrolytic capacitor is disclosed. In an embodiment a can for an electrolytic capacitor includes a bottom including a first area and a second area, wherein the first area is recessed relative to the second area at an outer surface of the bottom of the can.

Claims

1-18. (canceled)

19. A can for an electrolytic capacitor comprising: a bottom comprising a first area and a second area, wherein the first area is recessed relative to the second area at an outer surface of the bottom of the can.

20. The can of claim 19, wherein the first area has a first thickness and the second area has a second thickness, and wherein the second thickness is greater than the first thickness.

21. The can of claim 20, wherein the second thickness is at least 1.5 times the first thickness.

22. The can of claim 19, wherein the first area is plain with the second area at an inner surface of the bottom.

23. The can of claim 19, further comprising a safety vent for enabling pressure relief, wherein the safety vent is located in the first area.

24. The can of claim 23, wherein the safety vent comprises at least one groove.

25. The can of claim 23, wherein the safety vent enables pressure relief before bulging of the first area results in the first area protruding beyond the second area when high pressure builds up inside the can.

26. The can of claim 19, wherein the bottom does not comprise a safety vent for enabling pressure relief.

27. The can of claim 19, wherein the second area laterally encloses the first area.

28. The can claim 19, wherein the second area encloses the first area without any gaps.

29. The can of claim 19, wherein the first area has a shape of a circular disc.

30. The can of claim 29, wherein the second area has a shape of a circular ring.

31. The can of claim 19, wherein a geometry of the first and second areas are such that bulging of the first area does not result in an overall bulging of the can.

32. The can of claim 19, wherein the can is configured to be mounted to a mounting device such that a gap is located between the second area and the mounting device.

33. The can of claim 19, wherein the can comprises AlSi.sub.1MgMn.

34. An electrolytic capacitor comprising: the can according claim 19; and a capacitor element mounted in the can.

35. An assembly comprising: the electrolytic capacitor according to claim 19; and a mounting device, wherein the electrolytic capacitor is mounted on the mounting device, and wherein a gap is located between the second area and the mounting device such that gas discharged from a safety vent is enabled to be released through the gap.

36. A can for an electrolytic capacitor comprising: a bottom, wherein a base material of the bottom comprises AlSi.sub.1MgMn.

37. An electrolytic capacitor comprising: the can according to claim 36; and a capacitor element mounted in the can.

38. An assembly comprising: the electrolytic capacitor according to claim 36; and a mounting device, wherein the electrolytic capacitor is mounted on the mounting device, and wherein a gap is located between the second area and the mounting device such that gas discharged from a safety vent is enabled to be released through the gap.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further features, refinements and expediencies become apparent from the following description of the exemplary embodiments in connection with the figures.

[0029] FIG. 1 shows a sectional view of a can for an electrolytic capacitor;

[0030] FIG. 2 shows a view of an outer surface of the bottom of the can of FIG. 1;

[0031] FIG. 3 shows a view of an inner surface of the bottom of the can of FIG. 1;

[0032] FIG. 4 shows a schematic sectional view of a capacitor; and

[0033] FIG. 5 shows a diagram of bulging versus pressure.

[0034] Similar elements, elements of the same kind and identically acting elements may be provided with the same reference numerals in the figures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0035] FIG. 1 shows a can 1 for an electrolytic capacitor in a schematic sectional view.

[0036] The can 1 has the shape of a circular cylinder. The can 1 comprises a bottom 2 closing the can 1 at a first side, a lateral area 3 and an opening 4 at a second side opposite the first side. During operation of the capacitor, the opening 4 may be closed by a cover member. The can 1 may be used for housing a capacitor element impregnated with a liquid electrolyte.

[0037] The can 1 may be formed in one piece. The can 1 may comprise a metal. As an example, the can 1 may comprise aluminium. The base material composition may be an aluminium alloy, for example.

[0038] In order to increase the mechanical stability of the can 1, the bottom 2 comprises a specific geometrical design. The bottom 2 comprises a first area 5 and a second area 6, wherein the first area 5 is recessed relative to the second area 6 at the outer surface 7. In particular, the first area 5 and the second area form a stepped geometry at the outer surface 7. At an inner surface 8 of the can bottom 2, the first area 5 may be non-discernible from the second area 6. In other words, the bottom 2 may have a plain inner surface 8.

[0039] The thickness d.sub.2 of the second area 6 is larger than the thickness d.sub.1 of the first area 5. As an example, the second thickness d.sub.2 may be at least 1.5 times the first thickness d.sub.1. The increased thickness d.sub.2 of the second area 6 leads to an increase of the overall stability of the can bottom 2 and to a decrease of overall component bulging. Nevertheless, the first area 5 enables a certain amount of component bulging and, thereby reduces the overall mechanical stress.

