Electrolytic capacitor module with high vibration resistance

Abstract

Electrolytic capacitor module (1), in particular for installation in a housing (2) of a motor vehicle control unit, comprising a cylindrical electrolytic capacitor (4) with a capacitor can (5) and two covers (7, 8) each arranged on an end face of the capacitor can (5), which fix a capacitor winding (9) in the interior of the capacitor can (5), and a carrier plate (3) with a chamber (6) for receiving the electrolytic capacitor (4), wherein the capacitor cup (5) has at least one opening (10), wherein in the interior of the electrolytic capacitor (4) the space between the inner wall of the capacitor can (5) and the capacitor winding (9) is at least partially filled with casting compound (12), and the electrolytic capacitor (4) is at least partially surrounded on its outer side in the region of the chamber (6) with the same casting compound (12).

Description

[0001] The invention relates to an electrolytic capacitor module, a method for its production and a motor vehicle control unit with an electrolytic capacitor module according to the invention.

[0002] In automotive engineering, it is now common practice to integrate engine or transmission control units into the vehicle assembly to be controlled, particularly the engine or transmission. Transmission control units, in particular, form an extremely compact unit as a local control unit. Compared to the conventional use of external control units, this arrangement offers enormous advantages in terms of quality, cost, weight, and functionality. In particular, it results in a significant reduction in the number of connectors and cables, and thus in potential causes of failure.

[0003] The integration of the control unit into the transmission places high demands on its thermal and mechanical resilience. Functionality must be ensured both over a wide temperature range (approximately -40°C to 150°C) and under extreme mechanical vibrations (up to 40g).

[0004] In the automotive sector, electrolytic capacitors are used in local control units, among other things, preferably as charging capacitors in the DC circuit, e.g. in rectifier circuits.

[0005] Larger, cylindrical electrolytic capacitors in particular exhibit a higher failure rate under high vibration loads. An electrolytic capacitor is a polarized capacitor consisting of two layers as capacitor plates and a dielectric between them. One layer is a metal foil, particularly aluminum foil, and forms the anode. The other layer is the electrolyte, an electrically conductive liquid on an absorbent material, and forms the cathode. The dielectric between the layers is a thin oxide layer on the surface of the metal foil. Another aluminum foil is used to contact the electrolytic layer. Electrolytic capacitors are wound capacitors, which are available primarily in can shapes with radial (both connections on one end) and axial connecting wires (one connection per end).

[0006] One cause of failure when vibrations occur, for example due to rapidly rotating masses in the motor or gearbox, is that the solder connections between the connecting wires of the electrolytic capacitor and, for example, a circuit board outside the capacitor become loose.

[0007] Another reason for the failure of an electrolytic capacitor due to vibration loads is its internal structure. The winding of the electrolytic capacitor is held or axially clamped in the capacitor can at each end, in particular by a cover. Depending on the design, one connecting wire is arranged on each cover, or both connecting wires are arranged on one cover. The connecting wires are electrically connected to the winding, for example, by welding. In the event of strong vibrations, there is a risk that the winding could move relative to the surrounding can. In the worst case, the electrical connection between the winding and the connecting wires inside the electrolytic capacitor becomes loose. This also leads to the failure of the electrolytic capacitor.

[0008] DE 202 18 520 U1 discloses an arrangement comprising an electronic circuit having at least one electrolytic capacitor, a printed circuit board, and a potting compound that protects the electrolytic capacitor and the electronic circuit from harmful environmental influences, such as dirt, moisture, and / or salt spray. The electrolytic capacitor is electrically connected to conductor tracks of the printed circuit board and is arranged in a protective can, which is arranged between the electrolytic capacitor and the component carrier.

[0009] JP 2008 - 166 303 A discloses a structure for preventing electrolyte leakage from an electrolytic capacitor. For this purpose, a high voltage is applied to an electrolytic capacitor via a substrate. A region containing the electrolytic capacitor is formed by the casing of an electric compressor and an auxiliary element. An insulator is provided to cover the side surface and the bottom of the casing of the electrolytic capacitor. The insulator is formed of a contractible material. The insulator is compressed between the side surface of the casing of the electrolytic capacitor and the inner wall surface of the capacitor-containing region.

