Cooling of electrolytic capacitors in electrical climate compressors

Abstract

A system for mounting at least one cylindrical electrolytic capacitor on a heat sink, the heat sink having at least one bore for at least partially receiving a cylindrical electrolytic capacitor, and the bore partially or fully encompassing the cylindrical electrolytic capacitor once it has been received, wherein lateral surfaces of the cylindrical electrolytic capacitor are mechanically and thermally connected to surfaces forming the bore. The system providing thermal cooling of the electrolytic capacitor and enabling substantially uniform thermal cooling of the capacitor. A method for producing a connection between the at least one cylindrical electrolytic capacitor and the heat sink, and to a connection, obtainable by the method, between the at least one electrolytic capacitor and the heat sink.

Claims

1. A method for producing a connection between at least one cylindrical electrolytic capacitor and a heat sink, wherein the heat sink has at least one bore for at least partially receiving the at least one cylindrical electrolytic capacitor and the at least one bore partially or fully encompasses the at least one cylindrical electrolytic capacitor, and wherein a first section having a constant or variable diameter extends from an outer edge of the at least one bore and terminating inside the at least one bore at a workpiece edge, wherein the first section merges inside the at least one bore into a second section having a constant diameter smaller than the diameter of the first section, the method comprising the steps of: a) applying a thermally conductive adhesive in the first section, wherein the applied adhesive protrudes over the workpiece edge into an interior of the at least one bore, and b) inserting the at least one electrolytic capacitor at least partially into the second section of the at least one bore before the adhesive is cured, so a portion of the uncured adhesive is pushed into the at least one bore and a lateral surface of the at least one electrolytic capacitor is wetted by the uncured adhesive.

2. The method according to claim 1, wherein the thermal adhesive is applied by a metering tip of a metering unit.

3. The method according to claim 1, wherein the first section extends from the outer edge of the at least one bore and terminates inside the at least one bore at a stepped shoulder which includes the workpiece edge where the first section merges inside the at least one bore into a second section.

4. The method according to claim 1, wherein a wall forming the at least one bore in the first section is configured at least partially as a bevel, wherein the diameter of the first section decreases constantly.

5. The method according to claim 1, wherein the thermally conductive adhesive is electrically insulating.

Description

DRAWINGS

(1) Additional details, features and advantages of embodiments of the invention are provided in the following description of embodiment examples, with reference to the accompanying set of drawings. The drawings show:

(2) FIG. 1: a system for mounting electrolytic capacitors for cooling on an electric refrigeration compressor of the prior art,

(3) FIG. 2: a system for mounting electrolytic capacitors on an electric refrigeration compressor,

(4) FIG. 3: a schematic representation of the application of the adhesive in a shoulder of a blind-hole bore according to one embodiment example of the present invention, and

(5) FIG. 4: a schematic representation of the insertion of an electrical component and wetting of the lateral surface thereof with a thermally conductive adhesive.

DETAILED DESCRIPTION

(6) FIG. 1 is a schematic illustration of a prior art assembly 1 for cooling electrolytic capacitors 2 or a system 1 for mounting electrolytic capacitors 2 for their cooling on an electric refrigeration compressor. In addition to electrolytic capacitors 2, assembly 1 also comprises a power electronics circuit board 3, to which the electrolytic capacitors 2 are mechanically connected via retaining clips 4. Electrolytic capacitors 2 are connected to a power electronics circuit board 3 both electrically and mechanically by means of retaining clips 4. For active cooling, the surface of electrolytic capacitor 2 must be attached to heat sink 5 or to cooling surface 5a with the lowest possible thermal resistance. From this prior art example, it is known that electrolytic capacitors 2 are potted or adhesively bonded individually, or a plurality of capacitors 2 are potted or adhesively bonded, using a plastic resin 6. This may be achieved by using either flexible thermopads 6 or special thermally conductive adhesive 6. The two electrolytic capacitors 2, as FIG. 1 shows, are seated in a trough-shaped receiving region, which is part of housing 5 of the refrigeration compressor. FIG. 1 shows the outcome of a known procedure for mounting electrolytic capacitors 2, in which cylindrical electrolytic capacitors 2 are mounted horizontally, with a small portion of their lateral surface in contact with cooling surface 5a of housing 5. In other words, electrolytic capacitors 2 are positioned with their lateral surface lying flat on a housing 5 of an electric refrigeration compressor as a heat sink 5, which is filled with a cooling medium 7, and are adhesively bonded thereto by means of plastic resin 6 as an adhesive 6. In this process, thermally conductive adhesive 6 is first applied by means of a metering unit not shown in FIG. 1, after which electrolytic capacitor 2 is placed in adhesive 6. It is further known to adhesively bond electronic components by overmolding or potting. FIG. 1 also schematically illustrates the cooling/heat dissipation of electrolytic capacitors 2, indicated by arrows 8 representing dissipated heat 8.