[0040] Due to the recessed arrangement of the first area 5 relative to the second area 6, bulging of the first area 5 may not lead to a large total bulging of the can bottom 2, because the bulging occurs within the outer dimensions set by the second area 6. Preferably, the first area 5 is recessed sufficiently, such that it does not protrude beyond the outer surface of the second area 6 even in case of high pressure inside the can 1. The second area 6 may not show large bulging due to its increased thickness.

[0041] The second area 6 is arranged nearer to the lateral edge of the bottom 2 than the first area 5. In particular, the first area 5 may form a central part of the bottom 2. The second area 6 may fully enclose the first area 5.

[0042] FIG. 2 shows a view from the outside on the bottom 2 of the can 1, i.e., on the outer surface 7 of the bottom 2. As can be seen in FIG. 2, the second area 6 may have the shape of a circular ring. As an example, an outer radius r.sub.2 of the circular ring may correspond to the radius of the can bottom 2. As an example, the radius of the can bottom 2 may be in a range of 10 mm to 60 mm.

[0043] The first area 5 may have the shape of a circular disk, which may be located inside the second area 6, in particular, the circular ring. The second area 6 fully encircles the first area 5, i.e., without any gaps in the second area 6. The radius of the circular disk may correspond to the inner radius r.sub.1 of the circular ring. The inner radius r.sub.1 depends on the intended opening pressure of the safety vent. The second area 6 extends in an area of the bottom 2, which is not covered by the lateral area 3.

[0044] The can 1 may comprise a safety vent 9 located in the bottom 2. The safety vent 9 enables controlled pressure relief. The safety vent 9 may enable a discharge of the gas when the inner pressure approaches a critical value. Thereby, an uncontrolled explosion of the capacitor may be prevented. As an example, the safety vent 9 may be designed to burst in case of a critical pressure. Bulging of the first area 5 may occur well before the safety vent 9 provides the pressure relief function. The safety vent 9 may be configured to open before bulging of the first area 5 leads to a protrusion of the first area 5 beyond the second area 6.

[0045] The safety vent 9 may be located in the first area 5. The total surface of the first area 5 is much larger than the safety vent 9. The thickness d.sub.1 of the first area 5 is chosen such that the opening mechanism of the safety vent 9 is enabled and depends on the intended opening pressure of the safety vent 9. The thickness d.sub.2 of the second area 6 can be optimized in respect of bulging, because the safety vent 9 does not extend into the second area 6.

[0046] The safety vent 9 may be formed by three equiangular arranged grooves 10, 11, 12. Other shapes, for example, a shape of a cross, a star or a Z may be equally possible. As an example, the safety vent 9 may be stamped in the bottom 2.

[0047] In the shown embodiment, the safety vent 9 extends to the edge of the first area 5. In particular, the length of the grooves 10, 11, 12 corresponds to the radius r of the first area 5. In further embodiments, the safety vent 9 may not extend up to the edge of the first area 5.

[0048] FIG. 3 shows a view from the inside of the can 1 on the bottom 2 of the can 1, i.e., on the inner surface 8 of the bottom 2. The inner surface 8 is plain, apart from the safety vent 9. From inside the can 1, the first area 5 is not discernible from the second area 6. The safety vent 9 is visible from inside and from outside the can 1. For enabling gas discharged from the safety vent 9 to be released to the outside in a mounted arrangement of the can 1, the can 1 may be configured to be mounted such that a gap is present between the second area 6 and a mounting device.

[0049] Alternatively or additionally to the outside stepped geometry described above, the material of the can 1, in particular of the can bottom 2 may have a high resistance to pressure. In this case, bulging of the can bottom 2 can be kept at a low level. As an example, the base material may comprise the alloy EN AW-6082 (AlSi.sub.1MgMn). When using this alloy, the bulging resistivity may additionally increase by 20% for the same geometry in comparison to the base material EN AW-1050A (Al99,5).

[0050] FIG. 4 shows an electrolytic capacitor 13. The capacitor 13 comprises a can 1 as described above. A capacitor element 14 is mounted in the can 1. The capacitor element 14 comprises a wound shape. The capacitor element 14 may comprise foils, in particular aluminium foils. The capacitor element 14 may be impregnated with a liquid electrolyte.

[0051] The capacitor 13 comprises terminals 15, 16 for electrically connecting the capacitor 13. The terminals 15, 16 may be configured as screw-type terminals.

[0052] The opening 4 of the can 1 is closed by a cover member 17. The cover member 17 may have the shape of a disc. The cover member 17 may seal the can 1. The cover member 17 may comprise a rubber material or another elastic material. The terminals 15, 16 are lead through the cover member 17.

[0053] FIG. 5 shows a diagram of total bulging B of the can bottom 2 versus pressure p inside a can 1 for two different designs.

[0054] The solid line shows bulging for a standard flat bottom design with the base material EN AW-1050A. The dashed line shows bulging for a reverse stepped geometry according to FIG. 1 with the base material EN AW-6082. As can be clearly seen from the diagram, the mechanical stability of the can expressed as bulging is considerably increased due to the geometrical changes and the changes in the base material.