[0010] DE 10 2009 003 079 A1 discloses a damping element for an electrical or electronic component, in which the component is electrically contacted via connections with a circuit carrier, in particular with a printed circuit board. The damping element is arranged in contact with both the component and the circuit carrier. The damping element is designed as an element that expands in volume under the influence of heat and / or chemical substances. After expansion, the element fills a gap between the component and the circuit carrier, thereby coming into contact with both the circuit carrier and the component.

[0011] DE 101 52 342 A1 discloses a capacitor with increased vibration resistance. For this purpose, a capacitor winding is partially inserted into a housing, forming a positive fit with the housing. The capacitor winding is then impregnated, causing it to expand and additional compressive forces to develop between the winding and the cup wall, which fix the capacitor horizontally. In a final process step, the capacitor is then vertically fixed between a lid and the base of the cup-shaped housing.

[0012] It is therefore an object of the present invention to provide an electrolytic capacitor module which protects the electrical connections of the connecting wires of the electrolytic capacitor from damage during vibration loads, both for contacting outside the capacitor and for contacting the capacitor winding inside the capacitor.

[0013] This object is achieved according to the invention by an electrolytic capacitor module having the features of claim 1. Advantageous further developments are the subject of the claims which directly or indirectly refer back to claim 1.

[0014] According to the invention, the capacitor can of the electrolytic capacitor has at least one opening, wherein the space between the inner wall of the capacitor can and the winding of the electrolytic capacitor is at least partially filled with casting compound. This prevents the capacitor winding from moving relative to the surrounding capacitor can and the electrical connection between the winding and the connecting wires from becoming loose.

[0015] Furthermore, the electrolytic capacitor is arranged in a chamber of the electrolytic capacitor module such that the electrolytic capacitor's outer surface, in the area of ​​the chamber, is at least partially surrounded by the same casting compound as the winding inside the electrolytic capacitor. This prevents the electrical connections between the electrolytic capacitor's connecting wires and contacts outside the capacitor can from becoming loose due to vibrations, e.g., caused by rapidly rotating parts in the motor or transmission.

[0016] Depending on the application, the opening of the capacitor cup can be designed as a slot or as a substantially circular opening. Multiple openings can also be arranged in the capacitor cup, with one preferably serving as an inlet opening and one as a vent opening. In particular, the vent opening is positioned higher than the inlet opening relative to the fill level of the casting compound in the module chamber.

[0017] Advantageously, the chamber of the electrolytic capacitor module has vias that enable electrical connection between the electrolytic capacitor's connecting wires and components outside the electrolytic capacitor module. The vias can be arranged either on the inner or outer surface of the chamber.

[0018] A further object of the present invention is to provide a method for producing an electrolytic capacitor module according to one of claims 1 to 3.

[0019] This object is achieved according to the invention by a method having the features of claim 4 or 5.

[0020] The method according to the invention comprises the steps: a) providing a carrier plate comprising a chamber and an electrolytic capacitor, b) Inserting the electrolytic capacitor into the chamber of the carrier plate, c) Electrically connecting the connecting wires of the electrolytic capacitor to the vias, d) filling a casting compound into the chamber until the electrolytic capacitor is at least partially surrounded by the casting compound on its outside, and the space between the inner wall of the capacitor can and the winding is at least partially filled with the same casting compound inside the electrolytic capacitor, and e) Curing of the casting compound, e.g., by means of UV radiation.

[0021] In an alternative process, the casting compound is first poured into the chamber of the electrolytic capacitor module, the electrolytic capacitor is inserted into the chamber, and then the electrolytic capacitor's connecting wires are electrically connected to the vias. This alternative process has the advantage that the filling level of the casting compound in the chamber can be better controlled.