(7) To improve the cooling of electrolytic capacitors, each of these is placed individually in a bore that fully or partially encompasses the lateral surface of the cylindrical capacitor. FIG. 2 schematically illustrates a system 1 for mounting two cylindrical electrolytic capacitors 2, which are electrically and mechanically connected to a power electronics circuit board 3, into two bores 9 embodied as blind holes 9. This system according to the invention offers improved cooling as compared with the prior art. Each of bores 9 is designed to at least partially accommodate one cylindrical electrolytic capacitor 2. Each bore 9 partially or fully encompasses the cylindrical electrolytic capacitor 2 once it has been received, with the lateral surfaces of the cylindrical electrolytic capacitor 2 being mechanically and thermally connected to the surfaces of bore 9. In system 1 of FIG. 2, this is accomplished by gluing or pressing the lateral surfaces of cylindrical electrolytic capacitor 2 into bore 9 using a thermally conductive adhesive 6. Heat 8 can thereby be transferred from capacitors 2 through adhesive 6 and the walls of the bore 9 to housing 5 of the electric refrigeration compressor.

(8) A first section 11 having a first diameter extends starting from an outer edge 10 of bore 9, and terminating inside bore 9 at a stepped shoulder 12. This stepped shoulder 12 has an inner edge 13. At this inner edge 13, first section 11, which has the first diameter, merges inside bore 9 into a second section 14 having a smaller, second diameter. Thus, first section 11 having the first diameter serves as the area for receiving cylindrical electrolytic capacitor 2, whereas electrolytic capacitor 2 reaches a depth stop at shoulder 12. Furthermore, in the event of a fault/safety hazard, the expansion valve of the electrolytic capacitor 2 can expand into cavity 14, or second section 14, formed beneath the depth stop.

(9) FIG. 3 and FIG. 4 schematically illustrate a method for producing a connection between at least one cylindrical electrolytic capacitor 2 and a cooling surface 5a, according to one embodiment of the present invention. This method involves the application of thermally conductive adhesive 6 to electrolytic capacitors 2 in an electric refrigeration compressor. Heat sink 5 in this case has two bores 9, each designed to at least partially accommodate one cylindrical electrolytic capacitor 2. According to the representations of FIG. 3 and FIG. 4, these bores 9 are designed as blind holes 9. Bore 9 partially or fully encompasses cylindrical electrolytic capacitor 2 once it has been received, and a first section 15 having a first diameter of bore 9 extends, starting from an outer edge 10 of bore 9, and terminating inside bore 9 at a stepped shoulder 16, at the inner edge 17 of which, as workpiece edge 17, first section 15 having the first diameter merges inside bore 9 into a second section 18 having a smaller, second diameter. In this embodiment example, second section 18 serves as a space for receiving electrolytic capacitor 2, with second section 18 terminating inside bore 9 at an additional stepped shoulder 19, which provides a depth stop for electrolytic capacitor 2. Beneath the depth stop, a third section 20 having a third diameter, a cavity 20, is formed. The expansion valve of the electrolytic capacitor 2 can expand into this cavity 20 in the event of a fault/safety hazard.

(10) A shoulder 16 is thus provided in the region of outer edge 10 of bore 9. On this shoulder 16, thermally conductive adhesive 6 is applied by means of a metering tip 21 of a metering device, as shown in FIG. 3. First section 15 thus serves in this case as an application area for adhesive 6. A thermally conductive adhesive 6 is applied to shoulder 16 in such a way that the applied adhesive 6 protrudes beyond inner edge 17 of shoulder 16, which corresponds to the smaller, second diameter, into the interior of bore 9. When electrolytic capacitor 2, as shown schematically in FIG. 4, is then inserted at least partially into second section 18 in corresponding bore 9, this electrolytic capacitor 2 will pull the as yet uncured adhesive 6 along with it into bore 9. The lateral surface of electrolytic capacitor 2 is wetted, and is adhesively bonded with low thermal impedance.

LIST OF REFERENCE SIGNS

(11) 1 system, assembly for cooling electrolytic capacitors 2 electrolytic capacitors 3 power electronics circuit board 4 retaining clips 5 heat sink, housing of a refrigeration compressor, cooling surface 5a cooling surface 6 adhesive, plastic resin, thermopads, thermal adhesive, thermally conductive adhesive 7 cooling medium 8 heat, dissipated heat, heat transfer 9 bore, blind hole 10 outer edge of bore 9 11 first section (of bore 9) having a first diameter (as an area for receiving cylindrical electrolytic capacitor 2) 12 shoulder (for depth stop) 13 inner edge of shoulder 14 second section (of the bore) having a second diameter (below the area for receiving cylindrical electrolytic capacitor 2), cavity 15 first section (of bore 9) having a first diameter (as area of application for adhesive 6) 16 shoulder (for the application of adhesive 6) 17 inner edge, workpiece edge 18 second section 19 stepped shoulder (for depth stop) 20 third section, cavity 21 metering tip