[0022] Both processes ensure that a portion of the casting compound from the carrier plate chamber flows through an opening in the electrolytic capacitor's can into the interior of the electrolytic capacitor, at least partially filling the space between the inner wall of the capacitor can and the capacitor winding with casting compound. After the casting compound has hardened, the capacitor winding is fixed, preventing the capacitor winding from moving relative to the surrounding capacitor can and the electrical connection between the winding and the connecting wires from breaking under vibration.

[0023] The electrolytic capacitor module is preferably installed in motor vehicle control units, whereby the carrier plate of the electrolytic capacitor module is connected to the housing of the control unit in a form-fitting or force-fitting manner, for example by means of a screw or a rivet.

[0024] In the following description, the features and details of the invention are explained in more detail in conjunction with the accompanying drawings using exemplary embodiments. The features and relationships described in individual variants are generally applicable to all exemplary embodiments. The drawings show: Fig. 1 a top view of the electrolytic capacitor module, Fig. 2a an electrolytic capacitor with slot-shaped openings, Fig. 2b an electrolytic capacitor with circular openings, and Fig. 3 a section through the electrolytic capacitor module and a housing cutout.

[0025] Fig. 1 shows an electrolytic capacitor module 1 for installation in a housing 2 of a motor vehicle control unit, in particular a so-called local control unit. The electrolytic capacitor module 1 essentially comprises a cylindrical electrolytic capacitor 4 with a capacitor can 5 and a carrier plate 3 with a chamber 6 filled with a hardenable casting compound 12. The electrolytic capacitor 4 is arranged in the chamber 6 such that its outer side, in the region of the chamber 6, is at least partially surrounded by the casting compound 12.

[0026] The connecting wires 15, 16 of the electrolytic capacitor 4 are electrically connected, for example, welded or soldered, to vias 13, 14, which are integrated here into a wall of the chamber 6. This enables an electrical connection between the connecting wires 15, 16 of the electrolytic capacitor 4 and components outside the electrolytic capacitor module 1. However, the vias 13, 14 can also be arranged on an outer surface of the chamber 6.

[0027] In the carrier plate 3, a fastening device in the form of an opening 11 is arranged, in particular, on two opposite sides in the region of the chamber 6. By means of this opening 11, the electrolytic capacitor module 1 can be connected to the housing 2 of the control unit in a form-fitting or force-fitting manner, for example by means of a screw or a rivet.

[0028] Fig. 2a and Fig. 2b each show a cylindrical electrolytic capacitor 4 with a capacitor can 5 and two covers 7, 8, each arranged on an end face of the capacitor can 5, which fix a capacitor winding 9 (not shown here) inside the capacitor can 5. The connecting wires 15, 16 are arranged in this case on an end face of the capacitor can 5. However, it is also possible for a connecting wire 15, 16 to be arranged on each end face. Fig. 2a, the capacitor cup 5 has three slot-shaped openings 10 and Fig. 2b, the capacitor cup 5 has three circular openings 10. However, the openings 10 could also have a different shape, for example, an ellipse.

[0029] A single opening 10 would also be sufficient to allow casting compound 12 to flow from chamber 6 into the interior of electrolytic capacitor 4. In particular, if there is more than one opening 10, one can serve as a vent opening and thus accelerate the flow of casting compound 12 into the interior of electrolytic capacitor 4.

[0030] Fig. Figure 3 shows a section through the electrolytic capacitor module 1 and a housing 2 of a control unit connected to the electrolytic capacitor module 1, with the housing 2 only being shown in detail. The electrolytic capacitor 4 is at least partially surrounded on its outer side in the region of the chamber 6 with casting compound 12.

[0031] As already mentioned above, this prevents, in particular, the electrically conductive connections between the connecting wires 15, 16 of the electrolytic capacitor 4 and the vias 13, 14 of the chamber 6 from being damaged when vibrations occur.

[0032] Through the opening 10 in the capacitor can 5 of the electrolytic capacitor 4, casting compound 12 can flow from the chamber 6 into the interior of the electrolytic capacitor 4 and at least partially fill the space between the inner wall of the capacitor can 5 and the capacitor winding 9 of the electrolytic capacitor 4 with casting compound 12. As already explained, this prevents the capacitor winding 9 from moving relative to the surrounding capacitor can 5 and the electrical connection between the winding 9 and the connecting wires 15, 16 from becoming loose.

[0033] As in Fig.1, a fastening device in the form of an opening 11 is arranged in the carrier plate 3, in particular on two opposite sides in the region of the chamber 6. By means of this opening 11, the electrolytic capacitor module 1 can be connected to the housing 2 of the control unit in a form-fitting or force-fitting manner, for example by means of a screw or a rivet.

[0034] Optionally, the space between the electrolytic capacitor 4 and the housing 2 can be filled with thermal paste. This serves as an additional vibration dampening measure, and it also dissipates the heat generated in the electronic component to the housing. List of reference symbols: 1 electrolytic capacitor module 2 Housing of a motor vehicle control unit 3 Carrier plate 4 Electrolytic capacitor 5 capacitor cups 6 chamber 7, 8 lid 9 capacitor windings 10 Opening in the condenser cup 11 Fastening device 12 Casting compound 13, 14 vias in the chamber 15, 16 connecting wires of the electrolytic capacitor

Claims

[1] Electrolytic capacitor module (1), in particular for installation in a housing (2) of a motor vehicle control unit, comprising a cylindrical electrolytic capacitor (4) with a capacitor cup (5) and two covers (7, 8) each arranged on an end face of the capacitor cup (5), which fix a capacitor winding (9) in the interior of the capacitor cup (5), and a carrier plate (3) with a chamber (6) for receiving the electrolytic capacitor (4), wherein the capacitor cup (5) has at least one opening (10), wherein in the interior of the electrolytic capacitor (4) the space between the inner wall of the capacitor can (5) and the capacitor winding (9) is at least partially filled with casting compound (12), and the electrolytic capacitor (4) is at least partially surrounded on its outer side in the region of the chamber (6) with the same casting compound (12). [2] Electrolytic capacitor module (1) according to claim 1, wherein the opening (10) is formed as a slot or as a substantially circular opening. [3] Electrolytic capacitor module (1) according to one of the preceding claims, wherein the chamber (6) has vias (13, 14) which enable an electrical connection between connecting wires (15, 16) of the electrolytic capacitor (4) and components outside the electrolytic capacitor module (1). [4] A method for producing an electrolytic capacitor module (1) according to claim 1, comprising the steps of: a) providing a carrier plate (3) comprising a chamber (6) and an electrolytic capacitor (4), b) Inserting the electrolytic capacitor (4) into the chamber (6) of the carrier plate (3), c) Electrically connecting the connecting wires (15, 16) of the electrolytic capacitor (4) to the through-contacts (13, 14), d) filling a casting compound (12) into the chamber (6) until the electrolytic capacitor (4) is at least partially surrounded on its outside with the casting compound (12), and in the interior of the electrolytic capacitor (4) the space between the inner wall of the capacitor cup (5) and the winding (9) is at least partially filled with the same casting compound (12), and e) Hardening of the casting compound (12). [5] A method for producing an electrolytic capacitor module (1) according to claim 1, comprising the steps of: a) providing a carrier plate (3) and an electrolytic capacitor (4), b) filling a casting compound (12) into the chamber (6) of the carrier plate (3), c) inserting the electrolytic capacitor (4) into the chamber (6) so that the electrolytic capacitor (4) is at least partially surrounded on its outside by the casting compound (12), and so that in the interior of the electrolytic capacitor (4) the space between the inner wall of the capacitor cup (5) and the winding (9) is at least partially filled with the same casting compound (12), d) Electrically connecting the connecting wires (15, 16) of the electrolytic capacitor (4) to the through-contacts (13, 14), e) Hardening of the casting compound (12). [6] Motor vehicle control unit with an electrolytic capacitor module according to claim 1, wherein the carrier plate (3) of the electrolytic capacitor module (1) is connected to the housing (2) of the control unit in a form-fitting or force-fitting manner.

Images